Escape Peak Research Articles

MEASUREMENT OF GERMANIUM ESCAPE PEAKS IN PIXE SPECTRA RECORDED USING HIGH PURITY Ge (HPGe) DETECTOR

This paper deals with studies on Ge K α and K β escape peaks in particle induced X-ray emission (PIXE) spectra recorded by a high purity germanium (HPGe) detector. A knowledge of the energies and intensities of these escape peaks is desirable for accurate qualitative as well as quantitative analysis of elements by PIXE. The spectral interferences caused by Ge K escape peaks in the determination of Fe in U by PIXE are highlighted for illustration. A simple theoretical approach based on the production of Ge K X-rays inside the Ge crystal of the detector during the process of detection of the incident characteristic X-rays and the subsequent escape of a fraction of the produced radiations from the crystal, is described to calculate the intensity ratio of the Ge escape peak to its parent characteristic X-rays. The calculated values are in agreement with the experimental values and those estimated using the formulation provided in GUPIX software for PIXE. The Ge K escape peaks are very prominent; the intensities of Ge K α escape peaks, from bromine to silver, range from 15% to 6% of those of their respective K α X-rays. These intensities are, in general, considerably higher compared to those of Si escape peaks in spectra recorded by Si ( Li ) detector. Ge K escape peaks therefore may give rise to severe interferences. The present approach provides a precise (~8%) determination of the intensity of an escape peak and thereby facilitates a reliable PIXE analysis.

Trace metal analysis on hafnium silicate deposited Si wafer by Total Reflection X-ray Fluorescence

Hafnium silicate is a so-called high- k material, which is a new key material in the semiconductor field. This material is difficult to analyze by a conventional W-Lβ1TXRF source due to the high background originating from Hf-Lα lines. In this paper, the capability of Ir source TXRF analysis on hafnium silicate films is investigated with intentional contamination of Ti, Cr, Fe, Ni and Cu elements. The spectral fitting is discussed where X-ray resonant Raman scattering and escape peak of Ir-Lα overlap with Ni-Kα peak. The detection limits are estimated to 0.9 × 10 10 to 2 × 10 10 atoms/cm 2 for the transition metals.

Neutron inelastic scattering processes as a background for double-β decay experiments

We investigate several Pb$(n,{n}^{'}\ensuremath{\gamma}$) and Ge$(n,{n}^{'}\ensuremath{\gamma}$) reactions. We measure \ensuremath{\gamma}-ray production from Pb$(n,{n}^{'}\ensuremath{\gamma}$) reactions that can be a significant background for double-\ensuremath{\beta} decay experiments which use lead as a massive inner shield. Particularly worrisome for Ge-based double-\ensuremath{\beta} decay experiments are the 2041-keV and 3062-keV \ensuremath{\gamma} rays produced via Pb$(n,{n}^{'}\ensuremath{\gamma}$). The former is very close to the $^{76}\mathrm{Ge}$ double-\ensuremath{\beta} decay endpoint energy and the latter has a double escape peak energy near the endpoint. We discuss the implications of these \ensuremath{\gamma} rays on past and future double-\ensuremath{\beta} decay experiments and estimate the cross section to excite the level that produces the 3062-keV \ensuremath{\gamma} ray. Excitation \ensuremath{\gamma}-ray lines from Ge$(n,{n}^{'}\ensuremath{\gamma}$) reactions are also observed. We consider the contribution of such backgrounds and their impact on the sensitivity of next-generation searches for neutrinoless double-\ensuremath{\beta} decay using enriched germanium detectors.

Sulfur determination on stone monuments with a transportable EDXRF system

AbstractAn important part of the world's cultural heritage is represented by stone monuments. A very dangerous weathering process that deteriorates stone monuments and is caused by human activity is air pollution. One of the worst pollutants for stone monuments is associated with sulfur compounds, especially with gypsum. Gypsum is a rather soluble compound that may be washed away by rain. It leaves the surface of the stone clean but eroded and open to new corrosive processes.With transportable energy dispersive x‐ray fluorescence (EDXRF) instruments it is possible to conduct in situ investigations, mappings, registrations and evaluations of the stone‐degradation phenomena related to sulfate formation on stone and stone‐like materials by quantifying sulfur concentrations directly associated with the presence of gypsum.The EDXRF instrument used in this project is a commercial system comprising a miniaturized low‐power, air‐cooled tungsten x‐ray tube and a silicon drift detector (SDD) Peltier‐cooled detector.The EDXRF instrument was calibrated using a series of standard samples specifically developed for this project with a sulfur content ranging from 0.5 to 15%. Correlating the sulfur peak counts with sulfur concentrations, a straight calibration line (R2 = 0.9985) was obtained. Several high voltage levels of the x‐ray tube were tried to define the best operating conditions. The silicon escape peak of calcium had to be accounted for owing to its interference with the sulfur peak.In this paper we shall discuss the working method adopted and the results achieved following the examination of a number of stone monuments such as the “Fanciulla di Anzio” and other ancient Roman statues housed in the Roman National Museum, and the Sarcophagus of Pope Boniface VIII sculpted by Arnolfo di Cambio and situated in the Crypt of the Vatican Basilica. Copyright © 2007 John Wiley & Sons, Ltd.

Measurement of Compton scattering on bound electrons by the coincidence method

A review of results of the new method for measuring the Compton scattering on bound electrons in germanium, introduced by the presented authors, is given. It is based on the application of two detectors that operate in the coincidence mode. One detector is used as the scatterer and the other as the detector of scattered radiation. Two conditions, simultaneity of pulses from the two detectors and constant energy sum, result in very clean spectra in broad energy regions. Normalization of the Compton spectra to the Ge K X-ray escape peaks, which are measured simultaneously with the Compton spectrum, gives reliable double-differential Compton-scattering cross sections on an absolute scale. Several versions of the impulse approximation are compared to the cross sections obtained by the present method for incident photon energies in the range from 60 to 105 keV. The non-relativistic impulse approximation gives the best agreement to the experimental data. We point out the suitability of the new method for an investigation of the incoherent scattering function at small photon momentum transfer.

The spectral response of silicon X-ray detectors

A discrete analytic calculation of the spectral response of silicon drift detectors for X-rays is presented. The results are compared with measurements at BESSY II using monochromatic synchrotron radiation in the energy range from 0.2 to 2 keV. All Gaussian features (main, escape, and Al fluorescence peak) as well as the background are included in the model. The peak intensities are calculated from energy dependent probability distributions. The non-Gaussian background is produced by charge-loss in the entrance window. The charge loss of energetic photo and Auger electrons and the diffusion of low-energy secondary electrons into the aluminum dead layer are considered. The secondary electrons disperse in a Gaussian charge distribution with the width σ sec , which is the only free parameter of the model. All collected charge is summed up for every possible process and convoluted with electronic and Fano noise, yielding the energy distribution of the background. Its intensity is given by the probability of the process. This method generates all observed spectral background features using a single fundamental calculation scheme. It can, in principle, be applied to any type of semiconductor detector. The calculations are in very good agreement with the measurements.

THEORETICAL DESCRIPTION OF DOUBLE BETA DECAY TRACKS IN A GERMANIUM DETECTOR AND OF THEIR DEPENDENCE ON PARTICLE AND NUCLEAR PHYSICS — A REVIEW

In this review for the first time a theoretical description of the tracks of events of nuclear double beta decay in a large Ge detector is presented. It is obvious that in principle the shapes and sizes of these tracks — and the corresponding time structure of pulses — depend on particle physics and nuclear physics parameters such as neutrino mass, right-handed current parameters, and nuclear matrix elements. The knowledge of this dependence is of importance, since the key to probe the existence of 0νββ decay beyond observation of a signal at the Q value of the process, Qββ, is the discrimination of ββ events from background γ events (or other events), in almost any double beta decay experiment (see Refs. 2 and 3). In this review Monte-Carlo simulations of tracks of neutrino-accompanied (2νββ) and neutrinoless double beta decay (0νββ) events, and of various kinds of background processes such as multiple and other γ interactions are reported for a large Ge detector. The time history of the evolution of the individual events is followed and the sizes of the events (volumes in the detector inside which the energy of the event is released) are investigated. Effects of the angular correlations of the two electrons in ββ decay, which again depend on the above nuclear and (for 0νββ decay) particle physics parameters, are taken into account and have been calculated for this purpose for the first time on basis of the experimental half-life of 76 Ge and of realistic nuclear matrix elements. It is shown for ββ decay of 76 Ge , that 0νββ events are to a large extent separable from Compton scattering of γ events of the same energy, while double escape peaks of γ-lines show very similar behavior as 0νββ events, and in that sense can be useful for corresponding "calibration" of pulse shapes of the detector. The possibility to distinguish 0νββ events from γ events is found to be essentially independent of the particle physics parameters of the 0νββ process. A brief outlook is given on the potential of future experiments with respect to determination of the particle physics parameters 〈mν〉, 〈λ〉, 〈η〉. It is suggested, that the strategy in future 0νββ research should be, to combine confirmation of the HEIDELBERG-MOSCOW result with determination of the mechanism of the dominating decay, instead of repeating earlier experiments or ideas. The future experiment thus should not use 76 Ge or 136 Xe , but instead 124 Xe .

First detection of gamma-ray peaks by an undoped InSb Schottky detector

The compound semiconductor InSb, because of its very small band-gap energy, high density and high atomic number, is suitable for the substrate of X-ray detectors with high-energy resolution and high efficiency. An InSb Schottky detector is fabricated with an undoped InSb wafer and is used in the measurement of 133Ba gamma-rays. Here, the first observation of an escape peak of 81 keV gamma-rays emitted by 133Ba using an InSb detector is reported. The event ratios of the escape and 81 keV gamma-rays were estimated by a Monte Carlo simulation code as a function of depletion layer thickness and were compared with experimental result.

Characterisation of a Compton suppressed Clover detector for high energy gamma rays [formula omitted

Gamma ray spectra of two ( p , γ ) resonances have been utilised for the characterisation of the Clover detector at energies beyond 5 MeV. Apart from the efficiency and the resolution of the detector, the shapes of the full energy peaks as well as the nature of the escape peaks which are also very crucial at higher energies have been analysed with special attention. Proper gain matching in software have checked deterioration in the energy resolution and distortion in the peak shape due to addback. The addback factors show sharp increasing trend even at energies around 11 MeV.

Suitability of nuclear medicine gamma cameras as gamma spectrometers in the event of a radiological emergency

Nuclear medicine gamma cameras are large area NaI(Tl) scintillation detectors that measure both the position and energy of incident gamma rays. A typical, commercial, large field-of-view (LFOV), gamma camera has about 2000 cm 3 of useful detector volume with an entrance window of 50×40 cm 2 by 1 cm thickness. A 3″×3″ NaI(Tl) detector, by comparison, has 17.4% of the volume and 2.3% of the area of the LFOV gamma camera. A 2002 survey reported 11,700 gamma cameras as being installed in hospitals and clinics in the US. In the event of a radiological emergency, the ability to utilize some of this installed detector capacity would be desirable. This work investigates the feasibility of using the gamma camera as a large area gamma spectrometer for detecting and quantifying isotopes likely to be involved in a radiological emergency caused by dispersion of radioactivity by a so called “dirty bomb.” Monte Carlo modeling was used to analyze detection sensitivity as a function of energy for the camera vs. the 3″×3″ cylinder. For a point source positioned 100 cm from the face of the detector, the ratio of total extrinsic efficiency of the camera to that of the 3″×3″ cylinder varied from 40.3 at 140 keV to 7.3 at 5 MeV. Ratios for extrinsic efficiency of peaks (including the full energy peak, single escape, and double escape peaks) varied from 41.1 at 140 keV to 5.5 at 5 MeV. Modifications that will be required to enable the cameras to function as spectrometers over a wide energy range are described and discussed. Given the large sensitivity advantage, the fact that the camera is shielded on three sides, and that cameras are already present at many locations to where victims of a disaster would be transported, it is desirable that such system capabilities be investigated.

Monte Carlo assessment of soil moisture effect on high-energy thermal neutron capture gamma-ray by 14N

Among many conventional techniques, nuclear techniques have shown to be faster, more reliable, and more effective in detecting explosives. In the present work, neutrons from a 5 Ci Am–Be neutron source being in water tank are captured by elements of soil and landmine (TNT), namely 14N, H, C, and O. The prompt capture gamma-ray spectrum taken by a NaI (Tl) scintillation detector indicates the characteristic photo peaks of the elements in soil and landmine. In the high-energy region of the gamma-ray spectrum, besides 10.829 MeV of 15N, single escape (SE) and double escape (DE) peaks are unmistakable photo peaks, which make the detection of concealed explosive possible. The soil has the property of moderating neutrons as well as diffusing the thermal neutron flux. Among many elements in soil, silicon is more abundant and 29Si emits 10.607 MeV prompt capture gamma-ray, which makes 10.829 MeV detection difficult. The Monte Carlo simulation was used to adjust source–target–detector distances and soil moisture content to yield the best result. Therefore, we applied MCNP4C for configuration very close to reality of a hidden landmine in soil.

Position resolution and energy spectra from a two-dimensional gas proportional detector in the region of the krypton K-edge

Results are presented of the position resolution and energy spectra from a two-dimensional gas proportional detector in the region of the krypton K-edge of 14.326 keV. Measurements were made with a gas mixture of Kr/10%CO 2 and the position resolution was fit by a simple model based on the photoelectron and Auger electron range. In the energy region below the K-edge, X-rays interact primarily in the L-shell, yielding an energetic photoelectron that limits position resolution to no better than several hundred μm. For X-rays with energy just above the K-edge, position resolution in the range of 90 μm FWHM was achieved using the technique of escape peak gating. We found broad low-level wings forming about 31% of the total area in the position spectrum above the K-edge, indicating that the L-shell interactions are included (and inseparable) in the gating technique of photopeak events within this energy range. Furthermore, the shape of the position spectrum was well explained when the energy dependence of σ L / ( σ K + σ L ) was considered above the K-edge.

MO‐E‐T‐618‐06: Correcting LDR Spectroscopy for Fine Energy Resolution Applications

Purpose: To use high purity Germanium spectrometry to measure output energy spectra of LDR brachytherapy seeds in order to provide better dosimetric information than what is currently available. Such spectral information can provide a platform for energy based dosimetry of LDR seeds as well as provide ‘energy output’ benchmarks for Monte Carlo simulation of these sources. Method and Materials: Low energy Germanium spectroscopy suffers from several inherent defects of the spectrum collection process. Peak energy broadening and generation of fluorescence escape peaks are two defects, both of which can complicate and contaminate measured spectra. A correction algorithm is presented to overcome these defects and reproduce the true energy spectra without detector produced artifacts and without a priori assumptions as to the internal LDR seed structures. Collection of output spectra from various LDR seeds was obtained using an n‐type Germanium spectrometer. A detector response function matrix (8037 element square) was constructed via detailed MCNP Monte Carlo simulations to characterize the detection process from the detector's entrance window to particle termination, spanning interactions from 1352 keV down to 3.75 keV. The correction algorithm is based upon an iterative algorithm used in high‐ to moderate‐energy physics, as detailed in the literature for Germanium spectroscopy. This modified algorithm in conjunction with the response matrix reconstructs the spectrum as it was prior to interaction with the detector. Results: Corrected results have shown excellent agreement with expected theoretical spectral outputs, and spectral peak resolutions of less than 0.5 keV have been achieved. High resolution output spectra have been catalogued for multiple seed designs. Spectral Air Kerma Strength calculations, utilizing corrected spectra, agree with NIST traceable calibrated Air Kerma Strengths to within 3%. Conclusion: This technique allows corrections to be made to acquired spectra thus yielding data for high resolution applications of non‐energy‐integrated dosimetry of LDR seeds.

Contributions to precision and accuracy of monazite microprobe ages

We examine the factors controlling accuracy and precision of monazite microprobe ages, using a JEOL 733 Superprobe equipped with 4 PET crystals, and both 1-atm gas flow Ar X-ray detectors and sealed Xe X-ray detectors. Multiple PET crystals allow for simultaneous determination of Pb concentration on up to 3 detectors, and the effects of different detector gases on spectral form can be addressed. Numerous factors in the X-ray production, detection, and counting sequence affect spectral form, including: choice of accelerating voltage, changes in d -spacing of the diffraction crystal, use of X-ray collimation slits, and type of detector gas. The energy difference between Ar K α X-rays and Xe L α X-rays results in, for 1-atm Ar detectors, escape peaks of second-order LREE L line X-rays that cannot be filtered using differential mode PHA. The second-order LREE energies are passed to the counter and produce, for a 140 mm Rowland circle, several problematic interferences in the Pb region of a monazite wavelength-dispersive (WD) spectrum. WD monazite spectra produced with Xe detectors are free from second-order LREE interferences in the Pb region; escape peaks of the second-order LREE are filterable with differential mode PHA if Xe detectors are employed. Silicon, Ca, Y, Ce, P, Th, U, and Pb (2 spectrometers) are measured as part of the monazite microprobe dating protocol; ±2σ variations in elements fixed for ZAF corrections do not affect the age outside of analytical uncertainty. Th M α, U M β, and Pb M α are the analyzed lines of the age components. Corrections for interference of Th M ζ1,2 and Y L γ2,3 on Pb M α are significant, but can be done precisely, and reduce the precision of the M α analysis by a trivially small amount. Th M γ, M 3- N 4, and M 5- P 3 interferences on U M β can be corrected, as well, but Th M 5 and M 4 absorption edges in high-Th samples make estimation of U M β background problematic. Background fits for U M β peaks show that linear vs. exponential fits for U M β do not, in general, produce statistically significant differences in microprobe ages. However, linear vs. exponential background fits for Pb M α peaks do produce significantly different ages, most likely because of (1) low Pb concentrations relative to U; (2) Th M ζ1 interference on backgrounds between Th M ζ1 and Pb M β; and (3) S K α and K β interference in S-bearing monazite. For 6-min analyses (3 min peak, 3 min background) at 25 keV and 200 nA, 1σ Pb precisions are approximately 3–4% at 1700 ppm and 9.5% at 750 ppm; at 15 keV, precision decreases by roughly 25% of the 25 keV value. These precisions are constant for fixed current, analysis time, and concentration, but the statistical precision of distinct populations of monazite grains (domains) is a function of the total number of analyses within the domain. Instrumental errors (current measurement, dead time, pulse shift, d -spacing change) add 1–10% to random errors, but errors caused by pulse shift and d -spacing changes can be accounted for and corrected. Decreasing accelerating voltage from 25 to 15 keV decreases ZAF correction factors by as much as 50% relative, but replicate age analyses of Trebilcock monazite at 15 and 25 keV are statistically indistinguishable. Grain orientation, miscalculated background intensity, uncorrected interferences, and surface effects also introduce systematic errors. Accurate background interpolation and interference correction reduces systematic error to approximately 5–20% in addition to random (counting) error. Microprobe ages (~420 Ma) and 208Pb/232Th SIMS ages (~430 Ma) of monazite from Vermont are in agreement to within ~10 m.y. The discrepancy between U-Th-total Pb microprobe ages and 208Pb/232Th ages is removed when the high background measurement for Pb M α is shifted to the short-wavelength side of Pb M β, removing a possible Th M ζ1 interference.

A new approach to the determination of the Fano factor for semiconductor detectors

AbstractValues of the Fano factor are widely scattered in the literature, indicating the difficulties in its determination. We chose to analyze both the escape peaks and parent peaks of Ge detector spectra where the parent peak penetration depth and the escape peak escape depth are much larger than the size of the incomplete charge collection region. Hence, the escape peaks are expected to be free of low‐energy tailing as, although the actually deposited energy is low, it is deposited beyond the incomplete charge collection region. It was found that the product of electron–hole pair creation energy (ε) and the Fano factor (F) has an energy dependence at low energies, as is expected from electron transport theories. Although ε is expected to have its own energy dependence, if a reference value of 2.96 eV is assumed for ε, then the Fano factor values varied between 0.059 and 0.083. The escape peak is less advantageous for Si, hence a different method was used for Si(Li) detectors. Assuming the reference value of 3.8 eV for ε, the Fano factor was found to be 0.063 at 5.9 keV x‐ray energy. We consider the Fano factors reported here as upper limits, rather than the mean values. Copyright © 2004 John Wiley & Sons, Ltd.

Intrinsic energy resolution and light yield nonproportionality of BGO

The intrinsic energy resolution and nonproportionality of the light yield as a function of gamma ray energies, in the energy range of 14 keV to 1.33 MeV, were studied for small BGO (Bi/sub 4/Ge/sub 3/O/sub 12/) crystals at room and liquid nitrogen (LN/sub 2/) temperatures. The study showed that the intrinsic resolution of BGO and the light yield nonproportionality as a function of energy do not depend on the crystal temperature. High light outputs of 14000/spl plusmn/300 electron-hole pairs and energy resolution of 6.5% /spl plusmn/ 0.2% for 662keV gamma rays were measured with the 9 mm diameter, 4 mm thick crystals, coupled to large area avalanche photodiodes and cooled down to LN/sub 2/ temperature. Special attention was paid to analyzing the energy resolution of the escape peaks, which were well separated from the full-energy peaks due to the good energy resolution of BGO at LN/sub 2/ temperatures and the energy of bismuth KX-rays. The intrinsic energy resolution of the BGO crystal for escape peaks does not show deviations from analysis of total energy absorption photopeaks. This is in spite of the fact that the contributions of X-rays and Auger electron cascade in creation of escape peaks are much smaller than in full-energy peaks. In the small volume crystal, mainly electrons produced in the photoelectric absorption create the escape peaks.

Evaluation of low-energy tailing parameters of a HPGe X-ray detector to be used in GUPIX software library for PIXE analysis

Accurate description of the response function of X-ray detectors is important for quantitative PIXE analysis. For analytical description of low-energy tailing in PIXE spectra, the GUPIX approach was used, i.e. a combination of Hypermate type functions. The low-energy tailing parameters of a low-energy high purity germanium X-ray detector in the region 1.3–9.2 keV was determined by systematic fitting of X-ray spectra from thin MicroMatter standards. Except for the main Gaussian peak and germanium escape peaks, one shelf, one truncated shelf, one exponential function and KMM radiative Auger feature was applied to fit the spectral data collected with this low-energy Ge X-ray detector. The overall trend of different tail parameters shows similar characteristic as those for Si(Li) X-ray detectors used in this energy range, i.e. very strong tailing at low X-ray energies and a rapid fall off with increasing X-ray energy. The fitted parameters, as a function of X-ray energy, were then incorporated into the GUPIX library for PIXE analysis.

Analysis of the 237Np– 233Pa photon spectrum using the full response function method

A study has been made of X- and γ-ray emission from 237Np in equilibrium with 233Pa using the full response function method. This analysis process is characterised by photon spectrometry in which the entire spectrum is modelled in a pseudo-empirical way by means of elementary functions describing the total absorption and escape peaks, the Compton diffusion internal and external to the detector and the peaks resulting from detection of internal conversion electrons. This method has been applied to determine the L X-, K X- and γ-rays emission probabilities in 237Np and 233Pa decay studies.

Uniformity and reproducibility studies of low-pressure-grown Cd0.90Zn0.10Te crystalline materials for radiation detectors

A large number of room-temperature detectors have been produced from CdZnTe crystals grown with 10% Zn and 1.5% excess tellurium by the low-pressure, vertical-Bridgman technique. Radiation spectra obtained by these crystals using a 241Am source reveal the characteristic 59.5-keV line as well as the six low-energy peaks, which include the Cd and Te escape peaks. Similarly, 57Co spectra obtained also show a very well-defined 122-keV peak with a 3:1 peak-to-valley ratio. Seven CdZnTe crystals have been grown for reproducibility studies. Four of these crystals have resistivities over 1E9 Ω-cm. Considering that the indiumdoping level is on the order of 2E15 cm−3, the reproducibility is excellent. The theoretical basis of the high-resistivity phenomenon in CdZnTe is discussed in reference to a previous paper. The uniformity of these 6-in.-long CdZnTe crystals is studied, and various measurements are carried out, both laterally and vertically, along the boule. It is determined that, in general, roughly a 3.5-in. section near the middle of the 6-in. boule has sufficient resistivity for producing radiation detectors. This nonuniformity along the vertical direction is caused mostly by the composition change of Cd, Zn, Te, and In-doping level in the growth melt caused by differences in the segregation coefficients of these elements. Although, variations in resistivity are seen across some of the wafer slices, most show very good uniformity with high breakdown voltage. Some of the variations are attributed to the different grains within the boule. Similar results are seen in the measured radiation spectra obtain on 4 mm × 4 mm × 2 mm samples from different locations across the wafer, where some samples show well-resolved secondary peaks, while others display only the primary spectral lines.

Effects of excess tellurium on the properties of CdZnTe radiation detectors

Room-temperature radiation detectors have been fabricated on high-resistivity, indium-doped Cd0.90Zn0.10Te crystals grown under different amounts of excess Te. The effects of the excess Te on the properties of the detectors are explained by a simple model using only three parameters: the density of Cd vacancies, the density of Te antisites (Te at Cd sites), and the deep level of doubly ionized Te antisites. The best detectors, which can resolve the low-energy Np-L and Te-K peaks as well as Cd and Te escape peaks of 241Am, are produced from crystals grown with 1.5% excess Te. The detectors fabricated from crystals grown without excess Te are unable to resolve any characteristic-radiation peaks of 241Am and 57Co. This result is explained by a model of networked p-type domains in an n-type matrix or vice versa, which is caused by the lack of sufficient deep-level Te antisites. Such conduction-type inhomogeneity causes massive electron and hole trapping. As for the detectors fabricated from Cd0.90Zn0.10Te crystals grown with 2% and 3% excess Te, they are able to resolve the 241Am 59.5-keV, 57Co 122-keV, and 57Co 136-keV radiation peaks. However, the full-width at half-maximum (FWHM) values of these peaks are broadened, especially the high-energy 57Co peaks. These phenomena are attributed to the hole and, possibly, electron trapping by Cd vacancies and Te antisites, respectively. The result of the analysis indicates that sufficient Te antisites and a low density of carrier traps in Cd0.90Zn0.10Te are essential for producing high-quality radiation detectors. In the analysis, it was discovered that most of the excess Te, on the order of 1–2 × 1020 cm−3, remain electrically inactive. A possible explanation for this phenomenon is that the excess Te atoms form neutral Te-antisite and Cd-vacancy complexes, such as TeCd·(VCd)2, during the post-growth cooling process.