E906/SeaQuest MARS15 Simulation
The E906/SeaQuest spectrometer is designed to measure high energy muons produced in the forward direction by interactions of the 120 GeV Main Injector proton beam with a variety of targets. The spectrometer consists of two dipole magnets (both of which deflect charged particles in the horizontal plane) and a collection of tracking detectors. The first spectrometer magnet (FMAG) is a solid iron magnet. This magnet serves as a beam dump as well as a muon analysis magnet. A series of MARS15 simulations were done by Nikolai Mokhov to verify and guide the design of concrete shielding around FMAG and the target area immediately upstream of FMAG. The result of the fourth and last round of simulations is summarized here. This was a high statistics simulation that required approximately 48 cpu-weeks of computing time on the APC Energy Deposition Group cluster. The MARS15 simulation used a model of FMAG and its surroundings. The model includes air gaps in the concrete shielding, the largest of which are required because of the geometry of the saddle coils. A small volume surrounding the beam line just upstream of the magnet is filled with borated polyethylene. The borated polyethylene extends into the air gap necessitated by the saddle coils. With the exception of the top layer of six 'H' blocks, the concrete shielding is modeled in detail. The top layer of blocks are intended to shield the roof and downstream end of NM4 in the event of a loss of beam accident well upstream of the target; they provide only a small benefit in the normal running condition simulated by MARS.