Li Detector Research Articles

Angular Dependence of L_α/Ll, Lα/Lβ and Lα/Lγ X-ray Intensity Ratios of Lead at 59.54 keV Photon Energy

L_α/L_l, L_α/L_β and L_α/L_γ x-ray intensity ratios of lead have been calculated at an angular range 85˚-135˚ at 59.54 keV photon energy by using a Si (Li) detector. The results showed that the L_α/L_β and L_α/L_γ intensity ratios decreased as the scattering angle increased. The correlations between the L_α/L_β and L_α/L_γ intensity ratios and scattering angles were also high. On the other hand the variation of L_α/L_l intensity ratio with the scattering angle is irregular.

Comment on “Limitation of uranium and thorium traces in charnockite matrix‐PIXE analyses at 3 MeV with Si (Li) detector”

Comment on “Limitation of uranium and thorium traces in charnockite matrix‐PIXE analyses at 3 MeV with Si (Li) detector”

Reply to comment on “Limitation of uranium and thorium traces in charnockite matrix‐PIXE analyses at 3 MeV with Si (Li) detector”

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Non-destructive evaluation of thickness of material plates through Compton back-scattering technique using Si(Li) detector

This study aims to develop the system for the non-destructive evaluation of the thickness of material plates based on the Compton back-scattering technique using a Si(Li) detector and 241Am radioactive sources. The calibration curve is constructed based on the areas under the Compton scattering peak obtained from the measurements of reference samples. This calibration curve is used to determine the saturation thickness, the maximum measurable thickness (MMT) with the desired accuracy, and the unknown thickness of a sample. To validate the reliability of the system, we have performed thickness measurements for seventeen aluminum samples with different thicknesses in the range of 4.40–21.07 mm. The samples are measured seven times, except for two samples with thicknesses of 11.52 mm and 14.98 mm up to twenty times. The Pearson's correlation coefficient between the reference and measured thicknesses presented a strong positive correlation. The average relative deviation between the reference and measured thicknesses is less than 1%.

EPMA and PIXE Analyses of High Grade Metamorphic Rocks

Background/Objectives: The demand for exact quantification analyses in complex ore assemblages is increasing rapidly as mineral processing studies become more sophisticated. In response to this need, an Electron Micro Probe Analysis and Proton Induced X-ray Emission complementary based analytical tool procedure for the chemical characterization of minerals was employed to study the metamorphic rocks. Methods : In this work, we compare the quantitative analysis of high-grade metamorphic rocks by proton induced X-ray emission (PIXE) with that of the previous analyses by electron probe microanalysis (EPMA). During this investigation, the PIXE analytical method on a nuclear microprobe was added to the previously well-known EPMA for the chemical quantification of high-grade metamorphic rocks from the Charnockite Hill, Visakhapatnam, A.P., India. For the evolution and geochemical characterization of the metamorphic rocks, the above two methods are compared and discussions are made with respect to certain elements. Findings: Particle-induced X-ray emission is well-matched except for certain elements for the chemical characterization of metamorphic rocks belonging to earth material samples. This comparison with EPMA demonstrates the elemental quantification characteristics for such analyses. Not only is an exploratory study of proton induced X-ray emission benefit presented, but also a synopsis of comparison with electron probe microanalysis aimed at a responsible reply to metamorphic rock analytical questions. Novelty: The complementary technique, especially EPMA, is required to fill the elemental gaps that are not determined in the case of matrix complex charnockite compositional analysis by PIXE with 3MeV and a Si (Li) detector. Keywords: Electron and Proton Microprobes; Complementary Techniques; Metamorphic Rocks; Elemental Analysis

Proton microprobe analysis with 3 MeV and Si (Li) detector at Z < 17 elements in charnockite composition

The low Z elements in the matrix charnockite composition are the problem, according to proton induced X-ray emission analysis with 3 MeV energy and a Si (Li) detector. The charnockite composition analysis with a proton microprobe is affected by the energy of the ion beam, the X-ray yield of a number of atoms, the ionisation cross-section, the energy-dependent detection efficiency of the semiconductor detectors used, and several other aspects. It's difficult to compute the absolute concentration of component Z < 17 in an unknown charnockite matrix. As a result, modifying the dimensions of the detector, window, or incident proton beam energy can be used to evaluate light elemental sensitivity. Low Z elements in charnockite matrix materials can also be discovered using complementary analytical methods.

Evaluation of porous structure by Kr and Xe desorption halftimes with X-Ray Fluorescence analysis

X-Ray Fluorescence analysis based on excitation with 109 Cd source and registration of characteristic X-rays with Si(Li) detector was used to record the kinetics of desorption of Kr and Xe from carbonaceous samples of 1–100 mg after their treatment with the inert gases at temperatures from 20 to 700 °C. Activated coals with a known pore distribution were used to demonstrate that the Kr desorption half-life is inversely proportional to the square of the pore diameter in the range from 0.7 nm to 50 nm. Although the absorption of Xe was 2–10 times higher in the same pores than the absorption of Kr, the desorption of Xe was about 2.83 times slower than the desorption of Kr. The later fact speaks in favor of using Kr and Ar as a marker for evaluating porous structures rather than Xe. • Simultaneous ED-XRF control of Kr, Xe, Fe, Cu, Zn, Pb, and H in carbon samples. • Evaluation of pore diameters by halftimes of Kr and Xe desorption. • Clarification of correlations between metallic admixtures and pore distribution. • In the same pores, Xe desorption is by 2.83 times slower than that of Kr.

Application of silicon drift detector in PIXE tomography system of Fudan University

In the Nuclear Microprobe Laboratory of Fudan University, particle induced X-ray emission (PIXE) has invariably used the Si(Li) detector. Although it is a widely used X-ray detector, the Si(Li) detector has a low counting rate. In recent years, high-counting rate detectors such as the silicon drift detector (SDD) have developed rapidly. This paper demonstrates the feasibility of applying the SDD to PIXE tomography (PIXE-T) for the first time. We placed the Si(Li) detector and the SDD in symmetrical positions to collect X-rays emitted from a Cl-doped inertial confinement fusion (ICF) target simultaneously. The counting rate of the SDD is about 5 times that of the Si(Li) detector. The maximum likelihood expectation maximization (MLEM) algorithm was used to reconstruct the projection slice by slice. The quality of the projections and the reconstructed images is improved using the SDD thanks to the higher number of events collected in the detector.

New measurement of the β-spectrum of 210Bi with a silicon 4πβ-spectrometer

The shape of 210Bi β-spectrum was measured using a spectrometer based on Si(Li) detectors with a 4π geometry. Full absorption spectrometer allows for a direct measurement of the β-spectra without using the electron backscattering corrections for the response function. The measured value of nuclear shape factor C(W)=1+(-0.4378±0.0072)W+ (0.0526±0.0021) W2 is in agreement with the results of previous studies.

Low-Noise Analog Channel for the Readout of the Si(Li) Detector of the GAPS Experiment

This work is focused on the design and the experimental characterization of an analog channel developed for the readout of lithium-drifted silicon detectors of the General AntiParticle Spectrometer (GAPS) experiment aimed at the search for dark matter. The instrument is designed for the identification of antideuteron particles from cosmic rays during an Antarctic balloon mission scheduled for late 2022. A low-noise analog front-end, featuring a dynamic signal compression to comply with the wide input range, has been designed in commercial 180-nm CMOS technology. The channel was fabricated in 2018 and is the first building block toward the development of a multichannel readout ASIC. The article will provide a description of the design criteria, the architecture of the channel, and a summary of the results of the experimental characterization.

SLICES: Spes Low-energy Internal Conversion Electron Spectrometer

The Spes Low-energy Internal Conversion Electron Spectrometer (SLICES) is a new electron spectrometer designed to perform off-beam measurements at the beta decay station of the SPES facility at the Legnaro National Laboratories (LNL). SLICES consists of a large area Si(Li) detector cooled at −150 °C and a magnetic transport system. Four permanent N52 magnets, located around a central photon shield focus the electrons on the detector. In this paper, a detailed description of the SLICES components is presented. The strength of the measured magnetic field has been compared with calculations. The efficiency of the apparatus has been simulated and compared with the experimental data obtained using a radioactive 207Bi source. The commissioning of the spectrometer at the CN accelerator at LNL is also presented.

Physical Processes during the Formation of Silicon-Lithium p-i-n Structures Using Double-Sided Diffusion and Drift Methods.

In this paper, we described a method of double-sided diffusion and drift of lithium-ions into monocrystalline silicon for the formation of the large-sized, p-i-n structured Si(Li) radiation detectors. The p-i-n structure is a p-n junction with a doped region, where the “i-region” is between the n and the p layers. A well-defined i-region is usually associated with p or n layers with high resistivities. The p-i-n structure is mostly used in diodes and in some types of semiconductor radiation detectors. The uniqueness of this method is that, in this method, the processes of diffusion and drift of lithium-ions, which are the main processes in the formation of Si(Li) p-i-n structures, are produced from both flat sides of cylindrical-shaped monocrystalline silicon, at optimal temperature (T = 420 °C) conditions of diffusion, and subsequently, with synchronous supply of temperature (from 55 to 100 °C) and reverse bias voltage (from 70 to 300 V) during drift of lithium-ions into silicon. Thus, shortening the manufacturing time of the detector and providing a more uniform distribution of lithium-ions in the crystal volume. Since, at present, the development of manufacturing of large-sized Si(Li) detectors is hindered due to difficulties in obtaining a uniformly compensated large area and time-consuming manufacturing process, the proposed method may open up new possibilities in detector manufacturing.

The antinucleus annihilation reconstruction algorithm of the GAPS experiment

The General AntiParticle Spectrometer (GAPS) is an Antarctic balloon-borne detector designed to measure low-energy cosmic antinuclei (<0.25GeV/n), with a specific focus on antideuterons, as a distinctive signal from dark matter annihilation or decay in the Galactic halo. The instrument consists of a tracker, made up of ten planes of lithium-drifted Silicon Si(Li) detectors, surrounded by a plastic scintillator Time-of-Flight system. GAPS uses a novel particle identification method based on exotic atom capture and decay with the emission of pions, protons, and atomic X-rays from a common annihilation vertex.An important ingredient for the antinuclei identification is the reconstruction of the “annihilation star” topology. A custom antinucleus annihilation reconstruction algorithm, called the “star-finding” algorithm, was developed to reconstruct the annihilation star fully, determining the annihilation vertex position and reconstructing the tracks of the primary and secondary charged particles. The reconstruction algorithm and its performances were studied on simulated data obtained with the Geant4-based GAPS simulation software, which fully reproduced the detector geometry. This custom algorithm was found to have better performance in the vertex resolution and reconstruction efficiency compared with a standard Hough-3D algorithm.

Characterization of matrix effects for Pb L-shell energy dispersive X-ray fluorescence (EDXRF) in binary compounds of cadmium, copper, molybdenum, and zinc

Matrix effects on the intensity of characteristic L X-rays were investigated for X-ray fluorescence (XRF). Lead was selected to be the analyte and samples were prepared with powders of several elements. In XRF analysis, if the sample analyzed is a composite, the emitted characteristic X-rays of an element can be enhanced or weakened by emission from other elements. The weight fraction of Pb and accompanying element in the matrices prepared as tablets of PbCCu1-C, PbCZn1-C, PbCMo1-C and PbCCd1-C by powder metallurgy using pure powders were varied from 10% to 90% with 10% intervals. The K shell absorption edge of Cu and Zn is just below the characteristic L X-ray energies of Pb. However, Mo and Cd emits K X-rays with energies just above the L shell absorption edge of Pb when stimulated by primary photons. All samples were analyzed by XRF using a Si(Li) detector with good resolution and an Am-241 radioactive source to provide characteristic X-ray spectra. The intensities for and X-rays were plotted as a function of the Pb concentration and the results were evaluated to characterize matrix enhancement and absorption upon L-shell X-rays.

Limitation of uranium and thorium traces in charnockite matrix-PIXE analyses at 3 MeV with Si (Li) detector

In the geochemical analysis of charnockite matrix, PIXE results do not show either the minor or traces of thorium and uranium even though they are present in that charnockite composition. Because of a continuous range of elements in charnockite composition and characteristic X-rays of some elements present at similar to characteristic X-rays of thorium and uranium. Therefore, Th and U traces quantification are limited due to the interferences in the PIXE spectrum at similar characteristic X-ray energies of the elements. Otherwise, it is possible for quantification, if the composition does not contain the elements at similar characteristic X-rays of Th and U or using complementary techniques.

LI Detector: a framework for sensitive colony-based screens regardless of the distribution of fitness effects.

Microbial growth characteristics have long been used to investigate fundamental questions of biology. Colony-based high-throughput screens enable parallel fitness estimation of thousands of individual strains using colony growth as a proxy for fitness. However, fitness estimation is complicated by spatial biases affecting colony growth, including uneven nutrient distribution, agar surface irregularities, and batch effects. Analytical methods that have been developed to correct for these spatial biases rely on the following assumptions: (1) that fitness effects are normally distributed, and (2) that most genetic perturbations lead to minor changes in fitness. Although reasonable for many applications, these assumptions are not always warranted and can limit the ability to detect small fitness effects. Beneficial fitness effects, in particular, are notoriously difficult to detect under these assumptions. Here, we developed the linear interpolation-based detector (LI Detector) framework to enable sensitive colony-based screening without making prior assumptions about the underlying distribution of fitness effects. The LI Detector uses a grid of reference colonies to assign a relative fitness value to every colony on the plate. We show that the LI Detector is effective in correcting for spatial biases and equally sensitive toward increase and decrease in fitness. LI Detector offers a tunable system that allows the user to identify small fitness effects with unprecedented sensitivity and specificity. LI Detector can be utilized to develop and refine gene–gene and gene–environment interaction networks of colony-forming organisms, including yeast, by increasing the range of fitness effects that can be reliably detected.

A Silicon 4π Spectrometer of β-Decay Electrons with Energies of up to 3 MeV

A 4π β spectrometer consists of two Si(Li) detectors with a sensitive region that is more than 8-mm thick. Using this total-absorption spectrometer it is possible to make a direct measurement of β spectra without correcting the response function for the electron backscattering from the crystal surface. The β spectra of transitions to the excited states of daughter nuclei have been measured using an additional 3'' BGO detector of γ rays, which is connected in coincidence with the pair of Si(Li) detectors.

Determination of Si(Li) detector efficiency by experimental and Monte Carlo simulation methods

In this study, a Si(Li) detector was modeled by MCNP (Monte Carlo n-particle) code and its efficiency was estimated by Monte Carlo simulation in the photon energy range of 5.9–59.54 keV. Experimental measurements using 55Fe, 57Co, and 241Am radioactive standard sources were performed for validation of the applied simulation code. The primary results of the simulation were compared with the experimental ones and considerable discrepancies were observed, especially in the low energy region. Since the dead layers’ thicknesses are not always precisely provided by the manufacturer and even can change during detector aging, they were assumed as the cause of these discrepancies (front dead layer’s thickness being a critical parameter for low energy photons). After adjusting the thicknesses of the front and rear dead layers in a step-by-step procedure, a reasonable agreement was achieved between the simulated and experimental results. The results of this study indicate that if performing an experiment by the detector is difficult for any reason in some energies, one can rely on the MCNP code as an operational tool by interpolation or extrapolation of the available experimental efficiency data (in low energy region).

Chemical characterization of PM10 in two small towns located in South Poland

Abstract The purpose of this study is to analyse the elements and PM10 concentrations in air samples gathered in the winter of 2017/2018 in two small towns, namely Skala and Wadowice. The chemical elements were identified for each sample using the energy dispersive X-ray method. The spectrometer was equipped, among others, with an Mo-X-ray tube which was the source of the photons and the Si(Li) detector. The following chemical elements: Cl, K, Fe, Ca, Zn, Pb, Br, Ti, Cu, Mn, V, Co, Rb, Ni, Sr, and Cr were identified in the samples. In addition, As and Se were identified in Wadowice. First, the results were compared with each other and then with the results for the nearest city. It was observed that the PM10 concentrations were significantly higher than the UE limit value for PM10, which equals 50 μg·m−3 per 24 h. Moreover, the high concentrations of, among others, K, Pb, Cl or Zn, are likely to be linked with fossil fuels combustion and biomass burning. The levels of element concentrations in Wadowice and Skala resemble the levels observed several years earlier in Krakow.

Determination of the effect of temperature on relative L X-ray intensity ratio of gadolinium, dysprosium and erbium

In this study, Lα/Lβ1 and Lα/Lβ2 X-ray intensity ratios for gadolinium, dysprosium and erbium elements were experimentally determined. L X-ray intensity ratio measurements were gauged at several temperatures (50, 100, 50, 150, 200, 250, 300, 350 and 400 °C) using an excitation energy of 59.54 keV γ-rays emitted from a 100 mCi 241Am radioactive source. L X-ray emission spectra were detected using a Si (Li) detector system with a resolution of 160 eV at 5.96 keV coupled with a computer-controlled multi-channel analyzer. L X-ray production cross-sections (σLα, σLβ1 and σLβ2) of the lanthanide elements were calculated by assessing the emission spectra. The variation with temperature of each parameter was given in graphical forms and tabulated. It was observed that the parameters were affected by temperature. According to these results, it is determined that the L X-ray intensity ratios and L X-ray production cross-sections of pure Gd, Dy and Er elements changed and were affected by temperature.