Detection Of X-ray Radiation Research Articles

Optical Diagnostics in Rarefied Flows

This article reviews the instrumental developments accomplished at ONERA in order to perform precise non-intrusive measurements of hypersonic flows using laser- and electron-beam-based optical techniques. Point line of sight and imaging measurements are possible. Point measurements have been implemented with Electron Beam Fluorescence (EBF) using detection of X-ray radiation and Coherent anti-Stokes Raman Scattering (CARS). When spatial resolution is not required, diode laser absorption spectroscopy yields results integrated along a line. EBF imaging using a high energy pulsed electron gun is also quite promising. Rotational and vibrational populations of nitrogen and nitric oxide have been measured in various hypersonic hyperenthalpic facilities, as well as rotational state-resolved velocities in shocks and boundary layers.

Application of CVD diamonds as dosimeters of soft X-ray emission from plasma sources

The thermoluminescent properties of polycrystalline chemical vapour deposition (CVD) diamond, as free-standing CVD cutting tool material, type CVDITE-CDM (De Beers Company), were studied with respect to its use in the dosimetry of soft X-ray emission from laser-produced plasma. The range of linearity for 5.9-keV radiation was measured to be only two orders of magnitude, ranging from a sensitivity threshold of ∼0.01 to ∼2 Gy. In this linearity range, the sensitivity of CVD diamonds is about 65 times lower than the sensitivity of TLD-100 dosimeters. The unpolished (grained) face of CVD diamonds shows ∼1.5-times higher thermoluminescence (TL) response after irradiation than the polished face, in the high-temperature range, but the polished face shows slightly higher TL response in the low-temperature range. A strong TL sensitivity to the blue portion of the visible light spectrum was measured. Simultaneous irradiation of TLD-100 dosimeters and CVD diamonds by soft X-rays emitted from a laser-produced plasma showed that CVDITE-CDM diamonds can be applied as detectors of intense soft X-ray radiation.

X-ray radiation detectors of “scintillator-photoreceiving device type” for industrial digital radiography with improved spatial resolution

Main types of photoreceivers used in X-ray digital radiography systems are luminescent screens that transfer the optical image onto charge collection instruments, which require cooling, and semiconductor silicon detectors, which limit the contrast sensitivity. We have developed and produced X-ray radiation detectors of “scintillator-photoreceiving device” (S-PRD) type, which are integrally located on the inverse side of the photodiode (PD). The receiving-converting circuit (RCC) is designed for data conversion into digital form and their input into PC. Software is provided for RCC control and image visualization. Main advantages of these detectors are high industrial resolution (3–5 line pairs per mm), detecting activity up to 20μm, controlled sensitivity, low weight and small size, imaging low (0.1–0.3mrad) object dose in real time. In this work, main characteristics of 32-, 64- and 1024-channel detectors of S-PRD type were studied and compared for X-ray sensitivity with S-PD detectors. Images of the tested objects have been obtained. Recommendations are given on the use of different scintillation materials, depending upon the purpose of a digital radiographic system. The detectors operate in a broad energy range of ionizing radiation, hence the size of the controlled object is not limited. The system is sufficiently powerful to ensure frontal (through two walls) observation of pipelines with wall thickness up to 10cm.

New semiconductor scintillators ZnSe(Te,O) and integrated radiation detectors based thereon

Data are presented on properties of a new type of scintillator based on isovalently doped crystals of zinc selenide. Depending upon concentration of activating dopants Te and O, the wavelength of the luminescence maximum is 590-640 nm, response time is 1-50 /spl mu/s, and afterglow level after 5 ms is not more than 0.01-0.05%. Conversion efficiency is 3-6% higher, and radiation stability is /spl sim/1000 times higher than for CsI(Tl) crystals. Accounting for their optical and physical properties, this type of scintillator is the most suitable for tomography uses in "scintillator-photodiode" detectors. The combination of semiconductor properties and characteristics of a highly efficient scintillator, which is observed in ZnSe(Te), makes it possible to create integrated scintielectronic detectors of X-ray radiation of the type "photosensitive heterostructure A/sup II/B/sup VI/ -semiconductor scintillator ZnSe(Te)." Detectors of charged particles and ultraviolet radiation based on the Schottky barrier structure of "metal-nZnSe(Te)" have been also developed, with quantum efficiency of 0.3-0.4 electron/quantum in the region 0.20-0.47 /spl mu/m.

LiF detectors application for detection of X-ray radiation from plasma

Abstract The LiF detectors of a commercial device with the measurement range from 25 keV to 1.3 MeV were successfully used for of the monitoring X-ray from the imploding liner plasma on the high current pulse generator S-300. The detector readings were discovered to decrease more than ten times behind a thin lavsan filter of 2 μm thick in comparison with the open detector readings. This result demonstrates a possibility of using the LiF detector for registration of soft X-ray less than 1 keV. The detectors work in the regime of fuli absorption of the incident X-ray radiation up to the energy of about 10 keV. The stability of the detector readings under identical experimental conditions allows one to use them for integral monitoring of the X-ray plasma radiation.

Comparison of four types of gamma- and X-ray detectors for environmental applications in the 10–450 keV energy range

The performance of four types of γ- and X-ray radiation detectors for environmental applications was evaluated in the 10–450 keV energy range. Two cadmium zinc telluride (CdZnTe) room temperature semiconductor detectors were evaluated along with a cryogenically cooled semiconductor detector and two different types of scintillation detectors. The energy resolution, absolute peak detection efficiency and peak-to-background ratio of each of the detectors were calculated and intercompared. The advantages and disadvantages of environmental applications of each detector, along with their performance results, are summarized.

The effect of elemental and hydrocarbon impurities on mercuric iodide gamma ray detector performance

Mercuric iodide is a room temperature semiconductor material that is used for gamma ray and x-ray radiation detection. Mercuric iodide is synthesized from mercuric chloride and potassium iodide and is then purified by a series of melts and sublimation steps and by zone refining. The mercuric iodide is grown into crystals and platelets and then fabricated into detectors. Elemental contamination may be a determining factor in the performance of these detectors. These contaminates may be present in the starting material or may be introduced during, or be unaffected by, the purification, growth or fabrication steps. Methods have been developed for the analysis of trace levels of elemental contamination. Inductively Coupled Plasma/Mass Spectroscopy (ICP/MS), Inductively Coupled Plasma/Optical Emission Spectroscopy (ICP/OES) and Gas Chromatography/Mass Spectroscopy (GC/MS) are used to determine sub ppm levels of many trace elemental impurities. Trace levels of many elemental impurities in the raw mercuric iodide are significantly reduced during the purification and zone refining processes. Though the levels of impurities are reduced, poor performing mercuric iodide detectors have contamination levels remaining or reintroduced which are higher for Ag, Al, Ca, Cu, Mg, Mn, Na, Pb and Zn than detectors with good gamma ray response. This paper will discuss the analytical methodology, the effects of purification on impurity levels, and the correlation between detector performance and impurity levels.

Physical-Chemical Considerations for Semiconductor Room-Temperature Radiation Detectors

ABSTRACTPhysical properties of large band gap semiconductors such as: HgI2, CdTe, Cd0.8Zn0.2Te, CdSe, Cd0.7Zn0.3Se, GaAs, PbI2 and TlBr are briefly reviewed and discussed in terms of their use as room temperature operating x-ray and gamma ray radiation detectors. It is shown that HgI2 which has the largest drift length for holes, λ=μτE i.e., the product of the mobility μh, life time τh and the electrical field E, is at present the leading material, being followed by the newly developed Cd0.8Zn0.2Te. Chemical defects in HgI2 were enhanced by doping the material with aliphatic, aromatic and oxyhydrocarbons as well as with excess Hg and I2 and the increase in unit cell parameter was studied as a function of the amount of dopant. The value of τ was measured as a function of dopant concentration and it was found that Hg doping causes the most severe trapping defects. Low temperature studies of τh down to 170K allowed the identification of the trapping energy levels and concentration of electrically active defects. Shallow traps of 0.13-0.18 eV stemming from deviation from stoichiometry of H-gI2 were found to be in the ppm level whereas deeper traps of 0.4-0.5 eV stemming from hydrocarbons were found to be in the ppb level. It is concluded that only extensive research on the physical, chemical and structural defects correlated with improved crystal growth and device fabrication methods, would lead, in the future, to improvements in λh also of the other large Eg semiconductor detector materials.

Use of UF-R and UF-VR photographic plates in laser plasma diagnostics based on continuous x-ray radiation in 0.1–1 nm spectral range

The results are given of an experimental investigation of a possible use of UF-R and UF-VR photographic films for diagnostics of a high-temperature plasma formed as a result of focusing of 1.06 μ laser radiation on the surface of a flat bulk Al target. These films were used to record continuous x-ray radiation in the 0.1–1 nm range. An analysis was made of the method of multichannel detection of x-ray radiation by photographic films. The method was applied to the measurement of the electron temperature of a plasma generated by laser radiation of 1013–1015 W/cm2 power density. The absolute and relative sensitivities of the UF-R and UF-VR photographic films to x-ray radiation were determined experimentally.

Detection Units for X-Ray Radiation

Units for the detection of X-ray radiation are described. Each unit consists of a multiproportional counter detector, a gas supply system and accompanying electronics, including an automatic gas gain - stabilization circuit. In the units detectors filled with Ne/CO2 as well as Ar/CO2 gas mixtures are being used. Measures are described to overcome pressure variations in the detector, total as well as partial, due to gas diffusion through the detector window.