GSI, Darmstadt
ORNL, Oak Ridge, Tennessee
IAP, Frankfurt am Main
CEA, Gif-sur-Yvette
Funding: We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 ‘‘Structuring the European Research Area’’ program (CARE, Contract No. RII3-CT-2003-506395).
Beam dynamics experiments with high intensity beams have been conducted at the GSI UNILAC in 2006-2008 with the goal of benchmarking four major simulation codes, i.e. DYNAMION, PARMILA, TraceWin/PARTRAN and LORASR with respect to transverse emittance growth along a DTL. The experiments comprised measurements of transverse phase space distributions in front of as well as behind the DTL. Additional longitudinal bunch length measurements at the DTL entrance allowed for estimate and control of mismatch in all three planes. Measured effects of mismatch and of theoretically predicted space charge resonances (equipartitioning and others) are compared with simulations for a wide range of transverse phase advance along the DTL. This contribution is the first report on the successful measurement of a space charge driven fourth order resonance in a linear accelerator.
ORNL, Oak Ridge, Tennessee
Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy
The Spallation Neutron Source (SNS) is a second generation pulsed-neutron source and designed to provide a 1-GeV, 1.44-MW proton beam to a mercury target for neutron production. Since the initial commissioning of accelerator complex in 2006, the SNS has begun neutron production operation and beam power ramp-up has been in progress toward the design goal. Since the design beam power is almost an order of magnitude higher compared to existing neutron facilities, all subsystems of the SNS were designed and developed for substantial improvements compared to existing accelerators and some subsystems are first of a kind. Many performance and reliability aspects were unknown and unpredictable, for which it takes time to understand the systems as a whole and/or needs additional performance improvements. A power ramp-up plan has been revised based on the operation experiences and understandings of limits and limiting conditions through extensive studies with an emphasis on machine availability. In this paper the operational experiences of SNS Superconducting Linac (SCL), the power ramp-up status and plans will be presented including related subsystem issues.
ORNL, Oak Ridge, Tennessee
BINP SB RAS, Novosibirsk
Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
A transverse phase space emittance scanner is proposed and under development for the 1-GeV H- SNS linac, using a laser beam as a slit. For a 1 GeV H- beam, it is difficult to build a slit because the stopping distance is more than 50 cm in copper. We propose to use a laser beam as an effective slit by stripping off the outer electron of the H- (making it neutral) upstream of a bend magnet and measuring the stripped component downstream of the bend magnet. The design and modeling of the system will be discussed. We are expecting to make a preliminary measurement in 2009.
ORNL, Oak Ridge, Tennessee
GSI, Darmstadt
The 4ν=1 resonance of a linac is demonstrated when the depressed tune is around 90 deg. It is observed that this fourth order resonance is dominating over the better known envelope instability and practically replacing it. Simulation study shows a clear emittance growth by this resonance and its stopband. One of the authors [DJ] made a proposal to GSI to measure the stopband of this resonance. The experiment was conducted successfully and the experiment data will be presented separately in the conference.