Testing and Evaluation of PHENIX Reaction Plane Detector Photomultiplier Tubes

The PHENIX Reaction Plane Detector (RxnP) at the Relativistic Heavy Ion Collider is designed to determine the reaction plane in heavy ion collisions. Currently the reaction plane is determined using the Beam Beam Counters. However, the RxnP will increase the resolution by nearly a factor of two over the currently achievable levels. This detector's location in the central region of PHENIX will expose it to a magnetic field of approximately 1 Tesla. The curvature of the field lines makes it necessary to understand the relationship between the angle of the photomultiplier tubes (PMTs) in the magnetic field and the PMTs' output. Results of bench-top tests of the PMTs in similar magnetic fields and their impact on the final design will be presented.