Fundamental parameter approach to XRF spectroscopy measurements of arsenic in polyester resin skin phantoms

A fundamental parameter (FP) approach that explicitly incorporates the energy‐broadening response of the detector was developed. The ratio between Kα fluorescence peak area and the sum of coherently and incoherently scattered peak areas was used as an indicator of trace element concentration. The peak ratio was theoretically calculated using the FP method. The energy‐broadening response curve of the Si(Li) detector was estimated by matching the theoretical and experimental values of this ratio. The method was implemented for the analysis of the K‐shell x‐ray fluorescence (K‐XRF) spectra of six polyester resin samples corresponding to six different arsenic concentrations. A ¹⁰⁹Cd radioactive source provided the excitation radiation for spectra acquisition. The predicted detector energy resolution expressed as full width at half‐maximum (FWHM) for Fe Kα fluorescence peak (208 ± 5 eV at 6.4 keV) and As Kα fluorescence peak (222 ± 5 eV at 10.5 keV) were in agreement with the experimental measurements. Copyright © 2008 John Wiley & Sons, Ltd.     

Recording X‐ray spectra with an audio digitizer

X‐ray spectra were recorded with a notebook computer and analyzed by software on the computer, without a pulse height analyzer (PHA) or a digital signal processor (DSP). An audio (microphone or line) input on a personal computer has a built‐in analogue‐to‐digital converter (ADC) for digital audio recording. The output signal of the X‐ray detector is recorded through the audio input of the computer and then analyzed by software on the computer. On the basis of this method, X‐rays from a radium source were measured with a cadmium telluride detector. K X‐rays of bismuth were detected. Full width at half maximum (FWHM) was 5.6 keV at Kα of bismuth (77.1 keV), enough to separate Kβ (87.3 keV) from Kα of bismuth. The present method achieved almost equal energy resolution as that of the regular method (5.3 keV FWHM at 77.1 keV). Copyright © 2010 John Wiley & Sons, Ltd.     

Design and performance of a 2-D multi-wire position sensitive X-ray detector

A 2-D multi-wire position sensitive detector for X-ray diffraction and small angle X-ray scattering studies is described. The detector has an active area of 100 mm × 100 mm and consists of an anode plane with 10 μm SS wires at 3 mm spacing and a pair of orthogonal cathode readout planes with 25 μm SS wires placed at 1.5 mm spacing. The position information is obtained using charge division method and recorded using a laboratory built data acquisition system. The resolution and gas gain was measured for 5.9 keV X-rays (⁵⁵Fe-source) as a function of the anode wire voltage and gas pressure. It was observed that the proportional region of the PSD at 100 kPa pressure extended up to a high voltage value of around 1.5 kV and it shifted to high values up to 2 kV for gas pressure of 300 kPa. The energy resolution improved from 18% (FWHM) to 12% with increase in pressure. The spatial resolution of the PSD also showed improvement, with a value of 1.2 mm × 1.4 mm at 300 kPa gas pressure. A maximum gain of 5 × 10⁴ is obtained.     

Performance of a four‐element Si drift detector for X‐ray absorption fine‐structure spectroscopy: resolution, maximum count rate,and dead‐time correction with incorporation into the ATHENA data analysis software

The performance of a four‐element Si drift detector for energy‐dispersive fluorescence‐yield X‐ray absorption fine‐structure measurements is reported, operating at the National Institute of Standards and Technology beamline X23A2 at the National Synchrotron Light Source. The detector can acquire X‐ray absorption fine‐structure spectra with a throughput exceeding 4 × 10⁵ counts per second per detector element (>1.6 × 10⁶ total counts per second summed over all four channels). At this count rate the resolution at 6 keV is approximately 220 eV, which adequately resolves the Mn Kα and Kβ fluorescence lines. Accurate dead‐time correction is demonstrated, and it has been incorporated into the ATHENA data analysis program. To maintain counting efficiency and high signal to background, it is suggested that the incoming count rate should not exceed ～70% of the maximum throughput.     

A gas proportional‐scintillation counter for x‐ray spectrometry in the 0.1–3 keV range

Results for the energy resolution of a uniform‐field gas proportional‐scintillation counter are presented for the range 0.1–3 keV. A comparison with results from the literature shows that the detector is most suitable for this energy range. Examples of x‐ray fluorescence pulse‐height distributions from geological and industrial samples are presented. Copyright © 2004 John Wiley & Sons, Ltd.     

Two-dimensional thermal neutron detector

A two-dimensional thermal neutron detector for neutron diffraction experiments has been developed and designed at the St. Petersburg Nuclear Physics Institute, Russian Academy of Sciences. The detector is based on a multiwire proportional chamber with cathode-strip delay line readout. The detector aperture is 170 × 300 mm² and the anode wire spacing is 4 mm. The chamber is filled with a 1.5 atm ³He + 2 atm CF₄ gas mixture. To conserve high purity of the gas mixture, all electrodes are made of quartz glass. The spatial resolution of the detector is 2.5 mm and the detection efficiency is 60% for 9 Å neutrons.     

天文观察用超软X射线探测器的标定

在北京同步辐射装置3W1B光束线上,对天文观测用超软X射线(0.2keV—3.5keV)正比计数管探测器进行了系统地标定.得到了正比计数管的死时间、计数率坪曲线、能量线性、能量分辨、窗材料透过比曲线;借助于已标定过的光电二极管探测器,测量了正比管探测器的能量响应效率,标定不确定度在10%—18%之间.另外,还对正比管系统在卫星上的六道记录和在实验室里的多道记录进行了对比,两种记录方式符合得很好.     

EDXRF with an audio digitizer

We utilized an audio digitizer in energy‐dispersive X‐ray fluorescence (EDXRF) with a silicon drift detector and achieved a full width at half maximum (FWHM) of 178 eV at Mn Kα (92‐µs peaking time). To confirm the ability of EDXRF with an audio digitizer, we also examined energy versus channel number linearity and output count rate. We applied it to EDXRF analysis of (ZnCd)S : Ag and showed a proper energy versus channel number linearity from 5.9 keV (Mn Kα) to 26.1 keV (Cd Kβ). And, the maximum output count rate of more than 10 kcps was obtained with 23‐µs peaking time (296‐eV FWHM). Copyright © 2011 John Wiley & Sons, Ltd.     

Kβ/Kα x‐ray intensity ratios for bromine and iodine compounds

Kβ/Kα x‐ray intensity ratios of some Br and I compounds were studied. The samples were excited by 59.5 keV γ‐rays emitted from an Am‐241 radioisotope source and characteristic K x‐rays emitted from the samples were counted by means of an Si(Li) detector which has a resolution 155 eV at 5.9 keV. The experimental values were compared with the calculated theoretical values for elemental Br and I. Copyright © 2003 John Wiley & Sons, Ltd.     

Performances of a metallic magnetic calorimeter for the measurement of hard X‐ray emission intensities

The energy spectrum analysis of X‐ray intensities with semiconductor detectors is often difficult because their energy resolution is usually not good enough to separate the different X‐ray lines. Metallic magnetic calorimeters (MMCs) can be an alternative; they can offer both high energy resolution and high intrinsic detection efficiency from 0 to 100 keV. MMCs are thermal detectors; that is to say, the energy of each absorbed photon is measured as a temperature elevation. At very low temperature, typically few tens of mK, a very large pulse height‐to‐noise ratio can be obtained that is an essential condition for high energy resolution. We are involved in the development of MMCs for metrology applications such as the determination of hard X‐ray emission intensities. For that purpose, we conceived an MMC with an energy resolution of 57 eV around 30 keV. The absorber is made of gold providing high intrinsic detection efficiency even for a small volume, greater than 90% below 60 keV. We will describe the physical principle and the practical realisation of this detector and discuss its performances by analysing the energy spectrum obtained from a ¹³³Ba source. Preliminary outcomes of relative emission intensities of the K X‐ray of cesium are presented and compared with other experimental data and theoretical calculations. Copyright © 2012 John Wiley & Sons, Ltd.     

Application of a pnCCD in X‐ray diffraction: a three‐dimensional X‐ray detector

The first application of a pnCCD detector for X‐ray scattering experiments using white synchrotron radiation at BESSY II is presented. A Cd arachidate multilayer was investigated in reflection geometry within the energy range 7 keV < E < 35 keV. At fixed angle of incidence the two‐dimensional diffraction pattern containing several multilayer Bragg peaks and respective diffuse‐resonant Bragg sheets were observed. Since every pixel of the detector is able to determine the energy of every incoming photon with a resolution ΔE/E? 10^?2, a three‐dimensional dataset is finally obtained. In order to achieve this energy resolution the detector was operated in the so‐called single‐photon‐counting mode. A full dataset was evaluated taking into account all photons recorded within 10⁵ detector frames at a readout rate of 200 Hz. By representing the data in reciprocal‐space coordinates, it becomes obvious that this experiment with the pnCCD detector provides the same information as that obtained by combining a large number of monochromatic scattering experiments using conventional area detectors.     

Development of new CdZnTe detectors for room‐temperature high‐flux radiation measurements

Recently, CdZnTe (CZT) detectors have been widely proposed and developed for room‐temperature X‐ray spectroscopy even at high fluxes, and great efforts have been made on both the device and the crystal growth technologies. In this work, the performance of new travelling‐heater‐method (THM)‐grown CZT detectors, recently developed at IMEM‐CNR Parma, Italy, is presented. Thick planar detectors (3 mm thick) with gold electroless contacts were realised, with a planar cathode covering the detector surface (4.1 mm × 4.1 mm) and a central anode (2 mm × 2 mm) surrounded by a guard‐ring electrode. The detectors, characterized by low leakage currents at room temperature (4.7 nA cm^?2 at 1000 V cm^?1), allow good room‐temperature operation even at high bias voltages (>7000 V cm^?1). At low rates (200 counts s^?1), the detectors exhibit an energy resolution around 4% FWHM at 59.5 keV (²⁴¹Am source) up to 2200 V, by using commercial front‐end electronics (A250F/NF charge‐sensitive preamplifier, Amptek, USA; nominal equivalent noise charge of 100 electrons RMS). At high rates (1 Mcounts s^?1), the detectors, coupled to a custom‐designed digital pulse processing electronics developed at DiFC of University of Palermo (Italy), show low spectroscopic degradations: energy resolution values of 8% and 9.7% FWHM at 59.5 keV (²⁴¹Am source) were measured, with throughputs of 0.4% and 60% at 1 Mcounts s^?1, respectively. An energy resolution of 7.7% FWHM at 122.1 keV (⁵⁷Co source) with a throughput of 50% was obtained at 550 kcounts s^?1 (energy resolution of 3.2% at low rate). These activities are in the framework of an Italian research project on the development of energy‐resolved photon‐counting systems for high‐flux energy‐resolved X‐ray imaging.     

A high‐spatial‐resolution three‐dimensional detector array for 30–200 keV X‐rays based on structured scintillators

A three‐dimensional X‐ray detector for imaging 30–200 keV photons is described. It comprises a set of semi‐transparent structured scintillators, where each scintillator is a regular array of waveguides in silicon, and with pores filled with CsI. The performance of the detector is described theoretically and explored in detail through simulations. Based on available hardware, a spatial resolution of 1 µm is obtainable. The resolution of a single screen is shown to be determined only by the pitch, at least up to 100 keV. In comparison with conventional homogeneous screens, an improvement in efficiency by a factor of 5–15 is obtainable. The cross‐talk between screens in the three‐dimensional detector is shown to be negligible. The three‐dimensional concept enables ray‐tracing and super‐resolution algorithms to be applied.     

Superconducting tunnel junctions as detectors for high‐resolution x‐ray spectroscopy

Superconducting tunnel junctions (STJs) are a type of cryogenic detector with a working temperature of about 100 mK. They allow the combination of low energy threshold, high quantum efficiency and good count rate capability with an excellent energy resolution; at an x‐ray energy of 5.9 keV an energy resolution of 10.8 eV (FWHM) has been achieved. The detector system described is based on STJs which consist of two superconducting Al electrodes separated by a thin dielectric tunnel barrier. The tunneling process of quasi‐particles created by deposition of energy in the electrodes leads to a detectable current signal. The STJ is equipped with a superconducting Pb absorber which is read out via phonons. The Pb absorber increases absorption efficiency (～50% at 6 keV) and suppresses detector artefacts. The degeneration of Pb, most probably due to oxidation, is overcome by the introduction of a protective SiO layer on top of the absorber. This layer leads to a slight reduction of energy resolution. Nevertheless, a resolution of 9.7 eV at 1.7 keV and of ～20 eV at 5.9 keV could be realized with a prototype detector. Currently this STJ‐based detector system is being incorporated into a prototype cryogenic spectrometer for XRF analysis. Copyright © 2004 John Wiley & Sons, Ltd.     

Response function of the CdZnTe SPEAR detector

The response function of the SPEAR CdZnTe detector developed by eV Microelectronics was studied in detail. This compact detector includes a CdZnTe crystal and a preamplifier. It is operational at room temperature. The energy range of the detector is between 10 keV and 1 MeV, and its relative resolution is less than 4% at 122 keV. The goal of our study was to establish an empirical analytical approximation of the response function to be used in Monte Carlo simulations (e.g. for spectrum unfolding). Various radionuclides were used for the study. The energy spectrum obtained from the detector not only showed smooth peaks but also had a tail on the low‐energy side of the peak. This tail part was more prominent at higher energies. By using the experimental spectrum for various nuclides such as ²⁴¹Am, ¹⁰⁹Cd, ⁵⁷Co and ¹³⁷Cs, the parameters required to replicate the experimental response with a peak plus exponential model were evaluated. Copyright © 2011 John Wiley & Sons, Ltd.     

Combining CdTe and Si detectors for Energy‐Dispersive X‐Ray Fluorescence

Most energy‐dispersive X‐ray fluorescence (EDXRF) instruments use Si diodes as X‐ray detectors. These provide very high energy resolution, but their sensitivity falls off at energies of 10–20 keV. They are well suited for measuring the K lines of elements with Z < 40, but for heavier elements, one must use K lines at low efficiency or use L or M lines that often overlap other lines. Either is a challenge for accurate quantitative analysis. CdTe detectors offer much higher efficiency at high energy but poorer energy resolution compared with Si diodes. In many important EDXRF measurements, both high and low Z elements are present. In this paper, we will compare the precision and accuracy of systems using the following: (1) a high resolution Si detector, (2) a high efficiency CdTe detector, and (3) a composite system using both detectors. We will show that CdTe detectors generally offer better analytical results than even a high resolution silicon drift detectors for K lines greater than 20 or 25 keV, whereas the high resolution Si detectors are much better at lower energies. We will also show the advantages of a combined system, using both detectors. Although a combined system would be more expensive, the increased accuracy, precision, and throughput will often outweigh the small increase in cost and complexity. The systems will be compared for representative applications that include both high and low Z elements. Copyright © 2012 John Wiley & Sons, Ltd.     

X射线探测器的脉冲标定技术

利用强流电子束技术产生通量密度为10¹⁸—10¹⁹X-ray photon/sr·s的脉冲CuKX射线源,标定PIN型硅二极管半导体探测器对X光子的脉冲灵敏度。用绝对X射线监测器——P10气体脉冲电离室作为脉冲X射线通量密度的标准。脉冲电荷自动测量仪由微处理机进行程序控制,并予以实时校准。该电离室测量通量密度的精度为±5％,适用的能通量率范围可达4×10^-9—2×10²W/cm²,适用的光子能量范围为1.5—10keV,标定探测器的精度为±7.0％,并发现PIN型硅二极管的脉冲灵敏度比稳态X射线束标定的灵敏度高30％左右。 关键词：     

Characterization of a triple-GEM position sensitive detector for X-ray fluorescence imaging

In this work, we characterized an X-ray position sensitive gaseous detector based in a triple stack of gas electron multipliers. The readout circuit is divided in 256 strips for each dimension and using a resistive chain interconnecting the strips, we are able to reconstruct the radiation interaction points by resistive charge division. The detector achieved gains above 10⁴, energy resolution of 15.28% (full width at half maximum) for 5.9 keV X-rays, and position resolution of 1.2 mm, while operating in Ar/CO₂(90/10) at atmospheric pressure.     

Microfluidic sample preparation for elemental analysis in liquid samples using micro X‐ray fluorescence spectrometry

The integration of microfluidic devices with micro X‐ray fluorescence (micro‐XRF) spectrometry offers a new approach for the direct characterization of liquid materials. A sample presentation method based on use of small volumes (<5 µl) of liquid contained in an XRF‐compatible device has been developed. In this feasibility study, a prototype chip was constructed, and its suitability for XRF analysis of liquids was evaluated, along with that of a commercially produced microfluidic device. Each of the chips had an analytical chamber which contained approximately 1 µl of sample when the device was filled using a pipette. The performance of the chips was assessed using micro‐XRF and high resolution monochromatic wavelength dispersive X‐ray fluorescence, a method that provides highly selective and sensitive detection of actinides. The intended application of the device developed in this study is for measurement of Pu in spent nuclear fuel. Aqueous solutions and a synthetic spent fuel matrix were used to evaluate the devices. Sr, which has its Kα line energy close to the Pu Lα line at 14.2 keV, was utilized as a surrogate for Pu because of reduced handling risks. Between and within chip repeatability were studied, along with linearity of response and accuracy. The limit of detection for Sr determination in the chip is estimated at 5 ng/µl (ppm). This work demonstrates the applicability of microfluidic sample preparation to liquid characterization by XRF, and provides a basis for further development of this approach for elemental analysis within a range of sample types. Copyright © 2014 John Wiley & Sons, Ltd.     

Development of a microstrip-based neutron detector

A gas-filled microstrip detector for thermal neutrons has been built and successfully tested in our laboratory. The detector has an active area of 20 mm × 15 mm and consists of alternate anodes and cathodes of widths 12 μm and 300 μm respectively. The anode to cathode gap is 150 μm and the pitch is 612 μm. A high resistance, meandering type horizontal strip connects the anodes at one end and aids in position sensing by charge division method. The detector is tested with gas mixtures³He+Kr (1: 2) and³He+CF₄ (2:1) at pressure of 3 atmospheres and using a Pu-Be neutron source. The pulse height spectrum shows energy resolution of ∼8% (FWHM) for the 764 keV peak at anode voltage of 525 V for³He+Kr and ∼15% at anode voltage of 800 V for³He+CF₄. Gas gains up to 6.3 × 103 and 3.6 × 103 are obtained respectively with these gas mixtures. The overall efficiency of the detector along the sensitive length is tested by exposing the active area to neutrons and recording the position spectrum. The detector shows fairly uniform efficiency (∼45%) over the active length.