Multiwire position-sensitive neutron detector with two layers of boron-10 has been developed to detect both thermal and fast neutrons. Sensitive dimensions of two coordinate neutron detectors are 50 × 50 mm. New detector characteristics are compared with those of a 100 × 100 mm detector built earlier which we used in neutron flux spatial distribution measurements. Plane-parallel design of the new detector has symmetrical structure with respect to wire anode and also includes two intermediate grids and two cathodes made of parallel wires with 2 mm pitch and two silicon substrates coated with boron-10 layers of 0.003 mm thickness. Detector geometry and working gas mixture and pressure are chosen so as to ensure full absorption of secondary alpha particle from reaction with thermal neutron within detector gas medium half thickness. Neutron coordinates are determined from measured ionization loss pulse heights produced by secondary nuclei. The detector expected efficiency to thermal neutrons is about 5

A position-sensitive detector, which is a neutron target at the same time, is presented to study the interaction reactions of fast neutrons of above 1 MeV with light nuclei, in particular, with the 10B nucleus. It contains two boron-10 layers and a system of wire electrodes to identify secondary nuclei, in particular 3H and 4He, and to determine energy loss and departure angle. Thus the neutron energy can be determined.

The features of the processes of initiation and development of spark discharges in microstructural gas detectors of ionizing radiation in laboratory conditions and on charged-particle beams in accelerators are considered. Such aspects as the Raether charge limit, secondary electron emission, avalanche cross-overlap, positive ion feedback, explosive electron emission, cascading of detectors, and the charge density have been analyzed in detail. The better understanding of these effects will make it possible to make a further step in the development of new-type position-sensitive gas detectors.

A study is performed of the directional sensitivity of a two-coordinate neutron detector based on a 3 μm 10B layer and a wire chamber. The suppression of scattered neutron detection by the detector is observed, relative to data from the 3He counter. This is explained by strong absorption of neutron flux in the 10B layer when it is incident at a large angle to the plane of the detector, and by the energy of the 4He or 7Li secondary nucleus being insufficient to exceed the threshold energy if the nucleus is produced immediately after entering the 10B layer.

The causes of breakdowns in micro-pattern gas detectors have been investigated. According to the experimental data, this process is based on three independent sources: a corona discharge, a streamer discharge, and polarization of a dielectric when charges flow inside the detector. Several methods for increasing the resistance of devices of this type to damage from sparks are shown.

The results of a study of the characteristics of a thick gas electron multiplier based on a fiberglass plate with a 0.8–2.0-mm-thick double-sided copper coating in which 1 mm holes were drilled at a spacing of 1.5 mm are presented. The gas filling of the multiplier is a mixture of Ar + 5% isobutane. The energy resolution for the 55Fe line is 21%, the spatial resolution is 0.7 mm, the temporal resolution is better than 10 ns, and stable operation is provided up to an irradiation intensity of ~105 mm–2.

Разработан четырехслойный газовый детектор для определения интенсивности и энергии электронов и других заряженных частиц. Представлены результаты измерений с использованием разработанного детектора, показывающие возможность определения энергии заряженных частиц.

The results obtained in the study of the avalanche process of electron multiplication in a thick gas amplifier of a new design are presented. The main feature of the device is the separation of the upper and lower parts of the amplifier by a gas gap with the preservation of the polyimide film as an insulator on the inner surface of the hole electrodes. The width of this gap can vary in the range of 0.1–1.0 mm, depending on the electrode size. With this separation, the surface leakage currents are absent between the electrodes and the charge is not induced on the inner surface of the gas-discharge gap. Due to this solution, it is possible to minimize the probability of both surface and volume streamer phenomena that turn into a Geiger or spark discharge. As a result, a pulse amplitude of a few volts was measured across a load of 50 Ω in a gas mixture of Ar + 20% CO2 when the detector was irradiated with a 90Sr β source.

A four-layer gas detector for electrons and other charged particles is developed. A charged particle passing through a thin window produces ionization in four consecutive gas gaps separated by absorbers. The gas gain about of 104 allows one to determine four signal amplitudes under the control of any combination of these signals. Simultaneous measurement of the ionization losses of the particle in the successive layers of the detector makes it possible to determine the energy of the passing particle.

Aerogel has been successfully used as a radiator in Cherenkov detectors. In 2004, a multilayer aerogel providing Cherenkov ring focusing was proposed and produced. FARICH (Focusing Aerogel Rich Imaging CHerenkov) detectors such as ARICH for Belle-II (KEK, Japan), Forward RICH for PANDA detector (FAIR, Germany), and FARICH for the Super Charm-Tau factory project (BINP, Novosibirsk) have been developed based on this aerogel. Prototypes of FARICH detector based on MRS APD and Philips DPC photosensors were developed and tested in the framework of this project. An angular resolution for Cherenkov rings of 3.6 mrad was achieved.

РАБОТЫ С КОНФЕРЕНЦИИ 5 УДК 621.382  В. В. Лундин, Е. Е. Заварин, А. В. Сахаров, А. Ф. Цацульников, В. М. Устинов РЕАКТОРЫ ДЛЯ МОС-ГИДРИДНОЙ ЭПИТАКСИИ НИТРИДА ГАЛЛИЯ: НАСТОЯЩЕЕ И БУДУЩЕЕ Представлен анализ ситуации, сложившейся на рынке оборудования для МОС-гидридной эпитаксии соединений на основе нитрида галлия, и видение проблем и открывающихся возможностей

The paper considers one of the understudied aspects of the use of low-voltage halogen counters of the Geiger-Muller, associated with the choice of the operating point voltage in the middle of the plateau of the counting characteristics. It is shown that the difficulties can be caused in determining of the beginning of counting characteristics by the appearance of streamer discharge pulses in a zone of limited proportionality to the transition to a stable corona discharge. The use of the Raether criterion to estimate the necessary and sufficient conditions for the appearance of a streamer makes it possible to introduce some clarity into the essence of this

Timing resistive plate chamber with thickness of 70~mg/cm is constructed as alternative to plastic scintillation detector in particle physics. Chamber gives high rate capability up to 1MHz per cm in sensitive area 10 cm. To avoid contamination and damage under strong ionization the gas forced jet device and cleaning circulation system including nuclear filtres are applied. Chamber consists of anode which is 5 μm-polyimid film coated cuprum and gold and cathode which is 330 μm silicium plate with diamand-like film on surface. Gap between cathode and anode is 0.2 mm. Fast preamplifier is connected to anode. Signal from preamplifier feeds constant fraction discriminator with time reference of 20 ps. Negative power supply is connected to cathode. Time between signal from plastic scintillation detector and resistive plate chamber is measured with time reference of 20 ps. Four-component gas mixture of noble gases containing 73%C2H2F4, 20%Ar, 5%CO2 and 2%SF6 is circulated through chamber. Test of chamber is performed with radioactive source Sr(Y). Time resolution 270 ps is obtained at maximum possible counting rate.

This paper presents the results of studies of the characteristics of alpha particles detector like TGEM ("Thick" Gas Electron Multiplier) working in an open air environment. The main advantages of these devices are simplicity, low cost, and high sensitivity to the different kinds of irradiation. One of the possible applications of these new wireless gas detectors is alpha particle or radon background monitors, which can serve also as a dosimeter or as a smoke detector in houses. This detector is able to measure the trace of alpha particles with efficiency close to 100% operating in open air in the avalanche mode at high gas gain (up 10 4 ). The tests were carried out in duty of three summer months. It should be noted that the stability of the results is high enough despite the wide range of temperature and humidity during of testing.

This paper presents a modification of the metal gas electron multiplier (MGEM), free from one of the main drawback of this type of detectors namely the surface dielectric breakdown in the gap between the metal electrodes with holes.The high gas gain (104-105) with simple gas mixture or air offers the measurement for traces of alpha particles or high energy x-ray photon.It factor is very attractive for using of MGEM as background monitor of alpha particles or therapeutic beam counter.

In June 2012 a FARICH prototype from Philips Digital Photon Counting (PDPC) based on a photon camera with dimensions of 200×200 mm has been tested at CERN. Remarkable particle separation has been achieved with a 4-layer aerogel sample: the π/K separation at a 6 GeV/c momentum is 3.5σ, the μ/π separation is 5.3σ at 1 GeV/c. The analysis of the data has shown that the main contribution to the accuracy of the ring radius measurement comes from aerogel. The development of focusing aerogels is proceeding in two main directions: tuning of production technology of multilayer blocks and development of a new production method with continuous density (refractive index) gradient along the block depth. The beam test was carried out in December 2012–January 2013 at the electron beam test facility at the VEPP-4 M e+e− collider. The goal of this test was to measure different single layer and focusing aerogel samples, both multilayer and gradient. Aerogel samples were tested with a PDPC FARICH prototype. A part of DPC SPADs in each pixel was disabled to form an active area of 1×1 mm2. The collected data proved that gradient aerogel samples focus Cherenkov light.