Research on isomer decay with the NEPTUNE spectrometerS. Oberstedt1, A. Oberstedt2, A. Plompen1, V. Semkova1, G. Lövestam1 and M. Gawrys3
1 EC-JRC Institute for Reference Materials and Measurements, 2440 Geel, Belgium
2 Department of Natural Sciences, Örebro University, 70182 Örebro, Sweden
3 Department of Fundamental Physics, Chalmers University of Technology, 41296 Göteborg, Sweden
Published online: 21 May 2008
A new spectrometer has been built at the EC-JRC IRMM to investigate isomer decay in the millisecond range and activation cross sections of isotopes, where isomeric states exist and are populated. The spectrometer is equipped with high-resolution gamma-ray detectors and an ionisation chamber for the measurement of charged particles, e.g., fission fragments. NEPTUNE provides pulsed quasi mono-energetic neutrons at pulse repetition frequencies up to 5 kHz and tuneable neutron pulse widths ranging from 10 µs into the ms-region. For this purpose a beam chopper based on a parallel-plate capacitor has been integrated into the accelerator beam line in order to deflect the charged-particle beam onto a tantalum beam dump. First research has been performed with the NEPTUNE spectrometer dedicated to the shape isomer search in the odd-A uranium isotopes 235U, 237U and 239U. In further experiments the population of long-lived spin isomers was investigated.
© CEA 2008