High-energy neutron-radiation reference field

Abstract

The technique and results of measurements performed of the neutron spectrum behind the top shielding of the U-70 experimental hall using a Bonner spectrometer based on indium and carbon activation detectors are presented. The integral characteristics of the neutron field are presented; such a field could be useful in various areas of dosimetry, radiation physics, and radiobiology, in assuring radiological safety during flights in airplanes and in space, as well as in the study of malfunctions induced in microelectronics by high-energy neutrons.Low-energy reference neutron-radiation fields [1] were produced at the Institute of High-Energy Physics (IFVE) in the 1990s on the basis of 239 Pu-Be and 252 Cf radionuclide sources for the purpose of simulating the low-energy neutron spectra behind the shielding of the U-70 proton synchrotron at 70 GeV and for calibrating dosimetric apparatus. Subsequent measurements of the spectra showed that high-energy neutrons make a considerable contribution behind the top concrete shielding of the U-70 experimental hall [2]. This has led to the practical necessity of developing high-energy neutron fields with stable spectral characteristics for testing radiation monitoring detectors as well as for applications in other applied problems. Specifically, high-energy reference fields which were produced as part of the scientific program of the European Union "Radiological Safety of Flying in Airplanes" for simulating neutron spectra generated by cosmic rays in the atmosphere at altitude ~10 km, have been widely used at CERN since 1993.The problem of radiological safety of flying arose after ICRP Publication No. 60 [4] was released. According to this publication the irradiation dose limit to the general public is lowered to 1 mSv/yr, as a result of which the airplane crew entered the category of professionally irradiated personnel. The conceptual changes in the system of dosimetric quantities and dose limits are also reflected in the domestic radiological safety norms (NRB-99) [5]. Aside from radiological safety problems, high-energy neutron reference fields are a tool for studying various effects, including malfunctions of electronic equipment exposed to high-energy hadrons; this problem is becoming increasingly urgent under conditions of flights in space and in the atmosphere; such fields are also a tool for experiments in modern high-energy accelerators.At the IFVE a high-energy reference field can be created in an experimental hall behind the shielding of the U-70 proton synchrotron. The eastern section of the top shielding is most suitable for this; here, the No. 58 (RM-58 below) automated radiation monitoring system is used to monitor the dose rate of the neutron radiation. The maximum neutron dose rate 0.5-1 mSv/h in the experimental hall has been observed in this section for many years at times when the accelerator was operating. This region of the top protection is closest to the interior targets of the ring hall of the accelerator; the secondary radiation from these targets larg...

Photon detection efficiency of a germanium semiconductor spectrometer

“…The geometry of the Marinelli polyethylene vessel with a volume of 1 L, which was filled with graphite with a density of 1.7 g/cm 3 , was considered. The 12 С(n, 2n) 11 С reaction with a threshold of 20 MeV is widely used in experimental studies behind the shield of the IHEP synchrotron, in particular, in measurements of high energy neutron spectra [11]. The performed cal culations of the photon detection efficiency allow one to increase the measurement accuracy using a carbon detector in the Marinelli vessel geometry.…”