Browsing by Subject "Beta decay"

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Bremsstrahlung intensity distributions of pure beta-emitting isotopes
(2006-05) Reinert, Dustin Ray, 1982-; Biegalski, Steven R.
Experiments have been conducted to assess the bremsstrahlung continuum produced when the beta particles from ³⁶Cl and ⁸Li are incident upon metallic shields. The combination of the high energy beta decay and the high atomic numbered metals used in piping for ⁷Li liquid metal nuclear reactor coolants is a scenario in which bremsstrahlung production may be a principal shielding concern. A series of fast pneumatic activation experiments have been performed to obtain the spectral distributions of bremsstrahlung photons transmitted when ⁸Li beta particles are shielded by stainless steel. Experimental results agree well with the electron transport and bremsstrahlung production models utilized in the MCNP code.
From atoms to astronomy : new approaches in neutrino physics
(2010-08) Jerkins, Melissa Travis; Raizen, Mark G.; Klein, Joshua; Keto, John; Lang, Karol; Komatsu, Eiichiro
In this thesis I present research in neutrino physics utilizing tools from both atomic physics and astrophysics. Recent advances in atomic physics enable a new type of beta decay experiment to measure the absolute mass scale of the neutrino using a sample of ultracold atomic tritium. These initial conditions enable the detection of the helium ion in coincidence with the beta. I construct a two-dimensional fit incorporating both the shape of the beta spectrum and the direct reconstruction of the neutrino mass peak. I present simulation results of the feasible limits on the neutrino mass achievable in this new type of tritium beta decay experiment. The same advances in atomic physics that enable the creation of an atomic source for tritium beta decay also suggest a new method of achieving large-scale isotope separation. Multiple experiments that are investigating the absolute mass scale of the neutrino through neutrinoless double beta decay could benefit from this new technique, which applies generally to many elements, including the double beta emitter Nd-150 that is particularly difficult to separate in large quantities. The method is based on an irreversible change of the mass-to-magnetic moment ratio of a particular isotope in a supersonic atomic beam, followed by a magnetic multipole whose gradients deflect and guide the atoms. I present numerical simulations of isotope separation for a range of examples and demonstrate that large-scale isotope separation should be possible using ordinary inexpensive magnets and the existing technologies of supersonic beams and lasers. Additionally I report results from a search for low-multiplicity neutrino bursts in the Sudbury Neutrino Observatory (SNO). Such bursts could indicate detection of a nearby core-collapse supernova explosion. The data were taken from November 1999 to May 2001 when the detector was filled with heavy water (Phase I), as well as data from July 2001 to August 2003 when NaCl was added to the detector (Phase II). The search was a blind analysis in which the potential backgrounds were estimated and analysis cuts were developed to eliminate such backgrounds with 90% confidence before the data were examined. The search maintained a greater than 50% detection probability for standard supernovae occurring at a distance of up to 60 kpc for Phase I and up to 70 kpc for Phase II. No low-multiplicity bursts were observed during the data-taking period.
Search for neutrinoless double beta decay of Cd-116 with the NEMO-3 experiment
(2010-08) Pahlka, Raymond Benton; Lang, Karol; Ritchie, Jack; Kopp, Sacha; Hoffmann, Gerald; Aziz, Adnan
This dissertation describes the approach taken in measuring two neutrino double beta decay of Cd-116 to the ground state of Sn-116 and in searching for the effective Majorana neutrino mass by placing a lower limit on the half-life for neutrinoless double beta decay of Cd-116 using the powerful technique of a combined tracking chamber and calorimeter with the NEMO-3 detector. The description of the detector, its natural background contamination, and the tools used to perform the analysis are discussed. The single electron channel was used to identify source foil contamination from [beta]-emitters and the electron-gamma channel was used to confirm the previous measurements of Tl-208 and Bi-214 contaminations in the source foil. Using these backgrounds, the two neutrino double beta decay half-life of Cd-116 was measured for the single states dominance hypothesis and the higher states dominance hypothesis. The final data set was defined to be data from Phrase One and Phase Two for the medium and low activity regions. Using 1471 days of data, the values of the half-life for the single data dominance hypothesis and the higher states dominance hypothesis were found.
Search for neutrinoless double beta decay of ¹¹⁶Cd and ⁸²Se and calorimeter simulations for the SuperNEMO experiment
(2014-05) Liptak, Zachary John; Lang, Karol, 1955-
Using the NEMO-3 detector, 410.4 g of ¹¹⁶Cd with a total exposure of 1.65 kg• y and 932 g of ⁸²Se with a total exposure of 3.75 kg• y were used to measure the half-life of two-neutrino double beta decay (2[nu][beta][beta]) to the ground states of ¹¹⁶Sn and ⁸²Kr and to place a lower limit on the neutrinoless double becay decay (0[nu][beta][beta]) to the same ground states. Under the single-states dominance hypothesis, the 2[nu][beta][beta] half-lives are found to be T 1/2(¹¹⁶Cd) = (2.90 ± 0.03(stat) ± 0.15(syst)×10¹⁹ yr and T 1/2(⁸²Se) = [10.62±0.11(stat)±0.56(syst)]×10¹⁹ yr. 0[nu][beta][beta] is excluded to 90% confidence level at T 1/2 ≥ 1.12 × 10²³ yr for ¹¹⁶Cd and T 1/2 ≥ 3.90 × 10²³ yr for ⁸²Se. These half-lives correspond to effective Majorana neutrino masses of m ≤ (4.33 - 5.54) eV and m ≤ (2.28 - 2.82) eV, respectively, in the light Majorana exchange mechanism.