Title :
Quadrupole image-current effects in the ITS 6-MeV, 4-kA linac
Author :
Allison, Paul ; Moir, David C.
Author_Institution :
Los Alamos Nat. Lab., NM, USA
Abstract :
The eight accelerating cells for the ITS linear induction accelerator (LIA) are driven with two 50-Ω lines at 250 kV for 60 ns. The wall return currents for the 4-kA beam then pass through these lines, generating a weak steady-state quadrupole field of ~3 G integrated strength on axis, which causes a small asymmetry in the nominally round beam at the linac exit. Beam-dynamics simulations with the particle-tracing code SCHAR show that if uncorrected, this would increase the beam emittance at the end of the DARHT 20-MeV linac, therefore quadrupole-corrector coils (QC) were added to each cell, in addition to the existing dipole steering coils. Measurements of the asymmetry of the ITS beam as a function of excitation current of these corrector coils are in good agreement with simulations, giving confidence that there will be negligible emittance degradation from this effect for DARHT
Keywords :
accelerator magnets; collective accelerators; electromagnets; high energy physics instrumentation computing; linear accelerators; particle beam diagnostics; particle beam dynamics; 20 MeV; 250 kV; 3 G; 4 kA; 50 ohm; 6 MeV; 60 ns; DARHT linac; ITS linac; SCHAR code; accelerating cells; asymmetry measurements; beam emittance; beam-dynamics simulations; dipole steering coils; linear induction accelerator; particle-tracing code; quadrupole image-current effects; quadrupole-corrector coils; wall return currents; weak steady-state quadrupole field; Acceleration; Coils; Current measurement; Degradation; Induction generators; Linear accelerators; Linear particle accelerator; Particle beam measurements; Particle beams; Steady-state;
Conference_Titel :
Particle Accelerator Conference, 1997. Proceedings of the 1997
Conference_Location :
Vancouver, BC
Print_ISBN :
0-7803-4376-X
DOI :
10.1109/PAC.1997.749955
