XXI International Baldin Seminar on High Energy Physics Problems, 2012

The study of basic properties of the ADS presented in the previous Baldin seminar was continued during the 2011-2012. For these experiments, uranium target assembly has been upgraded: the entrance window was created to reduce the albedo of the incident beam and a section was added to keep the effective mass of uranium to the beam axis. The newtarget assembly with a mass of 500 kg of natural uranium metal (diameter ~30cm and length 65cm) as named QUINTA. During the three runs of JINR NUCLOTRON the target assembly (TA) QUINTA was irradiated by deuterons with energies from 1 to 8 GeV and the total number of deuterons on the targetof (3-5) 10^13 for each energy.
The energy spectra of prompt neutrons inside and outside the target assembly and the time spectra of delayed neutrons (DN) between accelerator burstswere measured. Beside that the spatial distributions of fission rates inside TA have been measured with aidof solid state track detectors and independently by activation method. The last method was used for measurements of 239Pu nuclei production. All these measurements were made with the original TA QUINTA as well as with TA surrounded by a 10 cm thick lead blanket.
Total numbers of fissions and produced 239Pu nuclei were obtained by integration over QUINTA volume and normalized to one incident deuteron and one GeV. Both these numbers were constant within experimental errors of about 15 % for the deuteron energy range (1-8) GeV. In measurements with a lead blanket the absolute amount of produced 239 Pu nuclei increased by about 50% but staying constant in studied deuteron energy range, while the numbers of fissions remained virtually unchanged The group analysis of DN time spectra indicates a growth in the average energy of the neutrons initiating fission of target nuclei from 15 to ~ 40 MeV with an increase in energy of the incident deuterons from 1 to 8 GeV. This result should be verified by experiments planned at the end of 2012.