Photofission fragment characteristics of 234, 238U and 232Th in the barrier region

The bremstrahlung induced fission of 234, 238U and 232Th has been studied at the superconducting Darmstadt linear accelerator (SDALINAC) in the excitation energy region close to the fission barrier. In this contribution results on the fission fragment mass, total kinetic energy (TKE) and angular distributions will be presented. Fission fragment mass and TKE distributions from 234U were studied for the first time in this energy region. The results have been analyzed in terms of fission modes and a dominant yield of the mass asymmetric standard-2 mode was found in all studied nuclei. No strong dependence of the fission mode weights on the excitation energy of the compound nucleus were found. Correlations between mass, TKE and angular distributions have been investigated in 234U and 232Th. A correlation in form of an increased anisotropy for far-asymmetric masses and low TKE were found in both fissioning systems. A possible interpretation of this correlation in terms of fission modes is discussed

Recent developments for an active UF6 gas target for photon-induced fission experiments

Recent developments for an active uranium-hexafluoride-loaded gas target as well as results on the detector gas properties are presented. The gas of choice is a mixture of argon with small amounts of UF6. This contribution presents the experimental setup and focusses on the electron drift velocity with increasing UF6 content. A time-dependent decrease in electron drift velocity is observed in our setup.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Time response and its impact on prompt fission

The time dependence of prompt $$\gamma$$-ray spectral characteristics, in particular the multiplicity, was studied during the first 10 ns after the spontaneous fission of $${}^{252}$$Cf. The impact of prompt window and experimental time resolution on the determination of prompt multiplicities is assessed and described mathematically. As a consequence we are able to offer corrections that allow a reliable comparison of results from different measurements. An apparent discrepancy between a theoretical and an experimentally found time dependence is explained by the influence of a finite experimental timing resolution as well as the choice of the prompt timing window

Recent developments for an active UF 6

Recent developments for an active uranium-hexafluoride-loaded gas target as well as results on the detector gas properties are presented. The gas of choice is a mixture of argon with small amounts of UF6. This contribution presents the experimental setup and focusses on the electron drift velocity with increasing UF6 content. A time-dependent decrease in electron drift velocity is observed in our setup

Particle emission angle determination in Frisch grid ionization chambers by electron drift-time measurements

The double kinetic energy measurement of fission fragments with a double-sided Frisch grid ionization chamber allows a careful determination of the emission angle, which is essential in order to apply appropriate energy-loss corrections. We present a drift-time method, which uses the time that free electrons need to drift from the location of their creation, e.g. by a fission fragment in the counting gas, to the grid, before inducing a signal on the anode. Such a measurement leaves energy and angular information fully decoupled. We demonstrate the applicability of the drift-time method for the example of the 234,238U (g, f) reactions performed at the superconducting Darmstadt electron linear accelerator. The angular resolutions achieved with this method are comparable to those obtained with other methods