Spin dependent electron scattering with the BLAST detector

The Bates Larger Acceptance Spectrometer Toroid (BLAST) is a detector designed to study in a comprehensive and precise way the spin dependent electromagnetic response of few-body nuclei. The BLAST scientific program is focussed on the study of these systems in terms of nucleon structure, the ground state few body structure built from the nucleon-nucleon interaction and the nature of the interaction of the virtual photon forQ ²≤1 (GeV/c)²). To accomplish its scientific goals, BLAST utilizes the latest technology available in the form of polarized electron scattering from pure, polarized internal gas targets. The Bates Soung Hall Ring (SHR) delivers longitudinally polarized electrons at the location of the BLAST detector. Measurement are currently underway, and and a brief status report is presented here.     

Charge form factor of the neutron at low momentum transfer from the 2H-->(e-->,e'n)1H reaction

We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The neutron form factor ratio GEn/GMn was extracted from the beam-target vector asymmetry AedV at four-momentum transfers Q2=0.14, 0.20, 0.29, and 0.42 (GeV/c)2.     

Silicon detector technology development in India for the participation in international experiments

A specific research and development program has been carried out by BARC in India to develop the technology for large area silicon strip detectors for application in nuclear and high energy physics experiments. These strip detectors will be used as pre-shower detector in the CMS experiment at LHC, CERN for π ⁰/λ rejection. The fabrication technology to produce silicon strip detectors with very good uniformity over a large area of ∼40 cm², low leakage currents of the order of 10 nA/cm² per strip and high breakdown voltage of >500 V has been developed by BARC. The production of detectors is already under way to deliver 1000 detector modules for the CMS and 90% production is completed. In this paper, research and development work carried out to develop the detector fabrication technology is briefly described. The performance of the silicon strip detectors produced in India is presented. The present status of the detector technology is discussed.      

A capture-gated fast neutron detection method

To address the problem of the shortage of neutron detectors used in radiation portal monitors(RPMs),caused by the ~3He supply crisis, research on a cadmium-based capture-gated fast neutron detector is presented in this paper. The detector is composed of many 1 cm × 1 cm × 20 cm plastic scintillator cuboids covered by 0.1 mm thick film of cadmium. The detector uses cadmium to absorb thermal neutrons and produce capture γ-rays to indicate the detection of neutrons, and uses plastic scintillator to moderate neutrons and register γ-rays. This design removes the volume competing relationship in traditional ~3He counter-based fast neutron detectors, which hinders enhancement of the neutron detection efficiency. Detection efficiency of 21.66% ± 1.22% has been achieved with a 40.4 cm × 40.4cm × 20 cm overall detector volume. This detector can measure both neutrons and γ-rays simultaneously. A small detector(20.2 cm × 20.2 cm × 20 cm) demonstrated a 3.3 % false alarm rate for a ~(252)Cf source with a neutron yield of 1841 n/s from 50 cm away within 15 s measurement time. It also demonstrated a very low(0.06%) false alarm rate for a 3.21 × 10~5 Bq ~(137)Cs source. This detector offers a potential single-detector replacement for both neutron and the γ-ray detectors in RPM systems.     

Pyroelectric infrared detector for precision earth sensor

Two new types of infrared detectors have been developed for the precision earth sensor in the three axis stabilized satellite, Engineering Test Satellite VI (ETS-VI). Both detectors have a pair of infrared sensing elements, each of which is made of a pyroelectric material and mounted on an immersion lens. A-type element is a flake of lead titanate ceramic, and B-type is a sputtered epitaxial film of calcium-modified lead titanate.The precision earth sensor consists of a scanning mirror and an infrared telescope containing an objective lens, plus either type of infrared detector.Detectivity of each type at 120Hz, which is the nominal frequency of the earth sensor's signal, is 1.5×10⁹Hz^1/2/W(A-type) and 2.7×10⁹Hz^1/2/W(B-type) at 1416.25m. Each value is 2.5 and 4.5 times as high as the previous model in ETS-V.A-type detector passed the space environmental test and the random error cf attitude measurement was 0.03 deg with the preliminary model of the earth sensor being ahead of the breadboard model. This measurement accuracy is nearly equal to that of the foremost earth sensor. A-type was chosen as the detector for ETS-VI.The random error of the earth sensor with B-type detector is 0.012deg, smaller than a half of the A-type sensor's error. Investigation of B-type is being continued in order to confirm its reliability for space use.     

Operating temperature and the responsivity of split-off band detectors

A GaAs/AlGaAs heterojunction is used as a spin-split-off band IR detector operating at or around room temperature. This detector structure followed a similar layer architecture to the quantum well IR photo detectors (QWIP) and Heterojunction Interfacial Work function Internal Photoemission (HEIWIP) detectors. Compared to QWIPs, the emitter layer thickness is increased to avoid confinement. Unlike either the QWIPs or HEIWIPs, these detectors will have two energy gaps (barriers) to obtain the wavelength threshold which could be used to design detectors either for optimum operating temperature or optimum responsivity. The free carrier energy gap is determined by the Al fraction and the spin-split-off transition energy provides another handle on controlling the effective threshold of the detector. Unlike QWIPs, these will also detect normal incidence radiation. A preliminary detector showed a peak responsivity of 0.29 mA/W at 2.5 μm at room temperature.     

A comparative study of gamma radiation effects on track properties of different PADC detectors

Track properties of gamma-irradiated polyallyldiglycol carbonate (PADC) detectors (Homalite, Pershore and Trastrack) are studied in the dose range of 10¹–10⁶ Gy. Results show that the bulk and track etch rates of all three types of PADC detector increase at doses higher than 10⁴ Gy. This increase is more pronounced in post-gamma exposed detectors. The change in etch rate ratio (S) for post-gamma exposed PADC–Homalite detectors is more significant when compared with the other detectors. The critical angle for etching shows that etching at a low temperature of 60 °C is more effective, and the critical angle value is decreased to a significant extent for all three types of PADC detectors. Etching efficiency of post-gamma exposed samples is found to be much higher than the pre-gamma exposed sample at the highest dose of 10⁶ Gy. When compared, it was found that of the three PADC detectors, PADC–Homalite detectors seem to be more sensitive to gamma irradiation.     

狭缝式高灵敏裂变中子探测系统

研制了狭缝-外延式高灵敏大面积PIN裂变中子探测系统. 其对14MeV，2.5MeV中子灵敏度可达10^-16C·cm²，比原有典型的脉冲裂变中子探测系统高4个量级. 采用外延式铅狭缝准直结构，研制灵敏区尺寸为60mm，厚度为200μm—300μm的大面积PIN半导体探测器、以Be膜为衬底，有效直径为60的²³⁵U裂变靶，解决了该探测器研制中的高灵敏度和n/γ分辨难题. 该系统已在实践中获得成功应用. 关键词： 裂变中子探测系统 大面积PIN探测器 大面积裂变靶 高灵敏探测系统     

CdZnTe <Emphasis Type="BoldItalic">γ</Emphasis> detector for deep inelastic neutron scattering on the VESUVIO spectrometer

In this paper it is shown that solid-state cadmium-zinc-telluride (CZT) is a promising photon detector for neutron spectroscopy in a wide energy interval, ranging from thermal (25 meV) to epithermal (70 eV) neutron energies. In the present study two CZT detectors were tested as part of the inverse-geometry neutron spectrometer VESUVIO operating at the ISIS pulsed neutron source. The response of the CZT detector to photon emission from radiative neutron capture in ²³⁸U was determined by biparametric measurements of neutron time of flight and photon energy. The scattering response function F(y) from a Pb sample has been derived using both CZT and conventional ⁶Li-glass scintillator detectors. The former showed both an improved signal to background ratio and higher efficiency as compared to ⁶Li glass, allowing us to measure F(y) up to the fourth ²³⁸U absorption energy (E_r=66.02 eV). Due to the small size of CZT detectors, their use is envisaged in arrays, with high spatial resolution, for neutron-scattering studies at high energy (>1 eV) and low wavevector (q <10 Å^-1) transfers. PACS 29.30.Hs; 29.30.Kv; 29.40.Kw; 61.12.Ek     

Nucleon form factors and the BLAST experiment

Measurements of the electric and magnetic form factors of the nucleon present a sensitive test of nucleon models and QCD-inspired theories. A precise knowledge of the neutron form factors at low Q² is also essential to reduce the systematic errors of parity violation experiments. At the MIT-Bates Linear Accelerator Center, the nucleon form factors have been measured by means of scattering of polarized electrons from vector-polarized hydrogen and deuterium. The experiment used the longitudinally polarized stored electron beam of the MIT-Bates South Hall Ring along with an isotopically pure, highly vector-polarized internal atomic hydrogen and deuterium target provided by an atomic beam source. The measurements have been carried out with the symmetric Bates Large Acceptance Spectrometer Toroid (BLAST) with enhanced neutron detection capability.     

History of infrared detectors

This paper overviews the history of infrared detector materials starting with Herschel??s experiment with thermometer on February 11^th, 1800. Infrared detectors are in general used to detect, image, and measure patterns of the thermal heat radiation which all objects emit. At the beginning, their development was connected with thermal detectors, such as thermocouples and bolometers, which are still used today and which are generally sensitive to all infrared wavelengths and operate at room temperature. The second kind of detectors, called the photon detectors, was mainly developed during the 20^th Century to improve sensitivity and response time. These detectors have been extensively developed since the 1940??s. Lead sulphide (PbS) was the first practical IR detector with sensitivity to infrared wavelengths up to ??3 ??m. After World War II infrared detector technology development was and continues to be primarily driven by military applications. Discovery of variable band gap HgCdTe ternary alloy by Lawson and co-workers in 1959 opened a new area in IR detector technology and has provided an unprecedented degree of freedom in infrared detector design. Many of these advances were transferred to IR astronomy from Departments of Defence research. Later on civilian applications of infrared technology are frequently called ??dual-use technology applications.?? One should point out the growing utilisation of IR technologies in the civilian sphere based on the use of new materials and technologies, as well as the noticeable price decrease in these high cost technologies. In the last four decades different types of detectors are combined with electronic readouts to make detector focal plane arrays (FPAs). Development in FPA technology has revolutionized infrared imaging. Progress in integrated circuit design and fabrication techniques has resulted in continued rapid growth in the size and performance of these solid state arrays.     

瞬时响应的粒子探测器模型

本文中将Unruh-DeWitt型粒子探测器改造成瞬时响应的粒子探测器。经过改进之后,所有理想的探测器应是等价的,尽管它们对同一物理状态的响应可能不一样。本文给出一个可行的方法用以计算在Minkowski真空中作任意运动的探测器的响应函数。 关键词：     

Study of fission track registration efficiency of γ-irradiated polyester track detector in solution medium

The fission track registration efficiency (K _wet) of the Garware polyester track (GPF) detector in solution has been determined with respect to the Lexan detector whose K _wet is very well known in the literature. The K _wet is found to be (1.2 ± 0.1) 10⁻³ cm. The track registration efficiency of the GPF detector in solution is better than the efficiencies of other nuclear track detectors reported in the literature. This implies that the threshold energies for track registration are different for different detectors and that GPF detector has a lower threshold-energy value. The effects of gamma irradiation in the dose range of 5–51 Mrad on the fission track registration efficiency (K _wet) of this track detector from the solution medium are also investigated. The results show that the K _wet values for the gamma-irradiated detectors in the above dose range in 2M HNO₃ solution medium decreases by ∼7–15%. The changes induced in the gamma-irradiated detectors as a function of gamma dose have also been studied by bulk-etch rate measurements.     

A STJ X-ray detector with a β-tantalum sublayer

The first step in the research and development of detectors for ¹⁸¹Ta Mössbauer spectroscopy based on superconductive tunnel junctions (STJ) is taken. The idea of using β-tantalum as a trapping layer for the inactivation of the base electrode in a detector with the structure β-Ta/Nb/Al, AlO _x /Al/Nb/NbN is successfully executed.     

Applicability of an X-ray and gamma-ray portable spectrometer for activity measurement of environmental soil samples

This paper presents a study on the applicability of a commercial X-ray and gamma-ray portable spectrometer (Rover) for in situ gamma-ray spectrometry. This portable spectrometer consists of a 3 × 3 × 1 mm (CdTe) Cadmium Telluride detector and a 30 × 30 mm [NaI (Tl)] Sodium Iodide detector. The radioactive sources used were ²⁴¹Am, ¹³³Ba, ¹⁵²Eu and ¹³⁷Cs tablet type, sealed with aluminum and polyethylene, as well as soil samples contaminated with ¹³⁷Cs. With the aid of these radioactive sources, this study determined the efficiency curve for both detectors. In addition, measurements were carried out to identify the minimum detectable activity (MDA) for both detectors, using time acquisition change ranging from 900 s to 138 h, depending on which detector was utilized and the sample distance. The results for the tablet-type sources were as follows: The MDA for the CdTe detector, while positioned 4.15 cm from the ¹³⁷Cs source, was 15 kBq and 6 kBq for energy lines 32 keV and 661.65 keV, respectively. However, when the distance between the source and detector was 100 cm, the 661.65 keV line presented a MDA of 68 kBq. Results for the soil samples were as follows: Using the CdTe detector, positioned 4.15 cm from the source, the MDA was 73 Bq for the ¹³⁷Cs 32 keV line. In relation to the ⁷Be soil samples, the MDA was 301 Bq when the detector was 4.15 cm from the source. Using the NaI (Tl) detector to analyze the ¹³⁷Cs 661.65 keV line, the MDA was 8 kBq when the detector was 100 cm from the tablet-type source. For the soil sample containing ¹³⁷Cs, the MDA was 7.4 Bq when the source was 2.8 cm from the NaI (Tl) detector. For those samples containing ⁷Be, and measured at the same distance (2.8 cm), the MDA was of 9.6 Bq. Based on the minimum detected activities obtained for both detectors, it is concluded that the in situ gamma-ray spectrometric system used to quantify soil sample activities with ¹³⁷Cs and ⁷Be is only appropriate when those activities are around one or more orders of magnitude larger than the usual radioactivity levels found in the environment. Even though it is a commercialized machine, the Rover system’s manufacturer does not provide the information cited in this abstract.     

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.     

Stressed and unstressed Ge:Ga detector arrays for airborne astronomy

We have constructed and used two dimensional arrays of both unstressed and stressed Ge:Ga photoconductive detectors for far-infrared astronomy from the Kuiper Airborne Observatory (KAO). The 25 element (5×5) arrays are designed for a new cryogenically cooled spectrometer, the MPE/UCB Far-Infrared Imaging Fabry-Perot Interferometer (FIFI). All of the pixels for the stressed array performed well on the first flights with FIFI; 25% of the detectors in the array are more sensitive than our best single element detector, with background limited noise equivalent powers (NEPs)3.0×10^–15 W Hz^–1/2 at 158 m and 40 km s^–1 spectral resolution. The average array element performs within±15% of this value. With a bias field of 0.1 V/cm, the average detector response is 20±6 Amp/Watt at 158 m. The cutoff wavelength and response also compare well with our single element detectors. The unstressed array delivers significantly better performance than our single element detector due to the lower thermal background in the new spectrometer. The average background limited NEp at 88 m and 35 km s^–1 spectral resolution is 7×10^–15 W Hz^–1/2. The least sensitive pixel is only 40% less sensitive. The unstressed array response at 88 m with a bias field of 1 V/cm is 5±1 Amp/Watt. Twenty four of the 25 elements worked on the first flights-on subsequent flights all channels have worked. Some of the exciting new science possible with far-infrared detector arrays is also discussed.     

Investigation of a CPG‐array CdZnTe γ‐ray imaging detector with single collecting electrodes readout

The single‐electrode readout method has been applied to a coplanar grid (CPG) array CdZnTe detector in order to halve the number of preamplifiers previously needed and to facilitate imaging applications of CPG detectors. A method of predetermining the width of the optimum collecting electrodes has also been proposed, using the calculated optimum relative gain factor G. Meanwhile, a detailed process for calculating the charge induction efficiency (CIE) is presented. To simplify the calculation process, the computational formula of the CIE was deduced through the integration of the weighting potential. For performance evaluation, a 2 × 2 CPG‐array CdZnTe detector was elaborately designed and tested with ¹³⁷Cs at 662 keV. Experimental results showed the capability of using the CPG‐array CdZnTe detector with single collecting electrode readout for γ‐ray imaging applications, with the same complexity of associated readout electronics as that of the pixelated CdZnTe detectors.     

Capabilities of the Gamma-400 Gamma-ray Telescope for Observation of Electrons and Positrons in the TeV Energy Range

The space-based GAMMA-400 gamma-ray telescope will measure the fluxes of gamma rays in the energy range from ∼20 MeV to several TeV and cosmic-ray electrons and positrons in the energy range from several GeV to several TeV to investigate the origin of gamma-ray sources, sources and propagation of the Galactic cosmic rays and signatures of dark matter. The instrument consists of an anticoincidence system, a converter-tracker (thickness one radiation length, 1 X₀), a time-of-flight system, an imaging calorimeter (2 X₀) with tracker, a top shower scintillator detector, an electromagnetic calorimeter from CsI(Tl) crystals (16 X₀) with four lateral scintillation detectors and a bottom shower scintillator detector. In this paper, the capability of the GAMMA-400 gamma-ray telescope for electron and positron measurements is analyzed. The bulk of cosmic rays are protons, whereas the contribution of the leptonic component to the total flux is ∼10⁻³ at high energy. The special methods for Monte Carlo simulations are proposed to distinguish electrons and positrons from proton background in the GAMMA-400 gamma-ray telescope. The contribution to the proton rejection from each detector system of the instrument is studied separately. The use of the combined information from all detectors allows us to reach a proton rejection of up to ∼1 × 10⁴.

     

The new micromegas X‐ray detectors in CAST

The last generation of micromegas, called microbulk, are ahead of classical gas detectors (or even other kind of micro‐pattern gas detectors) in gain stability, efficiency (by operation at high pressure), simplicity, robustness, energy resolution, readout features and radiopurity. This makes them a competent solution in the field of Rare Event Searches, a field where low background is the most appreciated feature of a detector. The CAST (CERN Axion Solar Telescope) experiment is the best example of their application in the X‐rays range. In CAST, these detectors have achieved background rates as low as 6 × 10^?6 counts keV^?1 cm^?2 s^?1. Beyond this nominal operation, there have been several periods where the background has been reduced to a level of 2 × 10^?7 counts keV^?1 cm^?2 s^?1, due to reasons which are under investigation. The CAST experiment will be presented, paying special attention to their microbulk micromegas, as well as the procedures to achieve low background. Latest news about the operation of these kinds of detectors for the first time in underground conditions will be advanced here. Copyright © 2011 John Wiley & Sons, Ltd.