Session C9: Techniques for Measuring Precision or Tiny Things

Quartz Detector Development for PVeS Experiments

The high luminosity requirements of Parity Violating electron Scattering (PVeS) experiments, such as Jefferson Lab's PREX, CREX and MOLLER, create several challenges for detector design. The main "integrating" detectors for these experiments must intercept and precisely count scattered electron fluxes at GHz rates over prolonged periods of time. The detector's active (Cherenkov) medium has been chosen to be high-purity, fused silica (Spectrosil 2000) quartz--which is known to maintain deep UV transparency during extreme radiation doses. Several detector prototypes have been built at Idaho State University and tested using the 850 MeV electron test-beam at the Mainz Microtron (MAMI). To aid in prototype development, an optical G4 Monte Carlo has been developed and now benchmarked using the real MAMI data. This talk will present some physics motivations, the PREX/CREX prototype detector designs, and their test-beam performance with comparisons to simulation.   

Polarization sensitivity in integrating detectors

Paritv violating experiments using a high current electron beam on a fixed target provide an ideal way to test the Standard Model. Using integrating detectors can lead to measurements of asymmetries on the part per billion level. However, integrating detectors can be polarization sensitive due to transverse scattering in the detector, a process that has not been thoroughly studied previously. We simulate such a transverse asymmetry using Geant4. Analyzing powers corresponding to simple Mott scattering model and a two-photon-exchange model are used to describe the polarization sensitive interaction of the electron with the detector. Potential application of these models to parity-violation experiments will be discussed.   

Update on the MUSE Proton Radius Measurement

The results of the test beam run in December 2015 for the MUSE experiment are presented and the current status of MUSE will be discussed. During this test run a study of 2 mm thick scintillators coupled to SiPMs was performed and the results are the focus of this talk. SiPMs from two different companies, AvanSiD and Hamamatsu, were tested and it was found the timing resolution is between 89 ps - 110 ps, depending on SiPM model, bar length, and momentum. The bars have an operational efficiency of at least 99\%.   

Investigation of a $^{129}$Xe magnetometer for the Neutron Electric Dipole Moment Experiment at TRIUMF

A non-zero neutron electric dipole moment (nEDM) would signify a previously unknown source of CP (or T) violation. New sources of CP violation are believed to be required to explain the baryon asymmetry of the universe. Employing a newly developed high-density UCN source, an experiment at TRIUMF aims to measure the nEDM to the level of $10^{-27}~e\cdot$cm in its initial phase. Precession frequency differences for UCN stored in a bottle subject to parallel and anti-parallel E and B fields signify a permanent nEDM. Magnetic field instability and inhomogeneity, as well as field changes resulting from leakage currents (correlated with E fields) are the dominant systematic effects in nEDM measurements. To address this, passive and active magnetic shielding are in development along with a dual species ($^{129}$Xe and $^{199}$Hg) atomic comagnetometer. Simultaneously introducing both atomic species into the UCN cell, the comagnetometer can mitigate false EDMs. $^{199}$Hg precession will be detected by Faraday rotation spectroscopy, and $^{129}$Xe precession will measured via two-photon excitation and emission. The present comagnetometer progress will be discussed, with focus on polarized $^{129}$Xe production and delivery.   

Laser Assisted Electric Field Monitoring in a Cryogenic Environment

The neutron EDM collaboration at the Spallation Neutron Source(ORNL) is using ultra-cold neutrons in liquid helium to improve the nEDM limit by two orders of magnitude. These neutrons will be stored in target cells located in a strong, stable electric field. Local radiation will generate charged particles which build up on the target cell walls reducing field strength and stability. The field fluctuations need to be kept below 1{\%}, making it necessary to study this cell charging behavior, determine its effect on the experiment and find ways to mitigate this. A more compact test setup was designed to study this effect using smaller electrodes and cell. Charged particles are generated by ionizing the helium with a $^{\mathrm{137}}$Cs source and the electric field is monitored via the electro-optic Kerr effect. Linearly polarized light is passed through the helium. The Kerr effect then introduces an ellipticity to the polarization that is proportional to the electric field squared. This allows an effective means of field monitoring. Nitrogen has a much stronger response to electric fields. This makes liquid nitrogen an ideal candidate for first tests. First results on the liquid nitrogen tests will be presented.   

Systematic and Statistical Errors Associated with Nuclear Decay Constant Measurements Using the Counting Technique

Typical nuclear decay constants are measured at the accuracy level of 10$^{\mathrm{-2}}$. There are numerous reasons: tests of unconventional theories, dating of materials, and long term inventory evolution which require decay constants accuracy at a level of 10$^{\mathrm{-4}}$ to 10$^{\mathrm{-5}}$. The statistical and systematic errors associated with precision measurements of decays using the counting technique are presented. Precision requires high count rates, which introduces time dependent dead time and pile-up corrections. An approach to overcome these issues is presented by continuous recording of the detector current. Other systematic corrections include, the time dependent dead time due to background radiation, control of target motion and radiation flight path variation due to environmental conditions, and the time dependent effects caused by scattered events are presented. The incorporation of blind experimental techniques can help make measurement independent of past results. A spectrometer design and data analysis is reviewed that can accomplish these goals.   

Environmental gamma radiation in the KATRIN Spectrometer Hall

The KATRIN (KArlsruhe TRItium Neutrino) experiment, presently undergoing final assembly in Germany, will use tritium $\beta$-decay to probe the electron antineutrino mass down to a sensitivity of 0.2 eV/c$^2$ (90\% confidence level). The experimental apparatus has been designed to limit the effect of known and predicted backgrounds near the beta endpoint energy. However, recent commissioning measurements with the main spectrometer have shown that an elusive background source still remains. In this talk, the interaction of environmental gamma radiation inside the KATRIN main spectrometer is studied as a potential background creation mechanism. Geant4 simulations of the gamma flux, derived from concrete radioassay measurements, are compared with detector background rates collected under multiple gamma radiation conditions.