LONGITUDINAL SPACE CHARGE EFFECT FOR SNS

Conference · Mon Jun 22 04:00:00 EDT 1998

OSTI ID:757114

ZHANG, S Y ^[1]; WENG, W T

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1. BROOKHAVEN NATIONAL LABORATORY

One of performance requirements of the Spallation Neutron Source (SNS) is to keep the uncontrolled beam loss in the storage ring to less than 2 x 10{sup {minus}4} per pulse. For 2 MW SNS, the maximum beam intensity is N = 2 x 10{sup 14} protons per ring. Since the bunch lengthening has impact on both the extraction beam loss and the lowering of e-p instability threshold, the longitudinal space charge effect requires attentions. Such a space charge effect has been studied both analytically and using computer simulations. The longitudinal space charge effect, which is a defocusing force below transition, is a plausible source of the bunch leakage. In this article, the total RF potential, which takes into account the space charge effect together with the RF power, is used to provide analytical predictions for the bunch lengthening. The prediction is confirmed by the computer simulation. It is found that for 2 MW SNS storage ring, the longitudinal space charge induced bunch leakage into the interbunch gap is not significant. Therefore, corrections to the longitudinal space charge impedance, such as the proposed ferrite insertion in the PSR ring, are probably not necessary. Applying an RF voltage ramping from 20 KV to 40 KV during the multiturn injection can further cut the bunch leakage to a negligible degree. The same approach applied to the PSR shows that the longitudinal space charge effect does cause sizable bunch leakage at the intensity limit encountered there.

• Research Organization: Brookhaven National Lab., Upton, NY (US)
• Sponsoring Organization: USDOE Office of Energy Research (ER) (US)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 757114
• Report Number(s): BNL--65645; KA0403; KA0403
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ACCELERATORS
BEAM INJECTION
COMPUTERIZED SIMULATION
INSTABILITY
NEUTRON SOURCES
PARTICLE BEAMS
PERFORMANCE
SPACE CHARGE
SPALLATION
STORAGE RINGS