The IPNS accelerator 50 MeV and 500 MeV transport lines

The Intense Pulsed Neutron Source (IPNS) accelerator delivers up to 500 MeV protons to a depleted uranium target producing spallation neutrons for material science and other research. A 70-80 ns bunch strikes the target at a rate of 30 Hz with an average beam current of 15 μA. The 50 MeV and 500 MeV beam lines transport protons from the Drift Tube Linac (DTL) to the Rapid Cycling Synchrotron (RCS) and from the RCS to the Neutron Generating Source (NGS) target, respectively. Through over 15 years of operation, the accelerator has been highly reliable with the 5 billionth pulse on target recorded March 12, 1997. During this time, IPNS operators have discovered tunes for various parts of the DTL/RCS accelerator allowing for continual improvement in average current delivered to the target; however, in numerous cases this has been achieved by moving significantly away from the original design parameters. A new attempt is being made to analyze the lines and develop computer models that can be used to alleviate some of the undesirable features of the present “best tune.” In the 500 MeV line, higher order elements will be included in the modeling with the goal of providing a uniform power density profile at the NGS target. This paper describes features of the present lines, and progress-to-date in analyzing and improving them