There has been investigated the capacitance of silicon micro pixel avalanche photodiodes (MAPD 3N) with deeply buried pixels under the effect of weak AC signal of different frequency (from 10 kHz to 1 MHz). A decreasing of the barrier capacitance with an increasing of AC signal frequency has been observed when small DC bias voltage (0-3 V) is applied to the structure. With the rise of voltage the observed dependence weakens and further saturates. It is established that capacity behavior like this within small voltage is referred to the peculiarity of MAPD structure under the investigation: presence of matrix of n +-regions between two epitaxial layers of p-type conductivity results in the appearance of some effective resistance between these layers connected in series with the measured capacity depending on AC signal frequency. The calculated values of ionized acceptor concentration from the slope of the dependence C-2 (U bias) in epitaxial layer are: N A1 = (2.4 ±0.3)•10 20 m-3 for U bias up to 3 V, N A2 = (1.08±0.05)•10 21 m-3 for U bias from 3 to 10 V and N A3 = (2.13±0.27)• 10 21 m-3 for U bias from 10 to 20 V respectively.

No abstract

The development of nuclear technologies, the production and active use of radioisotopes, and the production of radiopharmaceuticals, medical isotopes and other radioactive materials are increasing every year. Therefore, the importance of ensuring the safety of highly active isotopes, as well as providing the necessary instruments for measuring and identifying radioactive materials, must be taken into account. Modern equipment such as high purity germanium detectors (HPGe) is costly and requires specialized staff skills as well as special operating conditions such as low temperatures and high voltages. It is proposed to explore the possibilities of using a silicon photomultiplier (SiPM) with a deep pixel structure in nuclear gamma spectrometry, which will make it possible to increase the efficiency of scintillation detectors. The paper presents the results of a study of the newest silicon photomultipliers MAPD-3NM II assembled in a 16-element matrix, which was the detector part of the proposed LaBr3(Ce) scintillation spectrometer. The study was carried out using radioisotopes of uranium. The aim of the research is to reveal the possibility of differentiating depleted and natural uranium materials from each other without using special software by means of the proposed set of equipment.