STABILITY OF HALL SENSORS BASED ON THE GOLD AND MOLYBDENUM NANOFILMS IRRADIATED BY THE REACTOR NEUTRON FLUXES

Abstract

It was investigated experimentally the influence of long-term neutron irradiation up to the fluence of ~ 1024 n∙m-2 on Hall sensors made on the basis of gold and molybdenum nanofilms, that are intended for application in the plasma’s magnetic diagnostic systems of the new-generation steady-state fusion reactors of the ITER and DEMO type. The experiment was carried out in the irradiation channel #3 of the research nuclear fast neutron reactor IBR-2. The neutron flux intensity at the samples location was ~ 1.5×1017 n∙m-2∙s-1, the samples temperature was (130 ± 5) °C. During the irradiation it was carried out, the in-situ measurement of the sensors’ current-related sensitivity with the using of specially designed control electronics. For both types of samples, throughout the experiment, the sensitivity remained stable within the measurement error. For gold sensors, the sensitivity dependence on fluence has no signs that indicate the material degradation at further irradiation. For molybdenum sensors, there is a tendency of the sensitivity change in the high fluences range, which however does not correlate with the results of other authors regarding the neutrons influence on the electrophysical parameters of molybdenum. Therefore, such change may be connected with the rearranging of crystalline structure of molybdenum during long-term exposure at elevated temperature and/or with the atmosphere effect of it. The sensitivity stability under neutron irradiation, as well as the high thermal stability of gold and molybdenum, make Hall sensors based on these metals compatible with the severe operating conditions of magnetic field sensors in the plasma’s magnetic diagnostic systems of ITER and DEMO.