ORNL, Oak Ridge, Tennessee, USA
Beam loss is a critical issue in high intensity linacs, and much work is done during both the design and operation phases to keep the loss down to manageable levels. Linacs for H− ion beams have many more loss mechanisms compared to H+ (proton) linacs. Interesting H− beam loss mechanisms include residual gas stripping, H+ capture and acceleration, field stripping, and intra-beam stripping (IBSt). Beam halo formation, and ion source or RF turn on/off transients, are examples of beam loss mechanisms that are common for both H+ and H− accelerators. The IBSt mechanism has recently been characterized at the Oak Ridge Spallation Neutron Source, and we have found that it accounts for most of the loss in the superconducting linac. In this paper we will detail the IBSt measurements, and also discuss the other beam loss mechanisms that are important for high intensity linacs.
ORNL, Oak Ridge, Tennessee, USA
The Spallation Neutron Source is now operating in production mode at about 1 MW of beam power on target, which corresponds to more than 1014 protons per pulse at 60 Hz with energies exceeding 900 MeV. Although overall beam losses in production tune are low, the highest losses in the entire machine occur in the region downstream of the ring injection stripper foil. In order to better understand the contribution of scattering from the primary stripper foil to losses in the SNS ring, we have carried out calculations using the ORBIT Code aimed at evaluating these losses. These calculations indicate that the probability of beam loss within one turn following a foil hit is ~1.7·10-8*T, where T is the foil thickness in g/cm2, assuming a carbon foil. Thus, for a stripper foil of thickness T = 390 g/cm2, the probability of loss within one turn of a foil hit is ~6.7·10-6. This paper describes the calculations used to arrive at this result, presents the distribution of these losses around the SNS ring, and compares the the calculated loss distribution with that observed experimentally.
ORNL, Oak Ridge, Tennessee, USA
The Oak Ridge Spallation Neutron Source (SNS) accelerator complex routinely delivers 1 MW of beam power to the spallation target. Due to this high beam power, understanding and minimizing the beam loss is an ongoing focus area of the accelerator physics program. In some areas of the accelerator facility the equipment parameters corresponding to the minimum loss are very different from the design parameters. In this presentation we will summarize the SNS beam loss measurements, the methods used to minimize the beam loss, and a compare the design vs. the loss-minimized equipment parameters.
CERN, Geneva, Switzerland
ORNL, Oak Ridge, Tennessee, USA
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
- observation of beam losses (e.g. time structure, other parameters,…),
- reducing beam losses with operational parameters away from the design set points,
- reducing beam losses (or concentrating beam losses at a few locations) using collimators,
- minimizing beam losses due to beam transfer from one accelerator to the following accelerator - what parameters are important?