Energy Resolution Of Spectrometer Research Articles

Experimental determination of the gadolinium L subshells fluorescence yields and Coster‐Kronig transition probabilities

AbstractThe L subshell Coster‐Kronig (CK) transition factors of Gd have been experimentally determined by means of two different experimental approaches and compared to available literature data. On the one hand, reference‐free X‐ray fluorescence (XRF) analysis using an energy‐dispersive detector was applied. This method permitted in addition to determine the L subshell fluorescence yields since the absolute incident and emitted X‐ray photon flux can be determined. On the other hand, a wavelength‐dispersive spectrometer based on a modified von Hamos geometry using a full cylinder highly annealed pyrolithic graphite crystal was used for an experimental validation of the CK transition factors in an independent experiment. The use of this high energy resolution spectrometer allowed thanks to the capability to better discriminate the different X‐ray emission lines to validate the reference‐free XRF results. For both experiments, the use of calibrated instrumentation enabled the provision of a reliable uncertainty budget on the results obtained.

Experimental characterisation of diamond-based neutron spectrometer

The results of testing and characterisation of the neutron spectrometer based on a diamond detector are presented. It is shown that spectrometer calibration with monoenergetic electrons and alpha-particles leads to different results. The energy resolution of the spectrometer is estimated based on the experiments with alpha-particles and with DT-neutrons from NG-150M neutron generator. It has been shown experimentally that for neutrons with an energy of 14 MeV the energy resolution of a diamond-based spectrometer is 0.6%.

Sulfur accumulation in soil in a forested watershed historically exposed to air pollution in central Japan

Forest soils that have accumulated anthropogenic sulfur (S) as a result of historical air pollution may gradually or suddenly release inorganic sulfate either by desorption of inorganic sulfate or by mineralization of organic S, even after mitigation of previous air pollution. The release of inorganic sulfate from soil to surface water leads directly to watershed acidification. Thus, whether the organic S compounds that have accumulated in soils are resistant to microbial activity, due to formation of organo-mineral complexes, is essential information for management of forest soil ecosystem services. A nationwide air pollution monitoring survey by the Japanese Ministry of the Environment identified acidification of both surface water and soil in the Lake Ijira watershed of central Japan, presumably sourced from the Chukyo Industrial Area which lies upwind of the watershed. We compared the amount of S accumulated in the Ijira soils (Dystrudepts) with that in comparable soils in other watersheds in central Japan that were less affected by industrial air pollution. To determine how much mineral-associated organic S had accumulated in the Ijira soils, we measured pyrophosphate- extractable S. We used high-resolution x-ray fluorescence (HRXRF) spectroscopy with a double-crystal type high energy resolution spectrometer to estimate the oxidation states of both mineral-associated and free organic S. We also measured S isotope compositions to explore S dynamics in the soils. We found that more S had accumulated in the Ijira soils than in the comparable soils from other watersheds in central Japan. Concentrations of total S in the Ijira soils varied among soil horizons, reaching more than 1000 mg S kg−1 in some horizons. Mineral-associated organic S accounted for more than half of the total accumulated S. High-resolution x-ray fluorescence spectrum analyses showed that mineral-associated organic S was retained at both high and low oxidation states. The δ34S values of total S in the deeper horizons tended to be higher than those of the uppermost horizons of the Ijira soils and correlated positively with concentrations of extractable Al and Fe oxides (which characterize pedogenic minerals). Our results suggest that about half of total accumulated S in Ijira soils is stabilized in pedogenic minerals and the remainder comprises free organic S and adsorbed inorganic sulfates. There might have been repetitive mobilization and immobilization of S and the degraded organic S might have greater affinity with pedogenic minerals. Further, the ratio of total C to mineral-associated organic S correlated negatively with concentrations of extractable Al and Fe oxides, suggesting that organic S is more resistant to mineralization than organic C because S is preferentially associated with the pedogenic minerals. Monitoring of the chemical states of S compounds in soils historically exposed to air pollution is recommended to assist in prediction of the fate of the S compounds that have accumulated in them.

Investigation of radiation damage due to particle irradiation on Silicon Drift Detector for Chandrayaan-2 mission

This paper presents the work carrie dout in support of Silicon Drift Detector (SDD) characterization for the Chandrayaan-2 instruments namely Solar X-ray Monitor (XSM) and Alpha Particle X-ray Spectrometer (APXS). The XSM and APXS instruments use SDD to detect X-rays from the Sun and fluorescent X-rays from the lunar surface respectively. The aim of this study is to understand and quantify any spectroscopic performance degradation of these X-ray spectrometers due to space radiation in the SDD during its operational period. Any radiation damage to the SDD leads to increase in the detector leakage current and thus degrades the spectroscopic performance, mainly the energy resolution. The expected end-of-life (EOL) 10 MeV equivalent proton fluence was modeled using SPENVIS simulation software. The Silicon Drift Detector was irradiated with 10 MeV protons for the doses up to 24 krad in logarithmic steps and measured the energy resolution and the leakage current at each dose. The spectrometer energy resolution degraded from ∼ 142 eV at 5.9 keV to ∼ 250 eV for the cumulative proton dose of ∼ 11 krad for the mission life of one year. This satisfies the performance requirement of the SDD based X-ray spectrometers onboard Chandrayaan-2 mission.

A Thin-foil Proton Recoil spectrometer for DT neutrons using annular silicon detectors

The use of Thin-foil Proton Recoil (TPR) spectrometers to measure neutrons from Deuterium-Tritium (DT) fusion plasma has been studied previously and is a well established technique for neutron spectrometry. The study presented here focuses on the optimisation of the TPR spectrometer configurations consisting of Δ E and E silicon detectors. In addition an investigation of the spectrometer's ability to determine fuel ion temperature and fuel ion density ratio in ITER like DT plasmas has been performed.A Python code was developed for the purpose of calculating detection efficiency and energy resolution as a function of several spectrometer geometrical parameters. An optimisation of detection efficiency for selected values of resolution was performed regarding the geometrical spectrometer parameters using a multi-objective optimisation, a.k.a. Pareto plot analysis. Moreover, the influence of detector segmentation on spectrometer energy resolution and efficiency was investigated. The code also produced response functions for the two selected spectrometer configurations. The SPEC code was used to simulate the spectrometer's performance in determining the fuel ion temperature and fuel ion density ratio nt/nd.The results presented include the selected spectrometer configuration with calculated energy resolution and efficiency. For a selected spectrometer resolution of 5% a maximum efficiency of around 0.003% was achieved. Moreover, the detector segmentation allows for a 20% increase in spectrometer efficiency for an energy resolution of 4.3%. The ITER requirements for a 20% accuracy on the nt/nd ratio determination and 10% on the temperature determination within a 100 ms sampling window can be achieved using a combination of several TPR's of same type, in order to boost efficiency.

InGaP (GaInP) mesa p-i-n photodiodes for X-ray photon counting spectroscopy

In this paper, for the first time an InGaP (GaInP) photon counting X-ray photodiode has been developed and shown to be suitable for photon counting X-ray spectroscopy when coupled to a low-noise charge-sensitive preamplifier. The characterisation of two randomly selected 200 μm diameter and two randomly selected 400 μm diameter In0.5Ga0.5P p+-i-n+ mesa photodiodes is reported; the i-layer of the p+-i-n+ structure was 5 μm thick. At room temperature, and under illumination from an 55Fe radioisotope X-ray source, X-ray spectra were accumulated; the best spectrometer energy resolution (FWHM) achieved at 5.9 keV was 900 eV for the 200 μm In0.5Ga0.5P diameter devices at reverse biases above 5 V. System noise analysis was also carried out and the different noise contributions were computed.

Multifunctional synchrotron spectrometer of the National Research Center “Kurchatov Institute”: I. EXAFS in dispersive mode

The improved X-ray optical scheme, the system of registration, and the measurement procedure of the multifunctional synchrotron radiation spectrometer in the dispersive EXAFS mode are described. The results of the spectrometer energy resolution measurements are given. The advantages and disadvantages of traditional and dispersive EXAFS spectrometers are analyzed. Examples of EXAFS spectra measured in the dispersive mode are given.

A data acquisition system of high energy resolution spectrometer based on LabVIEW

A data acquisition system of high energy resolution spectrometer based on LabVIEW

Development status of the mechanical cryocoolers for the Soft X-ray Spectrometer on board Astro-H

Astro-H is the Japanese X-ray astronomy satellite to be launched in 2015. The Soft X-ray Spectrometer (SXS) on board Astro-H is a high energy resolution spectrometer utilizing an X-ray micro-calorimeter array, which is operated at 50mK by the ADR with the 30liter superfluid liquid helium. The mechanical cryocoolers, 4K-class Joule Thomson (JT) cooler and 20K-class double-staged Stirling (2ST) cooler, are key components of the SXS cooling system to extend the lifetime of LHe cryogen beyond 3years as required. Higher reliability was therefore investigated with higher cooling capability based on the heritage of existing cryocoolers. As the task of assessing further reliability dealt with the pipe-choking phenomena by contaminant solidification of the on-orbit SMILES JT cryocooler, outgassing from materials and component parts used in the cryocoolers was measured quantitatively to verify the suppression of carbon dioxide gas by their storage process and predict the total accumulated carbon dioxide for long-term operation. A continuous running test to verify lifetime using the engineering model (EM) of the 4K-JT cooler is underway, having operated for a total of 720days as of June 2013 and showing no remarkable change in cooling performance. During the current development phase, prototype models (PM) of the cryocoolers were installed to the test SXS dewar (EM) to verify the overall cooling performance from room temperature to 50mK. During the EM dewar test, the requirement to reduce the transmitted vibration from the 2ST cooler compressor was recognized as mitigating the thermal instability of the SXS microcalorimeter at 50mK.

Photoemission spectroscopy and microscopy of n-, p-GaAs(110) homostructures

Zinc-blend III–V semiconductors being cleaved along nonpolar (110) planes yield atomically clean surfaces due to their charge neutrality, which can be employed as mirror planes for optical resonators. As a result of the Ga3d core level photoemission measurements after the n-, p-GaAs (110) plane cleavage in situ of doped semiconductors with 14 nominally identical p-n homojunctions having optically flat cleaved surface under the optical microscope inspection, the estimate of the Fermilevel positions on energy scale were acquired for p- and n-epilayers. The two-dimentional photoemission image for p-n homojunction was studied as well, using the focused synchrotron radiation beam (diameter 0.7 μm, 95 eV, ∼1010 phot./s) at the scanning photoemission microscope. The average value of surface band bending for p-epilayer measured from the energy position of ideal flat-band conditions, was equal to 0.12 ± 0.05 eV, and that for n-epilayer—0.16 ± 0.08 eV, the spectrometer energy resolution being <0.15 eV. The detailed analysis of the experimental data was carried out in order to clarify the deviation fsrom ideal flat band conditions characteristic for absence of surface cleavage defects. Comparison was done with the well-known literature data on theoretical and experimental investigations of cleavage defects. The experimental results leading to different deviations from ideal flat-band conditions for each cleavage are explained by extrinsic local microscopic defects of cleavage which can appear accidentally and unpredictably, since the system dynamics during cleavage is a highly nonlinear many-body process with many degrees of freedom.

Effect of oriented crystalline converter temperature on spectrometer response

Cooling of a 1-mm crystalline tungsten converter oriented along the 〈111〉 axis situated in front of an electromagnetic spectrometer of thickness 25X0, recording showers of 28-GeV electrons, to a temperature of 77 K results in a decrease of the crystal radiation length by ∼30%, shifts the cascade curve of the shower development in the spectrometer by ∼7%, and improves the spectrometer energy resolution by ∼5% in comparison with similar parameters of the spectrometer at a crystal temperature of 293 K.

Absolute energy calibration for relativistic electron beams with pointing instability from a laser-plasma accelerator

The pointing instability of energetic electron beams generated from a laser-driven accelerator can cause a serious error in measuring the electron spectrum with a magnetic spectrometer. In order to determine a correct electron spectrum, the pointing angle of an electron beam incident on the spectrometer should be exactly defined. Here, we present a method for absolutely calibrating the electron spectrum by monitoring the pointing angle using a scintillating screen installed in front of a permanent dipole magnet. The ambiguous electron energy due to the pointing instability is corrected by the numerical and analytical calculations based on the relativistic equation of electron motion. It is also possible to estimate the energy spread of the electron beam and determine the energy resolution of the spectrometer using the beam divergence angle that is simultaneously measured on the screen. The calibration method with direct measurement of the spatial profile of an incident electron beam has a simple experimental layout and presents the full range of spatial and spectral information of the electron beams with energies of multi-hundred MeV level, despite the limited energy resolution of the simple electron spectrometer.

Development of mechanical cryocoolers for the cooling system of the Soft X-ray Spectrometer onboard Astro-H

Astro-H is the Japanese X-ray astronomy satellite planned for launch in 2014. The Soft X-ray Spectrometer (SXS) onboard Astro-H, is a high energy resolution spectrometer utilizing an X-ray micro-calorimeter array, which is operated at 50mK by the ADR with the 30-L superfluid liquid helium (LHe). The mechanical cryocoolers, 4K-class Joule Thomson (JT) cooler and 20K-class double-staged Stirling (2ST) cooler are key components to achieve a LHe lifetime for over 3years in orbit (5years as a goal). Based on the existing cryocoolers onboard Akari (2006) and JEM/SMILES (2009), modifications for higher cooling power and reliability had been investigated. In the present development phase, the Engineering Models (EMs) of these upgraded cryocoolers are fabricated to carry out verification tests for cooling performance, mechanical performance and lifetime. Nominal cooling power of 200mW at 20K for the 2ST cooler and 40mW at 4.5K for the JT cooler were demonstrated with temperature and power margin. Mechanical performance test for the 2ST cooler units proves tolerability for pyro shock and vibration environment of the Astro-H criteria. Continuous running of the 4K-class JT cooler combined with the 2ST precooler for lifetime test has achieved over 5000h without any degradation of cooling performance.

MERLIN, a new high count rate spectrometer at ISIS

MERLIN is designed to be a high intensity, medium energy resolution spectrometer. As such, it will complement the high-resolution MAPS spectrometer at ISIS. MERLIN will utilise all the latest advances in technology with a supermirror guide to enhance flux as well as 3 m long position-sensitive detectors in a vacuum making it ideal for single-crystal users. The detector bank will cover a massive π steradians of solid angle with an angular range from −45° to +135° degrees in the horizontal plane and ±30° degrees in the vertical plane. This will allow large swathes of Q, ω space to be accessed in a single run. The instrument will be ready for commissioning in February 2006. This paper presents details of design and performance of this new instrument.

Energy spectra of electrons quasi-elastically backscattered from solid surfaces

The energy distribution of electrons quasi-elastically backscattered from solids has been investigated. Monte Carlo (MC) simulations were performed for the study of the recoil energy shift and the broadening of this distribution for backscattered electrons from Si and Au. In these simulations, electron interaction cross sections were obtained from calculations based on the dielectric response theory for inelastic interactions, including volume and surface excitations, and elastic interactions. The depth-dependent electron inelastic mean free path for volume excitations and the probability of surface excitations were calculated using the dielectric functions derived from optical data. The relativistic partial-wave expansion method was applied to calculate the elastic scattering cross section for a potential of the atom in the solid. The Rutherford-type recoil energy was included in the MC simulations by either considering or neglecting the thermal effect of atomic vibrations. Such an effect was applied using the single scattering model. The intensity of electrons quasi-elastically backscattered from Si and Au was simulated for incident electrons of an energy distribution. The adjustment for the spectrometer energy resolution was allowed. An analytic expression for the intensity of backscattered electrons by a single scattering was derived explicitly. A comparison of simulated results with experimental data was made and discussed.

Unusual antiferromagnetic properties affected by antiferroquadrupolar interaction in TbB2C2

Abstract Neutron scattering experiments were carried out on TbB2C2 with T N =21.7 K under high energy resolution in order to investigate the diffuse scattering and the incommensurate structure in the antiferromagnetic state. At 3.9 K , the energy width of both the satellite peak and the diffuse scattering corresponding to the energy resolution of 0.2 meV . With increasing temperature, only the satellite peak was disappeared far below TN around 13 K where no anomaly was observed in the specific heat and the magnetic susceptibility. Since the disappearance temperature of the satellites depends on the energy resolution of spectrometer, the dynamical component would affect the incommensurate structure in TbB2C2.

Merlin project begins

On June 11, 2002, a meeting was held at Milton Hill near the Rutherford Appleton Laboratory to discuss the MERLIN project with the user community. The project started in February 2002 with an official announcement that EPSRC was to fund the construction of the MERLIN chopper spectrometer at ISIS through grants to Keith McEwen (UCL), Stephen Hayden (Bristol), and Martin Dove (Cambridge). MERLIN is designed to be a high intensity, medium energy resolution spectrometer, using supermirror guides to provide a high neutron flux onto the sample. Position sensitive gas detectors, like those used on MAPS, will be used to provide more than JC steradians of solid angle coverage with an angular range from −45° to 135° in the horizontal plane and ±30° in the vertical plane. This will allow large swathes of q,ω space to be accessed simultaneously.

Asymmetry modulated SQUIDs made by direct focused ion beam milling

We have developed a fabrication method using a focused ion beam microscope that allows us to produce SNS junctions in which thermally energetic electrons can enter the normal metal region. The SNS junctions are fabricated in a normal metal/low T C superconductor bilayer by removing narrow (∼50 nm) region of the superconductor. Connecting either a normal metal resistive heater of a photon-absorbing pixel with a lateral connection to the normal metal layer of the bilayer in the vicinity of the junction will inject hot electrons into the junction, thus reducing the critical current. In a superconducting quantum interference device (SQUID) such an effect is manifested as an adjustable asymmetry parameter which results in a change in the flux–modulation curve. We are developing SQUIDs utilising this concept for application as high energy resolution spectrometers. In order to realise these devices, we are fabricating SNS junctions with critical current ( I C)–normal resistance ( R N) products in excess of 0.1 mV and temperature dependent critical currents operating at 0.3 K. The use of the focused ion beam affords great flexibility in the design of our devices. Here we discuss the parameters for the optimum design and selection of materials and present our latest results from our prototype devices.

Evaluation of the energy‐dispersive x‐ray spectra of high‐Z elements using Gaussian and Voigt peak shape profiles

AbstractThe AXIL computer program, aimed at x‐ray spectral deconvolution, was extended in order to take into account the broadening of peaks of K‐series radiation of high‐Z elements (Z &gt; 50) due to the increasing contribution of the natural linewidth to the peak width. This effect needs to be taken into account in energy‐dispersive spectrometry of K‐series radiation of heavy elements, such as W, Au, Pb and U. The so‐called Voigt peak profile function was implemented into the AXIL computer code. Based on the published literature data, a library of natural atomic level widths was created, containing the data for K, L1, L2, L3 atomic level widths of elements up to Z = 94. The database was necessary to calculate the Voigt peak profiles. The AXIL program user interface and the fitting procedures were adapted, allowing us to perform spectral evaluation using either Gaussian or Voigt peak profiles. The relevance of fitting the x‐ray spectra of K‐series radiation of high‐Z elements with the Voigt peak shape model versus Gaussian peak approximation was thoroughly examined with the aid of simulated and measured spectra. The experimental x‐ray spectra were measured using a high‐voltage x‐ray tube spectrometer utilizing a 130 kV/65 W tungsten anode x‐ray tube and an ultra‐low energy germanium detector. The results obtained showed that when using the Gaussian peak model the calculated peak areas and fitted peak widths are systematically biased. It was found that the value of the systematic error is a linear function of the ratio of the natural linewidth to the spectrometer energy resolution at the peak position. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Site-selective XAFS spectroscopy tuned to surface active sites of copper catalysts

To overcome the problem of X-ray absorption fine structure (XAFS) spectroscopy in which the obtained information is the average for all sites in sample, Rowland-type fluorescence spectrometer was designed to measure site-selective XAFS spectra by utilizing the chemical shift of emission peak for each site. Johansson-type cylindrically-bent Ge(111) crystal and scintillation counter were mounted on the spectrometer. The improvement of energy resolution of spectrometer was discussed when the primary beam size and two slit size in the Rowland circle were varied. The energy resolution was ∼1.1 eV, smaller than the core-hole lifetime width for Cu Kα1 (2.11 eV). The site selection of the Cu0 and CuI site-tune spectra was experimentally measured for the physical mixture of Cu metal+CuI and for Cu/ZnO catalyst. Obtained experimental site selection was compared to the theoretical estimations.