Initial measurements of beam breakup instability in the advanced test accelerator

Conference · Tue Oct 01 04:00:00 EDT 1985 · IEEE Trans. Nucl. Sci.; (United States)

OSTI ID:6062277

Chong, Y P; Caporaso, G T; Struve, K W

This paper reports the measurements of beam breakup (BBU) instability performed on the Advanced Test Accelerator (ATA) up to the end of February 1984. The main objective was to produce a high current usable electron beam at the ATA output. A well-known instability is BBU which arises from the accelerator cavity modes interacting with the electron beam. The dominant mode is TM130 at a frequency of approximately 785 MHz. It couples most strongly to the beam motion and has been observed to grow in the Experimental Test Accelerator (ETA), which has only eight accelerator cavities. ATA has one hundred and seventy cavities and therefore the growth of BBU is expected to be more severe. In this paper, BBU measurements are reported for ATA with beam currents of 4 to 7 kA. Analysis showed that the growth of the instability with propagation distance was as expected for the lower currents. However, the high current data showed an apparent higher growth rate than expected. An explanation for this anomaly is given in terms of a ''corkscrew'' excitation. The injector BBU noise level for a field emission brush cathode was found to be an order of magnitude lower than for a cold plasma discharge cathode. These injector rf amplitudes agree very well with values obtained using the method of differenced Btheta loops.

• Research Organization: Lawrence Livermore National Laboratory, Livermore, CA
• OSTI ID: 6062277
• Report Number(s): CONF-850504-
• Conference Information: Journal Name: IEEE Trans. Nucl. Sci.; (United States) Journal Volume: NS-32:5
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
430200* -- Particle Accelerators-- Beam Dynamics
Field Calculations
& Ion Optics
430303 -- Particle Accelerators-- Experimental Facilities & Equipment
ACCELERATORS
BEAM CURRENTS
BEAM DYNAMICS
BEAM INJECTION
BEAMS
CURRENTS
ELECTRON BEAM INJECTION
ELECTRON BEAMS
INSTABILITY
INSTABILITY GROWTH RATES
KILO AMP BEAM CURRENTS
LEPTON BEAMS
LINEAR ACCELERATORS
PARTICLE BEAMS
TESTING