Measurement of neutron induced fission of ²³⁵U, ²³³U and ²⁴⁵Cm with the FIC detector at the CERN n_TOF facility

Abstract

Abstract.A series of measurements of neutron induced fission cross section of various TRU isotopes have been performed at the CERN n TOF spallation neutron facility, in the energy range from thermal to nearly 250 MeV. The experimental apparatus consists in a fast ionization chamber (FIC), used as a fission fragment detector with a high efficiency. Good discrimination between alphas and fission fragments can be obtained with a simple amplitude threshold. In order to allow the monitoring of the neutron beam and to extract the n TOF neutron flux, the well known cross section of the 235 U(n,f) reaction, considered as a fission standard, has been used. Preliminary results for the cross section are shown for some selected isotopes such as 235 U, 233 U and 245 Cm in the energy range from 0.050 eV to about 2 MeV.

CERN antiproton target: Hydrocode analysis of its core material dynamic response under proton beam impact

“…After 2016 a new upgrade of the CERN AD facility is planned, including an optimized redesign of the full antiproton production system in order to enhance its performance, reliability as well as to guarantee the continuity of the antiproton physics for the next 20 years [7][8][9].The present configuration of the CERN antiproton target dates back to the late 1980s and it was obtained after more than 10 years of iterations and improvements of the material choice and conceptual designs. Copper, tungsten, rhenium and iridium were employed during this decade.…”

“…This energy deposition map is then applied as an internal energy load to the commercial hydrocode ANSYS AUTODYN® via an internal user subroutine and the user function EXSIE3. The energy is applied consistently with the PS beam parameters, whose proton beam is composed by 4 proton bunches spaced by 105 ns, bunch length of 30 ns for a total pulse intensity of 1.5 × 10 13 protons per pulse [9]. The total energy deposited in the target core is approximately 1.34 kJ, which results in 11.17 GW considering that it is deposited only in 120 ns.…”

Simultaneous measurement of the neutron capture and fission yields of 233U

“…One can see a perfect agreement between Guber's data [14] and Calviani's data [15] in the energy range of interest but slighly above Weston's [2] and ENDF/B-VII [10] for neutrons energies above ≈100 eV. On the contrary Cao's data [13] above around 500 eV gives the lowest cross section.…”

“…This factor has also been taken into account to derive the capture cross section. Figure 4 shows a comparison between our scaled fission cross section (in black) and the ones given by Weston et al [2] (in red) measured at RPI facility, Cao et al [13] (in cyan) measured at GELINA, Guber et al [14] (in blue) recently measured at ORELA, Calviani et al [15] (in magenta) recently measured at CERN by using a fission chamber, togheter with the latest ENDF/B-VII [10] (in green) evaluation, for neutrons incoming energy below 20 eV. The overall agreement between all datasets is excellent.…”

Neutron resonance spectroscopy at n_TOF at CERN

“…Two Fission Ionization Chambers (FIC) have been developed for use at the n TOF facility using deposits of fissile isotopes on 100 µm thick aluminum foils. The FIC-0 detector was used for the low activity samples while the FIC-1 detector was used for the samples with higher activity [41].…”