A consistent description of the nuclear α-decay process
The essential features of a new theory of α decay and the need for such a theory are reviewed. An approximate relationship between half life and α-particle energy is deduced and checked for the decay of even polonium isotopes. Detailed calculations of one-body widths and spectroscopic factors for the polonium decays are presented and the implications of the results are discussed. It is also shown that the result for the α decay of 212Po is consistent with the reverse α-transfer reaction.
A comparison of α-transfer and α-decay in the lead region
Abstract Differential cross sections have been measured for the 204, 207, 208 Pb( 16 O, 12 C) 208, 211, 212 Po and 209 Bi( 16 O, 12 C) 213 At ground state transitions at a bombarding energy of 93 MeV; the cross section leading to the first excited state of 212 Po was also measured. These data were quantitatively compared with the corresponding α-decay data via R -matrix theory using the same target-plus-α nuclear potential. Good agreement between the absolute reduced widths determined from α-transfer and α-decay suggests that in the transfer reactions, as in α-decay, an α-particle in its ground state is transferred in a one-step process.
rPET detectors design and data processing
Small animal PET systems based on rotating planar detectors posses some interesting advantages for high sensitivity, high resolution imaging. We have designed the rPET detectors based on MLS crystals assembled on a 30times30 matrix optically coupled to a flat-panel PS-PMT. Weighted position readout circuits pre-process the 64 signals from the 8times8 anodes matrix, which are digitized using a charge-integrating converter. The amplification electronics, including the trigger output for coincidence detection, and the high voltage supply are integrated in a three PCBs stack that forms the base attached to the back of the PMT. The whole assembly is enclosed in a light tight, lead (Pb) shielded aluminum box. The detectors are mounted on a rotating gantry with more than 180 degrees rotation span. The digitized events are screened and histogramed, and a modified center of gravity algorithm removes from the position calculation those signals with poor signal to noise ratio. Apparent mean crystal size on the 511 keV field-flood images is 0.6 mm, mean peak-to-valley ratio is better than 8, and intrinsic resolution is 1.5 mm at the central row, with the energy window wide open. Sensitivity (CPS) for a pair of these detectors set in coincidence at 160 mm distance is 1%