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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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Simulations of the nEDM@SNS light collection system efficiency

Here, a system for collecting the scintillation light produced by the capture of ultra-cold 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 detects 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.

47 OTHER INSTRUMENTATION↗

Search for a Non-Zero Value of the Electric Dipole Moment of the Neutron (Final Technical Report)

The research grant addressed in this final report began its most recent 3-year segment June 1, 2022 and terminated May 31, 2025. The work funded by the grant supported our group at the Massachusetts Institute of Technology (MIT) in its collaboration on the nEDM@SNS (SNS refers to the Spallation Neutron Source) project at the Oak Ridge National Laboratory (ORNL). This project had as its goal the measurement of a non-zero value of the electric dipole moment of the neutron (nEDM). If indeed the neutron has a non-zero electric dipole moment, it will tell us very important information about the Standard Model of Nuclear and Particle Physics. The Standard Model is remarkably successful in describing much of the world we live in, but we know it is not complete. A non-zero nEDM would indicate the existence of strong CP violation, which would be a major addition to the Standard Model.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Characterization of the new Ultracold Neutron beamline at the LANL UCN facility

The neutron electric dipole moment (nEDM) experiment that is currently being developed at Los Alamos National Laboratory (LANL) will use ultracold neutrons (UCN) and Ramsey’s method of separated oscillatory fields to search for a nEDM. Here, in this paper, we present measurements of UCN storage and UCN transport performed during the commissioning of a new beamline at the LANL UCN source and demonstrate a sufficient number of stored polarized UCN to achieve a statistical uncertainty of δd n = 2 x 10 -27 e cm in 5 calendar years of running. We also present an analytical model describing data that provides a simple parameterization of the input UCN energy spectrum on the new beamline.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Electric charging effects on insulating surfaces in cryogenic liquids

Here, this paper presents a new technique to study the adsorption and desorption of ions and electrons on insulating surfaces in the presence of strong electric fields in cryoliquids. The experimental design consists of a compact cryostat coupled with a sensitive electro-optical Kerr device to monitor the stability of the electric fields. The behavior of nitrogen and helium ions on a poly(methyl methacrylate) (PMMA) surface was compared to a PMMA surface coated with a mixture of deuterated polystyrene and deuterated polybutadiene. Ion accumulation and removal on these surfaces were unambiguously observed. Within the precision of the data, both surfaces behave similarly for the physisorbed ions. The setup was also used to measure the (quasi-)static dielectric constant of PMMA at T ≈ 70 K. The impact of the ion adsorption on the search for a neutron permanent electric dipole moment in a cryogenic environment, such as the nEDM@SNS experiment, is discussed.

Cryogenics↗

A novel silicon photomultiplier readout architecture for low-light applications

In this article we describe the photon detection readout electronics for the nEDM@SNS experiment. The chosen "photon counting" architecture, which utilizes high-efficiency silicon photomultipliers (SiPMs) and is appropriate for low-light applications, allows the use of a relatively high SiPM operating voltage. This maximizes photon detection efficiency and minimizes gain/efficiency voltage-dependence while eliminating direct optical cross-talk.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

MEOP based 3 He polarization and injection system for experiments below 1 K

Metastability exchange optical pumping (MEOP) is a widely used technique for producing polarized 3 He. In connection with an experiment to search for the electric dipole moment of the neutron (nEDM) we have built a MEOP based 3 He polarization and injection system to prepare 80 % polarized 3 He at room temperature which will be injected into a ∼ 400 mK measurement cell filled with superfluid 4 He. We describe the polarization and injection system, which is designed to allow for final concentrations of 10 -8 –10 -10 of 80% polarized 3 He in the superfluid filled measurement cell. Only ≈ 0.72% polarization loss due to gradients is expected during injection.

Gas systems and purification↗

Rosen Scholar

Dr. Tim Chupp is a professor of physics, applied physics, and biomedical engineering from the University of Michigan. As Rosen Scholar he will work with the Subatomic Physics group’s Neutron Team to develop the LANL RoomTemperature Neutron Electric Dipole Moment (nEDM) experiment that will used at LANSCE's world-leading Ultracold Neutron Facility. The electric dipole moment is the electrical stretching of neutrons or atoms along their spin axis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Particle physics at the European Spallation Source

Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world’s brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. Furthermore, these encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗