0000000000021426
AUTHOR
Gerd Marissens
Smallest KnownQValue of Any Nuclear Decay: The Rareβ−Decay ofIn115(9/2+)→Sn115(3/2+)
The ground-state-to-ground-state Q_{beta;{-}} value of ;{115}In was determined to 497.68(17) keV using a high-precision Penning trap facility at the University of Jyvaskyla, Finland. From this, a Q_{beta;{-}} value of 0.35(17) keV was obtained for the rare beta;{-} decay to the first excited state of ;{115}Sn at 497.334(22) keV. The partial half-life was determined to 4.1(6) x 10;{20} yr using ultra low-background gamma-ray spectrometry in an underground laboratory. Theoretical modeling of this 2nd-forbidden unique beta;{-} transition was also undertaken and resulted in Q_{beta;{-}} = 57_{-12};{+19} eV using the measured half-life. The discrepancy between theory and experiment could be attr…
Search for the radioactivity of 180mTa using an underground HPGe sandwich spectrometer
Abstract The radioactivity of 180m Ta has never been detected. The present attempt to detect it was carried out using a newly developed HPGe sandwich spectrometer installed 500 m water equivalent underground in the HADES laboratory. The sample consisted of 6 discs of tantalum of natural isotopic composition with a total mass of 1500 g and a total mass for 180 Ta of 180 mg. The sample was measured for 68 days and the resulting lower bound for the half-life of 180m Ta was 2.0×10 16 y, which is a factor of 2.8 higher than the previous highest value.
Low-level gamma-ray spectrometry for analysing fusion plasma conditions
Abstract A new method, combining activation by neutrons and charged particles with ultra low-level gamma-ray spectrometry, aimed at obtaining a better understanding and more adequate measurements of MeV particle leaks in magnetic fusion devices was studied here. A total of 36 samples containing Ti, LiF, B 4 C and W were placed in a boron-nitride holder mounted on the ceiling of the JET Tokamak. The samples were activated by 63 pulses from a D– 3 He plasma and were later measured using underground gamma-ray spectrometry. The radionuclides 7 Be, 46 Sc, 54 Mn, 56 Co, 57 Co, 58 Co, 124 Sb, 181 Hf, 182 Ta, 181 W and 185 W were detected in several of the samples, with very low levels of activity …