On the decay of compound nuclei following alpha-particle and12C induced reactions

Multiple coincidence rates have been measured using a detector system consisting of a Ge(Li) spectrometer and eight NaI(Tl) or eight liquid scintillators. Reactions induced byα-particles with energies of 51–55 MeV and 118 MeV12C ions are studied. The data are analysed to give the first and second central moments of the distribution of the number ofγ-rays feeding individual levels in the final nuclei. When these numbers are compared to spin distributions calculated with the statistical model code GROGI the relative importance of dipole and quadrupole deexcitation modes can be ascertained. In particular, in the122Te(α, 4n)122Xe reaction theγ-decay prior to the entry into the ground band is we…

WITHDRAWN: A scintillator based time-of-flight hodoscope with a new type of emitter follower divider

Design and commissioning of the GSI pion beam

We describe the design of the secondary pion beam-line installed at the SIS 18Tm synchrotron at GSI, Darmstadt, and discuss the commissioning results. The experiments were performed with proton and C-12 primary beams at several energies using beryllium production targets. Pion yields in a momentum range between 0.4 and 2.8 GeV/c were identified, At the highest primary beam energies of 3.5 GeV for proton and 2.0 A GeV for carbon ions, the latter beam produces the highest low-momentum pion yield while at momenta of 1.5 GeV/c the yields are comparable and at 2.8 GeV/c the proton beam is superior. A momentum resolution of around 0.5% is achieved and the time resolution (a) ranges from 100 to 15…

High spin shell model excitations in149Gd

The high spin level structure of the three-neutron nucleus149Gd has been investigated by in-beamγ-ray and electron spectroscopy with (α, xn) reactions. The observed levels are characterized as members of the shell model multipletsνf 7 2/3 ,νh 9/2 f 7 2/2 ,νf 7 2/3 ×3−,νh 9/2 f 7 2/2 ×3−, and tentativelyνf 7 2/3 ×(3−)2. The energies of theν f 7 2/3 states agree only moderately with those calculated using empirical two-nucleon interactions taken from148Gd, which indicates the importance of long range contributions already atN=85.

A scintillator based time-of-flight hodoscope with a new type of emitter follower divider

A high precision, time-of-flight hodoscope has been constructed to analyse the secondary pion beam at GSI, Darmstadt. The hodoscope comprises three scintillator planes with the individual scintillator rods read out by photomultipliers in both ends. A new active base of the emitter follower type has been developed for stabilization of voltages at the last dynodes of the photomultiplier. The time resolution of this system was found to be sigma less than or equal to 150 ps for counting rates up to 2 MHz.