An experimental setup for studying neutron-neutron final state interaction on the neutron channel of the Moscow Meson Factory

A setup for measuring the singlet nn-scattering length in the n + d → p + n + n reaction is described. It is composed of a neutron hodoscope with an angular aperture of 12° and a scintillation detector for protons escaping at an angle of 90° with the beam direction. The exit angles and the energies of a proton and both neutrons are measured. The neutron energies are measured using the time-of-flight method. At a time resolution of ∼0.6 ns and a flight base of ∼5.5 m, the accuracy in measuring the neutron energy is ∼1% at an energy of ∼15 MeV. The dependence of the reaction yield on the relative energy of two neutrons is investigated. The neutron-neutron final-state interaction manifests itself as a peak in this distribution.     

Calibration of the LHCb electromagnetic calorimeter using the technique of neutral pion invariant mass reconstruction

Calibration of the electromagnetic calorimeter for the LHCb experiment is aimed at measuring the electron and photon energies with an accuracy of 2% or better. A number of calibration techniques are sequentially used for this purpose. One of these techniques is based on reconstruction of the π⁰ meson invariant mass in a two-photon decay. Using this procedure, it is possible to calibrate the electromagnetic calorimeter in the transverse energy range of 300–1500 MeV. An important advantage of this technique is its independence of the states of the other LHCb spectrometer systems. Statistics sufficient for attaining the declared purpose can be rapidly acquired owing to the large cross section of neutral pion production in deep inelastic events. The algorithm has been implemented as a part of the LHCb software. The calibration procedure using neutral pions takes no more than 2 weeks and helps achieve the required accuracy.     

An adaptive γ-ray spectrometer with a high event processing rate

A fast γ-ray spectrometer adaptable to the scintillator type is described. This spectrometer is capable of processing a γ-ray energy spectrum (with a resolution of <4% in the energy range from 20 keV to 10 MeV) in a sequence of time intervals in the real-time mode at a counting rate of up to 10⁶ cps. Digitization of the detector signals by a 14-bit ADC with a sampling rate of 64 MHz and real-time data stream processing are used to separate overlapping events and correctly generate energy spectra.     

A detector for imaging of explosions on a synchrotron radiation beam

Synchrotron radiation (SR) offers a unique chance to study the structure of a substance in fast processes. Since SR is emitted by electron bunches in a storage ring, the SR burst corresponding to a single bunch may be very short. Should a detector capable of detecting SR from a single bunch without mixing signals from different bunches be available, it is possible to obtain information on changes in the state of the material in a sample under investigation with a very high time resolution. A detector for imaging of explosions on an SR beam—DIMEX—has been developed by the Budker Institute of Nuclear Physics (Siberian Division of the Russian Academy of Sciences, Novosibirsk). This detector is a high-pressure ion-ization chamber with a strip readout at a pitch of 0.1 mm. The electron component of primary ionization is collected within 50 ns, which is substantially shorter than the orbital period of a bunch in the VEPP-3 storage ring (250 ns). The DIMEX is filled with a Xe—CO₂ mixture (3: 1) at an absolute pressure of 7 atm. The spatial resolution of the detector is ∼210 μm, and its efficiency for radiation with an energy of 20 keV is ≥50%. The dynamic range of the detector is ∼100, which allows one to measure the signal with an accuracy of ∼1%. In this case, the maximum flux of X-ray photons, at which the DIMEX operates in a linear region, is ∼10¹⁰ photons/(channel s). Today, the detector has been used in experiments aimed at studying evolution of the density in detonation waves and processes of nanoparticle production at the VEPP-3 storage ring by employing the small-angle X-ray scattering technique.     

Investigation of a LYSO crystal for a low-energy calorimeter

The results of studying a calorimeter cell in the low-energy region, ~50 MeV, which consists of a LYSO crystal and two avalanche photodiodes, are presented. The use of two photodiodes per crystal made it possible to perform a preliminary measurement of the calorimeter energy resolution using one calorimeter cell and cosmic muons. The coefficient of the stochastic contribution to the calorimeter energy resolution and the crystal luminescence time were measured (0.115% and 50 ns, respectively).     

A silicon position-sensitive detector of charged particles and radiations on the basis of functionally integrated structures with nano-micron active regions

A novel pixel array two-coordinate detector with internal amplification is described. Linear amplification of the primary ionization current is attained by using functionally integrated structures of a p-i-n diode and a bipolar transistor in the detector pixel. It is shown that a 16-fold decrease (from 0.64 to 0.04 μm²) in the emitter area of the functionally integrated structures allows the current gain of pixel bipolar structures to be increased from 10 to 80 at a pixel collector current of ∼1 nA. As a result, it is possible to obtain spectra of radiations weakly interacting with the silicon (e.g., γ rays) and to reduce the response time of the position-sensitive detectors by an order of magnitude, down to 100 ns and less. It is demonstrated that the detector can be used in fast position-sensitive detection of particles with time, coordinate, and energy resolutions of ≤100 ns, ≤25 μm, and ≤12%, respectively.     

A parallel plate avalanche detector for low energy ion identification

A setup for identifying low-energy (1–10 MeV) ions with charges Z ≥ 1 by simultaneously measuring the energy losses and the time of flight is described. The setup is composed of a multiwire proportional chamber and a strip silicon detector, which are used to measure the ion energy, and two low-pressure avalanche wireless detectors for measuring the energy losses and the time of flight. Results obtained in measuring α particles from ²²⁶Ra source and p, Be, C, and O ions produced on the ITs-100 cyclotron at the Flerov Laboratory of Nuclear Reactions are presented.     

CsI(Tl)-calorimeter calibration with positive-kaon decay products

The CsI(Tl) calorimeter was calibrated in the KEK-E246 experiment withK _μ2-andK _π2-positivekaon decays. The following calorimeter parameters were obtained: an energy resolution (σ) of 4.1% forE=242.5 MeV, a π⁰ invariant-mass resolution (σ) of 5.6%, and an angular resolution (σ) of 3.1^o.     

A new method for charged particles identification with a CsI(Tl) crystal

A spectrometer for detecting and identifying light charged particles with low energies (>∼1 MeV) is described. The spectrometer consists of a thin CsI(Tl) crystal, an ФЭУ-176 photomultiplier, and a waveform digitizer. Digital oscillograms of anode pulses are stored and analyzed in off-line processing. In order to reconstruct the energy and specific energy losses, the two-component character of the scintillation fluorescence decay in a CsI(Tl) crystal and the dependence of the fast component on the specific loss value are used. A digital particle identification method is proposed. The results of experimental studies of the CsI(Tl) crystal scintillation properties and efficiency in identifying electrons, protons, and α-particles in an energy range of ∼1–10 MeV are presented. It is shown that the efficiency of the digital method for proton and α-particle identification is 1.5–2 times higher than that of the known analog methods.     

Response function of a fast neutron capture-gated spectrometer

The response function of a fast neutron capture-gated detector with a simple geometry has been simulated with the aim of studying the mechanism of its formation. The Geant4 package and the DGEOM program developed by the Institute for Nuclear Research especially for studying processes of fast neutron moderation in an organic medium have been used for numerical simulation of the response function. The response functions and the detection efficiencies of an actual detector for neutron energies of 1.2, 2.4, 5.0, and 14.6 MeV have been reconstructed and analyzed. The behavior of the response function has been comprehensively analyzed in the neutron energy range of 1–14 MeV. It is shown that our simulation adequately represents the experimental data and that the response function of the detector has a double-peak structure deteriorating its energy resolution. Taking into account the interaction with carbon for neutrons with energies of <15 MeV affects the response function only slightly. The consistency of the physical model involved in the DGEOM program and the adequacy of the simulation results obtained using this program are demonstrated.     

Characteristics of the detecting equipment for the nanosecond tagged-neutron technology

Detecting equipment for the nanosecond tagged-neutron technology has been developed, and its characteristics have been studied. The principles of arrangement and operation of the readout electronics based on the selection of useful events according to specified criteria and data accumulation by a buffer-memory unit with subsequent transfer of data arrays to a remote computer for processing and visualization. The main selection criterion is the presence of signals from α- and γ detectors within the time gate and amplitude ranges in the absence of overlapped events. A prototype of a setup for testing the developed equipment was assembled and experimental studies of its characteristics were performed. The time resolution attained in the recording of α-γ coincidences is 1.0 ± 0.1 ns at an amplitude resolution of the γ detector of 3.6–3.8%. Original Russian Text ? K.A. Balygin, M.D. Karetnikov, A.I. Klimov, K.N. Kozlov, E.A. Meleshko, I.E. Ostashev, G.V. Yakovlev, 2009, published in Pribory i Tekhnika Eksperimenta, 2009, No. 2, pp. 122–132.     

Circular one-dimensional position-sensitive time-of-flight microchannel plate detector using resistive anode for space plasma measurements

We have developed circular one-dimensional position-sensitive time-of-flight microchannel plate (MCP) detector for space plasma measurements. The MCP detector is equipped with a 354.375 degrees resistive anode and a grid anode for obtaining position and timing signals simultaneously from one start event. The resistive anode provides high-resolution and continuous position sensing with two electronic channels alone. The grid anode generates start signals with pulse width of 1 ns for time-of-flight measurements. The resistive anode is formed on an alumina substrate which is installed behind the output side of the MCP plates. The grid anode is installed between the MCP plates and the resistive anode for the simultaneous detection of position and start signals. Stop signals are obtained from stop events by a center anode formed on the alumina substrate behind the MCP plates. On the basis of the test experiments, we have evaluated that the MCP detector functionally deals with the position and timing signals.     

A coaxial broadband detector of high-power nanosecond microwave pulses on the hot-electron effect

The design and characteristics of a liquid-nitrogen-cooled hot-carrier detector of microwave pulses detecting electromagnetic radiation in the range 2–10 GHz with a resolution no worse than 1 ns are considered. The conversion coefficient of the voltage at the input cable into the output amplitude of a detected signal is 1.2 × 10⁻².     

A photomultiplier tube for a NT-200 deep-underwater neutrino telescope

A fast, high-sensitive photomultiplier tube (PMT) with a 25-mm diameter bialkali photocathode is being developed to be used as part of a KBA3AP-370 hybrid photodetector. Its linearity is ∼ 150 mA. The rise time of an anode current pulse is ∼ 2 ns. The transit time difference of photoelectrons originating from different points of the photocathode does not exceed 1 ns. Deceased.     

Measuring Energy Releases in a Scintillation Detector and the Afterpulses of the Photomultiplier Tubes

A procedure for measuring energy releases in scintillation detectors by using a logarithmic RC converter in combination with a device that suppresses photomultiplier tube afterpulses is described. The total range of measured energies is 5.8 MeV to 11.6 GeV. The afterpulse suppression ratio is more than 200. The output pulse of the RC converter is synchronized with the leading edge of the anode signal from the photomultiplier tube.__________Translated from Pribory i Tekhnika Eksperimenta, No. 4, 2005, pp. 26–33.Original Russian Text Copyright © 2005 by V. Volchenko, G. Volchenko, Dzaparova, Karpov, Petkov, Yanin.     

A Matrix Carbon Detector for Measuring the Energy Flux of a High-Power Beam of Hydrogen Ions

A matrix detector consisting of small calorimeters based on УПВ-1 pyrolytic carbon is described. The detector allows measurements of the spatial distribution of the energy flux of a high-power hydrogen ion beam to be taken over its cross section. Each calorimeter occupies an area of 4 cm², and the area of its working body is 0.25 cm². An unambiguous relation between the heat flux value, the irradiation time, and the calorimeter temperature is established by calculations. The calorimeter measurement error was estimated at ～4%, and the spread of the sensitivity coefficients between the calorimeters was 5–6% (1σ). The detector was used to measure the distribution of the energy flux of hydrogen ions over the cross section of the “scanned” beam 10 cm in diameter from a high-current accelerator of the НГ-12И facility.     

A technique for identifying nuclei in the MONICA experiment

We discuss the results of comparison and optimization of (ΔE − E) methods for identifying nuclei with the aid of a multilayer Si detector that will be used in the MONICA satellite-based experiment aimed at studying the nuclear component of cosmic rays from hydrogen to nickel in the energy range of 10–300 MeV/nucleon. The residual-range and Bethe-Bloch curve approximation methods are considered. Using the GEANT4 simulation, it is shown that the Bethe-Bloch curve approximation method not only ensures a better mass resolution (which is particularly important for identification of heavy nuclei), but also provides a means for identifying “drift” nuclei with satisfactory charge (<0.3) and energy (<3%) resolutions. The results can be used to prepare new experiments in which (ΔE − E) nuclear identification methods are expected to be employed.     

A study of the possibility of improving the time resolution of the PHOS spectrometer

Experimental investigations have shown that a timing device based on a constant-fraction discriminator is capable of providing a time resolution of approximately 0.5 ns and a timing error of approximately ±0.25 ns in the energy range of 0.8?1.8 GeV. In the region of “low” energies (<0.6 GeV), the time resolution is decreased by the influence of detector noise, whose level is ~3–5 mV for most scintillation detectors under investigation.     

Coordinate accuracy of mini-drift tubes in detection of an induced signal

The coordinate accuracy of mini-drift tubes was measured by detecting the signal induced on their external electrodes. The electrodes (1-cm-wide strips) located perpendicularly to the anode wires were used to determine the particle coordinate. The rms coordinate accuracy of ∼0.4 mm was attained for four tube layers.     

Development of fast-response portable NDIR analyzer using semiconductor devices

In this paper, a novel fast response NDIR analyzer (FRNDIR), which uses an electrically pulsed semiconductor emitter and dual type PbSe detector for the PPM-level detection of carbon dioxide (CO₂) at a wavelength of 4.28 μm, is described. Modulation of conventional NDIR energy typically occurs at 1 to 20 Hz. To achieve real time highspeed measurement, the new analyzer employs a semiconductor light emitter that can be modulated by electrical chopping. Updated measurements are obtained every one millisecond. The detector has two independent lead selenide (PbSe) with IR band pass filters. Both the emitter accuracy and the detector sensitivity are increased by thermoelectric cooling of up to —20 degrees C in all semiconductor devices. Here we report the use of semiconductor devices to achieve improved performance such that these devices have potential application to CO₂ gas measurement and, in particular, the measurement of fast response CO₂ concentration at millisecond level.