Scanning a Silicon Photomultiplier with a Laser Beam

Physics of Particles and Nuclei Letters - The Silicon Photomultiplier (SiPM) is a novel semiconducting photodetector which can detect single photons. It consists of many microcells (pixels)...     

Small angle X-ray scattering investigations on vinylpyridine-butadiene rubbers

Methylvinylpyridine-butadiene copolymers vulcanized by various α, ω dibromo-alkanes were investigated by X-ray small angle scattering. In these systems, employing the Hosemann-Joerchel analysis, only one cluster dimension of about 45 Å has been found with a polydispersity not exceeding 35 per cent. Stretched rubbers show interference effects both in the meridional and equatorial directions.     

Technology of manufacturing micropixel avalanche photodiodes and a compact matrix on their basis

A technology for manufacturing a new micropixel avalanche photodiode (MAPD) with deeply buried pixels (including two epitaxial layers between which an array of n ⁺) regions is formed by ionic doping) is described. A new method for manufacturing the compact MAPD matrices with minimum dead zone is proposed.     

Micropixel avalanche photodiodes and the possibility for their application in positron-emission tomography

Micropixel avalanche photodiodes (MAPDs) are new instruments for detecting low-intensity light. They consist of many microcounters (pixels integrated on a common silicon wafer). A unique design by the Joint Institute for Nuclear Research (JINR) (Z. Sadygov)??deep-microwell MAPD??provides an order of larger pixel densities without losses in photon-detection efficiency. These instruments are beginning to find use in precision electromagnetic calorimetry. MAPDs can be most widely applied as photodetectors in scanners for positron-emission tomographs (PETs), particularly the time-of-flight PETs becoming popular now. The possibility of using MAPDs in PETs is shown, and the time resolution of a pair of quanta detected by Lutetium Fine Silicate scintillation crystals with MAPD readout is obtained at the level of 400 ps.     

Alpha particle detector based on micropixel avalanche photodiodes

The main goal of this work is to study the possibility of detecting alpha particles with a micropixel avalanche photodiode (MAPD) in combination with Lutetium Fine Silicate (LFS) scintillators (500 μm thick). The results show that alpha detectors based on the MAPD are expected to be useful in many applications: public security (associated particle imaging for explosives and drugs detection), radioactive contamination monitoring in various environments, and detection of charged particles from nuclear reactions.     

Development of radiation medicine at DLNP, JINR

The Dzhelepov Laboratory of Nuclear Problems’ activity is aimed at developing three directions in radiation medicine: 3D conformal proton therapy, accelerator techniques for proton and carbon treatment of tumors, and new types of detector systems for spectrometric computed tomography (CT) and positron emission tomography (PET). JINR and IBA have developed and constructed the medical proton cyclotron C235-V3. At present, all basic cyclotron systems have been built. We plan to assemble this cyclotron at JINR in 2011 and perform tests with the extracted proton beam in 2012. A superconducting isochronous cyclotron C400 has been designed by the IBA-JINR collaboration. This cyclotron will be used for radiotherapy with proton, helium and carbon ions. The ¹²C⁶⁺ and ⁴He²⁺ ions will be accelerated to an energy of 400 MeV/amu, the protons will be extracted at the energy 265 MeV. The construction of the C400 cyclotron was started in 2010 within the framework of the Archarde project (France). Development of spectrometric CT tomographs may allow one to determine the chemical composition of a substance together with the density, measured using traditional CT. This may advance modern diagnostic methods significantly. JINR develops fundamentally new pixel detector systems for spectrometric CT. The time-of-flight (TOF) system installed in the positron emission tomograph (PET) permits essential reduction in the detector noise from occasional events of different positron annihilations. The micropixel avalanche photodiodes (MAPDs) developed at JINR allow a factor of 1.5 reduction in the resolution time for the PET TOF system and suppression of the noise level as compared to commercial PET. The development of a combined PET/MRI is of considerable medical interest, but it cannot be made with the existing PET tomographs based on detectors of compact photomultipliers due to strong alternating magnetic field of MRI. Change-over to detectors of micropixel avalanche photodiodes permits making a combined PET/MRI.     

Hypersonic flow structure in a large-scale multi-diaphragm shock tube

The results of an experimental and theoretical study of the structure of the shock wave and the gas flow behind it are presented, together with data on the duration of the high-temperature working flows, the contact zones and the regions of uniform cold-flow parameters in the large (channel diameter 0.5 m, length 200 m, gas tank diameter 3 m, length 23 m) interchangeable-nozzle shock tube of the Central Scientific Research Institute of Mechanical Engineering.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 158–165, September–October, 1993.     

Problems of heat transfer and thermal protection of entry vehicles for an unmanned mission to mars

The problems of heat transfer and thermal protection for an orbitalMartian lander touching down on the planetary surface are investigated. A broad scenario of the mission is given and several possible aerodynamic shapes are considered. Several versions of the landing on the planetary surface are studied. The version with intermediate orbiting of an artificial Mars satellite using aerodynamic deceleration in the atmosphere is adopted as the main variant. The landing on the planetary surface is realized from satellite orbit. This landing pattern requires reusable thermal protection. The convective and radiative heat fluxes are calculated at characteristic points on the surface of a vehicle of the chosen shape. For this shape the necessary weight of thermal protective coating consisting of indestructible reusable TZMK material, used previously for shielding the Buran orbiter, is determined.     

Heat and mass transfer near the stagnation point with injection and suction of various gases through the body surface

Numerical solutions of the equations of the laminar boundary layer in the vicinity of the stagnation point of an axisymmetric blunted body with injection of single-component gases into a homogeneous external stream are obtained and generalized. More than 30 different pairs of gases are investigated. The heat and mass transfer in a multicomponent laminar boundary layer with the injection of a gas mixture, and also with simultaneous injection and suction of different gases through the body surface, is analyzed. An approximate method is proposed for calculating the heat and mass transfer in a laminar boundary layer.Notation density - T temperature - J enthalpy - M molecular weight - c_i mass concentration - x_i molar concentration - viscosity coefficient - heat conductivity - D_ij binary diffusion coefficient - D_i generalized diffusion coefficient - V_i diffusion velocity - q convective heat flux - surface friction - G over-all mass flow rate through the surface - G_i flow rate of the i-th component through the surface - /c_p heat transfer coefficient - _i mass transfer coefficient of the i-th component - _q injection coefficient for heat transfer (2. 7) - injection coefficient for mass transfer (2. 7) - , are the parameters of the intermolecular interaction potential function - /c _p =q/(J _e -J _wo), _i = (pc _i Vi) _w /(c _iw -c _ie ) (pc _i V _f) _w /(c _iw –c _ie ) The author wishes to thank V. S. Dranichkin, M. V. Gusev, and A. I. Noikin, who assisted with the computer calculations and the analysis of the computer results.