Simulations of the nEDM@SNS light collection system efficiency

Abstract

A system for collecting the scintillation light produced by the capture process of ultracold neutrons (UCN) on polarized 3 He is discussed and results from simulations of its performance are presented. This system will be implemented in nEDM@SNS, the experiment searching for the neutron electric dipole moment (nEDM) at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. Simulation results show that the light collection system collects on average 17 photoelectrons per UCN-3 He capture event (sufficient to generate a robust signal), reconstructs the event location in the beam direction to approximately 3 cm accuracy, detects capture events with a high and spatially uniform efficiency (0.95 with 1% variation), and rejects greater than 50% of beta decay background events. K: Simulation methods and programs, Photon detectors for UV, visible and IR photons (vacuum) (photomultipliers, HPDs, others), Scintillators, scintillation and light emission processes (solid, gas and liquid scintillators)

Electric dipole moments and the search for new physics

“…The nEDM@SNS experiment uses challenging technologies involving large-scale cryogenic systems (for the current experimental design, see Ahmed et al [149]). Considerable results have been obtained from the R&D efforts in all areas, including: polarized 3 He [170][171][172][173][174][175][176], dressed spins [177][178][179], magnetic field monitoring [180], non-magnetic feedthrough [181], SQUID based magnetometers [182], noble gas scintillation and its detection [183][184][185][186][187][188], electrical breakdown in LHe [150,151], HV generation in superfluid helium [189], cryogenic magnetic field studies [190], possible systematic effects [127,155,157,159,160,[191][192][193][194], and apparatus for studying spin dressing and systematic effects [138]. The SNS project is the only project making use of a superconducting shield, meaning it will not be affected by intrinsic fluctuations in the room temperature ferromagnetic shields, a technology which has not been tested at sensitivities below 10 −26 e • cm, and is relied on by all the other nEDM projects discussed above.…”