The unveiling of neutrino oscillation from observing the change in solar neutrino flux triggered physicists’ interest in studying the nature of the neutrino mass. The prevailing theory of explaining the tiny neutrino mass is called the “see-saw” mechanism, which postulates that the neutrino flavor eigenstate is the mixing between mass eigenstate of active neutrinos of a small mass and (left-) right-handed “sterile” (anti-)neutrinos of a large mass. The sterile neutrino is believed to be a new physics beyond the Standard Model, which can explain many other outstanding physical problems, like warm dark matter, asymmetry of baryon, etc. The HUNTER (Heavy Unseen Neutrinos from the Total Energy-momentum Reconstruction) experiment is a collaboration for searching for keV-mass range sterile neutrinos, and brings together an interdisciplinary team of researchers from Temple University, UCLA, Princeton University and the University of Hustonto develop an apparatus capable of searching for sterile neutrinos with high precision.
In the HUNTER proposal, the radiation source generating neutrinos will be a cloud of atoms laser cooled and suspended by laser beams, the decay products except neutrinos will be detected by corresponding detectors, and their initial vector momenta will be reconstructed from the data recorded by the corresponding detectors. The missing mass in the decay, taken away by the neutrino, can then be evaluated from the energy and momentum conservation. The radiation sources of electron-capture decay are preferred for laboratory neutrino experiments because of the absence of energetic electrons in the decay products. 131-Cs is chosen by HUNTER to study the sterile neutrino mass and the mixing between sterile neutrinos and active neutrinos because of its short lifetime, simply decay products, and its alkali element spectral structure which enhances laser cooling and trapping.
The Phase 1 HUNTER experiment targeting sterile neutrinos in the range 20-300 keV/c^2 requires the design of spectrometers with momentum resolution of a part in a thousand or better. To detect a 131-Xe ion, a spectrometer consisting of numbers of annular electrodes has been designed. The potentials of the electrodes of the ion spectrometer were carefully optimized to form an electrostatic lens, with time focusing and spatial focusing to achieve a high momentum resolution for ions despite the extended source presented by the magneto-optical trap. The optimization algorithm presented in this dissertation achieves a momentum precision of ∼0.12% (∼0.03%) for the high acceptance (high resolution) tune.
An electron spectrometer was designed without “double focusing” for detecting the electrons produced in 131 Cs decays. The electron trajectories are guided by a uniform electric and magnetic field. An octagonal shaped, magnetic shield was designed to diminish the influence of external magnetic fields on the electron trajectories. The achieved electron momentum resolution is ∼0.1 keV including extended source effects, sufficient for the desired missing mass resolution.
Other issues like the systematic errors of the ion spectrometer and the eddy current induced in the electrodes by periodically switching on/off the anti-Helmholtz coils of the magneto-optical trap were studied. The deformation of the spectrometer under its gravity was simulated using Autodesk Inventor. / Physics
| Identifer | oai:union.ndltd.org:TEMPLE/oai:scholarshare.temple.edu:20.500.12613/6592 |
| Date | January 2021 |
| Creators | Yu, Xunzhen |
| Contributors | Martoff, Charles Jeffrey, Metz, Andreas, Surrow, Bernd, Stanley, Robert J. |
| Publisher | Temple University. Libraries |
| Source Sets | Temple University |
| Language | English |
| Detected Language | English |
| Type | Thesis/Dissertation, Text |
| Format | 143 pages |
| Rights | IN COPYRIGHT- This Rights Statement can be used for an Item that is in copyright. Using this statement implies that the organization making this Item available has determined that the Item is in copyright and either is the rights-holder, has obtained permission from the rights-holder(s) to make their Work(s) available, or makes the Item available under an exception or limitation to copyright (including Fair Use) that entitles it to make the Item available., http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | http://dx.doi.org/10.34944/dspace/6574, Theses and Dissertations |
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