The photofission yields of Bi, Pb, Au and Pt induced by a coherent bremsstrahlung beam from 1000 MeV electrons striking a diamond single crystal have been measured. The experiment has been performed at sixteen different energies of the main peak of the photon spectrum, in the energy range between 220 MeV and 500 MeV, by detecting the fission fragments with glass sandwiches. All the photon spectra have been measured simultaneously to the exposures of the fissionable samples by means of a magnetic pair spectrometer and a real-time acquisition system with an on-line computer. An appropriate unfolding method was developed in order to deduce the behaviour of the photofission cross-section from the experimental yields. The estimated cross-section curves clearly show a first resonance at a photon energy of about 320 MeV with a FWHM ≈125 MeV, whilst there is only a hint of a second broad resonance centred at k≈750 MeV. The very good agreement between the position of the first resonance put in evidence in the present experiment and the energy of the first baryon resonance in the pion photoproduction is attributed to a predominance of the photomesonic mechanism in the photofission process of the investigated elements.
Fission of Bi, Pb, Au and Pt Induced by a Coherent Photon Beam from 1000 MeV Electrons
BELLINI, Vincenzo;
1976-01-01
Abstract
The photofission yields of Bi, Pb, Au and Pt induced by a coherent bremsstrahlung beam from 1000 MeV electrons striking a diamond single crystal have been measured. The experiment has been performed at sixteen different energies of the main peak of the photon spectrum, in the energy range between 220 MeV and 500 MeV, by detecting the fission fragments with glass sandwiches. All the photon spectra have been measured simultaneously to the exposures of the fissionable samples by means of a magnetic pair spectrometer and a real-time acquisition system with an on-line computer. An appropriate unfolding method was developed in order to deduce the behaviour of the photofission cross-section from the experimental yields. The estimated cross-section curves clearly show a first resonance at a photon energy of about 320 MeV with a FWHM ≈125 MeV, whilst there is only a hint of a second broad resonance centred at k≈750 MeV. The very good agreement between the position of the first resonance put in evidence in the present experiment and the energy of the first baryon resonance in the pion photoproduction is attributed to a predominance of the photomesonic mechanism in the photofission process of the investigated elements.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
