Experimental results of the MIT 17 GHz RF gun

Journal Article · Mon Jul 12 00:00:00 EDT 1999 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.58934· OSTI ID:21205432

Brown, W J; Trotz, S; Kreischer, K E; Pedrozzi, M; Shapiro, M A; Temkin, R J ^[1]

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1. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

We report on experimental results of a 17 GHz RF photocathode electron gun. This is the first photocathode electron gun to operate at a frequency above 2.856 GHz. The 1.5 cell, {pi}-mode, copper cavity was tested with 50 ns pulses from a 17.150 GHz klystron amplifier built by Haimson Research Corp. A Bragg filter was used at the RF gun to reduce the reflection of parasitic modes back into the klystron. Coupling hole theory in conjunction with cold test measurements was used to determine the field profile in the RF gun. The particle in cell code MAGIC was used to simulate the beam dynamics in the RF gun. With power levels of 4 MW, the on axis electric field at the cathode exceeds 300 MV/m, corresponding to an average accelerating gradient of 200 MV/m over the first half cell of the gun. Breakdown was observed at power levels above 5 MW. Electron bunches were produced by 20 {mu}J, 1 ps UV laser pulses impinging on the RF gun copper photocathode and were measured with a Faraday cup to have up to 0.1 nC of charge. This corresponds to a peak current of about 100 A, and a density at the cathode of 8.8 kA/cm{sup 2}. Multiple output electron bunches were obtained for multiple laser pulses incident on the cathode. Phase scans of laser induced electron emission reveal an overall phase stability of better than {+-}20 deg., corresponding to {+-}3 ps synchronization of the laser pulses to the phase of the microwave field. A Browne-Buechner magnetic spectrometer indicated that the RF gun generated 1 MeV electrons with a single shot rms energy spread of less than 2.5%, in good agreement with theoretical predictions.

• OSTI ID: 21205432
• Journal Information: AIP Conference Proceedings, Vol. 472, Issue 1; Conference: 8. workshop on advanced accelerator concepts, Baltimore, MD (United States), 6-11 Jul 1998; Other Information: DOI: 10.1063/1.58934; (c) 1999 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ACCELERATORS
AMPLIFIERS
BEAM DYNAMICS
CAVITY RESONATORS
ELECTRIC FIELDS
ELECTRON BEAMS
ELECTRON EMISSION
ELECTRON GUNS
ELECTRON SOURCES
FARADAY CUPS
GHZ RANGE
KLYSTRONS
LASERS
MAGNETIC SPECTROMETERS
PHASE STABILITY
PHOTOCATHODES
PHOTOEMISSION
PULSES
RF SYSTEMS
SYNCHRONIZATION