High Energy Radiation Detection Research Articles

Growth and characterization of Cd 1− xZn xTe thin films prepared from elemental multilayer deposition

Cd 1− x Zn x Te is a key material for fabrication of high-energy radiation detectors and optical devices. Conventionally it is fabricated using single crystal growth techniques. The method adopted here is the deposition of elemental multilayer followed by thermal annealing in vacuum. The multilayer structure was annealed at different temperatures using one to five repetitions of Cd–Zn–Te sequence. X-ray diffraction pattern for the multilayer with five repetitions revealed that annealing at 475 °C yielded single-phase material compared to other annealing conditions. EDX spectroscopy was carried out to study the corresponding compositions. Photoluminescence properties and change of resistance of the multilayer under illumination were also studied. The resistivity of the best sample was found to be a few hundreds of Ω cm.

Scintillation mechanisms of inorganic materials: From crystal characteristics to scintillation properties

Finding new inorganic scintillator crystals with better performance for demanding applications, such as high-energy physics, medical imaging, and radiation detection, has been a long-standing challenge. Thanks to an intensive interdisciplinary effort between theoreticians, experimentalists and crystal growers, current scintillator performances are reaching the intrinsic limits imposed by the crystal. However, demand continues for more efficient scintillators with higher light output, better energy resolution and lower cost of production. This article discusses the basic concepts of scintillation in inorganic materials, focusing on how physics can provide pathways to assist in scintillator discovery.

Growth of Thick Epitaxial CdTe Films by Close Space Sublimation

This paper reports on a detailed study of the development of the close space sublimation method, which has been widely used in the preparation of polycrystalline CdTe/CdS solar cells, as an epitaxial method for the growth of thick CdTe single crystal films over 200 μm on GaAs and Ge substrates for high-energy radiation detectors. The resulting microscopic growth phenomena in the process are also discussed in this paper. High-quality single crystalline CdTe thick films were prepared with x-ray rocking curves full width at half maximum (FWHM) values, which were ∼100 arcsec on Ge substrates and 300 arcsec on GaAs substrates. The quality of thick films on Ge(100) showed a substantial improvement with nucleation in a Te-rich growth environment. No Te inclusions in the CdTe films grown on GaAs(211)B and Ge(100) were observed with IR transmission imaging. Photoluminescence of CdTe/Ge shows a large reduction in the 1.44 eV defect energy bands compared with films grown on GaAs substrates. The film resistivity is on the order of 10 10 Ω cm, and the film displayed some sensitivity to alpha particles.

Crystal Growth and Characterization of CdTe and Cd0.9Zn0.1Te for Nuclear Radiation Detectors

AbstractCdTe and Cd0.9Zn0.1Te (CZT) crystals have been studied extensively at EIC Laboratories, Inc. for various applications including x- and γ-ray imaging and high energy radiation detectors. The crystals were grown from in-house zone refined ultra pure precursor materials using a vertical Bridgman furnace. The growth process has been monitored, controlled and optimized by a computer simulation and modeling program (MASTRAPP). The grown crystals were thoroughly characterized after sequential surface passivations and post-growth annealing treatments with and without component overpressures. The infrared (IR) transmission images of the post-treated CdTe and CZT crystals showed average Te inclusion size of ∼10 μm for CdTe crystal and ∼8 μm for CZT crystal. The etch pit density was ≤ 5×104 cm−2 for CdTe and ≤ 3×104 cm−2 for CZT. Various planar and Frisch collar detectors were fabricated and evaluated. From the current-voltage measurements, the electrical resistivity was estimated to be ∼1.5×1010 Ω·cm for CdTe and 2-5×1011 Ω·cm for CZT. The Hecht analysis of electron and hole mobility-lifetime products (μτe and μτh) showed μτe=2×10−3 cm2/V (μτh=8×10−5 cm2/V) and μτ3-6×10−3 cm2/V (μτh=4-6×10−5 cm2/V) for CdTe and CZT, respectively. Final assessments of the detector performance have been carried out using 241Am (60 keV) and 137Cs (662 keV) energy sources and the results are presented in this paper.

Detection of Very High Energy Radiation from the BL Lacertae Object PG 1553+113 with the MAGIC Telescope

In 2005 and 2006, the MAGIC telescope observed very high energy gamma-ray emission from the distant BL Lac object PG 1553 + 113. The overall significance of the signal was 8.8 sigma for 18.8 hr of observation time. The light curve shows no significant flux variations on a daily timescale; the flux level during 2005 was, however, significantly higher compared to 2006. The differential energy spectrum between similar to 90 and 500 GeV is well described by a power law with photon index. Gamma = 4.2 +/- 0.3. The combined 2005 and 2006 energy spectrum provides an upper limit of z = 0.74 on the redshift of the object.

Characterization of the vapour grown CdTe crystals for high energy radiation detectors

AbstractGrowth steps and set‐up for the pure and chlorine doped cadmium telluride single crystals preparation by a vertical configuration of sublimation travelling heater method without seeding are described. The structural, electrical and transport properties of as‐grown material were investigated by different techniques: infrared transmission spectroscopy, double‐crystal X‐ray diffractometry, Hall effect, conductivity, photoelectric measurements and chemical etching. It was concluded that the most suitable material for fabrication of X‐ray and γ‐ray non‐cooling detectors are single crystals doped with Cl in the range of NCl = 1018–1019 cm–3. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Observation of PeV Gamma Rays from the Monogem Ring with the Tibet Air Shower Array

We searched for steady PeV gamma-ray emission from the Monogem ring region with the Tibet air shower array from 1997 February to 2004 October. No evidence for statistically significant gamma-ray signals was found in a region 111$\degr$ $\leq$ R.A. $<$ 114$\degr$, 12$\fdg$5 $\leq$ decl. $<$ 15$\fdg$5 in the Monogem ring where the MAKET-ANI experiment recently claimed a positive detection of PeV high-energy cosmic radiation, although our flux sensitivity is approximately 10 times better than MAKET-ANI's. We set the most stringent integral flux upper limit at a 99% confidence level of 4.0 $\times$ 10$^{-12}$ cm$^{-2}$ s$^{-1}$ sr$^{-1}$ above 1 PeV on diffuse gamma rays extended in the 3$^{\circ}$ $\times$ 3$^{\circ}$ region.

Image Intensification in Silver Halide Photographic Materials for Detection of High-Energy Radiation by Reprecipitation of Elemental Silver

A process for the intensification of silver images on AgHal photographic materials designed for detection of high-energy (X- and γ-ray) radiation was proposed, which is based on the “reprecipitation” of elemental silver and a decrease in its dispersion and comprises the treatment of silver with an aqueous solution containing potassium hexacyanoferrate(III) and potassium chloride or bromide at the first step and with a solution containing tin(II) chloride, potassium thiocyanate, sodium N,N′-ethylenediamine tetraacetate, and potassium hydroxide at the second step. By this process, the optical densities of image over a wide (0.5–2.0) range was increased by a factor of 3–5; as a result, the photographic sensitivity S0.85 and S2.00 was enhanced by almost an order of magnitude with the retained or slightly increased gradient g, fog density D0, and resolving power of the material.

Growth of CdZnTe and CdSeTe crystals for p–i–n radiation detectors

High-energy radiation detectors being operated at room temperature have been extensively studied on the bulk CdZnTe. Metal organic chemical vapor deposition (MOCVD) technique has been intensively investigated in the low substrate temperature of epitaxial film growth. Hydrogen radicals generated by inductively coupled RF remote plasma are introduced into the reaction region with source materials. These epitaxial growth processes are carried out at a low substrate temperature below 200°C. The results obtained suggest that the remote plasma-enhanced MOCVD method can be one of the promising methods for CdZnTe–CdSeTe epitaxial growth. These growths are proposed for fabrication of the high-energy radiation detector. Using this technique, p-type CdZnTe layer and n-type CdSeTe epitaxial layer are formed on intrinsic CdZnTe substrate to form p–i–n diode.

Keys to the Enhanced Performance of Mercuric Iodide Radiation Detectors Provided by Diffraction Imaging

ABSTRACTHigh resolution monochomatic diffraction imaging is playing a central role in the optimization of novel high energy radiation detectors for superior energy resolution at room temperature. In the early days of the space program, the electronic transport properties of mercuric iodide crystals grown in microgravity provided irrefutable evidence that substantial property improvement was possible. Through diffraction imaging, this superiority has been traced to the absence of inclusions. At the same time, other types of irregularity have been shown to be surprisingly less influential. As a result of the knowledge gained from these observations, the uniformity of terrestrial crystals has been modified, and their electronic properties have been enhanced. Progress toward property optimization through structural control is described.

Enhancement of Mercuric Iodide Detector Performance Through Crystal Growth in Microgravity: the Roles of Lattice Order

AbstractThe hole-mobility•carrier-lifetime product of α mercuric iodide high energy radiation detectors has been enhanced through vapor crystal growth in microgravity. This improvement is closely correlated with specific characteristics of the crystal lattice, which have been identified by high resolution synchrotron x-ray diffraction imaging. These structural features and the associated performance are now being approached in terrestrial growth of α mercuric iodide.Gravity may affect the uniformity of this crystal lattice in two distinct ways: 1) directly through deformation that it imposes on the lattice during growth and 2) indirectly through convection, which mixes any extraneous material. Inclusions associated with these processes harden the lattice and facilitate lattice folding. These changes affect the electronic parameters of detectors made from the crystals. As purification procedures are optimized, the incorporation of extraneous material is curtailed, enhancing electronic properties in spite of lattice flexing through loss of precipitation hardening.These studies provide insight into the contribution of various aspects of crystalline order in α-mercuric iodide crystals to property improvement. This knowledge has led to modification of requirements for starting materials, adjustment of physical vapor growth procedures, and change in crystal handling procedures. As a result, the electronic performance of terrestrially grown radiation detectors has been improved, and we provide evidence that further enhancement is still possible.

EGRET detection of high-energy gamma radiation from the OVV quasar 3C 454.3

High-energy gamma radiation has been observed from the optically violent variable quasar 3C 454.3 (PKS 2251 + 158) by the Energetic Gamma-Ray Experiment Telescope on the Compton Observatory. During the 1992 January-February observation, the emission showed a power-law photon spectrum with an exponent of -2.18 +/- 0.08. The flux density (greater than 100 MeV) was observed to vary within the range (0.4-1.4) x 10 exp -6 photon/sq cm s on a time scale of less than a week. Lower sensitivity observations during 1992 April and May also detected emission within that range, but with lower statistical significance. An earlier low-sensitivity exposure during 1991 August gave a 95 percent confidence upper limit of 0.26 x 10 exp 6 photon/sq cm s. The similarity of the gamma-ray emission of 3C 454.3 to that of 3C 279 parallels the similarity of these two objects at lower frequencies.

Detection of high-energy gamma radiation from quasar 3C 279 by the EGRET telescope on the Compton Gamma Ray Observatory

Intense gamma radiation has been observed from the direction of the quasar 3C 279 throughout the energy range from 30 MeV to over 5 GeV by the Energetic Gamma Ray Experiment Telescope (EGRET) during the period June 15-28, 1991. Its spectrum is well represented by a photon differential power-law exponent of 2.0 +/- 0.1, with a photon intensity above 100 MeV of (2.8 +/- 0.4) x 10 exp -6/sq cm s. For E is greater than 100 MeV, the 2-sigma upper limits were 1.0 x 10 exp -6/sq cm s in 1973 from the SAS 2 observations and 0.3 x 10 exp -6/sq cm s for the combined 1976, 1978, and 1980 COS B observations. Hence, there has been a large increase in high-energy gamma-ray intensity relative to the earlier times, as there has been in the radio, infrared, optical, and X-ray ranges. This source is the most distant and by far the most luminous gamma-ray source yet detected.

Radiation-induced conductivity: High-speed detection of X rays and neutrons

Radiation-induced conductivity (RIC) is a generalized term for photoconductivity expanded to include nonelectromagnetic radiation. RIC offers several distinct advantages for the detection of high-energy radiation: (i) the speed of response of a detector is determined by a bulk property of the material, the carrier lifetime; (ii) the detector can be directly illuminated by the signal radiation-no dead layer; and (iii) the selection of the detector material and its geometry is very flexible. This paper will discuss the principles of RIC for X rays and neutrons, the fabrication of detectors, and applications. RIC detectors have been fabricated from Si, InP, GaAs, and diamond. Bulk and thin film materials have been used. The carrier lifetime was varied by the introduction of trapping sites in the material. This can be done in the material production process in the case of doping (e.g., Fe in InP) and thin films or produced from radiation damage of a pure crystalline material. Lifetimes as short as a few picoseconds have been observed. A variety of detectors have been tested using pulsed optical, X ray, and neutron sources. Absolute sensitivities and temporal response has been measured and compared to theoretical models of the detector's performance for both X rays and neutrons. Finally, applications of these detectors to inertial confinement fusion measurement will be shown.

Constraints on models of Cygnus X-3 from high-energy gamma-ray absorption at source

view Abstract Citations (34) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Constraints on Models of Cygnus X-3 from High-Energy Gamma-Ray Absorption at Source Protheroe, R. J. ; Stanev, Todor Abstract Very high energy gamma rays have been observed from the directions of several X-ray binaries. Using Cygnus X-3 as an example, consideration is given to the important issues of the absorption of the high-energy radiation on the optical and infrared light at source. Many models of this source have been proposed to explain the modulation of the X-ray and IR emission of Cygnus X-3. Such models are examined from the viewpoint of the propagation of high-energy gamma rays and, it is concluded that the interactions of high-energy gamma rays on the thermal radiation must play a significant role in the modulation of the observed fluxes. The detection of high-energy gamma-ray radiation from Cygnus X-3 restricts the dimensions and the temperatures of the hot plasma at and around the system, and of the stellar companion. Publication: The Astrophysical Journal Pub Date: November 1987 DOI: 10.1086/165777 Bibcode: 1987ApJ...322..838P Keywords: Absorption Spectra; Astronomical Models; Gamma Ray Astronomy; Wave Propagation; X Ray Binaries; Cygnus Constellation; Infrared Radiation; Thermal Plasmas; Astrophysics; GAMMA RAYS: GENERAL full text sources ADS | data products SIMBAD (1)

GAMMA RAY ASTRONOMY WITH COS‐B

Observational results in the field of gamma-ray astronomy that have been obtained to date with the COS-B satellite are discussed and questions raised by these observations are summarized. Following a brief review of the instrumental characteristics of COS-B and the extent of COS-B gamma-ray coverage of the sky, particular attention is given to the questions raised by the discovery of many unidentified gamma-ray sources with no apparent optical, X-ray or radio counterparts and the detection of high-energy gamma radiation from the quasar 3C 273, which suggests the role of gamma-ray emission in the creation of other radiation.

Bismuth germanate scintillators as detectors for high-energy gamma radiation

The properties of bismuth germanate (BGO) relevant to the detection of high-energy gamma-rays are discussed on the basis of a comparison between a 76 mm diameter by 76 mm long BGO scintillator and a 152 mm diameter by 254 mm long NaI(Tl) crystal. The two detectors were exposed to monoenergetic gamma rays from the 12C(p, p′γ) 12C reaction at the proton energy 17 MeV ( E γ = 4.44, 12.71 and 15.11 MeV) and from the 1H(t, γ) 4He reaction at the triton energy 9 MeV( E γ = MeV). The bismuth germanate detector has several properties which are important for the detection of high-energy gamma radiation.

Energy storage effect and retrieval in manganese doped zinc silicate

It is shown that a significant amount of energy can be stored at room temperature for long periods in the manganese activated zinc silicates upon excitation by short wavelength UV photons (>3.65eV), and X-ray radiation. The stored energy can be stimulated by long wavelength photons (infrared and red) resulting in visible green emission. This effect has potential application in high energy radiation detection and imaging.

The Detection of High Energy Radiation - Measurement of Flux Density and Spectra

First an outline of the principal methods of high energy physics to detect and to discriminate different particles within an unknown particle field is given. After that the instruments for Health Physics purposes are dealt with in some detail. Time-of-flight methods, spark chambers, Bonner spheres and activation detectors are reviewed with respect to particle energies of 1 to about 1000 MeV.