C.W. Peters

Publications (9)5.87 Total impact

• Article: Cathode effects on a relativistic magnetron driven by a microsecond e-beam accelerator

  M.R. Lopez, R.M. Gilgenbach, D.W. Jordan, S.A. Anderson, M.D. Johnston, M.W. Keyser, H. Miyake, C.W. Peters, M.C. Jones, V. Bogdan Neculaes, Yue Ying Lau, T.A. Spencer, J.W. Luginsland, M.D. Haworth, R.W. Lemke, D. Price
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  ABSTRACT: Experiments have been performed on a relativistic magnetron driven at e-beam accelerator peak parameters: voltage = -0.4 MV, current = 16 kA, and pulselength = 0.5 μs. The magnetron is a six-vane device operating at about 1 GHz with extraction from two cavities. For equal power in both extraction waveguides, the peak microwave power of this device is between 200 and 300 MW. Microwave pulse-shortening limits pulselengths to the range of 10-100 ns. Time-frequency analysis of microwave emission indicates operation at about 1.03 GHz, close to the pi mode frequency identified from cold tests and the three-dimensional MAGIC code. Two cold cathodes were tested: 1) an emitting aluminum knob in the vane region with no endcap and 2) an extended cathode with a graphite fiber emission region in the vanes and endcap outside the vanes. Electron endloss current has been measured for the two cathodes. With no endcap, the cathode exhibited endloss current fraction up to 50% of the total; with one endcap, the cathode reduced the endloss current fraction to as little as 12%. Both cathodes produced peak total-electronic efficiency in the range of 14%-21%.
  IEEE Transactions on Plasma Science 07/2002; · 1.17 Impact Factor
• Conference Proceeding: Relativistic magnetron experiments and novel theory on the limiting current in a relativistic, magnetically-insulated diode

  M.R. Lopez, R.M. Gilgenbach, Y.Y. Lau, D.W. Jordan, S Anderson, M.D. Johnston, M.W. Keyser, H Miyake, C.W. Peters, M.C. Jones, V. Bogdan Neculaes, T.A. Spencer, J.W. Luginsland, M. Haworth, R.W. Lemke, D Price
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  ABSTRACT: This paper is a progress report on the relativistic magnetron experiment. It also presents, for the first time, the maximum emission current density for time-independent, relativistic, cycloidal electron flows in a magnetically insulated diode.
  Vacuum Electronics Conference, 2002. IVEC 2002. Third IEEE International; 02/2002
• Article: Long-pulse, high-power, large-orbit, coaxial gyrotron oscillator experiments

  R.L. Jaynes, R.M. Gilgenbach, C.W. Peters, W.E. Cohen, M.R. Lopez, Y.Y. Lau, W.J. Williams, T.A. Spencer
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  ABSTRACT: Long-pulse, large-orbit, coaxial gyrotrons are currently under investigation. The electron beam is generated by the Michigan Electron Long Beam Accelerator (MELBA) with parameters: V=-0.8 MV, I_anode⩽~4 kA, I_tube=0.2-2 kA, and pulse length=0.5-1 μs. Large-orbit, axis-encircling electron beams are generated by a magnetic cusp. Experimental gyrotron performance with coaxial cavities (unslotted and slotted) is compared to a noncoaxial cavity. The coaxial gyrotron demonstrated superior current transport and microwave production over the noncoaxial gyrotron. The coaxial rod apparently raises the limiting electron beam current in the diode, allowing higher currents to be extracted. The unslotted, coaxial gyrotron showed microwave power levels of 20-40 MW with pulse lengths of 10-40 ns, This coaxial gyrotron operated in two main modes: TE₁₁₁ and TE₁₁₂ with frequencies of 2.34 and 2.5 GHz, respectively. The gyrotron frequency is tunable between the respective modes by changing the magnetic field. The slotted, coaxial gyrotron showed the highest power of 60-90 MW and extremely short pulse lengths of 10-15 ns. For all three gyrotrons, the microwave pulse-shortening mechanisms of mode hopping and mode competition are definitively identified by time-frequency analysis of heterodyned microwave data
  IEEE Transactions on Plasma Science 07/2000; · 1.17 Impact Factor
• Conference Proceeding: Investigations of microwave pulse shortening in a high powercoaxial gyrotron

  R.M. Gilgenbach, W.E. Cohen, C.W. Peters, M.R. Lopez, R.L. Jaynes, S.A. Anderson, Y.Y. Lau, M. L. Brake, W.J. Williams, T.A. Spencer
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  ABSTRACT: Experiments have been performed on a coaxial gyrotron driven by the Michigan Electron Long Beam Accelerator (MELBA) at parameters: V=-0.8 MV, I=1-10 kA, and pulselength=0.5-1 microsecond. Microwave pulse shortening has been investigated by spectroscopic plasma diagnostics to characterize plasma effects inside the operating gyrotron. Radio-frequency plasma processing has been applied to clean the inside of the gyrotron in order to reduce the deleterious effects of plasma on the microwave pulselength and energy. Results show that plasma cleaning can extend the microwave pulselength and increase the integrated microwave energy output by 15-245% in this gyrotron
  Infrared and Millimeter Waves, 2000. Conference Digest. 2000 25th International Conference on; 02/2000
• Article: Velocity ratio measurement diagnostics and simulations of a relativistic electron beam in an axis encircling gyrotron

  R.L. Jaynes, R.M. Gilgenbach, J.M. Hochman, N. Eidietis, J.I. Rintamaki, W.E. Cohen, C.W. Peters, Y.Y. Lau, T.A. Spencer
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  ABSTRACT: This paper reports on diagnostic experiments and simulations of a large-orbit, axis-encircling gyrotron. The electron's perpendicular to parallel velocity ratio α is measured. The experimental diagnostic consists of an apertured portion of the beam which is passed through a cusped magnetic field then collected on a glass plate. The cross section of the beam is recorded on the glass plate in a radiation darkened pattern. From the gyro-radius, B-field, and beam energy, α can be calculated. Particle distributions of the radiation darkened plate are in excellent agreement with numerical simulations of single particle orbits derived from the relativistic equations of motion. The experimental measurement of α yields values from 0.9 to 1.4. The simulations predict an α of 1.0 to 1.5
  IEEE Transactions on Plasma Science 03/1999; · 1.17 Impact Factor
• Conference Proceeding: Optical spectroscopy of plasma and plasma processing in high power microwave pulse shortening experiments

  W.E. Cohen, R.M. Gilgenbach, R.L. Jaynes, J.I. Rintamaki, C.W. Peters, Y.Y. Lau, T.A. Spencer, G.P. Scheitrum, L.L. Laurent
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  ABSTRACT: Summary form only given, as follows. Spectroscopic measurements have been performed to characterize the undesired plasma in a multi-megawatt coaxial gyrotron. This gyrotron is driven by the Michigan Electron Long Beam Accelerator (MELBA) at parameters: V=-800 kV, I_tube=0.3 kA, and pulselengths of 0.5-1 μs. Pulse shortening typically limits the highest (~40 MW) microwave power pulselength to 50-100 ns. Potential explanations of pulse shortening are being investigated, particularly plasma production inside the cavity and at the e-beam collector. The source of this plasma is believed to be due to water vapor. Plasma H-α line radiation has been characterized and correlated with microwave power and microwave cutoff. Experiments are underway to determine the effects of RF plasma processing of the coaxial cavity and collector. A collaborative effort is underway with the Stanford Linear Accelerator Center/U.C. Davis to study RF cavity breakdown. A SEM is being used to examine the surface effects of RF processing cavity parts
  Plasma Science, 1999. ICOPS '99. IEEE Conference Record - Abstracts. 1999 IEEE International Conference on; 02/1999
• Conference Proceeding: Optical spectroscopy of plasma in high power microwave pulse shortening experiments driven by a microsecond electron beam

  W.E. Cohenm, R.M. Gilgenbach, J.M. Hochman, R.L. Jaynes, J.I. Rintamaki, C.W. Peters, D.E. Vollers, Y.Y. Lau, T.A. Spencer
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  ABSTRACT: Summary form only given, as follows. Spectroscopic measurements have been performed to characterize the undesired plasma in a multi-megawatt coaxial gyrotron and a rectangular-cross-section (RCS) gyrotron. These gyrotrons are driven by the Michigan Electron Long Beam Accelerator (MELBA) at parameters: v=-800 kV, I_tube=0.3 kA, and pulselengths of 0.5-1 μs. Pulse shortening typically limits the highest (~10 MW) microwave power pulselength to 100-200 ns. Potential explanations of pulse shortening are being investigated, particularly plasma production inside the cavity and at the e-beam collector. The source of this plasma is believed to be due to water vapor absorbed on surfaces which is ejected, dissociated, and ionized by electron beam impact. Plasma H-α line radiation has been characterized in both time-integrated and temporally-resolved measurements and correlated with microwave power and microwave cutoff. Measurements from a residual gas analyzer (RGA) will be used to support this interpretation. Experiments involving RF plasma cleaning of the coaxial cavity are planned
  Plasma Science, 1998. 25th Anniversary. IEEE Conference Record - Abstracts. 1998 IEEE International on; 07/1998
• Article: Optical spectroscopy of plasma in high power microwave pulse shortening experiments driven by a μs e-beam

  R.M. Gilgenbach, J.M. Hochman, R.L. Jaynes, W.E. Cohen, J.I. Rintamaki, C.W. Peters, D.E. Vollers, Y.Y. Lau, T.A. Spencer
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  ABSTRACT: Microwave pulse shortening experiments have been performed on a rectangular-cross-section (RCS) gyrotron driven by the Michigan Electron Long Beam Accelerator (MELBA) at parameters V=-800 kV, I_tube=0.3 kA and pulselengths of 0.5-1 μs. Pulse shortening typically limits the highest (10 MW level) microwave power pulselength to 100-200 ns. Potential explanations of pulse shortening are being investigated, particularly plasma production inside the cavity and at the e-beam-collector. We report the first optical spectroscopy diagnostic measurements inside an operating gyrotron as a means of exploring plasma effects on pulse shortening. Plasma hydrogen H-α line radiation has been characterized in both time-integrated and temporally-resolved measurements and correlated with microwave power/cutoff. Hydrogen is believed to originate from water absorbed on internal tube surfaces in the gyrotron
  IEEE Transactions on Plasma Science 07/1998; · 1.17 Impact Factor
• Article: Polarization control of microwave emission from high power rectangular cross-section gyrotron devices

  J.M. Hochman, R.M. Gilgenbach, R.L. Jaynes, J.I. Rintamaki, Y.Y. Lau, W.E. Cohen, C.W. Peters, T.A. Spencer
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  ABSTRACT: Results are summarized of experiments on a gyrotron utilizing a rectangular-cross-section (RCS) cavity region. The major issue under investigation is polarization control of microwave emission as a function of magnetic field. The electron beam driver is the Michigan Electron Long Beam Accelerator (MELBA) at parameters: V=0.8 MV, I_diode=1-10 kA, I_tube=0.1=0.5 kA, and t_e-beam=0.4-1.0 μs. The annular e-beam is spun up into an axis-encircling beam by passing it through a magnetic cusp prior to entering the RCS interaction cavity. Experimental results show a high degree of polarization in either of two orthogonal modes as a function of cavity fields. The RCS gyrotron produced peak powers of 14 MW in one polarization (TE₁₀) and 6 MW in the cross-polarized mode (TE ₀₁). Electronic efficiencies for this device reached as high as 8% with transverse efficiency of 16%. Experimental results on the beam alpha (α=V_⊥/V_||) diagnostics, where alpha is the ratio of the e-beam's transverse velocity to its parallel velocity, agree well with the single electron trajectory code. MAGIC code results are in qualitative agreement with microwave measurements. Microwave emission shifts from the dominant fundamental mode polarization (TE₁₀□ ), to the next higher order mode polarization (TE₀₁□) as the solenoid magnetic field is raised from 1.4-1.9 kGauss. Frequency measurements using heterodyne mixers support mode identification as well as MAGIC code simulations
  IEEE Transactions on Plasma Science 07/1998; · 1.17 Impact Factor