Powered by Indico
v3.2.8
발표제목: Low temperature detector with various molybdate scintillation crystals for 100Mo neutrinoless double beta decay
From the neutrino oscillation observation, physicists have made an effort to figure out the neutrino mass. There are several isotopes of double beta decay. The neutrinoless double beta decay (0 nu beta beta) can occur in case that the neutrino is a Majorana particle. If the (0 nu beta beta) is observed, the neutrino is the Majorana particle and the neutrino mass can be calculated from the (0 nu beta beta) half-life.
The 100Mo is a double beta decay isotope, has a high Q-value (Q=3034 keV) and can be easy to be enriched. Advanced molybdenum based rare process dxperiment (AMoRE) project has an aim to search the (0 nu beta beta) of 100Mo.
A low temperature detector is one of the most developed particle detec- tors. The AMoRE project used Molybdenum based scintillation crystal as a source and a detector by itself . In principle, this “source=detector” tech- nique can provide a detection eciency close to be 100%. The scintillation crystals absorb energy by radioactive decay or interaction, a small portion is emitted as a scintillation light and large portion is going through as a thermal heat into the lattice. The heat is converted to the signal with a low temperature thermometer. We made the low temperature light detector to detect the scintillation light and heat simultaneously at low temperature.The different scintillation light yield following the absorbed particle types, alpha and beta/gamma, which can make the particle discrimination and high (0 nu beta beta) detection efficiency with removing the alpha background events.
The AMoRE-pilot has been finished with 1.9 kg CaMoO4 crystals using 48Ca-depleted calcium and 100Mo-enriched molybdenum. Our final goal is the success of the AMoRE-II with 200 kg target crystals. CaMoO4 crystals have a good energy resolution and high particle discrimination power. Non- hygroscopic CaMoO4 crystals also have an advantages in handling. However the diculty of the crystal growing and purification of the powder require the high costs of time and money for a large scale project. Therefore surveying the other proper Molybdenum based crystal was needed.
We made a small size detector for 1x1x1 cm3 crystal study. Making experimental condition of a few tens mili-Kelvin temperature is relatively easier for the small scale. We made the detector for convenient study of the phonon and scintillation properties of various Molybdate crystals and have successfully studied CaMoO4, Na2Mo2O7 and Li2MoO4 crystals.
From the results of the 1 cm3 crystal, we made R&D set-up for a Li2MoO4 crystal of real experimental size for the next step of the AMoRE project, AMoRE-I. Although the crystal have a hygroscopicity issue, but it has been performed a proper energy resolution and particle discrimina- tion. Even more, the internal background level seems to be lower than 48depCa100MoO4crystals which were used for the AMoRE-pilot.
Thesis Advisor: Prof. Hongjoo Kim