Beam-breakup calculations for the DARHT accelerator
- Los Alamos National Lab., NM (USA)
- Lawrence Livermore National Lab., CA (USA)
We have modeled an induction linac that will accelerate a 4-MeV, 3-kA beam of electrons to 16- to 20-MeV in 64 gaps. To suppress beam- breakup (BBU) instabilities induced by excitation of rf deflecting modes, the growth factor {Gamma} must be kept sufficiently small (e.g. < 3). On prototype DARHT cavities, rf measurements have shown that the normally degenerate TM modes are split in frequency by the asymmetry that the two pulsed-power drive rods present to the cavity. If half the cavities had vertical and half had horizontal drive-rod orientations, the effective number of gaps would be reduced by half if there were no coupling between the modes by the solenoidal focusing and if the split modes had no overlap. The LLNL code BREAKUP was used to study BBU growth for drive rod alternation patterns of blocks of 1, 2, 4, 8, 16, 24, 32, or 64 (no alternation) for both constant and alternating polarity solenoids. For alternating polarities the optimum alternation pattern is 2 or 4, whereas for constant polarities BBU is approximately independent of pattern. 9 refs., 5 figs. 2 tabs.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (USA)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5741052
- Report Number(s):
- LA-UR-91-1546; CONF-910505-209; ON: DE91013657
- Resource Relation:
- Conference: 1991 Institute of Electrical and Electronics Engineers (IEEE) particle accelerator conference (PAC), San Francisco, CA (USA), 6-9 May 1991
- Country of Publication:
- United States
- Language:
- English
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