3P: Space Plasmas

Intense Beam Microwave Devices

Fast Wave Devices

Slow Wave Devices

Plasmas for Lighting

Pulsed Power and Other Plasma Technology Applications

Space Plasmas

Space Plasmas

3P01: Effect of Ion-parallel Viscosity on the Propagation of Surface Waves on an Interface. N. Kumar1 and H. Sikka2 Department Of Mathematics, K.G.K(P.G) College Moradabad-244001(U.P) India

3P02: Parametric Instabilities in Ionospheric Heating Experiments^* S.P. Kuo Department of Electrical Engineering, Polytechnic University Polytechnic University, Route 110, Farmingdale, NY 11735

Intense Beam Microwave Devices

3P03: Simulation Study of High Power Microwave Generation by Virtual Cathode Oscillation in Coaxial Vircator Y. Jung, M.C. Choi, K.B. Song, G.Y. Sung, and E.H. Choi* Charged Particle Beam and Plasma Lab. PDP Research Center/Department of Electrophysics, Kwangwoon Univ, Seoul 139-701, Korea

3P04: Relativistic and Nonrelativistic Magnetron Experiments and A Novel Theory of Relativistic Crossed-Field Limiting Current* M.R. Lopez, R.M. Gilgenbach, V.B. Neculaes, D.W. Jordan, Y.Y. Lau, M.D. Johnston, M.C. Jones, T.A. Spencer^a, J. W. Luginsland^b, M. Haworth^a, R.W. Lemke^c, David Price^d Intense Energy Beam Interaction Lab Nuclear Engineering and Radiological Sciences Department University of Michigan, Ann Arbor, MI 48109-2104 ^a Air Force Research Laboratory, Phillips Research Lab, Kirtland AFB, NM ^b SAIC

3P05: Experimental Test of Focusing Electrodes on Repetitively-Pulsed MILO Cathodes M. Haworth, K. Cartwright, K. Golby^†, M. LaCour^†, J. Luginsland^†, D. Ralph^†, M. Sena^†, D. Shiffler, and R. Umstattd^‡ Air Force Research Laboratory Directed Energy Directorate Kirtland AFB, New Mexico 87117

3P06: HPM Investigation of Gas Breakdown K.J. Hendricks Air Force Research Laboratory 3550 Aberdeen Ave, SE AFRL/DEHP Kirtland AFB, NM 87117-5776

3P07: Dielectric Cherenkov Maser with a Magnetically Conned Plasma Column in a Dielectric rod Slow-Wave Waveguide B. Shokri, H.Ghomi Department of Physics and Laser Research Center of Shahid Beheshti University, Evin, 19839, Tehran, Iran and Institute for studies in theo. and math. science, P.O.BOX 19395-1795, Tehran. Iran.

Fast Wave Devices

3P08: Update on the Development of a 10MW, 91 GHz Gyroklystron J.M. Neilson, R.L. Ives, M. Read. M. Mizuhara, T. Robinson, D. Marsden Calabazas Creek Research, Inc. 20937 Comer Drive Saratoga, California 95070 Wesley Lawson, Bart Hogan Institute for Research in Electronics and Applied Physics 223 Paint Branch Road

3P09: Experiment on a Cold Cathode Gyrotron　 Kazuo Minami, Yutaka Hayatsu, Tsukasa Sato, Masashige Sanmonji, Graduate School of Science and Technology Niigata University, Niigata City, 950-2181 Japan Victor L. Granatstein Institute for Research in Electronics and Applied Physics, University of Maryland, College Park MD 20742 USA

3P10: Design of a W-Band TE01 Gyro-TWT with High Power and Broadband Capabilities D.B. McDermott, H.H. Song, Y. Hirata, A.T. Lin¹, T.H. Chang², H.L. Hsu, K.R. Chu², and N.C. Luhmann, Jr. Department of Applied Science, University of California, Davis ¹ Department of Physics, UCLA, Los Angeles, CA ² Department of Physics, NTHU, Hsinchu, Taiwan, ROC

3P11: 30 GHz Second-Harmonic TE21 Cusp-Gun Gyro-TWT Amplifier S.B. Harriet¹, D.B. McDermott, N.C. Luhmann, Jr. Department of Applied Science, University of California at Davis Davis, CA 95616 1 Also NSWC Crane, Crane, IN

3P12: 34 GHz Fundamental-Mode Peniotron for High Device Efficiency L.J. Dressman¹, D.B. McDermott, N.C. Luhmann, Jr. D.A. Gallagher², T.A. Spencer³ Department of Applied Science, University of California at Davis Davis, CA 95616 1 Also NSWC Crane, Crane, IN 2 Northrop Grumman Corporation, Rolling Meadows, IL 3 Air Force Research Laboratory, Albuquerque, NM

3P13: Development of a C-band Harmonic Amplifier Peter H. Ceperley¹ and Jose E. Velazco Microwave Technologies Incorporated, Fairfax, VA 22030 ¹George Mason University, Fairfax, VA 22030-4444

Slow Wave Devices

3P14: Effect of Boundary Reflection on Helix Backward Wave Oscillator T.M. Abuelfadl*, G.S. Nusinovich*, A.G. Shkvarunets*, Y. Carmel*, T.M. Antonsen*, Jr., V.L. Granatstein* and D.M. Goebel** * Institute for Research in Electronics and Applied Physics, University of Maryland at College Park, College Park, MD 20742, USA. ** Electron Dynamic Devices, Boeing Co.

3P15: Investigation of Ultrawideband Pulses in Wideband Helix Traveling Wave Tubes* M.C. Converse, S.C. Hagness, J.H. Booske, J.G. Wohlbier, J.E. Scharer University of Wisconsin -Madison Dept of Electrical and Computer Engineering 1415 Engineering Dr Madison, WI 53706

3P16: Nonlinear Guiding-Center Electron Flow Equilibria in Crossed Field Devices J.A. Davies and C. Chen Plasma Science and Fusion Center Massachusetts Institute of Technology Cambridge, MA 02139 L.D. Ludeking and R.S. Smith Mission Research Corporation

3P17: Linear TWT Development* T.A. Hargreaves, C.M. Armstrong, R.B. True, R. Watkins, M.L. Barsanti, A. Schram Northrop Grumman Electron Devices 960 Industrial Road San Carlos, CA 94070

3P18: Amplitude Locking in a Gyro TWT Amplifier with a Delayed Feedback Amit Kesar, David Blank, and Eli Jerby§ Faculty of Engineering, Tel-Aviv University, Ramat Aviv 69978, Israel

3P19: Intermodulation Products in a Klystron M.W.Keyser, C.B. Wilsen^a), M.J. Newman^b), Y.Y. Lau, D. Chernin^c), R.M. Gilgenbach, C. Marchewka^b), J. Welter^b), S. Bhattacharjee^b), A. Singh^b), J.H. Booske^b), and J.E. Scharer^b) Department of Nuclear Engineering and Radiological Sciences University of Michigan, Ann Arbor, MI 48109-2104 ^a)Northrop-Grumman/Litton, San Carlos, CA ^b)University of Wisconsin, Madison ^c)Science Applications International

3P20: Numerical Analysis of the Influence of the Outer Conducting Wall in Helix-TWT H.S. Kim KMW Inc., TWT Lab 65 Youngchun-ri, Dongrtan-myun, Hwasung-si, Kyungki-do, Korea 445-813 H.S. Uhm Dept. of Molecular Science and Technology, Ajou University

3P21: Saddle Point Analysis of a High Power Backward Wave Oscillator near Cyclotron Absorption Kazuo Minami, Hoshiyuki Yamazaki, Yaduvendra Choyal, Graduate School of Science and Technology Niigata University, Niigata City, 950-2181 Japan Victor L. Granatstein Institute for Research in Electronics and Applied Physics, University of Maryland, College Park MD 20742 USA

3P22: An Electron Gun for A Sheet Beam Klystron M.E. Read, G. Miram, and R.L. Ives Calabazas Creek Research 20937 Comer Drive, Sarasota, CA, 95070-3753 A. Krasnykh and V. Ivanov Stanford Linear Accelerator Center 2575 Sand Hill Rd, Menlo Park, CA 94025 Calabazas Creek Research, Inc.(CCR)

3P23: Intermodulation Suppression in a Broad Band TWT* A. Singh, J. Scharer, M. Wirth, S. Bhattacharjee and J. Booske Univ. of Wisconsin, Madison

3P24: CTLSS Features Supporting Vacuum Electron Device Design S.J. Cooke, C-L. Chang, A.A. Mondelli, D.P. Chernin, T.M. Antonsen Jr. and B. Levush ^†, Science Applications International Corporation, McLean V, USA. ^† Vacuum Electronics Branch, Code 6840, NRL, Washington DC.

Plasmas for Lighting

3P25: UV and Visible Emission Processes in a Moly-Oxide Discharge* J.L. Giuliani, R.E. Pechacek^a, G.M. Petrov^b, A. Dasgupta, K. Bartschat^c, and R.A. Meger Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375

3P26: DBD-Based VUV Source for Advanced Photolithography* M. Laroussi, M.C. Gupta, A. El Dakroury and J. Yan Old Dominion University K.H. Becker and K. Martus Stevens Institute of Technology

3P27: Electron Density and Electron Temperature in Argon Microhollow Cathode Discharges M. Moselhy¹, F. Leipold¹, K.H. Schoenbach¹ I. Petzenhauser², and Klaus Frank^{2 1}Physical Electronics Research Institute Old Dominion University, Norfolk, VA 23529, USA ²Physikalisches Institut I, Univ. of Erlangen-Nuremberg, Germany

3P28: Ballast Free, Large Area Microdischarge Excimer Lamps Wenhui Shi and Karl H. Schoenbach Norfolk Applied Science, Inc. Norfolk, VA 23505, USA

3P29: Hg Density Imaging in a Metal-halide Arc Lamp J.J. Curry¹ and H.G. Adler^{2 1}National Institute of Standards and Technology Gaithersburg, Maryland ²OSRAM SYLVANIA Beverly, Massachusetts

3P30: Analysis of the Hg-Na Arc-W Cathode Interactions at Increasingly High Na Contents S. Coulombe CRTP/Plasma-Québec, Department of Chemical Engineering, McGill University, Montréal, Québec, Canada, H3A 2B2

3P31: Atomic Density Distribution over the Excited-States in High-Pressure Mercury Plasmas D. Karabourniotis Institute of Plasma Physics, Department of Physics Unversity of Crete, 71003 Heraklion Crete, Greece

Pulsed Power and Other Plasma Technology Applications

3P32: A Novel Crowbar Scheme for Capacitive Pulsed Power Systems Hongsik Lee, Taeho Lee, Kilsoo Seo, Yunsik Jin, Jongsoo Kim Korea Electrotechnology Research Institute Sungju-Dong 28-1 Changwon, 641-120 Korea

3P33: Fast Dielectric Volume Breakdown In Liquid Nitrogen^* A. Neuber, H. Krompholz, M. Haustein, J. Dickens Center for Pulsed Power and Power Electronics Research Departments of Electrical & Computer Engineering and Physics Texas Tech University Lubbock, TX 79409-3102

3P34: Repetitive Pulsed Power Modulator Using Static Induction Thyristor for Discharge Light Source Keiichi Yamashita, Keiichiro Nishikawa, Akitoshi Okino, Masato Watanabe, and Eiki Hotta, Department of Energy Sciences, Tokyo Institute of Technology Nagatsuta, Midori-ku, Yokohama 226-8502, Japan Kwang-Cheol Ko, Department of Electrical and Computer Engineering,

3P35: Effect of Material Strength Models on Numerical Prediction of Instability Growth in Solids Ann M. Kaul, Rickey J. Faehl Los Alamos National Laboratory, Los Alamos, NM akaul@lanl.gov, rjf@lanl.gov

3P36: Optimization of a Fuse Opening Switch M. PRAT, T. DESANLIS, G. GUILLOT, L. MAGNIN, R. NICOLAS, R. ROSOL, L. VERON and P. ZEHNTER Commissariat à l’Energie Atomique Polygone d’Expérimentation de Moronvilliers, France.

3P37: Modeling and Analysis of a Flux Compression Concept Designed for Driving PRS Loads J. Watrous¹ and J.R. Goyer^{2 1}NumerEx, 2309 Renard Pl. SE, STE 220, Albuquerque, NM 87106 ²Titan Systems Corp., Pulse Sciences Division, 2700 Merced Street, San Leandro, CA

3P38: Experimental Tests of Vacuum Closing and Opening Switches for a Current-Multiplier (Meatgrinder) Circuit* B.V. Weber, J.R. Boller,^a R.J. Commisso, G. Cooperstein, B. Moosman,^a S. J. Stephanakis, Plasma Physics Division, Naval Research Laboratory Washington DC, 20375-5346 USA W. Peter and O. Zucker APTI, Washington, DC 20037 USA

3P39: Transitional Processes in Combined Opening Switch (Vacuum Interrupter and PEOS) O.G. Egorov Troitsk Institute for Innovation and Fusion Research, Troitsk,Moscow reg.,Russia, 142190

Space Plasmas

3P01:

Effect of Ion-parallel Viscosity on the Propagation of Surface Waves on an Interface.

N.Kumar1 and H.Sikka2

Department Of Mathematics, K.G.K(P.G) College

Moradabad-244001(U.P) India

The behaviour of MHD Surface Waves propagating at a single interface is studied by incorporating viscous dissipation via the strongly anisotropic parallel viscosity term. We consider incompressible, linear, MHD equations with a strong background magnetic field. Applying boundary condition at the interface i.e. continuity of normal velocity and the total pressure across the interface, the dispersion relation is obtained for the surface waves. It is thens solved numerically and characteristic curves are plotted different values of propagating angle. It is found that modes of surface waves become damped owing to ion-parallel viscosity. The pattern of propagation shown graphically. It is conjectured then solved numerically and characteristic curves are plotted that the results are applicable for the situation in solarwind at 1 AU for values obtained from spacecraft data.

3P02:

Parametric Instabilities in Ionospheric Heating Experiments^*

S.P. Kuo

Department of Electrical Engineering, Polytechnic University

Polytechnic University, Route 110, Farmingdale, NY 11735

Parametric instabilities excited in ionospheric heating experiments are studied. The primary processes excited directly by HF heating (pump) waves include parametric decay instabilities, which decay the HF heating wave to a frequency-downshifted Langmuir/upper hybrid sideband together with an ion acoustic/lower hybrid wave as the decay mode, and oscillating two stream instabilities, which decay the HF heating wave to two oppositely propagating Langmuir/upper hybrid sidebands and a purely growing mode/field-aligned density irregularities. These instabilities provide effective channels to convert electromagnetic heating waves to electrostatic plasma waves in the F region of the ionosphere. The instability thresholds, growth rates, angular distribution, and regions of excitation are determined. The high frequency sidebands (Langmuir waves and upper hybrid waves) of primary parametric instabilities can be driven to large amplitudes. These waves then become new pump waves to excite secondary parametric instabilities, which provide cascade channels to broaden the spectra of plasma waves and generate short-scale density irregularities. The secondary parametric instabilities include cascades of Langmuir pump waves into Langmuir sidebands and ion acoustic waves/lower hybrid waves, and decay of upper hybrid waves to Langmuir sidebands and ion decay modes, as well as the filamentation of those high frequency electrostatic waves to generate field-aligned density irregularities. Again, the thresholds and growth rates of these instability processes are determined.

^*Work supported by the High Frequency Active Auroral Research Program (HAARP), Air Force Research Laboratory at Hanscom Air Force Base, Massachusetts and by the Office of Naval Research grant ONR-N00014-00-1-0938.

Intense Beam Microwave Devices

3P03:

Simulation Study of High Power Microwave Generation by Virtual Cathode Oscillation in Coaxial Vircator

Y. Jung, M.C. Choi, K.B. Song, G.Y. Sung, and E.H. Choi*

Charged Particle Beam and Plasma Lab.

PDP Research Center/Department of Electrophysics

Kwangwoon Univ, Seoul 139-701, Korea

We have numerically simulated the high power microwave generation by virtual cathode oscillation in a coaxial vircator with 3 dimensional PIC code “Magic”. It is noted that the coaxial vircator has the advantage of an enhancement of power efficiency and gaining of narrow bandwidth frequency. The study is focused on the design of a diode structure for a coaxial vircator suitable for “Chundoong” IREB pulser (Max. 600 kV, 85 kA, 60 ns). It consists of a center annular cathode, a cylindrical meshed-anode and a reflector. The simulation results showed that the coaxial vircator can indeed be operated at the selected frequency with the narrow bandwidth and the microwave output power strongly depends on the position and geometry of the reflector. From this simulation results we expect that the maximum microwave output power will be obtained by the reflector of 4 cm in width and also 4 cm in distance away from the IREB, where the resonant frequency of microwave from coaxial vircator is simulated to be 6.577 GHz.

* Present address : Center for Pulse Power and Power Electronics, Department of Electrical & Computer Engineering and Physics, Texas Tech University, Lubbock, TX 79409-3102, USA.

3P04:

Relativistic and Nonrelativistic Magnetron Experiments and A Novel Theory of Relativistic Crossed-Field Limiting Current*

M.R. Lopez, R.M. Gilgenbach, V. B. Neculaes, D.W. Jordan, Y.Y. Lau, M.D. Johnston, M.C. Jones,T. A. Spencer^a, J. W. Luginsland^b, M. Haworth^a, R.W. Lemke^c, David Price^d

Intense Energy Beam Interaction Lab

Nuclear Engineering and Radiological Sciences Department

University of Michigan, Ann Arbor, MI 48109-2104

^a Air Force Research Laboratory, Phillips Research Lab,

Kirtland AFB, NM

^b SAIC

^c Sandia National Laboratory

^d Titan Corporation

Relativistic magnetron experiments have generated over 200 MW total microwave output power. These experiments are driven by the MELBA long-pulse e-beam with parameters: Voltage =-0.4 MV, current = 1-10 kA, pulselength = 0.5 microsecond. The 6-vane magnetron is made by Titan and operates in the L-band near 1 GHz. Two types of cathodes were used: (1) a non-end-capped cathode with an Al explosive emission region in the center of the vanes, and (2) an end-capped cathode with a spherical knob placed at its end, beyond the vanes; the emission region is within the vanes. Endloss electron current is compared for the two cathodes.

Microwaves are extracted from two opposing cavities and power measurements are summarized as a function of magnetic field. Microwave pulselengths are in the range from 10-100 ns. Frequency is near 1.03 GHz, close to the Pi mode prediction. Nonrelativistic (4 kV) magnetron experiments (at 1 kW microwave power) are exploring the relationship between the quiet vs. noisy emission states and electron beam parameters.

The maximum injected current for a time-independent cycloidal flow in a relativistic, magnetically insulated diode has never been correctly solved. The classic paper by Lovelace and Ott [1] assumes the space charge limited (SCL) condition on the cathode surface. Surprisingly, Christenson [2] discovered that the maximum emission current density was not given by the SCL condition in the deeply nonrelativistic regime. She found that the maximum allowable current was slightly higher than that predicted from the SCL condition.

Thus, we extend the analytical theory of Lovelace-Ott by relaxing the SCL assumption. Our theory reduces to Christenson’s results in the deeply non-relativistic regime, and to the Lovelace-Ott results under the SCL assumption.

*This work was supported by AFOSR and DUSD (S&T) under the Innovative Microwave Vacuum Electronics MURI Program, managed by the Air Force Office of Scientific Research under Grant F49620-99-1-0297, and by the Northrop Grumman Industrial Associates Program.

[1] R. V. Lovelace and E. Ott, Phys. Fluids 17, 1263 (1974).

[2] P. J. Christenson, Ph.D. diss., U. Mich., Ann Arbor (1996).

3P05:

Experimental Test of Focusing Electrodes on Repetitively-Pulsed MILO Cathodes

M. Haworth, K. Cartwright, K. Golby^†, M. LaCour^†, J. Luginsland^†,

D. Ralph^†, M. Sena^†, D. Shiffler, and R. Umstattd^‡

Air Force Research Laboratory

Directed Energy Directorate

Kirtland AFB, New Mexico 87117

Experimental and computer simulation results on a magnetically insulated transmission line oscillator (MILO) have indicated that the large beam current density emitted from each end of the cathode leads to anode plasma formation. Recent computer simulations [1] have shown that implementation of the miniature Pierce focusing electrode concept of Umstattd et al. [2] can dramatically reduce the beam current density at both ends of the cathode. We report on preliminary experimental tests of this focusing electrode concept using a polymer velvet MILO cathode driven at 1 Hz by 500-kV, 5-W, 50-ns pulses.

[1] M. Haworth et al., “Improved electrostatic design for MILO cathodes,” IEEE Trans. Plasma Sci., vol. 30, 2002.

[2] R. Umstattd et al., “Design and implementation of a new UHV threshold cathode test facility,” Proc. SPIE, vol. 4031, pp. 185-194, 2000.

^†Science Applications International Corp., Albuquerque, NM 87106

^‡Naval Post Graduate School, Monterey, CA 93943

3P06:

HPM Investigation of Gas Breakdown

K.J. Hendricks

Air Force Research Laboratory

3550 Aberdeen Ave, SE

AFRL/DEHP

Kirtland AFB, NM 87117-5776

One of the fundamental parameters of HPM technology in question is the relationship between the electric field pulse, gas pressure, and pulse length. As HPM sources have increased in power this relationship is crucial to properly design antennas and radomes to remove the generated microwave pulse. To investigate this relationship we are in the process of re-assembling the Injection-Locked Relativistic Klystron Oscillator. The initial experiments focus on techniques to reduce the rate of change of the emitted beam current. Recall we have previously published that the microwave pulse length was experimentally observed to be limited to a finite change in the beam current. We will be presenting results of these experiments and the experimental changes employed to control the rate of change of the current. Once the current ramp is within acceptable limits, we will transistion to the gas breakdown experiments. We have designed and assembled double belljar system with a Vlasov antenna to allow adjustment of the gas pressure between the belljars. This pressure control allows determination of the Paschen breakdown curve in a microwave only environment. Because the microwave radiating structure is more than 25 feet from electron beam source, we know there are no x-ray sources beyond the background level. Also, the antenna does not contain any field distortion features to initiate the breakdown. We intend to investigate several gases for the E/p versus pt relationship; where E is the microwave electric field in the gas regioin between the belljar (<30 kV/cm calculated with 1.5 GW of power generated), p is the neutral gas pressure prior to breakdown (10 Torr - 760 Torr), and t is full-width at half-maximum (FWHM) microwave pulse width (< 500 nsec) limited by the pulsed power system available.

3P07:

Dielectric Cherenkov Maser with a Magnetically Conned Plasma Column in

a Dielectric rod Slow-Wave Waveguide

B. Shokri, H.Ghomi

Department of Physics and Laser Research Center of Shahid Beheshti University,

Evin, 19839, Tehran, Iran and

Institute for studies in theo. and math. science, P.O.BOX 19395-1795, Tehran. Iran.

Dielectric Cherenkov maser with a plasma column, an axial dielectric rod and a thin annular relativistic electron beam (TAREB) is studied in the presence of external magnetic _eld. The dispersion equations of the beam-wave interaction are derived. The growth rates of the wave are obtained, and the e_ects of the accelerating voltage, beam current and the background plasma density on the growth rate of the wave are numerically calculated and discussed. Also results are numerically compared with pervious work. We concluded that, by placing a dielectric rod in the axes of waveguide, the growth rate increases.

Fast Wave Devices

3P08:

Update on the Development of a 10MW, 91 GHz Gyroklystron

J.M. Neilson, R.L. Ives, M. Read. M. Mizuhara, T. Robinson, D. Marsden

Calabazas Creek Research, Inc.

20937 Comer Drive, Saratoga, California 95070

Wesley Lawson, Bart Hogan

Institute for Research in Electronics and Applied Physics

223 Paint Branch Road

University of Maryland, College Park, MD 20742

Calabazas Creek Research, Inc. (CCR) is funded by the U.S. Department of Energy to develop a high efficiency gyroklystron amplifier for W-Band linear collider applications. In particular, this program supports development of a W-Band accelerator now underway at the Stanford Linear Accelerator Center. CCR is developing a 91.392 GHz gyroklystron to produce 10 MW of RF power with efficiency greater than 40% and a gain of 55 dB. Achievement of 10 MW of peak power would advance the state of the art for W-Band amplifiers by two orders of magnitude and potentially lead to other applications, including land- and ship-based radar, medical accelerators, and materials processing.

The design uses the second-harmonic mode to reduce the magnetic field requirements and use available TWT drivers. The current circuit design employs six cavities consisting of an input cavity, three buncher cavities and a final output cavity. The input cavity is a fundamental cavity operating with the TE011 mode and uses radial coupling to the input rectangular waveguide. The following buncher cavities operate with the TE021 mode and are stagger-tuned to improve efficiency and bandwidth. The output cavity operates in the TE021 mode and has smooth-wall transitions. A conventional, double anode, magnetron injection gun generates the electron beam. Following the circuit, a large radial gap is introduced in the output waveguide to allow voltage depression of the beam collector to increase the overall efficiency. A hybrid mode is used (TE01/02) to maximize transmission across the gap. An internal elbow is included to prevent beam bombardment of the output window.

All major subassemblies of the gyroklystron have been fabricated and the cavity sections are currently being cold-tested. Completion of tube assembly is expected by the end of January with testing scheduled to begin in March 2002 at the Stanford Linear Accelerator Center.

3P09:

Experiment on a Cold Cathode Gyrotron　

Kazuo Minami, Yutaka Hayatsu, Tsukasa Sato,

Masashige Sanmonji

Graduate School of Science and Technology

Niigata University, Niigata City, 950-2181 Japan

Victor L. Granatstein

Institute for Research in Electronics and Applied Physics,

University of Maryland, College Park MD 20742 USA

A gyrotron oscillator operating at frequencies less than 20 GHz and driven by an electron beam from a cold cathode has been designed, fabricated and tested. The cavity with length 168 mm was installed in a solenoid coil which produced a magnetic field up to 1.2 T for 1 sec duration. Three aluminum cavities with various radii (viz., 10, 15, and 19 mm) were prepared. The beam source was placed 270 mm from the upstream end of the cavity, where the magnetic field strength was 33 % of that at the cavity. The anode was a stainless-steel disk with a circular hole of radius greater than the radius of the edge of the aluminum annular cathode. The cathode edge was wrapped with thin velvet to improve electron emission. The anode was at ground potential and a -80 kV high voltage pulse with duration of 100 nsec was applied to the cathode. The output microwave pulse was observed using an X-band horn antenna located 230 mm from the output glass disk window. A waveguide directional coupler divided the signal into two parts. One was fed to a crystal detector to observe the prompt signal through semi-rigid cable and coaxial attenuators. The other was fed to a 18.75 m waveguide delay line to form a delayed signal. Both prompt and delayed signals were displayed on a digital oscilloscope to measure the frequency and power.

Output pulses corresponding to TE(111), TE(211) and TE(011) modes were observed near the expected values of magnetic field for the three cavities. The frequency measurements ere restricted to a range near 10 GHz, because we had available only X-band waveguide delay line. The radiation patterns indicated multi-mode oscillations which might have been expected since the values of beam current were large. For cavity radii 15 and 10 mm, the outputs reached 50 kW. The frequency range of the measurement system was limited to be less than 20 GHz. We are improving the system by extending its frequency range up to 30 GHz.

3P10:

Design of a W-Band TE₀₁ Gyro-TWT

with High Power and Broadband Capabilities

D.B. McDermott, H.H. Song, Y. Hirata, A.T. Lin¹, T.H. Chang²,

H.L. Hsu, K.R. Chu², and N.C. Luhmann, Jr.

Department of Applied Science, University of California, Davis

¹ Department of Physics, UCLA, Los Angeles, CA

² Department of Physics, NTHU, Hsinchu, Taiwan, ROC

A high power gyrotron traveling wave amplifier operating in the low-loss TE01 mode is currently being tested at UC Davis that is driven by a 100 kV, 5 A electron beam with a pitch angle (v_^/v_z) of unity and velocity spread of 5%. The amplifier is predicted by large-signal simulations to generate 140 kW at 92 GHz with 28% efficiency, 50 dB saturated gain and 5% bandwidth. The stability of the amplifier from oscillation has been investigated with linear codes. The threshold current for the absolute instability of the TE01 operating mode for the chosen operating parameters is predicted to be 10 A. To suppress the potential gyro-BWO interactions, the interaction circuit with a cutoff frequency of 91 GHz has been loaded with distributed loss [1] so that the single-pass attenuation is 90 dB at 93 GHz as shown below. A coaxial input coupler with 3% bandwidth is employed with a predicted and measured coupling of 1 dB and 2 dB, respectively.

This research has been supported by AFOSR under Grants F49620-99-1-0297 (MURI MVE) and 49620-00-1-0339.

[1] K.R. Chu, et al., Phys. Rev. Lett. 81, 4760 (1998).

Dependence on frequency of TE01 mode’s insertion loss through 12 cm length circuit from HFSS simulation (curves) and measurement (symbols). The broken curve shows the HFSS predictions for a semiconductor tube with a resistivity 70,000 times copper within copper waveguide. The unbroken curves are the predictions for a metallic waveguide with the resistivity of copper and 70,000 times copper.

3P11:

30 GHz Second-Harmonic TE₂₁ Cusp-Gun Gyro-TWT Amplifier

S.B. Harriet¹, D.B. McDermott, N.C. Luhmann, Jr.

Department of Applied Science, University of California at Davis

Davis, CA 95616

1 Also NSWC Crane, Crane, IN

A second-harmonic TE₂₁ gyro-TWT amplifier with an axis-encircling beam is being constructed at UCD that is predicted to double the efficiency of our previous 200 kW, 12% efficient MIG TE⁽²⁾₂₁ gyro-TWT. The new device will avoid the loss in efficiency due to off-axis electrons interacting with a linear polarized mode. The 70 kV, 3.5 A axis-encircling beam with v_^/v_z = 1.2 will be produced by a Cusp electron gun delivered by Northrop Grumman. The amplifier is predicted by our large signal code to produce 50 KW in Ka-band with 20% efficiency, 30dB saturated gain and 3% saturated bandwidth.

An important advantage of harmonic gyro-TWTs is that they are capable of higher power than at the fundamental cyclotron harmonic because they are more stable to the absolute instability at cutoff of the operating mode. Due to the weaker strength of the harmonic interactions, the start-oscillation current is significantly higher for higher harmonic operation. This allows higher harmonic gyro-TWTs to operate stably with appreciably higher beam current. The second-harmonic TE₂₁ gyro-TWT amplifier is predicted to have a start oscillation current of 5 A for v_^/v_z = 1.2, Bo/Bg = 0.99 which yields a safety margin 30% for our planned operating parameters.

The device will employ a sliced mode-selective interaction circuit to destroy the odd order TE_m1 modes. The circuit is sliced with two orthogonal slices through the axis to interrupt the wall currents and is surrounded by a lossy cylinder to absorb radiated power. Also, loss will be added to the interaction circuit to suppress gyro-BWO. The interaction circuit will have a wall resistivity 2300 times copper to yield a stable interaction length of 220 r_w for the strongest gyro-BWO threat, the TE⁽⁴⁾₄₁ mode. The last 11.5 cm of the 42 cm circuit is not loaded to avoid attenuating the wave after it reaches high power levels.

Identical multi-hole 0 dB input and output couplers were designed with the HFSS code using the same design as the previous UCD experiment. The directional coupler contains an array of slots connecting the narrow wall of the TE₁₀ rectangular input waveguide to the TE₂₁ circular interaction waveguide. HFSS simulation results predict that the coupler will have less than 0.3 dB insertion loss over a bandwidth of 10%. All modes are matched in the coupler due to upstream termination. HFSS simulation results predict that the return loss will be greater than 19 dB for the TE₁₁ circular mode and 45 dB for the TE₂₁ circular mode over the 10% bandwidth.

Distribution Statement A: Approved for public release; distribution is unlimited.

This work has been supported by AFOSR under Grant F49620-99-1-0297 (MURI MVE).

3P12:

34 GHz Fundamental-Mode Peniotron for High Device Efficiency

L.J. Dressman¹, D.B. McDermott, N.C. Luhmann, Jr.

D.A. Gallagher², T.A. Spencer³

Department of Applied Science, University of California at Davis

Davis, CA 95616

1 Also NSWC Crane, Crane, IN

2 Northrop Grumman Corporation, Rolling Meadows, IL

3 Air Force Research Laboratory, Albuquerque, NM

The peniotron interaction has been proven capable of yielding electronic conversion efficiency as high as 75% [1]. This inherently high efficiency is due to the nature of the interaction in which the electrons move forward in phase by 360° with each cyclotron orbit. Therefore, the electrons see the transverse component of the resonant wave as a “DC” electric field, experience ExB drift, and lose all or most of their transverse energy to the wave. However, while high conversion efficiency has been demonstrated, practical application of the peniotron requires that high power be efficiently extracted from the device while competing gyrotron modes are suppressed. This is the objective of the UCD harmonic peniotron.

The UCD peniotron incorporates a four-vane slotted cavity with a vane radius of 1.82 mm and slot/vane radius ratio b/a of 1.45. The lowest order mode of this slotted circuit, the p/2 mode, is a TE₁₁-like mode with a large TE₃₁ component, which is necessary for the second-harmonic peniotron interaction. This mode is resonant (first axial mode) at approximately 34 GHz for the 31 mm cavity design length. The fundamental-mode interaction provides good separation from possible competing gyrotron modes with the nearest competition being the fourth-harmonic gyrotron. Simulation with a large-signal code however, indicates that the starting current of the fourth-harmonic gyrotron mode is above the peniotron operating current of 3.5 amps, further insuring stability. The cavity incorporates diffraction coupling through an output iris to achieve the desired loaded Q of 375 required for overcoupling of the device and maximum power output (approximately 125 kW). The iris output coupling also has the added benefit of heavily loading higher order axial modes, further enhancing stability. WR-28 ports are coupled directly into the slots of the resonant cavity to allow for power measurement and other diagnostics.

Large signal simulation of the device predicts an electronic conversion efficiency of 58% with a predicted device efficiency of 47%. The device is designed to be driven by a Northrop-Grumman Cusp electron gun.

[1] T. Ishihara, et al., IEEE Trans. on Electron Devices 46, 798 (1999).

Distribution Statement A: Approved for public release; distribution is unlimited.

This work has been supported by AFOSR under Grant F49620-99-1-0297 (MURI MVE).

3P13:

Development of a C-band Harmonic Amplifier

Peter H. Ceperley¹ and Jose E. Velazco

Microwave Technologies Incorporated, Fairfax, VA 22030

¹George Mason University, Fairfax, VA 22030-4444

We report on the status of a harmonic amplifier experiment being jointly conducted by Microwave Technologies Inc. and George Mason University. In this experiment a new resonator concept is used to provide scanning modulation to a 7 kV, 100 mA electron beam. The scanned beam is injected into a TM₁₁₀ extended-interaction cavity to efficiently produce C-band output radiation. We will present the latest results of this research, which has resulted in a prototype designed and assembled in our laboratories. The HARA has the potential to be very compact and does not require a beam focusing system making it well suited for applications where size, weight and efficiency are critical.

_____________________________

[1] J. E. Velazco and P. H. Ceperley, Proc.1997 Int. Conf. on IRMM, M4.6, 69, July, 1997.

Work supported by the Ballistic Missile Defense Organization and the National Aeronautics and Space Administration.

Slow Wave Devices

3P14:

Effect of Boundary Reflection on Helix Backward Wave Oscillator

T.M. Abuelfadl*, G.S. Nusinovich*, A.G. Shkvarunets*, Y. Carmel*, T.M. Antonsen*, Jr., V.L. Granatstein* and D.M. Goebel**

* Institute for Research in Electronics and Applied Physics, University of Maryland at College Park, College Park, MD 20742, USA.

** Electron Dynamic Devices, Boeing Co.

The operation of the PASOTRON (Plasma-assisted slow-wave oscillators) is studied in the BWO regime. The absence of the guiding magnetic field in this device allows for the 3D motion of beam electrons. Recent studies showed the possibility of obtaining high efficiency up to 50\%. This was realized due to not only 3D motion but also due to properly optimized reflections from the slow wave structure ends in the experiment.

Here, the effect of the boundary reflection on the PASOTRON BWO is investigated theoretically. A stationary solution for the backward wave field amplitude is obtained in a self-consistent treatment of the wave excitation in the helix BWO with beam electrons' 3D motion inside. The device electron efficiency and the oscillation frequency were obtained given a certain boundary reflection coefficient. At each value of the reflection coefficient, a number of different modes can be excited depending on the beam current. The efficiency of each of these modes was calculated.

The results of this study can be used to increase the device efficiency, through adjusting the boundary reflection coefficient to the proper value.

Acknowledgement: The authors gratefully acknowledge the support of AFOSR ‘New Worlds of Vistas’ program.

3P15:

Investigation of Ultrawideband Pulses in Wideband Helix Traveling Wave Tubes*

M.C. Converse, S.C. Hagness, J.H. Booske, J.G. Wohlbier, J.E. Scharer

University of Wisconsin -Madison

Dept of Electrical and Computer Engineering

1415 Engineering Dr

Madison, WI 53706

The study of pulse propagation and distortion in traveling wave tubes (TWTs) has many applications. First, it is an attractive "diagnostic method" to characterize important properties such as dispersion and nonlinear distortion over a broad frequency band. Second, it is relevant to assessing the utility of TWTs as amplifiers for impulse radio, impulse radar, or other ultrawideband signal applications. We present results of a new model for analysis and numerical simulation of transient TWT excitation. The analysis applies a 1D linear model to examine pulse propagation in a TWT, including dispersion, space charge effects, and attenuation. Nonlinear effects are investigated using a 1D numerical particle-in-cell simulation. Fields are calculated using the pseudo-spectral time-domain (PSTD) method with a modification to incorporate helix waveguide dispersion effects into a 1D model. Progress with experimental investigations on the XWING tube will be discussed. The XWING (eXperimental WIsconsin Northrop Grumman) tube is a Northrop Grumman custom modified wideband (2-6 GHz) traveling wave tube, with multiple access ports that allow diagnostic access to the wave as it propagates along the tube.

*This work was supported in part by AFOSR, and by DUSD(S&T) under the Innovative Microwave Vacuum Electronics Multidisciplinary University Research Initiative (MURI) program, managed by AFOSR

3P16:

Nonlinear Guiding-Center Electron Flow Equilibria in Crossed Field Devices

J.A. Davies and C. Chen

Plasma Science and Fusion Center

Massachusetts Institute of Technology

Cambridge, MA 02139

L.D. Ludeking and R.S. Smith

Mission Research Corporation

8560 Cinderbed Road, Suite 700, Newington, VA 22122

As a research initiative to identify the origin of and develop methods to control phase noise in crossed-field amplifiers, a guiding-center theory of nonlinear equilibrium electron flow in a crossed-field device is presented. Unlike most of well-known equilibrium theories, the effect of the periodic anode structure is treated rigorously. Several examples of nonlinear guiding-center electron flow equilibria are discussed for configurations consisting of an inner cathode cylinder and an outer periodically corrugated anode. MAGIC simulations are performed to investigate the accessibility of such equilibria.

This research was supported by AFOSR under an STTR project with Mission Research Corporation.

3P17:

Linear TWT Development*

T.A. Hargreaves, C.M. Armstrong, R.B. True, R. Watkins,

M.L. Barsanti, A. Schram

Northrop Grumman Electron Devices

960 Industrial Road

San Carlos, CA 94070

The digital communication industry requires RF amplifiers that provide constant gain at steadily increasing rated output power levels. One method to obtain linear operation in a traveling wave tube (TWT) is to operate the device well below its saturated power and to use a multi-stage depressed collector for energy recovery. This method, while effective, still has the disadvantage of operating at lower device efficiency than possible near saturation. One approach regularly used for extending the linear output power range of the device is to use an external linearizer circuit to condition the drive to the tube. While effective, the linearizer presents additional cost to the system while providing diminished effectiveness close to saturation. It is of continuing interest, therefore, to investigate and develop high power TWT designs with ultra-linear phase and amplitude transfer characteristics.

The design of a linear TWT was approached on several fronts. First, simple Pierce theory was used to obtain a baseline design and to investigate many of the tradeoffs between design parameters and the device transfer characteristics. Next, Christine 1D, a 1-dimensional, large-signal, helix TWT code developed by the Naval Research Laboratory was used to optimize and verify the design. Finally, Christine 3D, a 2 ½-dimensional, large-signal, TWT code will be used to model RF beam expansion and to calculate the spent beam distribution for collector optimization.

The optimized design is scheduled to be built and tested in the Spring, 2002. Available test data will be presented, as will the design tradeoffs and analysis.

__________________________

* Work sponsored in part by the Office of Naval Research.

3P18:

Amplitude Locking in a GyroTWT Amplifier with a Delayed Feedback

Amit Kesar, David Blank, and Eli Jerby§

Faculty of Engineering, Tel-Aviv University, Ramat Aviv 69978, Israel

Enhanced pulsed output is observed in a delayed-feedback gyroTWT amplifier. The gyroTWT consists of a rectangular WR90 waveguide divided to three stages of amplification. The first and third stages are loss-less, in order to enhance electron-bunching and output power, respectively, while the second stage has distribution wall losses in order to prevent backward-wave instabilities. A low-voltage low-current electron-beam (18 kV, 0.3 A) interacts with the em wave. An external 60 ns delay line operating as a feedback couples the output power to the RF-input port, through a set of isolators, attenuators, and a fast RF-switch. The closed-loop gain is slightly above unity. The switch is modulated externally at a frequency rate inversely proportional to the feedback loop delay time. The experimental observations are supported by a time-dependent numerical computations.

Correspondence: jerby@eng.tau.ac.il Tel/Fax +972-3-6408048

3P19:

Intermodulation Products in a Klystron

M.W. Keyser, C.B. Wilsen^a), M.J. Newman^b),

Y.Y. Lau, D. Chernin^c), R.M. Gilgenbach, C. Marchewka^b),

J. Welter^b), S. Bhattacharjee^b), A. Singh^b), J.H. Booske^b),

and J.E. Scharer^b)

Department of Nuclear Engineering and Radiological Sciences

University of Michigan, Ann Arbor, MI 48109-2104

^a)Northrop-Grumman/Litton, San Carlos, CA

^b)University of Wisconsin, Madison

^c)Science Applications International Corporation, McLean VA 22102

A general theory of intermodulation in klystron amplifiers has recently been developed [1]. The algorithm computes intermodulation products (IMP) of all orders, including harmonic generation at each gap in a multi-cavity klystron. It takes into account the combined effects of charge-overtaking and space charge force. It has great accuracy and spectral resolution. Figure 1 shows the code validation [2] against experiments at the University of Wisconsin. We shall present calculations of IMP with three drive signals, a subject of considerable interest to JPL’s Deep Space Network, where three space probes orbiting Mars may be subject to intermodulation distortion [3]. We also explore the possibility of suppressing the third order intermod (IM3) that results from two main drive signals by externally injecting a much weaker signal at the same frequency as IM3.

Fig. 1. Comparison between code and 4K3SL measurements for unbalanced drive: P₁ = 10dBm, and P₂ = 15dBm. The IM5 at 1849.725 MHz is too small for accurate measurement.

This work is supported by DUSD (S&T) under the Innovative Microwave Vacuum Electronics MURI Program, managed by the Air Force Office of Scientific Research under Grant F49620-99-1-0297; and by the Northrop-Grumman Industrial Associates Program.

[1] Lau, Chernin, Wilsen, Gilgenbach, IEEE Trans. Plasma Sci. 28, 959 (2000).

[2] C. B. Wilsen, Ph.D. dissertation, U. of Michigan, Ann Arbor (2001).

[3] T. Cornish, TMO Progress Report 42-144, Jet Propulsion Laboratory, Pasadena, CA (2001).

3P20:

Numerical Analysis of the Influence of

the Outer Conducting Wall in Helix-TWT

H.S. Kim

KMW Inc., TWT Lab

65 Youngchun-ri, Dongrtan-myun, Hwasung-si,

Kyungki-do, Korea 445-813

H.S. Uhm

Dept. of Molecular Science and Technology, Ajou University

San 5 Wonchon-Dong, Paldal-Gu, Suwon 442-749, Korea

Numerical Analysis has performed with MAGIC PIC code to investigate the influence of the outer conducting wall on eigenfrequency in a waveguide loaded with a tape helix. As it shown from the dispersion properties of the electromagnetic (EM) waves propagating through a tape helix located inside a waveguide, in the limiting case where the outer conducting wall is very close to the helix, the outer conducting wall completely eliminates the forbidden regions in the (w, k) parameter space, and is independent of the width of the helix tape. The MAGIC analysis also shows the performance and characteristics of TWT according to the variation of the distance between helix and conducting wall.

3P21:

Saddle Point Analysis of a High Power Backward Wave

Oscillator near Cyclotron Absorption

Kazuo Minami, Hoshiyuki Yamazaki, Yaduvendra Choyal

Graduate School of Science and Technology

Niigata University, Niigata City, 950-2181 Japan

Victor L. Granatstein

Institute for Research in Electronics and Applied Physics,

University of Maryland, College Park MD 20742 USA

The absolute and convective instabilities of high power backward wave oscillator (BWO) driven by an intense relativistic electron beam are analyzed through saddle point analysis assuming finite strength axial magnetic field within the scope of linear analysis. Using a dielectric tensor including the effect of finite strength magnetic field, we formulate and analyze numerically the dispersion relation of the TM(01) mode in a BWO with infinitely long slow wave structure and columnar electron beam on the axis. To identify the root corresponding to BWO operation among various roots in the relation, we reduce the imaginary part of frequency from a large positive value (initial state) to zero (steady state) keeping the real part unchanged; the loci of the roots are depicted on the complex wavenumber plane. If the locus crosses the real axis, the root corresponds to a convective instability, while if the root merges with another root before it reaches the steady state, the double roots (saddle point) correspond to an absolute instability, as found in a BWO.

We assume the parameters in the previous experiments at the University of Maryland. We calculate the loci of roots for the condition near cyclotron absorption. As an example, near a magnetic field of 1.02 T, the absolute instability disappears and the root becomes a convective instability for a range of magnetic field. The cessation of backward wave oscillations near cyclotron absorption was observed in the experiments and can be explained by the present analysis.

In the dielectric tensor in our analysis, perpendicular component can be included in addition to the parallel component of the beam velocity. No enhancement in spatial nor temporal growth rates of the TM(01) mode is obtained with increase in perpendicular velocity component for a given beam energy.

3P22:

An Electron Gun for A Sheet Beam Klystron

M.E. Read, G. Miram, and R.L. Ives

Calabazas Creek Research

20937 Comer Drive, Sarasota, CA, 95070-3753

A. Krasnykh and V. Ivanov

Stanford Linear Accelerator Center

2575 Sand Hill Rd, Menlo Park, CA 94025

Calabazas Creek Research, Inc.(CCR) is developinga rectangular, gridded, thermionic, dispenser-cathode gun for sheet beam devices. The first application is expected to be klystrons for advanced particle accelerators and colliders. The current generation of accelerators typically use klystrons with a cylindrical beam generated by a Pierce-type electron gun. As RF power is pushed to higher levels, space charge forces in the electron beam limit the amount of current that can be transmitted at a given voltage. The options are to increase the beam voltage leading to problems with X-Ray shielding and modulator and power supply design, or to develop new techniques for lowering the space charge forces in the electron beam.

The current program addresses issues related to beam formation at the emitter surface, design and implementation of shadow and control grids in a rectangular geometry, and is directed toward a robust, cost-effective, and reliable mechanical design. A prototype device will be developed that will operate at 415 kV, 250 A for an 80 MW, X-Band, sheet-beam klystron being developed by Stanford Linear Accelerator Center. The cathode will have 100 cm² of cathode area with an average cathode current loading of 2.5 A/cm². For short pulse formation, the use of a grid was chosen.

We will report the electrostatic and beam optics design in both 2- and 3-D as well as a thermal-mechanical analysis of the cathode region. The 2-D calculation gives the basis for the 3-D simulation, which, particularly with the grid structure, is expected to take a great deal of time per run. The modeling was done using Trak, a code from Field Precision. This code allows the use of variable mesh size, a feature that is essential for accurately including the grid structure. To minimize the power lost to the grid, the cathode has non-emitting segments in line with the grid. These segments are in the form of sections of arcs to help focus the beam around the grid, which is formed of 1.25 mm wire. With careful adjustment of this geometry and the grid potential, an emittance close to that of an ungridded gun can be achieved. At a beam current of 256A, the emitttance was 7 10^-5 π m rad. 3-D Modeling is in progress and will be reported at the conference.

This work is supported by the US Department of Energy Grant Number DE-FG03-01ER83209.

3P23:

Intermodulation Suppression in a Broad Band TWT*

A. Singh, J. Scharer, M. Wirth, S. Bhattacharjee and J. Booske

Univ. of Wisconsin, Madison

We examine methods for reducing two-tone intermodulation products in the custom-made XWING broadband traveling wave tube. Harmonic suppression and difference frequency techniques are used to demonstrate intermodulation suppression techniques and the spatial variation of their spectral evolution. Harmonic and difference frequency optimum drive levels and phase are determined which suppress the third order intermodulation product by more than 21 dB in the 2-6 GHz band. The variation of the suppression with drive level near saturation and two-tone difference frequency are examined. IM3 reduction using the harmonic injection technique is experimentally demonstrated in a broadband TWT distributed amplifier. The TWT used in this investigation, termed the XWING TWT (for eXperimental WIsconsin Northrop Grumman TWT), is a research version of a product manufactured by Northrop Grumman. This two-stage, helical TWT provides a moderate gain of 20-30 dB over a frequency range of 2-6 GHz. The upper fundamental and harmonic frequencies were set to 2.00 and 4.00 GHz, respectively. Since the phase of the injected harmonic must be referenced with respect to the higher frequency fundamental, two Agilent 83623B synthesizers were configured to share a common 10 MHz phase reference signal. The 4.00 GHz signal was sent through a Narda 3752 phase shifter, allowing the fundamental-to-second harmonic phase relationship to be adjusted in real-time. The lower fundamental frequency of 1.95 GHz was supplied by a Wavetek 3520 synthesizer, providing a 50 MHz difference between the two drive tones. The experiment was performed for fundamental drive tones of 15 and 18dBm/tone. First, the 1.95 and 2.00 GHz fundamental drive tones were independently set to 15 dBm/tone at the TWT input tap, and the output spectrum was captured on an Agilent E4407B digital spectrum analyzer. Next, the 4.00 GHz second harmonic tone was injected at the TWT input and the phase was varied, with respect to the 2.00 GHz fundamental, to achieve the lowest IM3 level. With the phase relationship optimized, the injected harmonic amplitude was varied until a maximum suppression in the upper IM3 level was observed. This occurred with injected harmonic amplitude of -2.1 dBm or 17.1 dB below f2. The upper IM3 was reduced by 21.3 dB, yielding an upper carrier to IM3 power ratio of 43.9 dB. The TWT output spectrum with and without harmonic injection is shown below. It can be seen that the upper IM3 is suppressed by 21.3 dB. The experiment was repeated at higher input drive levels of 18 dBm/tone and an IM3 reduction of 24.2 dB was observed. The optimum phase of the 4 GHz injected harmonic was measured at the TWT input tap and was found to lead the 2 GHz fundamental by 47.5 degrees, with respect to the fundamental period.

*This research is supported primarily by AFOSR Grant 49620-00-1-0088 and by DUSD (S&T) under the Innovative Microwave Vacuum Electronics Multidisciplinary University Research Initiative (MURI) program, managed by the United States Air Force Office of Scientific Research under Grant F49620-99-1-0297 and in part by the University of Wisconsin, Madison.

3P24:

CTLSS Features Supporting Vacuum Electron Device Design

S.J. Cooke, C-L. Chang, A.A. Mondelli, D.P. Chernin,

T.M. Antonsen Jr. and B. Levush ^†

Science Applications International Corporation, McLean V, USA.

^† Vacuum Electronics Branch, Code 6840, NRL, Washington DC.

The Cold-Test, Large-Signal Simulation Code (CTLSS) is being developed to provide a 3D electromagnetic simulation tool that is designed to interoperate with large-signal codes employed in microwave and millimeter-wave vacuum electron device design [1]. In this presentation, we describe capabilities recently introduced in CTLSS that directly support features of the large-signal simulation codes CHRISTINE 1D and CHRISTINE 3D [2].

For large signal models that operate in the frequency domain, it is necessary to specify device characteristics at selected operating frequencies. A new eigensolver capability has been developed in CTLSS to determine the eigenmode fields and related parameters (phase velocity, interaction impedances & admittances, etc.) of a dispersive periodic structure at a predetermined frequency. This contrasts with the more common approach, in which the frequency of a traveling wave is computed for a specified phase advance per period (Floquet boundary condition), and results later interpolated to the frequencies of interest. The new method reduces the total computation time required to obtain parameters for the large-signal models.

The CHRISTINE 3D code simulates the large-signal characteristics of slow-wave devices using a fast, parametric model that includes a fully three-dimensional representation of both particle motion and electromagnetic fields. The traveling-wave circuit field and the RF space-charge field are treated separately, but self-consistently, and in common with many existing parametric large-signal models, the space-charge fields are computed assuming that they exist only within a cylindrical pipe at the inner radius of the circuit structures. We describe a method for correcting the space-charge field to take account of the true 3D geometry, using correction terms that are pre-computed from the full circuit structure using CTLSS.

[1] S.J. Cooke et al., "CTLSS – An Advanced Electromagnetic Simulation Tool for Designing High-Power Microwave Sources," IEEE Trans. Plasma Sci., Vol. 28 No. 3, 841—866, June 2000

[2] D.Chernin et al., “A Three-Dimensional Multifrequency Large Signal Model for Helix Traveling Wave Tubes”, IEEE Trans. Electron Devices, 48 (1), Jan. 2001

Plasmas for Lighting

3P25:

UV and Visible Emission Processes

in a Moly-Oxide Discharge*

J.L. Giuliani, R.E. Pechacek^a, G.M. Petrov^b,

A. Dasgupta, K. Bartschat^c, and R.A. Meger

Plasma Physics Division,

Naval Research Laboratory, Washington, DC 20375

Due to the hazardous material designation of spent fluorescent lamps on board naval vessels, the Naval Research Laboratory has been investigating alternative lighting concepts which are free of mercury. A moly-oxide discharge driven by an inductively coupled RF coil at 13 MHz emits a broad spectrum in the visible range with strong line emission from the quintet spin levels of the Mo atom near the peak of the photopic curve. One limitation of such a discharge for direct white light applications is the near UV emission from the Mo septet resonance lines between 300 and 400 nm. Analysis of the excitation processes and channels for both the visible and UV emission will be presented based on a Boltzmann model for the electron energy distribution function and detailed atomic physics calculations for the cross sections. The results indicate that a Mo partial pressure of ~10 mTorr or more will render the resonance lines optically thick and concurrently increase the visible emission. Calibrated spectroscopic measurements throughout the UV and visible region will be reported as a function of power and pressure and compared, through actinometry, with the theoretical simulations.

*Supported by the Office of Naval Research.

^aSachs Freeman, Associates

^bBerkeley Scholars, Inc.

^cDepartment of Physics and Astronomy, Drake University

3P26:

DBD-Based VUV Source for Advanced Photolithography*

M. Laroussi, M. C. Gupta, A. El Dakroury and J. Yan

Old Dominion University

K. H. Becker and K. Martus

Stevens Institute of Technology

As the semiconductor industry pushes toward smaller and smaller chip feature size (below 0.1 μm), shorter and shorter wavelengths are sought for the photolithographic process. Here, we present a novel deep UV source based on a high-pressure, cylindrical DBD discharge [1], for advanced photolithography applications. The discharge unit consists basically of a hollow tube made of a dielectric material with two loop-electrodes wrapped around the outside wall of the tube. The discharge is generated inside the tube by means of a 13.56 MHz RF source. For good RF power transfer, an impedance matching network is introduced between the RF source and the discharge unit. Emissions at two wavelengths, 130 nm and 121.6 nm, are of particular interest. To generate 130 nm radiation, argon with a small admixture of oxygen (less than 0.1%) was used. Resonant energy transfer from argon dimers to atomic oxygen allows the emission of oxygen triplet lines around 130 nm [2]. To generate 121.6 nm radiation, neon with a small admixture of hydrogen (less than 0.1 %) was used. The hydrogen Lyman-α line at 121.6 nm was emitted via near-resonant energy transfer between neon excimers and H₂, which leads to the dissociation of H₂ and the excitation of atomic hydrogen [3]. Spectra, as measured by a 0.2 m McPherson Scanning Monochromator (1200 G/mm, 0.1 nm resolution), will be presented. The influence of the operating pressure, gas mixture ratio, and the applied RF power on the emission spectra, the emitted optical power, and the stability of the source will be discussed.

References:

[1] M. Laroussi, In Proc. IEEE Int. Conf. Plasma sci., p. 203,

Monterey, CA, June 1999.

[2] M. Moslehy et al., Appl. Phys. Lett. 78, 880, 2001.

[3] P. Kurunczi et al., J. Phys. B 32, 651, 1999.

* Work supported by DARPA grant DAAD19-99-1-0277.

3P27:

Electron Density and Electron Temperature in Argon

Microhollow Cathode Discharges

M. Moselhy¹, F. Leipold¹, K.H. Schoenbach¹

I. Petzenhauser², and Klaus Frank²

¹Physical Electronics Research Institute

Old Dominion University, Norfolk, VA 23529, USA

²Physikalisches Institut I, Univ. of Erlangen-Nuremberg, Germany

Direct current microhollow cathode discharges (MHCDs) operated in noble gases and in mixtures of rare gases and halides have been shown to emit excimer radiation with efficiency in the 0.5-10% range [1]. Even higher values in efficiency have been obtained (20% in xenon) when the discharge was pulsed with 20 ns pulses [2]. These relatively high values indicate a substantial density of electrons with energies greater than the excitation energy of rare gas atoms. We have measured, electron density and electron energy, for a microdischarge plasma with typical dimensions of 100 mm in argon at a pressure of 300 Torr, with 1% of hydrogen added. The discharge current was 4 mA, and the sustaining voltage 180 V. The electron density was obtained by measuring the Stark broadening of the hydrogen Balmer-b line at 486.1 nm. In direct current operation, the electron density was found to be 4x10¹⁴ cm^-3. Applying a 20 ns pulse of 750 V to a low current dc discharge resulted in an increase of the electron density by more than two orders of magnitude (10¹⁷ cm^-3). The temporal increase in electron density followed the current pulse; the exponential decay had a time constant of 50 ns. Electron temperature was obtained from line emission ratios of two argon lines at 810.6 and 811.8 nm by assuming a Maxwell-Boltzmann distribution for the electron energies. For dc operation the electron temperature was found to be approximately 60 eV. For the pulsed mode it is more than twice this value: approximately 140 eV. The data indicate that the efficiency of MHCD argon excimer emission at 128 nm can be substantially increased beyond the dc value of 0.7% [3] by pulsing the discharge.

[1] Karl H. Schoenbach, Ahmed El-Habachi, Mohamed M. Moselhy, Wenhui Shi, and Robert H. Stark, Physics of Plasmas 7, 2186 (2000).

[2] M. Moselhy, W. Shi, R. H. Stark, and K. H. Schoenbach, Appl. Phys. Lett. 79, 1240 (2001).

[3] M. Moselhy, R.H. Stark, K.H. Schoenbach, and U. Kogelschatz, Appl. Phys. Lett. 78, 880 (2001).

This material was based on work supported by NSF (CTS-0078618 and INT-0001438).

3P28:

Ballast Free, Large Area Microdischarge Excimer Lamps

Wenhui Shi and Karl H. Schoenbach

Norfolk Applied Science, Inc.

Norfolk, VA 23505, USA

By using a hollow cathode geometry, it is possible to generate stable, direct current high-pressure gas discharges even in electronegative gases. These discharges when either operated in noble gases or mixtures of noble gases and halogens have been proven to be very efficient sources of excimer radiation [1]. For dc discharges in xenon, with typical sustaining voltages of 200 V, efficiencies of 6% to 9% have been measured. When operated with nanosecond pulses, efficiencies of up to 20 % have been obtained [2]. By limiting the area of the cathode around a microhole, it is possible to operate the microdischarge in an abnormal glow mode at moderate currents of milliamperes or less. In this mode, parallel operation of microhollow cathode discharges can be achieved without ballasting the individual discharges. Experiments with xenon as excimer gas have been performed, and the spatial distribution of the excimer emission from microdischarge arrays has been measured dependent on pressure and current. The dielectric layer was formed by means of plasma spraying [3]. Various microhole patterns have been generated by using an excimer laser to drill sets of microholes with diameters of approximately 100 mm, and to selectively eliminate the dielectric layer around these holes. With increasing current the microdicharges turn-on sequentially, and eventually the plasma fills the space between the holes and the dielectric, generating a homogeneous surface plasma source. One-dimensional (strings) as well as two-dimensional arrays with up to 100 microdischarges covering an area of 1 cm² have been studied. Since these devices can easily be scaled in size, microdischarge arrays can be used as large area surface emitters with excimer radiation intensities exceeding 1 W/cm².

[1] K.H. Schoenbach, A. El-Habachi, M. Moselhy, W. Shi, and R.H. Stark, Physics of Plasmas 7, 2186 (2000).

[2] M. Moselhy, W. Shi, R.H. Stark, and K.H. Schoenbach, Appl. Phys. Lett. 79, 1240 (2001).

[3] T. Paul, R. Hartmann, J. Heberlein, W. Shi, R. Stark, and K.H. Schoenbach, “A Novel Method for Manufacturing of Micro-Discharge Devices,” to appear in Proc. International Thermal Spray Conference, Essen, Germany, March 3 - 6, 2002, published by ASM International, Materials Park, OH.

This work was supported by the AFOSR/NE under contract #F49620-C-0011.

3P29:

Hg Density Imaging in a Metal-halide Arc Lamp

J.J. Curry¹ and H.G. Adler²

¹National Institute of Standards and Technology

Gaithersburg, Maryland

²OSRAM SYLVANIA

Beverly, Massachusetts

We will report initial results from the imaging of Hg vapor in a metal-halide arc lamp using synchrotron x-ray radiation. These measurements extend previous work on x-ray absorption imaging in arc lamps using an x-ray tube¹. High flux synchrotron radiation and a digital detector make it possible to obtain time-resolved measurements. Monochromatic radiation improves the accuracy over what can be obtained with broadband radiation.

¹J. J. Curry, M. Sakai, and J. E. Lawler, J. Appl. Phys. 84, 3066 (1998).

3P30:

Analysis of the Hg-Na Arc-W Cathode Interactions at Increasingly High Na Contents

S. Coulombe

CRTP/Plasma-Québec, Department of Chemical Engineering,

McGill University, Montréal, Québec, Canada, H3A 2B2

The effect of increasingly high sodium contents on the attachment conditions of a DC mercury-sodium (Hg-Na) arc discharge on a tungsten (W) cathode is studied. A physical model based on the collisionless assumption is used for the description of the cathode sheath. The solution of this model; i.e. the plasma heat flux versus the cathode surface temperature, is coupled to a thermal model for the cathode bulk for a self-consistent solution of the problem under diffuse attachment conditions. Domains of existence for self-sustaining operation of the system in the electron temperature at the sheath edge – cathode surface temperatures space (T_e-T_S space) are obtained versus the Na content in the arc discharge and reveal the higher cathode surface temperature requirements as the Na content increases. For a typical set of HPS lamp operating conditions (p=1 atm, p_Hg=0.9p, p_Na=0.1p, I=3.2 A), the model predicts melting of the pure W cathode tip. The substantial increase of the operating tip temperature at increasingly high Na content is attributed to the increasingly high density of Na+ ions, itself associated with the much lower ionization potential of Na with respect to Hg, which must be sustained by the electron emission processes. Lowering the W cathode tip work function brings the operating temperatures to lower values in agreement with well-known experimental facts.

3P31:

Atomic Density Distribution over the Excited-States in

High-Pressure Mercury Plasmas

D. Karabourniotis

Institute of Plasma Physics, Department of Physics

Unversity of Crete, 71003 Heraklion Crete, Greece

Determination of the excited-state distribution of atoms in lighting plasmas is of paramount importance in the physics and the development of radiation sources. The development of a self-reversed line spectroscopy (SRLS) method, which is independent of plasma-equilibrium assumptions, made it possible to determine the electron temperature by identifying it to the distribution temperature between the mercury metastable levels as well as to deduced the densities of the ground and low-lying levels in a mercury discharge [1]. Comparing to active methods, observation of emission lines is most accesible experimentally and do not introduced plasma pertubation.

This work is aimed at applying SRLS for determining the excited-state distribution of atoms up to the ionization level. Two mercury discharges at 2 and 5 bar with 1 cm diameter operated on ac (50 Hz, 100 W/cm) were used. Side-on-phase resolved radiation intensity measurements were perfomed by means of an automated experimental set-up. The local values of the level-population temperatures referenced to the ground state were found as well as the ionization temperature at the moments of the maximum and the minimum emission phases. This enabled us to determine the nonequilibrium factor, i.e., the actual level density normalized to the Saha-equilibrium density at the electron temperature and the electron density prevailing in the discharge. Then, measuring the density of a sufficiently high-lying level by Abel-inverting an optically thin line, the density distribution of atoms over the excited-states at various radial positions was deduced.

It was found that the population temperature decreases as we go up the excitation space of the atom (nonequilibrium excitation), and the ground state is over-populated with respect to its Saha-equilibrium density. The deviation of the plasma parameters from those obtained asumming equilibrium conditions is also discussed.

[1] D. Karabourniotis, J. Appl. Phys. 90, 1090 (2001).

Pulsed Power and Other Plasma Technology Applications

3P32:

A Novel Crowbar Scheme

for Capacitive Pulsed Power Systems

Hongsik Lee, Taeho Lee, Kilsoo Seo, Yunsik Jin, Jongsoo Kim

Korea Electrotechnology Research Institute

Sungju-Dong 28-1 Changwon, 641-120 Korea

Capacitive pulsed power systems are based on the RLC circuits. According to the magnitude of the load resistance and the circuit characteristic impedance, the load current or capacitor voltage may swing or not. The current or voltage oscillation is often not allowed due to the load property or the voltage reversal limit of the energy storage capacitors. Crowbar circuits are inserted for the suppression of the oscillation in these cases. Usually diodes are used as a crowbar switch but when the system voltage and current become high it is not a practical system because the cost of the diodes goes up enormously. A novel crowbar scheme using a spark gap or vacuum gap switch which was triggered at a proper time after the current peak was proposed, implemented and tested. A Rogowski coil was used for sensing the current peak. Because the output of a Rogowski coil shows generally the time derivative of the current waveform, a diode inserted in parallel to the output signal can clamp the positive part of the induced voltage signal of the Rogowski coil. When the voltage arrives at a proper negative value, a square pulse voltage signal of 15V which triggers the trigger generator for the gap switch for crowbarring can be produced through an amplifier circuit. The implemented circuit shows successful crowbarring actions at a RLC circuit of 1236 uF, 160 uH, 100 mOhm with the capacitor charged up to17 kV, the peak current of 34 kA and the capacitor voltage reversal of 1.8 kV.

3P33:

Fast Dielectric Volume Breakdown In Liquid Nitrogen^*

A. Neuber, H. Krompholz, M. Haustein, J. Dickens

Center for Pulsed Power and Power Electronics Research

Departments of Electrical & Computer Engineering and Physics

Texas Tech University

Lubbock, TX 79409-3102

Miniaturization of electrical components along with growing superconductor technology requires a better understanding of the phenomenology of breakdown in liquid nitrogen. It is known that the time delay between breakdown-onset and final impedance-limited arc current can occur within a few nanoseconds. For a temporal resolution down to several 100 ps, a discharge apparatus was built and tested that uses a cable discharge into a coaxial system with axial discharge, and a load line to simulate a matched terminating impedance. Main experiments are done in self-breakdown mode in supercooled liquid nitrogen, pulsed breakdown at high over-voltages in standard electrode geometry is investigated as well. Transmission line type current sensors and capacitive voltage dividers with fast amplifiers/attenuators cover an amplitude range of 0.1 mA to 1 kA with a time resolution of 300 ps, providing complete information about discharge voltage and current. The light emission is measured with fast photomultiplier tubes (risetime 800 ps), and these optical measurements will be supplemented by high-speed photography and spectroscopic investigations on a nanosecond time scale. Preliminary results on self-breakdown in the surface flashover mode with a gap width of 2 mm and electrodes with 5 mm radius of curvature (breakdown voltage ~ 60 kV) show a three-phase development: the current rises from an unknown level to several mA during 2 ns, stays approximately constant for 100 ns with superimposed ns-duration spikes, and shows a final exponential rise to the full impedance limited current amplitude during several nanoseconds. The detailed optical and spectroscopic diagnostics along with the high-speed electrical diagnostics will in particular address the physical mechanisms initiating/assisting the liquid nitrogen volume breakdown, such as bubble formation during the pre-breakdown phase.

^*This work was solely funded by the Compact Pulsed Power MURI program funded by the Director of Defense Research & Engineering (DDR&E) and managed by the Air Force Office of Scientific Research (AFOSR).

3P34:

Repetitive Pulsed Power Modulator Using Static Induction Thyristor for Discharge Light Source

Keiichi Yamashita, Keiichiro Nishikawa, Akitoshi Okino

Masato Watanabe, and Eiki Hotta

Department of Energy Sciences, Tokyo Institute of Technology

Nagatsuta, Midori-ku, Yokohama 226-8502, Japan

Kwang-Cheol Ko

Department of Electrical and Computer Engineering,

Hanyang University,

Seongdong-ku, Seoul 133-791, Korea

Naohiro Shimizu and Katsuji Iida

Corporate Technical Center, NGK Insulators, Ltd

Suda-cho, Mizuho-ku, Nagoya 467-8530, Japan

A repetitive pulsed power modulator, which uses high voltage static induction thyristors as main switching devices, has been designed and constructed for the application to a discharge light source.

The main components of modulator are a pulse forming network (PFN) with 20 stages, a magnetic switch with a reset circuit and a stacked semiconductor switch. The PFN consists of 100 ceramic capacitors (each capacitance is 2000pF, 30kV) connected in parallel. The resulted electrical length, capacitance and impedance of the PFN are 213 ns, 0.283 uF and 0.75 ohm, respectively.

A current source, which provides 8 A, is used for resetting the magnetic switch. The leakage current flowing when the magnetic switch is unsaturated can be used as a pre-ionization current.

The semiconductor switch is made of 3 high voltage static induction thyristors connected in series. In order to get a high di/dt, it is important to supply a high gate current with a short risetime. Therefore, an inductive storage type gate driver, which is driven by an external optical signal, was made to provide a very large di/dt current to the gate. The significant feature of the static induction thyristor is that it has very low ON-state voltage. This feature is especially suitable for high rep-rate operation of pulsed power modulators, since energy loss by the switch can be remarkably reduced.

When the PFN was charged to 9 kV, the load voltage of 4 kV and the load current of 5 kA were obtained for the load resistance of 0.7 ohm. The measured risetime of current is 203 ns and the efficiency of 91 % is obtained.

Part of this work is supported by Grant-in-Aid for Scientific Research (B), the Ministry of Education, Culture, Sports, Science and Technology, Japan under Contract No.13450110.

3P35:

Effect of Material Strength Models on Numerical Prediction of

Instability Growth in Solids

Ann M. Kaul, Rickey J. Faehl

Los Alamos National Laboratory, Los Alamos, NM

Considerable research has been devoted to the subject of the instability phenomena that appear on material interfaces. While instability phenomena in perfect fluids and gases are reasonably well understood, the problem of characterizing these phenomena in real materials possessing strength, viscosity, compressibility or phase transitions remains an open question.

In 1999, researchers at the All Russian Scientific Institute of Experimental Physics (VNIIEF) conducted a series of tests on aluminum plates that had been given a small sinusoidal perturbation on one side. The plates in these tests are subjected simultaneously to a high pressure (~15 GPa) and a high strain rate (~10³ – 10⁶), a region for which testing mechanisms have only recently been developed. Results for a variety of wavelengths and amplitudes for the initial perturbations and of initial temperatures of the plate are presented in the report “Influence of Thermal Reduction of Strength on Instability Growth in Solids”.

The goal of my research is to use the data presented in this report in validating various material strength models, notably the Johnson-Cook, Steinberg-Guinan, Preston-Tonks-Wallace and Mechanical Threshold Stress models. The first question of the simulations is whether the different models predict different behavior for a given initial wavelength, amplitude of perturbation and temperature. If so, the next step is to see if there is a consistent pattern to the predictions in terms of wavelength or amplitude of the perturbation or in terms of initial temperatures. CHAD (Computational Hydrodynamics for Advanced Design), a 3-dimensional, parallel, unstructured-grid, finite-volume, Lagrangian method, was used to do the numerical simulations.

It is apparent that the various strength models predict different behaviors in the growth of the perturbation of the surface. The PTW and MTS models come closest to capturing the trends in the data. The Steinberg-Guinan model tends to underestimate the growth in amplitude of the perturbation. The Johnson-Cook results tend to overestimate this growth. Numerical simulations such as this one can be used to help determine the kinds of experiments that might provide useful data for researchers attempting to develop more realistic material strength models, especially in strain and strain rate regimes where little or no data currently exists. In particular, upcoming efforts will include simulations of Atlas pulsed-power experiments. LA-UR-02-185

* Work supported by the U.S. Department of Energy.

3P36:

Optimization of a Fuse Opening Switch

M. PRAT, T. DESANLIS, G. GUILLOT, L. MAGNIN, R. NICOLAS, R. ROSOL, L. VERON and P. ZEHNTER

Commissariat à l’Energie Atomique

Polygone d’Expérimentation de Moronvilliers, France.

Usually, the Fuses Opening Switch (FOS) are used as power amplifier in high current devices. This kind of device consists of a current generator (for instance capacitor or electrocumulative generator), a storage inductor, the FOS and a load (fixed or variable), in parallel with the FOS.

The geometry of the FOS is adapted for the high current device (section, length and diameter of wires) to obtain the highest power in the load. Furthermore, other parameters of the FOS can increase power. We studied particularly the medium surrounding the fuse and the material of the FOS.

We realized experiments with different medium surrounding the FOS : sand, plaster, silicon, water, liquid nitrogen, air and SF₆. The powers which are obtained with sand, plaster, silicon, water and nitrogen are very similar. We obtained a power 40 % higher with air and SF₆. However the duration of the power pulse is larger with SF₆. We also tested two different materials : copper and silver. The power amplification is 30 % higher with silver.

Finally, we used all theses experiment results to develop different numerical models to describe the behavior of a FOS, depending of the surrounding medium and the material of the FOS.

3P37:

Modeling and Analysis of a Flux Compression

Concept Designed for Driving PRS Loads

J. Watrous¹ and J.R. Goyer²

¹NumerEx, 2309 Renard Pl. SE, STE 220, Albuquerque, NM 87106

²Titan Systems Corp., Pulse Sciences Division, 2700 Merced Street, San Leandro, CA 94577

Flux compression in vacuum offers the possibility of using present pulsed-power technology to drive loads such as a plasma radiation source to regimes not otherwise accessible. There is a price in terms of energy efficiency, but there is a potential gain from reduced instability growth. Design of a flux compression experiment for the Decade Quad facility at Arnold Engineering Development Center in Tullahoma, Tennessee based on 0-D circuit and slug models will be presented. The 0-D modeling approach offers a means of rapidly assessing a variety of design options; empirical forms of losses, resistive diffusion, and instabilities provide some degree of realism. Multidimensional MHD modeling using the Air Force Research Laboratory’s code, MACH2, is used to study specific design issues. Multidimensional modeling has been helpful for examining the effect of the Rayleigh-Taylor instability on the behavior of the outer array, for examining the energy lost due to resistive heating of the outer array, and the loss of interior magnetic flux into the outer array due to resistive diffusion. An illustrative hardware design will be shown for the Decade Quad facility at Arnold Engineering Development Center in Tullahoma, Tennessee, and preliminary experimental results will be presented and discussed.

_____________________

This work was made possible by a subcontract with Titan Systems Corp. supported by the Defense Threat Reduction Agency,

Contract No. DTRA01-99-D-0042/0007

3P38:

Experimental Tests of Vacuum Closing and Opening Switches for a Current-Multiplier (Meatgrinder) Circuit*

B.V. Weber, J.R. Boller,^a R.J. Commisso, G. Cooperstein,

B. Moosman,^a S.J. Stephanakis,

Plasma Physics Division, Naval Research Laboratory

Washington DC, 20375-5346 USA

W. Peter and O. Zucker

APTI, Washington, DC 20037 USA

The meatgrinder is a current-amplification circuit developed by O. Zucker that utilizes closing and opening switches and coupled inductors. A scheme was devised to implement this circuit on the Hawk generator (700 kA, 1 ms quarter period) using POS opening switches and vacuum flashover surfaces as the closing switches. If successful, this circuit will result in an overall current gain of 1.3-1.4 on Hawk, and could therefore roughly double the energy coupled to an imploding PRS load. This initial experiment tested the switches using a simplified circuit. The required switching was demonstrated at a reduced current level (250 kA) on Hawk. Scaling the operation of the switches to higher current requires further work. The inside-out flashboard POS works best when current flow is from outside to inside, requiring positive polarity Marx charge. A posthole convolute also works best in positive polarity to eliminate premature surface flashover resulting from electron emission. The POS must open first, prior to the closing switches, or else it does not open. This is not the optimum switching sequence for the meatgrinder and results in a small efficiency penalty. The POS plasma and uv radiation must be isolated from the flashover switches using distance and baffles. This approach should be capable of operating at higher current on Hawk. An experiment could then be designed to demonstrate current gain. If successful, this technique could be considered as a way to drive a PRS load and to couple to higher power generators, such as Decade Quad.

* Work supported by DTRA

a. JAYCOR, McLean, Virginia, 22102

3P39:

Transitional Processes in Combined Opening Switch

(Vacuum Interrupter and PEOS)

O.G. Egorov

Troitsk Institute for Innovation and Fusion Research,

Troitsk,Moscow reg.,Russia, 142190

The opening switch combined of two opening switches - vacuum interrupter and plasma erosion opening switch is offered for consideration. Each of the interrupters has several physical and technical properties limits, which allow to integrate them in one construction [1,2]. Two designs of this combination are consider.

The current breaking process in combined opening switch (COS) have three stages. The first one - stage of vacuum interrupter i.e. energy accumulation in inductance store, the second one - stage of current zero i.e. vacuum gap recovery, and the third one - stage of plasma erosion opening switch, magnetic self insulation and energy transmission to a load. The offered designs allow to realize relation between time of energy storage in IS and time of energy output from IS to a load ~10⁶¸10⁷. Under it the power developed by COS on a load equals 10¹¹¸10¹²W.

Effect of different factors, in particular, presence of particles in vacuum gap to efficiency of energy transmission to a load is discussion in this paper.

Footnote:

1. Egorov O.G., Proc.Inter. Conf. “VI Zababakhin Scientific Talks”, Snezhinsk, Russia, 2001, p.97,

2. Egorov O.G., Proc.VI Inter. Symp. “Elect. Engin.-2010”, Moscow, Russia, 2001, Vol.3, p.314-316.

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