Investigation of the Internal Amplification Effect on Planar (p +–n–n +) Structures Made of High-Resistivity Silicon

The first results of studies of special strip and pixel silicon detectors are presented. The detector structures allow the creation of high electrical fields (5 × 10⁵ V/cm) near p–n junctions that are powerful enough to initiate an avalanche multiplication of charge carriers. The possibility of internal amplification in a semiconductor detector similar to the proportional amplification in gas counters is shown. The spectrum of particles from ²³⁸Pu (E = 5.5 MeV) demonstrates an amplified peak at an energy of 70.2 MeV and an energy resolution FWHM = 10.2 MeV.     

A Vacuum Photoemission Detector for X-ray Tomography on the ITER Facility

A vacuum photoemission detector designed for plasma tomography in X rays on the ITER facility is described. Such detectors allow X rays to be detected in the presence of intense neutron and -photon fluxes. The results of tests of a prototype of this detector on a ⁶⁰Co source of rays, its calibration using radiation from an X-ray tube, and tests of its serviceability on the T-10 facility are presented. The values of the valid signal and the signal-to-noise ratio are assessed for the parameters of the ITER facility. Selecting the number of detectors and their arrangement on the ITER facility to ensure the required spatial resolution of the diagnostics is considered.     

A Detector of Magnesium Atomic Beam

A detector of neutral Mg atoms is described. The operating principle of the detector is based on variations in the emissive ability of a tungsten filament exposed to an atomic Mg beam. The emission current of the detector reaches several tens of microamperes, with the flux density of Mg atoms being 10¹⁴ particles/(s cm²). The spatial resolution of the detector is of the order of magnitude of the filament diameter (0.1 mm). The results of the study of changes in the atomic Mg beam shape caused by variation of the temperature of the magnesium vapor source from 440 to 460°C are presented. The detector can be used for improving the spatial resolution of ion-beam profile meters based on the use of a magnesium vapor jet.     

An integral method for measuring the <Emphasis Type="Italic">P</Emphasis>-odd asymmetry on a reactor at neutron polarization switching frequencies higher than the frequencies of the main spectrum of the neutron noise power

P-odd asymmetry is measured when frequencies of switching neutron polarization exceed the frequencies of the reactor power fluctuations that govern the spectral density of noise power. A principle for recording the current signals in these measurements is described. This method was used for the first time at the Konstantinov Institute of Nuclear Physics in Gatchina (Russia). The results suggest that the accuracy of measurements at an increased equipment-switching frequency is even higher than the accuracy obtained using compensation for reactor power fluctuations; hence, this compensation becomes superfluous. Following this method, it is possible to take measurements with a single detector and to dispense with a monitor, thereby rendering the equipment and the measuring technique less complex. A strategy of measurements was developed. An experimental model of the facility was produced and tested with a small-amplitude calibration signal in the presence of reactor power fluctuations caused by rays from reaction ¹⁰B(n )⁷ Li* ⁷Li + . The results from the test measurements of the P-odd effect in reaction ³⁵Cl(n, )³⁶Cl are presented.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 62–71.Original Russian Text Copyright ¢ 2004 by Vesna, Shulgina.     

A Liquid-Argon Ionization Detector for the Study of Double β Decay

A multisection liquid-argon ionization detector has been developed by the DBA collaboration to study double decay of ¹⁰⁰Mo. The experiment has been carried out in the Gran Sasso underground laboratory in Italy. The detector design and main characteristics are described. The limits on the ⁴²Ar and ²²²Rn concentrations in liquid Ar are 4.3 · 10^–21 g/g and 1.2 · 10^–3 Bq/kg, respectively.     

A Direct-Charging Detector for Measuring the Pulse Shape, Absorbed Dose Rate, and γ-Radiation Dose

A method for the calculation and the results of experimental tests of direct-charging detectors of -radiation are described. The current sensitivities to monochromatic -rays with energies of 0.3–10 MeV for three plane detector designs with the thicknesses of the dielectric layers of 0.5 to 2 cm are presented. The sensitivity is a function of energy within this range, and its minimum and maximum values differ by a factor of ten. Therefore, when using direct-charging detectors for measuring the absorbed dose rate and radiation dose, the knowledge of the -radiation spectrum is necessary. The spectrum is unnecessary in radiation pulse-shape measurements. The detector amplitude characteristic is linear for values of the absorbed dose rate of 10¹⁵ rad/s.     

A Hemispherical Fission Chamber for the Neutron-Flux Monitoring

A fission ionization chamber has been designed to monitor neutron fluxes produced by the proton beam of the Van de Graaf accelerator in the ⁷Li(p, n)⁷Be nuclear reaction. A target producing neutrons is placed at the center of the chamber, which has a hemispherical shape. The neutrons escaping from the target are detected within the limits of a space angle a little larger than 2 sr. A ²³⁵U isotope is used as a fissile material. A U₃O₈ layer with a thickness of 300 g/cm² and an area of 80 cm² has already been deposited on the surface of the inner hemisphere using electrolysis. The chamber is filled with a gas mixture of 97% Ar + 3% CO₂. The detection efficiency of the chamber for neutrons with 1- to 150-keV energies is found to be 1.6 × 10^–5. Using this chamber, it is possible to measure (with a statistical accuracy of 1%) the integrated neutron yield in a thick target exposed for 20 min to a proton beam with a current of 3 A and an energy of 1942 keV, which is 60 keV above the threshold of the ⁷Li(p, n)⁷Be reaction. The design of the fission chamber is described, and the test results are presented.     

Determining the Characteristics of Cosmic-Radiation Nuclei in the Sileye Experiment on Board the Mir Orbital Station

An algorithm for reconstructing the characteristics (charge, mass, and energy) of cosmic-radiation nuclei with 20- to 200-MeV/nucleon energies is described. The detector is a telescope of three two-coordinate planes with two 1-mm-thick iron filters inserted between them. Each plane is composed of two strip silicon detectors with 3.6-mm-wide orthogonally oriented strips, an effective area of 6 × 6 cm², and a thickness of 380 m. The algorithm for reconstructing the nuclei characteristics is based on the analysis of how the specific ionization losses change as the nuclei pass through the filter material. The results of the Monte Carlo simulation are presented for the energy dependence of the telescope acceptance and the energy deposited in the detectors by different nuclei in view of the detector calibration on the nuclear beams of the accelerator. The mass resolution of the telescope is 30, 12, and 5% for He, N, and Al nuclei, respectively. The energy resolution, which is 20%, is much the same for all nuclei.     

A Coordinate Detector for Studying Horizontal Fluxes of Cosmic Rays

A DECOR coordinate detector is a multilayer system of plastic streamer tube chambers located around a NEVOD Cerenkov water calorimeter. The basic characteristics of the detector are as follows: the area is 100 m², the angular resolution is 1°, and the space resolution is 1 cm. The structure of the detector, data acquisition and trigger systems, and results obtained during the operation of a pilot assembly (8 chamber layers and a working area of 8.4 m²) are given.     

Reconstruction of Coordinates of Scintillations in a Large-Size Cylindrical Detector with Radially Arranged Photomultipliers

An algorithm for calculating the scintillation coordinates developed for a large-size coordinate-sensitive detector is developed. The detector based on a liquid scintillator has nine radially arranged -174 photomultipliers. The results of simulation of the dependence of the coordinate resolution at the detector center on -quanta energy between 0.2 and 8 MeV are presented. The experimental data obtained with a collimated beam of -quanta from a ⁶⁰Co source, which irradiated the central part of the detector, were processed by using this algorithm. The -ray spectrum measured by the detector and the results of determining the scintillation coordinates for a -quanta beam are presented. The accuracy of coordinate measurements at the central region of the detector with this algorithm is 10 mm.     

A Current Integrator for an Electrostatic Accelerator Energy Scale Calibration System

A circuit diagram of the current integrator intended for the measurements of a positive particle-beam charge arriving at a target is described. The device converts the charge into a number of pulses (target current into the pulse repetition rate). The conversion factor is 10⁹ pulses/C (10⁹ Hz/A), the error is no more than ±1%, the dead time is absent, the input impedance is close to zero, and the temperature drift is no more than 1.2 × 10^–12 /°.     

The PIBETA spectrometer for studying rare and forbidden decays of muons and pions

The construction and characteristics of the PIBETA spectrometer are described. This spectrometer is designed to implement a program of precise measurement of pion decay ^{+ 0} + e ⁺ + _e at the Paul Scherrer Institute (Switzerland). A spherical calorimeter, consisting of 240 crystals of pure CsI scintillator and embracing a solid angle of 3, is the main detector of the setup. In addition, the spectrometer is composed of an active collimator (which also acts as a beam degrader), a segmented active plastic target, two multiwire cylindrical proportional chambers, a 20-element cylindrical plastic hodoscope, and veto counters of cosmic muons.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 39–48.Original Russian Text Copyright © 2005 by Baranov, Kalinnikov, Karpukhin, Khomutov, A. Korenchenko, S. Korenchenko, Kravchuk, Kuchinskii, Mzhaviya, Rozhdestvenskii, Sidorkin, Tsamalaidze, Sakhelashvili, Frlez, Poanic, Li, Minehart, Smith, Stephens, Ziock, Bertl, Horisberger, Ritt, Schnyder, Wirtz, Ritchie, Supek, Kozlowski.     

Gas-Discharge Detectors for Monitoring the Total Neutron Yield in the International Thermonuclear Experimental Reactor

The design of two detector units made integral with their communications links is described. The detector unit composed of a KHT23-1 fission chamber and an assembly of CHM67 neutron counters is used to detect slow neutrons, while the detector unit based on a KHT23-8 threshold fission chamber is intended for fast neutrons. The parameters of these detector units along with their communications links are presented.     

Charge Losses through Recombination while Detecting Fast Neutrons with Gas Proportional Counters

A procedure of calculating the ionization defect in a methane proportional counter is described for the case of heavy charged particles (p, , ⁹, and ¹²C), which are products of the interaction of 14-MeV neutrons with hydrogen and carbon nuclei. A radial structure of a charged-particle track and its decay through diffusion and recombination processes in an electric field are modeled. Certain effects neglected earlier are taken into consideration. Comparing the calculated and counter-measured experimental amplitude distributions has shown that the theory developed for calculating the ionization defect yields qualitatively correct results. Analyzing the compared results has also shown that some important notions concerning the initial data on the differential cross sections of gas ionization by particles with charges Z > 1, electron temperature in the track plasma, and model concepts on the electron escape from the track need refinement.     

Methods of Coordinate Reconstruction in Gaseous Detectors with Cathode Readout

The methods for reconstructing the coordinates of charged particles in gaseous detectors with cathode readout are analyzed in detail. The spatial resolution is investigated using spatial-reconstruction procedures based on the known relations and the new formulas proposed in the paper. The use of this method is illustrated by processing the beam-test data of the charged-particle veto detector of the proton spectrometer for the ALICE experiment at the Large Hadron Collider (CERN). The spatial resolution of the detector based on the multiwire proportional chamber with cathode-pad readout (pad dimensions are 22 × 10.7 mm, the anode-wire pitch is 5.65 mm, and the anode–cathode gap is 5.5 mm), measured along and across the anode wires, is _x 0.14 cm and _y 0.15 cm, respectively.     

A Planar Light Source Pumped by a Transverse High-Frequency Discharge

The results of the development and optimization of the characteristics of an electric-discharge excimer–halogen light source based on argon, xenon, and chlorine mixtures (P 500 Pa) are presented. The wide-band source has a planar working aperture (S 100 cm²) and operates on a system of overlapping ArCl*, XeCl*, Cl^* ₂, and Cl^** ₂ molecular bands in the spectral range of 170–450 nm. The average power of the UV radiation is 15–50 W, and the efficiency of the lamp operation is 5–15%.     

The RFR-4 X-ray Streak Camera

The RFR-4 X-ray streak camera with a slit scan designed on the basis of an X-ray sensitive evacuated image tube is described. The obtained images are recorded using a charge-coupled device (CCD) camera. The basic parameters of the X-ray streak camera are as follows: (1) the recorded spectral range starts at 0.1 keV; (2) the time resolution is as high as 30 ps; (3) the spatial resolution is five pairs of lines per millimeter (for a contrast ratio of 0.5); (4) the dynamic recording range is as high as 2000; and (5) the detectability is 2 × 10⁵ quanta/(cm²ns) (for a quantum energy of 1.5 keV). The design of the device and the purpose and operation of its components are described. The streak camera is equipped with a gate-valve unit with an autonomous evacuation system; this allows one to use it in installations where the working-chamber pressure increases dynamically up to 0.1 Torr. The sharp-focusing operating mode, which allows one to increase the device's sensitivity by an order of magnitude without loss in the time resolution, is described. The streak camera was used to record the X radiation in experiments with various targets performed at the ISKRA-4 and ISKRA-5 laser installations and the SIGNAL-2 Z-pinch installation.     

Spectrometer for β- and X-ray Radiation

The design and characteristics of the spectrometry system for -particles and conversion electrons in an energy range of 15 to 3000 keV and X-rays in an energy range of 2 to 60 keV are described. The radiation is detected by a SiLi detector with a 500-mm² sensitive area 4.5 mm thick. The energy resolution for the conversion electrons with an energy of 624 keV is < 2.0 keV, and for X-rays with an energy of 5.9 keV, it is <280 eV.     

Setup for Stimulating and Measuring the Electrical Activity of an Olfactory Epithelium

A setup for recording the electrical activity of an insulated olfactory epithelium is described. The setup consists of the following basic elements: an electrophysiological chamber intended for supporting the vital activity of the olfactory epithelium, its isolation from outside smells, and stimulation by odor stimuli; a stimulation system intended for preparation of a saturated vapor of the stimulating substance, its dilution down to concentrations of 10^–4–5.6 × 10^–2 and application of air stimuli with a duration of 1–5 s and repetition period of 2–100 s; and a recording and control system, which is controlled manually or via a computer and synchronizes the stimulus application and olfactogram recording (K _amp = 10000, sensitivity is 10 V, bandwidth is 0–100 Hz) and automatic compensation of the transepithelial potential drift.     

Desorption Kinetics of Polyether Lubricants from Surfaces

Desorption or evaporation is one of the mechanisms for loss of perfluoropolyalkylether (PFPE) lubricants from the surfaces of data storage media. One approach to minimizing PFPE loss to desorption is the use of lubricants with increasing molecular weight or increasing average chain length. In order to understand the effects of chain length on the lubricant evaporation kinetics we have studied the desorption kinetics of monolayer films of oligomeric ethers with varying chain length adsorbed on the surface of graphite. The desorption pre-exponents, v, and desorption barriers, E _des , have been measured for poly(ethylene glycol) dimethyl ethers, CH₃O(CH₂CH₂O) _m CH₃, with m=1,2,3,4,8 and 10. These are models for the PFPE known as Fomblin Z, which has a structure CF₃O(CF₂CF₂O) _x (CF₂O) _y CF₃. The results show that the desorption pre-exponents are independent of chain length and have an average value of v=10^18.7±0.3 s^–1. The E _des for the poly(ethylene glycol) dimethyl ethers vary non-linearly with chain length and can be fit with a power law expression of the form E _des =a+bN , where N is the total number of atoms in the oligomer backbone (N=3m+3) and the scaling exponent has a value of 1/2. This non-linear dependence of E _des on chain length has also been observed in recent studies of the desorption kinetics of straight chain alkanes from graphite. A desorption mechanism is described that explains the non-linearity of E _des for the poly(ethylene glycol) dimethyl ethers. The implication for the lifetime of lubricants on data storage media is that the long chain PFPE lubricants desorb more rapidly than one might expect based on simple linear scaling of the E _des of lower molecular weight PFPEs.