Fission induced in^natTa,^natW and^natPt targets by 69 MeV monochromatic photons

Abstract

A study of photofission on " T a , ""W and ""Pt nuclei induced by monochromatic photons of 69MeV has been performed. The fission yields have been measured by using makrofoil sheets as fission-track detectors, in thick-target 277 geometry. The absolute photofission cross sections for the tantalum, tungsten and platinum targets are found, respectively, to be 4.8-t l.Opb, 5.2-t 1 I p b and 1O-t2pb, and the corresponding deduced fissilities are (3.2 -t 0.7) X (3.4 j: 0.8) X and (6.4 * 1.3) x NUCLEAR REACTIONS ""Ta(y, fission), ""W (7. Iission), and ""'Pt(7, fission) E? = 69 MeV; measured o(fission), deduced fissility.

Bremsstrahlung-induced fission and spallation of the pre-actinide nucleusTa181

“…The obtained measured total fission cross section at 50 MeV is in good agreement with the experimental value of 4.8±1.0 µb from Ref. [5] for photofission of nat Ta induced by 69 MeV monochromatic photons. For the higher energy photons (3500 MeV), the fission yield of the present work agrees well with the value of 0.64±0.06 mb obtained for reaction of bremsstrahlung with endpoint energy of 3770 MeV on 181 Ta [17].…”

“…[3,4,8]. The fissility obtained for bremsstrahlung endpoint energy of 50 MeV is consistent with the trends calculated for photofission on nat Ta induced by monochromatic photons of 69 MeV [5] and for photofission of 181 Ta at an incident monochromatic photon energy of 100…”

“…. The fissility obtained for bremsstrahlung endpoint energy of 50 MeV is consistent with the trends calculated for photofission on nat Ta induced by monochromatic photons of 69 MeV[5] and for photofission of 181 Ta at an incident monochromatic photon energy of 100 MeV[7]. The fissility for the higher endpoint energy (3500 MeV) is in agreement with the systematics of fissilities as a function of Z 2 /A for photofission reactions with Ta targets at intermediate energies up to 6.0 GeV[3].…”

“…Therefore, a large amount of photofission mass-yield distributions has been measured with bremsstrahlung spectra with a continuous energy distribution in the energy range of 300 to 1800 MeV [1][2][3][4]. Related to photofission on heavy nuclei, many works have been performed, with monochromatic photons at intermediate and high-energy regime, using different experimental techniques [5][6][7][8][9]. In these experiments, the photofission cross sections, and related fissility (the ratio of fission cross section to total nuclear photoabsoption cross section), were determined for pre-actinide targets with fissility parameter Z 2 /A < 31.…”

“…At low photon incident energies (≤ 30 MeV), pre-actinide nuclei do not exhibit the resonance pattern characteristic of the giant resonance excitation [2,7]. Although very important for very heavy elements, giant-resonance fission contribution is unimportant for elements with atomic number Z < 83 because of the high fission thresholds (22)(23)(24)(25)(26)(27) MeV [5]) and small values of the parameter Z 2 /A. For nuclei with mass number A < 210 the trends of the photofission cross section show, conversely, an increase of several orders of magnitude, for incident energy from the fission threshold (∼ 20-30 MeV) up to about 200 MeV [7].…”