Performance of SNS Front end and warm linac

The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H-injector, capable of producing one-ms-long pulses at 60 Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The 2.5 MeV beam from the Front End is accelerated to 86 MeV in the Drift Tube Linac, then to 185 MeV in a Coupled-Cavity Linac and finally to 1 GeV in the Superconducting Linac. With the completion of beam commissioning, the accelerator complex began operation in June 2006 and beam power is being gradually ramped up toward the design goal. Operational experience with the injector and linac will be presented including chopper performance, transverse emittance evolution along the linac, and the results of a beam loss study.

INTRODUCTION

The SNS Front End and warm linac consist of an H⁻ injector, capable of producing one-ms-long pulses with 38 mA peak current, chopped with a 68% beam-on duty factor and a repetition rate of 60 Hz to produce 1.6 mA average current, an 86 MeV Drift Tube Linac (DTL), a 185 MeV Coupled Cavity Linac (CCL), and associated transport lines [1]. After completion of the initial beam commissioning at a power level lower than the nominal, the SNS accelerator complex is gradually increasing the operating power with the goal of achieving the design parameters by 2009. Results of the initial commissioning can be found in [2]. In this paper we report the latest results of the Front End and warm linac performance with the focus on problems encountered and their short and long term resolution.