Anticoincidence Counter Research Articles

The Anticoincidence System of Space-Based Gamma-Ray Telescope GAMMA-400, Test Beam Studies of Anticoincidence Detector Prototype with SiPM Readout

The GAMMA-400 gamma-ray telescope is planned for the launch at the end of 2026 on the Navigator service platform designed by Lavochkin Association on an elliptical orbit with following initial parameters: an apogee $${\sim}$$ 300 000, a perigee $${\sim}$$ 500 km, a rotation period $${\sim}$$ 7 days and inclination of 51.4 $${}^{\circ}$$ . The apparatus is expected to operate for more than 5 years, reaching an unprecedented sensitivity for the search of dark matter signatures and the study of the unresolved and so far unidentified gamma-ray sources. The segmented anticoincidence counters surround the converter-tracker and calorimeter of the telescope with the purpose of vetoing to assure a clean track reconstruction and charged particle background suppression. The anticoincidence detector prototype based on long BC-408 scintillator with silicon photomultipliers readout was tested using 300-MeV positron beam of synchrotron C-25P ‘‘PAKHRA’’ of Lebedev Physical Institute. The measurement setup, design concepts for the prototype detector together with test results are discussed.

The AMS-02 Anticoincidence Counter

The AMS-02 detector will measure cosmic rays on the International Space Station. This contribution will cover production, testing, space qualification and integration of the AMS-02 anticoincidence counter. The anticoincidence counter is needed to to assure a clean track reconstruction for the charge determination and to reduce the trigger rate during periods of high flux.

Hard X-Ray Detector (HXD) on Board Suzaku

Abstract The Hard X-ray Detector (HXD) on board Suzaku covers a wide energy range from 10 keV to 600 keV by the combination of silicon PIN diodes and GSO scintillators. The HXD is designed to achieve an extremely low in-orbit background based on a combination of new techniques, including the concept of a well-type active shield counter. With an effective area of $142 \,\mathrm{cm}^{2}$ at 20 keV and $273 \,\mathrm{cm}^{2}$ at 150 keV, the background level at sea level reached $\sim 1 \times 10^{-5} \,\mathrm{cts} \,\mathrm{s}^{-1} \,\mathrm{cm}^{-2} \,\mathrm{keV}^{-1}$ at 30 keV for the PIN diodes, and $\sim 2 \times 10^{-5} \,\mathrm{cts} \,\mathrm{s}^{-1} \,\mathrm{cm}^{-2} \,\mathrm{keV}^{-1}$ at 100 keV, and $\sim 7 \times 10^{-6} \,\mathrm{cts} \,\mathrm{s}^{-1} \,\mathrm{cm}^{-2} \,\mathrm{keV}^{-1}$ at 200 keV for the phoswich counter. Tight active shielding of the HXD results in a large array of guard counters surrounding the main detector parts. These anti-coincidence counters, made of $\sim 4 \,\mathrm{cm}$ thick BGO crystals, have a large effective area for sub-MeV to MeV $\gamma$-rays. They work as an excellent $\gamma$-ray burst monitor with limited angular resolution ($\sim 5^{\circ}$). The on-board signal-processing system and the data transmitted to the ground are also described.

The Anti-Coincidence Counter shield of the AMS tracker

The AMS-02 tracker is surrounded by a highly efficient scintillator screen, the Anti-Coincidence Counter (ACC). It is used for suppressing tracks from outside the main tracker acceptance. We describe methods to ensure that the ACC works at very high efficiency and a high degree of homogeneity.

The mechanical design of a gas supply and mixing system for the AMS-02 particle detector onboard the international space station

The Alpha Magnetic Spectrometer 02 is a particle physics experiment that will search for antimatter, dark matter, and measure cosmic rays in space aboard the International space station for 3 years . It is comprised of an array of sub-detectors: Transition Radiation Detector (TRD); Time of Flight detector; Anti-Coincidence Counter; Silicon Tracker; Ring Imaging Cherenkov counter; Electromagnetic Calorimeter and requires the operation of a cryogenic super conducting magnet at its core. It is built by an international collaboration of more than 100 scientists spread all over Europe, USA and the far East. The TRD that is located above the Cryomagnet and Upper Time of Flight, consists of several layers of straw modules interleaved with a fiber fleece material and arranged in a conical octagon structure built out of a carbon fiber/aluminum honeycomb sandwich. A charged particle traversing this detector produces characteristic electromagnetic radiation in each layer that is measured in the gas filled array of straw tubes. From this, the mass and momentum of the particle can be measured provided the tubes are filled with the proper gas mixture. The TRD gas supply stores 50 kg of gas corresponding to 8100 l Xe and 2000 l CO 2 at 1 atm , filters, mixes, recirculates, and purges a daily supply of Xe/CO 2 (80%/20%) gaseous mixture, thus supplying the TRD with clean, mixed gas for the 3-year ISS mission. Designing and building this reliable, weight optimised system to withstand launch loads and the harsh space environment presented a formidable engineering challenge. Adding to the complexity of the system was that a flexible valve/pump arrangement was needed to control mixture ratio, circulation flow and pressure, and purging. These studies are presented in the paper.

The PAMELA experiment on satellite and its capability in cosmic rays measurements

The PAMELA equipment will be assembled in 2001 and installed on board the Russian satellite Resurs. PAMELA is conceived mainly to study the antiproton and positron fluxes in cosmic rays up to high energy (190 GeV for p ̄ and 270 GeV for e +) and to search antinuclei, up to 30 GeV/n, with a sensitivity of 10 −7 in the He / He ratio. The PAMELA telescope consists of: a magnetic spectrometer made up of a permanent magnet system equipped with double sided microstrip silicon detectors; a transition radiation detector made up of active layers of proportional straw tubes interleaved with carbon fibre radiators; and a silicon–tungsten imaging calorimeter made up of layers of tungsten absorbers and silicon detector planes. A time-of-flight system and anti-coincidence counters complete the PAMELA equipment. In the past years, tests have been done on each subdetector of PAMELA; the main results are presented and their implications on the anti-particles identification capability in cosmic rays are discussed here.

Pitch shifts of mistuned partials: a time-domain model.

Mistuning one partial of a complex harmonic tone makes that partial easier to hear as a tone separate from the complex. At the same time, two pitch shifts may be observed. First, the low pitch of the complex is shifted in the direction of the mistuning, as if it were "pulled" by the partial. Second, the mistuning of the partial is perceptually exaggerated, as if the pitch of the partial were "pushed" away from the harmonic series defined by the complex. This paper shows how the latter effect can emerge within a hypothetical neural circuit. The circuit involves a gating neuron fed by three pathways, one direct and excitatory and the other two delayed and inhibitory. The neuron responds to any excitatory input spike unless it is accompanied by an inhibitory input spike on either delayed input, thus acting as a kind of "anticoincidence counter." The first delay is fixed and tuned to the period of the background harmonic complex. Its purpose is to weaken correlates of in-tune components and allow the mistuned partial to stand out. The second delay is variable and used to estimate the period of the mistuned partial, by searching for a minimum output as a function of delay. With an appropriate choice of parameters, the estimate is subject to shifts that are of the same sign as the mistuning and that peak at about 4% mistuning and decrease beyond, as observed experimentally.

The ALPHA Magnetic Spectrometer

The ALPHA Magnetic Spectrometer (AMS) will be the first large magnetic spectrometer in space. It is scheduled to be installed on the future International Space Station ALPHA (ISSA) in the year 2002 to perform measurements of the charged particle composition to answer fundamental questions in particle physics and astrophysics. Before installation on ISSA, AMS will fly on the shuttle DISCOVERY for a period of 10 days starting in May 1998. This will enable AMS to perform a test of the apparatus and first measurements. The AMS detector has five major components: A permanent NdFeB magnet, six planes of Silicon double-sided microstrip detectors, a plastic scintillator time of flight hodoscope, a plastic scintillator anticoincidence counter and an Aerogel Cherenkov threshold counter. In addition, there are electronics, support infrastructure and interfaces.

A simple crystal spectrometer for low-energy x-rays emitted from radioactive sources

A crystal spectrometer has been designed for the study of low-energy x-rays (1–10 keV) emitted from radioactive sources. A position-sensitive proportional counter (PSPC) is used for the detection of x-rays diffracted by a plane crystal of LiF(220). An anti-coincidence counter mounted at the rear of the PSPC is used to reduce background counts caused by high-energy radiations. The energy resolution of 11.2 ± 0.5 eV (FWHM) for 5898.8-eV Mn-K αl line has been achieved with the aid of a simple device for the source arrangement.

The Argonne low level14C counting system

A low level14CO2 counting system is described. This system was used to process several thousand CO2 samples derived from atmospheric collections at various altitudes. Special features include counter construction utilizing electrolytic copper and shielding with neutron moderating and absorbing paraffin containing sodium metaborate. The effect of steel shielding thickness is shown, and the anticoincidence counters are described. Purification of the CO2 for proportional counting is discussed.

The use of microprocessors and microcomputers in liquid scintillation counting

The use of microprocessors is demonstrated in the case of an anticoincidence liquid scintillation counter which is used in environmental monitoring. The data reduction and the evaluation of results by means of microcomputers is described. Some results obtained by these methods are presented.

Multielement proportional counters for low-level 3H and 14C counting

A new type of proportional counter designed for low-level counting of soft beta and X-ray emitters is described. The counter consists of inner and ring anticoincidence counters. However, the simple inner counter is replaced by 7 ( 14C counter) or 55 ( 3H counter) element counters of the same dimensions arranged in a hexagonal form separated from each other by cathode wires. The background reduction is achieved by an internal and external system of anticoincidence. Counter characteristics are discussed for 3H and 14C counting using methane and propane gas fillings. Multielement proportional counters can be widely used for low-level radioactivity measurements of several radioisotopes as well as in other types of experiments, e.g. in orbital electron capture measurement.

An automatic carbon-14 gas analyzer for organic compounds and biological samples

The present paper concerns automatic measurement of the radioactivity of substances labeled with carbon-14 isotope. The organic compounds or biological samples are combusted in an oxygen chamber. The oxygen excess is converted by hydrogen into water vapor in a reactor filled with copper and copper oxide. The water is retained by condensation and the carbon dioxide is swept by means of a counting gas, preferably propane or butane or a mixture of such gases, into an anticoincidence counter. The carbon-14 gas analyzer allows the measurement of carbon-14 isotope with high accuracy and sensitivity in a fully automated way, entirely free of manual intervention.

University of Washington Dates IV

The dates reported in this list are for geologic and archaeologic samples only. During the interval since our last date list (R, 1966, v 8, p 498-506) most of our measurements have been on samples of sea water. These will be reported separately at a later time. The methods used are essentially those reported previously (R, 1963, v 5, p 80-81) but with the following notable changes and additions: We now prepare our methane counting gas as described in Buddemeier et al (1970). Our IL membrane counter has since been augmented by 3 additional counters. Two of these are IL quartz proportional counters inside geiger anticoincidence shields. Operating pressures are ca 1.5 to 4atm. Backgrounds of these 2 counters are in the neighborhood of 1.8 and 3cpm and the net counting rate of NBS oxalic acid ranges from 7 to 18.7cpm, depending on the pressure. The third counter (“minicounter”) is rather special: .IL quartz proportional counter inside a methane proportional anticoincidence counter. Sample and anticoincidence counting gases are introduced simultaneously with a differential pressure that never exceeds a few cm Hg. The sample filling side is constructed so as to minimize dead volume; over 80% of the sample gas is inside the active volume of the 14C counter. The range of filling pressures which are possible is ca 1 to 4atm.

Calibration of large area scintillation counters on cosmic rays

We report on the construction and calibration of a 6 m2 scintillation counter. The counter consisted of two 1.22×2.44×0.051 m pieces of clear Lucite which were optically joined along a common edge. Optically coupled on top of these were sixteen 0.61×0.61×0.019 m squares of NE 110 plastic scintillator. Light collection was achieved with eight photomultiplier tubes. This counter had an operational attenuation length of 4.8±0.9 m. Calibration of this counter with an anticoincidence counter to discriminate against multiple particle events is described. This anticoincidence counter permitted particles that passed through a small calibration area to be counted only if no other particles were passing through the remainder of the detector at the same time. Large area counters will often receive more than a single particle per event. Theoretical calculations for purely electromagnetic extensive air showers indicate that the 6 m2 counter tested receives an average of 2.5 particles per event. The calibration data yield 1.79±0.08 particles per event. These results imply that if calibration on the response from a single particle of an extensive air shower is desired, it is necessary to use the anticoincidence counter method described for counters of more than a few square meters area.

An extremely low-level X-ray spectrometer

An extremely low-level X-ray counter system has been constructed with heavy-mass and anticoincidence shieldings. The detector is made of oxygen-free copper and of cylindrical form. It operates as a proportional counter of gas-flow type (argon-methane), inside of which are put samples. It is surrounded by 7mm thick purified mercury, multiwire GM anticoincidence counters, 1 cm thick oxygen-free copper, 12 cm thick iron, and finally 10 cm lead. The whole assembly is built in an underground cell heavily shielded from major cosmic ray components with a rock cover of at least 100 mwe. After careful measurements of the background counting rate, it was found that oxygen-free copper still contains some radioactive impurities, constituting a considerable portion of background count. By coating the inside wall of sample holders with purified nickel or copper, the background counting rate was reduced to a great extent. The definitive background counting rate is 0.1 cpm/keV in the energy region of 4–5 keV for 940 cm 2 of sample area (2π geometry).

Vienna Radium Institute Radiocarbon Dates I

A dating system consisting of gas sample counter with internal anticoincidence counter ring, transistorized electronic equipment, and chemical apparatus was developed in the Institute (Felber and Vychytil, 1962; Felber, 1965). A high voltage supply Fluke Model 408B is used. For routine dating, begun in 1965, an improved 2.4 L counter with Teflon insulators is used, shielded on all sides by 20 cm of iron. The counter is run with methane at 760 torr/15°C. Spurious counts are carefully eliminated by a systematic procedure (Felber, 1966). Stability of electronics and counter is checked once a day by taking the topmost part of the peak of Mnα-X-rays following electron capture in Fe-55, radiated through a beryllium window. Checking is done with the same single channel analyzer (switched over to operation with small window) used for energy discrimination (switched over to two discriminator operation) during measurement. If any change should be observed, discriminator settings are corrected. Energy discrimination is not optimized (Felber, 1962) because a neutron generator using (d,t) reaction is run in the same building in which the samples are prepared: the lower discriminator is set above tritium maximum energy at 22 keV, the upper one at 120 keV, the highest possible energy absorption of C14β particles in the special counter. The background is 1.58 cpm, the net contemporary value (95% of NBS oxalic acid standard activity) is ca. 8.8 cpm.

Glasgow University Radiocarbon Measurements I

Two radiocarbon counting systems have been established in the Chemistry Department, University of Glasgow, since late 1967.The counting gas is methane, at pressures up to 10 atm, and 2 alternative procedures are followed for methane production, (a) high pressure synthesis in a stainless steel 4.5 1 reactor and (b) low pressure synthesis in an all glass flow-reactor. Both systems employ 0.5% ruthenium on alumina pellets as catalyst (Engelhard Industries Ltd.). Early samples synthesized with Air Products' hydrogen showed evidence of tritium contamination. This gas supply was later replaced with tritium-free hydrogen supplied by Messrs. Griesheim, Düsseldorf, Germany. Both detectors used for routine measurements are 0.5 1 internal gas counters supplied by Beckman Instruments Inc., California. The detectors are surrounded by a concentric-wall multiple anode anticoincidence counter. The entire counter assembly is encased within a 4-in.-thick lead shield manufactured from aged lead by J. Girdler and Co., London. Counter electronics, anticoincidence system and power supply are of Beckman design (Sharp and Ellis, 1965).

Br82mand Its Decay Scheme

The discovery of a new activity of bromine is reported and is assigned to a 2(-) isomeric state of ${\mathrm{Br}}^{82}$. The new activity is chemically identified as bromine and shown to be the short-lived parent of ${\mathrm{Br}}^{82}$. It decays primarily by a highly converted $M3$ transition ($\ensuremath{\alpha}=382\ifmmode\pm\else\textpm\fi{}75$) of 46 KeV to the 5(-) ground state of ${\mathrm{Br}}^{82}$. Two weak branches in the proposed decay scheme lead by beta emission to the 0.78-MeV level (0.15%) and the 1.48-MeV level (0.024%) of ${\mathrm{Kr}}^{82}$. Time-dependent gamma spectra, obtained with a large anticoincidence counter, demonstrate the growth of the 2.65-MeV sum peak of ${\mathrm{Br}}^{82}$ after thermal-neutron activation of N${\mathrm{H}}_{4}$Br. Short-lived gamma peaks at 46 keV, 0.78 MeV, and 1.48 MeV were observed in the gamma spectra of an activated sample of enriched N${\mathrm{H}}_{4}$Br (99.32% ${\mathrm{Br}}^{81}$). X-ray spectra of activated N${\mathrm{H}}_{4}$Br taken with an argon-methane proportional counter provide evidence that the short-lived component is a thermal-neutron activation product. One-component decay curves of the Br $K$ x rays over more than 6 half-periods define the half-life of ${\mathrm{Br}}^{82m}$ as 363\ifmmode\pm\else\textpm\fi{}2 sec.

Riken Natural Radiocarbon Measurements I

Natural C14 measurements at the Institute of Physical and Chemical Research (RIKEN) became routine in 1962. The counters presently used are made of stainless steel with a volume of about 2.7 L. They are surrounded by 2.5 cm of pure lead, a ring of 22 propane gas-flow anticoincidence counters, about 10 cm of boric acid and 20 cm of iron. When filled with dead CO2 up to 2 atm, they gave a background counting rate of about 9 cpm (Hamada, 1960).In this article, results obtained for geologic and archaeologic samples since 1962 are described. Dates have been calculated on the basis of the C14 half-life of 5568 yr, and 95% of NBS oxalic acid as modern standard. Correction for isotopic fractionation was not applied.