DETERMINING PHASE-SPACE PROPERTIES OF THE LEDA RFQ OUTPUT BEAM
Quadruple scans were used to characterize the LEDA RFQ beam. Experimental data were fit to computer simulation models for the rms beam size. The codes were found to be inadequate in accurately reproducing details of the wire scanner data. When this discrepancy is resolved, we plan to fit using all the data in wire scanner profiles, not just the rms value.
COMMISSIONING RESULTS FROM THE LEDA LOW-ENERGY DEMONSTRATION ACCELERATOR (LEDA) RADIO-FREQUENCY QUADRUPOLE (RFQ)
The LEDA RFQ is a 100% duty factor (CW) linac that delivers >100 mA of H + beam at 6.7 MeV. The 8-m-long, 350-MHz RFQ structure accelerates a dc, 75-keV, 110mA H + beam from the LEDA injector with ~94% transmission. After the ~200-µsec-long turn-on transient, RFQ output beams with currents >90 mA have RFQ transmission that is ~10% lower than the PARMTEQM prediction. Raising the rf cavity field level to 105-110% of the design field increases the RFQ transmission to the design value. Preliminary analysis of the 93-mA quadscan data suggests the RFQ output beam rms emittance, ex ≈=0.25 π mm mrad (normalized), is less than the measurement error away from the design, 0.23 π mm mrad.
Reduction of Surface Flashover of the Beam Screen of the LHC Injection Kickers
The LHC injection kicker magnets include beam screens to shield the ferrite yokes against wake fields resulting from the high intensity beam. The screening is provided by conductors lodged in the inner wall of a ceramic support tube. Operation with increasingly higher bunch intensity, and narrow bunches, now requires improved ferrite screening. This will be implemented by additional conductors; however the good high-voltage behaviour of the kicker magnets must not be compromised by the supplementary screening. Extensive studies and optimisations have been carried out, to better satisfy the often conflicting requirements for low beam coupling impedance, fast magnetic field rise-time, high vacuum and good high voltage behaviour. A new configuration is proposed which reduces significantly the electric field associated with the screen conductors and the secondary electron yield of the surface of the ceramic tube. Results of high voltage test results are also presented.