151Sm Sample Clauses

151Sm. A 151Sm source was electrodeposited on a 10 µm thick silver foil. The resulting samarium oxide/hydroxide layer was blackish and was considered not to be ideally thin. Therefore, the mechanical processing consisting in repeated folding and laminating of the metal foil with the radioactive material, as described in section 5.6, was applied to the silver foil with the 151Sm source. A piece with an expectred activity of ~ 7 Bq (0.8 mm × 0.8 mm × 7 µm) was cut from this source foil and was sandwiched between two silver foils (0.9 mm × 0.9 mm × 15 µm each) and the three foils were diffusion-welded to form the absorber (heat capacity: 29 pJ/K at 20 mK). Figure 30 shows the silver absorber containing the 151Sm source on the MMC chip together with the SQUID chip. The performance of the MMC during this measurement was as expected. An energy resolution ranging from about 45 eV (FWHM) at 6 keV to 70 eV at 25 keV and an energy threshold of 250 eV were observed. It should be mentioned here that under optimal conditions the energy resolution of an MMC is nearly energy-independent since it is only limited by noise. Various effects like temperature fluctuation of the thermal bath can, however, add some energy-dependent terms. The thermal time constant (1/e) of the detector was 460 µs; at a count rate of 8.7 s-1, the fraction of piled-up pulses was very low. After 14 days of data acquisition, the final spectrum contains 10.2 million events. 151Sm is the only non-pure beta emitter measured within the MetroBeta project: It has a main - decay branch (Q = 76.3 keV) to the ground state and a second - decay branch to the 21.54 keV excited level of 151Eu. Both transitions are first forbidden non-unique. The recommended values for the respective probabilities of the two decay paths are