Product yields for the photofission ofU238with 12-, 15-, 20-, 30-, and 70-MeV bremsstrahlung

Abstract

the photofission of '"U with 12-, 1S-, 20-, 30-, and 70-MeV bremsstrahlung. Changes in the characteristics of the mass distribution are studied. An enhanced yield in the mass region 133-134, decreasing with increasing end-point energy of the bremsstrahlung {E, ), is observed. From the determined independent yields the most probable charges Z (F. ,) are calculated using the value 0.8S for the width parameter c of the charge distribution as deduced from our results for mass chain 134. The determined Z (F. ,) values are very we11 described by the empirical relation of Nethaway except for the mass chain 136. This discrepancy for mass chain 136, which decreases with increasing end-point energy of the bremsstrahlung, is attributed to an abnormal low yield of " Cs. Fragment shell effects are discussed. From the isomeric ratios for ' 'Teg-' 'Te and ' P-' I average initial fragment spins are calculated using a statistical model analysis. NUCLEAR REACTIONS, FISSIONU(y', E), Ey m~=12, 15, 20, 30, 70 MeV; measured: fragment p-ray spectra; deduced: mass distributions, most probable J charges, isomeric ratios, average initial fragment spins.

Delayed neutron yields and spectra from photofission of actinides: data and calculations with Bremsstrahlung photons below 20 MeV

“…At this step, some experimental fission mass distributions are available to be compared to predicted ones. In figure 7, 235 U mass yields show a good agreement with Jacobs and Thierens data [11][12][13]. Similar quality is also obtained for 238 U, 237 Np and 239 Pu.…”

CTOF measurements and Monte Carlo analyses of neutron spectra for the backward direction from a lead target irradiated with 200–1000 MeV protons

“…30 shows examples of fission cross sections for proton-induced reactions on 186 Another example of some problems of the fission model of GEM2 based on systematics of measured data is shown in Fig. 31 for fragment mass distributions from several reactions induced by bremsstrahlung with the maximum energy E 0 of 15, 20, 30, and 70 MeV on 235 U and 238 U targets measued in [177] compared with results by CEM03.02 [63]. We see that the fission model of GEM2 used in our CEM03.02 describes surprisingly well these mass distributions of fission fragments at E 0 = 15, 20, and 30 MeV, where experimentasl data were available to fit the mass distribution of fission fragments in the GEM2 systematics, but fails to reproduce correctly such distribution at E 0 = 70 MeV, requiring an additional refitting of the GEM systematics at this energy to improve the agreement with the data.…”

Electromagnetic and nuclear fission of238U in the reaction of 100, 500, and 1000 A�MeV208Pb with238U

“…The fragment mass distribution was taken from [6], and the kinetic energy of the fragments was calculated according to the Viola systematics [7]. The parallel-momentum transfer to the 238U nucleus was taken as zero, and the perpendicular-momentum transfer distribution was calculated by using the Weizs~icker-Williams method described for example in [8], on the assumption that both 2~…”