저온검출기 기반 핵분광 연구: Nuclear Spectroscopy Study Based on Low-Temperature Detectors

by Yong Sik Jang (Ph.D Candidate)

Monday Nov 12, 2012, 4:50 PM → 5:40 PM Asia/Seoul

216-1호 (제1과학관)

Research on low-temperature detectors has been motivated primarily by particle physics and astrophysics, mainly because their energy sensitivities and thresholds are beyond the limit of conventional semiconductor-based detectors. Over the past few decades, remarkable improvements in low-temperature detectors have been achieved in terms of their energy resolution in many applications related to the detection and measurement of radiation. Temperature sensors such as Transition Edge Sensors (TESs) and Metallic Magnetic Calorimeters (MMCs) have been a major driving force behind the successful development of low-temperature detectors. In the present experiment, a MMC was used for an accurate measurement of the temperature change due to radioactive decay in conjunction with a gold foil absorber.
We developed alpha spectrometers using MMCs. The detector performance was investigated with an 241Am source. A comparison of the signal sizes for alpha and gamma peaks, showing a large difference in the energy level, demonstrated that the detector had good linear behavior. The energy resolution in the present experiment is the best resolution reported for alpha particles from 241Am.
Also, we established Q spectroscopy, a novel method for the study of alpha decay, by combing a 4π steradian detection scheme with a low-temperature detector. An enclosed metal absorber guarantees absolute measurement of the radioactivity without a loss of energy in the source and absorber. The samples used in the current investigation were commercially available plutonium isotopes and 226Ra contained in a solution. The plutonium isotopes were readily identified in the Q spectrum and two clear peaks were observed for 239Pu and 240Pu. The peaks corresponding to 226Ra, 222Rn, and 218Po were also easily identified by comparing their relative sizes with their expected Q values. However, the energy resolution of the method was affected by the low-energy tail of the spectrum at the left-hand side of the peak. Slow heat release to the absorber due to heat flow mechanisms is discussed here to explain the low-energy tailing effect.

Thesis Advisor: Prof. Hyeong-Cheol Ri