Title :
Measurements of velocity ratio in a 90 MW gyroklystron electron beam
Author :
Calame, J.P. ; Cheng, J. ; Hogan, B. ; Lawson, W. ; Striffler, C.D. ; Latham, P.E. ; Irwin, V.
Author_Institution :
Inst. for Plasma Res., Maryland Univ., College Park, MD, USA
fDate :
8/1/1994 12:00:00 AM
Abstract :
Measurements of the ratio of perpendicular to parallel velocity (α=υ⊥/υ,) in a 390-420 kV, 160-240 A, small orbit gyroklystron electron beam produced by a magnetron injection gun have been performed using a capacitive probe. The probe employed guard rings to reduce uncertainties in measurement and calibration due to fringing electric fields. These studies represent the first measurements of a in such a powerful rotating beam. Since the current levels in this experiment are two to three times higher than those in previous velocity ratio studies of beams with similar voltage. The effects of changes in voltage, current, and magnetic compression on the measured velocity ratio are investigated. Values of α in the range of 0.8-1.3 are typically observed, which are considerably higher than the values predicted by theoretical simulations. Errors in the modeling of space charge effects are ruled out as the cause of the discrepancy by the agreement between theoretical and experimental space charge current limits. Instead, a significant portion of the discrepancy is attributed to a reduction in cathode magnetic field by the self-axial magnetic fields of the electron beam
Keywords :
electron beams; gyrotrons; klystrons; particle beam diagnostics; space charge; 160 to 240 A; 390 to 420 kV; 90 MW; capacitive probe; cathode magnetic field; current; fringing electric fields; guard rings; gyroklystron electron beam; magnetic compression; magnetron injection gun; modeling; parallel velocity; perpendicular velocity; powerful rotating beam; self-axial magnetic fields; space charge effects; velocity ratio; voltage; Electron beams; Extraterrestrial measurements; Klystrons; Magnetic field measurement; Magnetic fields; Performance evaluation; Probes; Space charge; Velocity measurement; Voltage;
Journal_Title :
Plasma Science, IEEE Transactions on