Measured Energy Resolution Research Articles

Investigation of a LYSO crystal for a low-energy calorimeter

The results of studying a calorimeter cell in the low-energy region, ~50 MeV, which consists of a LYSO crystal and two avalanche photodiodes, are presented. The use of two photodiodes per crystal made it possible to perform a preliminary measurement of the calorimeter energy resolution using one calorimeter cell and cosmic muons. The coefficient of the stochastic contribution to the calorimeter energy resolution and the crystal luminescence time were measured (0.115% and 50 ns, respectively).

High energy-resolution measurements of x-ray into ultraviolet parametric down-conversion with an x-ray tube source

We describe high energy-resolution measurements of parametric down-conversion of x-rays into ultraviolet radiation using a standard laboratory x-ray tube source with very minor modifications. We measure the effect in diamond and in lithium fluoride crystals in the ultraviolet range from 30 eV to 65 eV. We show that the effect depends strongly on the fluorine LI edge at 37 eV and on the K edge of the lithium at 55 eV. The comparison with theory reveals that the classical model that was previously used for the description of the effect agrees with the experimental results in diamond. However, the discrepancies of the model with the experimental results in lithium fluoride are prominent.

Instrumental function of the SPECS XPS system

A simple method for the energy resolution measurement of a spectrometer, working in the fixed analyser transmission mode, is proposed and used to determine the resolution of a SPECS Phoibos 100 spectrometer, being a part of an X-ray Photoelectron Spectroscopy (XPS) setup. The spectrometer resolution was obtained from the O 1s photoelectron line profiles, taken from the oxidized boron-doped silicon single crystal vs. the analyzer pass energy. The measurements were performed for two entrance slits having respective widths of 1mm and 7mm. An excellent agreement with the theoretical expectations was obtained for the narrower slit, showing linear dependence on the pass energy. As for the wider slit, agreement with theory is achieved only for lower pass energies. At higher pass energies, the resolution shows non-linear behaviour and even saturation, while the analyzer transmission continues to grow. The instrumental function of the whole XPS system is determined as a convolution of the spectrometer instrumental function and the X-ray energy profile. The usefulness of the total instrumental function for the analysis of valence band spectra was also tested. For that purpose, a novel deconvolution procedure is introduced, giving a possibility to analytically calculate the position of the valence band maximum, providing excellent agreement in the case of high resolution spectra. When the valence band spectra are taken in lower resolution, deconvolution efficiently reduces the spectrum deviations due to the lower resolution, although the valence band maximum determination is less precise.

A parameterized energy correction method for electromagnetic showers in BGO-ECAL of DAMPE

DAMPE is a space-based mission designed as a high energy particle detector measuring cosmic-rays and γ-rays which was successfully launched on Dec.17, 2015. The BGO electromagnetic calorimeter is one of the key sub-detectors of DAMPE for energy measurement of electromagnetic showers produced by e±/γ. Due to energy loss in dead material and energy leakage outside the calorimeter, the deposited energy in BGO underestimates the primary energy of incident e±/γ. In this paper, based on detailed MC simulations, a parameterized energy correction method using the lateral and longitudinal information of electromagnetic showers has been studied and verified with data of electron beam test at CERN. The measurements of energy linearity and resolution are significant improved by applying this correction method for electromagnetic showers.

Development of a low-noise readout ASIC for Silicon Drift Detectors in high energy resolution X-ray spectrometry

ASIC with a low-noise readout channel for Silicon Drift Detectors in high energy resolution X-ray spectrometry was designed and prototyped in the AMS 350 nm CMOS process via Europractice as a miniASIC. For the analog readout channel tests there was used the detector module SDD-10-130-PTW LTplus-ic (PNDetector GmbH). The measured energy resolution of this module with the designed readout channel: 200 eV (FWHM) at 55Fe, -16 °C, 1 kcps and a peaking time of 8 μs.

Studying the spectrometric characteristics of an ionizing-radiation detector based on a LaBr3(Ce) scintillator and a silicon photomultiplier

The intrinsic background of a LaBr3(Ce) scintillator with a diameter of 5 mm and a height of 10 mm has been studied in comparison with LYSO and CeBr3 scintillators. It is shown that due to its high energy resolution the detector based on a LaBr3(Ce) crystal exhibits the lowest background count rate in a specified amplitude range. The measured energy resolution of the detector based on a LaBr3(Ce) crystal with dimensions of O5 mm × 10 mm in combination with a silicon photomultiplier with an active area of 3 × 3 mm2 are presented. It is demonstrated that a detector array with the proposed configuration (a scintillator + a silicon photomultiplier enclosed in a common container) exhibits an energy resolution of 4% for 661.7-keV γ rays and a background count rate of ~0.39 cps in the energy range of (140 ± 3σ) keV.

Electrostatic analyzer design for solar wind proton measurements with high temporal, energy, and angular resolutions

AbstractWe present the design study of an electrostatic analyzer that permits combined high temporal, energy, and angular resolution measurements of solar wind ions. The requirements for high temporal, energy, and angular resolutions, combined with the need for sufficient counting statistics, lead to an electrostatic analyzer with large radius (140 mm) and large geometric factor. The resulting high count rates require the use of channel electron multipliers (CEMs), instead of microchannel plates, to avoid saturation. The large radius further permits the placement of 32 CEM detectors at the analyzer focal plane, thereby providing very high angular resolution in azimuth (1.5°). Electrostatic simulations were performed to define the analyzer geometric factor, energy resolution, analyzer constant (K), elevation response, etc. Simulations were also performed to define the geometry of the deflectors and collimator that are used to provide the proper energy resolution, field of view, and angular resolution (1.5°) in elevation as well (the total field of view of the design is ±24° × ±24°). We show how this design permits unprecedented measurements of the fine structure of the solar wind proton beam and other important features such as temperature anisotropy. This design is used for the Cold Solar Wind instrument of the medium‐class Turbulent Heating ObserveR mission, currently in phase A at the European Space Agency. These unprecedented measurement capabilities are in accordance with and even beyond the requirements of the mission.

A miniaturized alpha spectrometer for the calibration of an avalanche-confinement TEPC

The design and development of a recent avalanche-confinement tissue equivalent proportional counter (TEPC) for microdosimetry and nanodosimetry applications required the selection of a proper miniaturized solid state detector (SSD) for detecting alpha particles emitted by a thick removable Cm-244 source embedded in the cylindrical TEPC chamber for characterization and calibration purposes. Since the available cavity for embedding the SSD detector is only 4.2 mm in diameter, no standard devices can be exploited. The selection of the best SSD for this application was based on the following requirements: very low size, proper energy resolution, cheapness. The performances of the finally selected SSD were assessed by exploiting a multi-peak calibration alpha source (Pu-239, Am-241, Cm-244). The measured energy resolution resulted about 25 keV FWHM. The TEPC calibration procedure, which exploits the selected SSD aligned to the built-in Cm-244 alpha source, is described in details.

Determining the resolution energy of a radiant source from the gamma energy of the source

This study was conducted to measure energy resolution by measuring energy gamma using HPGe detector, using radioactive sources 137Cs, 22Na, and 60Co. It was found that by determining the gamma energy of a radiant source from the selected sources of measurement the energy resolution could be found. The energy of gamma ray could also be found. The resolution of the HPGe detector was directly proportional to the energy of gamma-ray and its efficiency was exponentially proportional to the gamma-ray energy.

Characterization of X3 Silicon Detectors for the ELISSA Array at ELI-NP

Position-sensitive silicon strip detectors represent one of the best solutions for the detection of charged particles as they provide good energy and position resolution over a large range of energies. A silicon array coupled with the gamma beams at the ELI-NP facility would allow measuring photodissociation reactions of interest for Big Bang Nucleosynthesis and on heavy nuclei intervening in the p-process. Forty X3 detectors for our ELISSA (ELI-NP Silicon Strip Detectors Array) project have been recently purchased and tested. We investigated several specifications, such as leakage currents, depletion voltage, and detector stability under vacuum. The energy and position resolution, and ballistic deficit were measured and analyzed. This paper presents the main results of our extensive testing. The measured energy resolution for the X3 detectors is better than results published for similar arrays (ANASEN or ORRUBA).

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.

4H-SiC Schottky diode arrays for X-ray detection

Five SiC Schottky photodiodes for X-ray detection have been electrically characterized at room temperature. One representative diode was also electrically characterized over the temperature range 20°C to 140°C. The performance at 30°C of all five X-ray detectors, in both current mode and for photon counting X-ray spectroscopy was investigated. The diodes were fabricated in an array form such that they could be operated as either a 2×2 or 1×3 pixel array. Although the devices showed double barrier heights, high ideality factors and higher than expected leakage current at room temperature (12nA/cm2 at an internal electric field of 105kV/cm), they operated as spectroscopic photon counting soft X-ray detectors uncooled at 30°C. The measured energy resolution (FWHM at 17.4keV, Mo Kα) varied from 1.36 to 1.68keV among different diodes.

Laser-Assisted Photoelectric Effect from Liquids.

The laser-assisted photoelectric effect from liquid surfaces is reported for the first time. Photoelectrons generated by 35.6eV radiation from a liquid microjet of water under vacuum are dressed with a ℏω=1.55 eV laser field. The subsequent redistribution of the photoelectron energies consists in the appearance of sidebands shifted by energies equivalent to ℏω, 2ℏω, and 3ℏω. The response has been modeled to the third order and combined with energy-resolved measurements. This result opens the possibility to investigate the dynamics at surfaces of liquid solutions and provide information about the electron emission process from a liquid.

Concept of proton radiography using energy resolved dose measurement

Energy resolved dosimetry offers a potential path to single detector based proton imaging using scanned proton beams. This is because energy resolved dose functions encrypt the radiological depth at which the measurements are made. When a set of predetermined proton beams ‘proton imaging field’ are used to deliver a well determined dose distribution in a specific volume, then, at any given depth x of this volume, the behavior of the dose against the energies of the proton imaging field is unique and characterizes the depth x. This concept applies directly to proton therapy scanning delivery methods (pencil beam scanning and uniform scanning) and it can be extended to the proton therapy passive delivery methods (single and double scattering) if the delivery of the irradiation is time-controlled with a known time-energy relationship.To derive the water equivalent path length (WEPL) from the energy resolved dose measurement, one may proceed in two different ways. A first method is by matching the measured energy resolved dose function to a pre-established calibration database of the behavior of the energy resolved dose in water, measured over the entire range of radiological depths with at least 1 mm spatial resolution. This calibration database can also be made specific to the patient if computed using the patient x-CT data. A second method to determine the WEPL is by using the empirical relationships between the WEPL and the integral dose or the depth at 80% of the proximal fall off of the energy resolved dose functions in water.In this note, we establish the evidence of the fundamental relationship between the energy resolved dose and the WEPL at the depth of the measurement. Then, we illustrate this relationship with experimental data and discuss its imaging dynamic range for 230 MeV protons.

Statistical theory of relaxation of high-energy electrons in quantum Hall edge states

We investigate theoretically the energy exchange between electrons of two co-propagating, out-of-equilibrium edge states with opposite spin polarization in the integer quantum Hall regime. A quantum dot tunnel-coupled to one of the edge states locally injects electrons at high energy. Thereby a narrow peak in the energy distribution is created at high energy above the Fermi level. A second downstream quantum dot performs an energy resolved measurement of the electronic distribution function. By varying the distance between the two dots, we are able to follow every step of the energy exchange and relaxation between the edge states - even analytically under certain conditions. In the absence of translational invariance along the edge, e.g. due to the presence of disorder, energy can be exchanged by non-momentum conserving two-particle collisions. For weakly broken translational invariance, we show that the relaxation is described by coupled Fokker-Planck equations. From these we find that relaxation of the injected electrons can be understood statistically as a generalized drift-diffusion process in energy space for which we determine the drift-velocity and the dynamical diffusion parameter. Finally, we provide a physically appealing picture in terms of individual edge state heating as a result of the relaxation of the injected electrons.

Characterization of GaSb photodiode for gamma-ray detection

We extract the carrier mobility-lifetime products for epitaxially grown GaSb and demonstrate the spectral response to gamma rays of a GaSb p–i–n photodiode with a 2-µm-thick absorption region. Under exposure from 55Fe and 241Am radioactive sources at 140 K, the photodiode exhibits full width at half maximum energy resolutions of 1.238 ± 0.028 and 1.789 ± 0.057 keV at 5.89 and 59.5 keV, respectively. We observe good linearity of the GaSb photodiode across a range of photon energies. The electronic noise and charge trapping noise are measured and shown to be the main components limiting the measured energy resolutions.

Fabrication and characterization of rectangular strontium iodide scintillator coupled to TSV-MPPC array

Europium-doped strontium iodide (SrI2(Eu)) is a promising material for the scintillation crystals in a Compton imaging system, which requires an excellent energy resolution, as an alternative to NaI(Tl) crystals. Rectangular SrI2(Eu) crystals with dimensions of 10×10×10mm3 are fabricated, aiming for coupling with semiconductor-based photodetectors, especially silicon photomultipliers (SiPMs) in array detectors. The fabricated crystals are evaluated by coupling with a through silicon via (TSV)-type multipixel photon counter (MPPC) with dimensions of 12.6×12.6mm2. The saturation response of the SiPMs is corrected by using several photopeaks of isotopes with a fitting function. The measured energy resolution is approximately 4.4% at 662keV compared with an energy resolution of 3.4% with a PMT, and the crystals exhibit the best energy resolution with a shaping time of 6μs. All of the five prepared samples exhibit very stable performance and are promising for our future Compton imaging system for environmental radiation monitoring.

Energy resolution measurements of CeBr3 and LaCl3:Ce detectors

The energy resolution of LaCl3:Ce and CeBr3 detectors were measured from gamma rays produced due to thermal neutron capture in CeBr3 and LaCl3:Ce detector’s material using a portable DD neutron generator-based prompt gamma ray neutron activation analysis (PGNAA) setup. The energy resolution of CeBr3 detector varies from 6.64 ± 0.04 to 2.75 ± 0.04 % over 368–2223 keV gamma rays while for LaCl3:Ce it varies from 7.09 ± 0.02 to 0.90 ± 0.01 % over 272–8579 keV gamma rays. The energy resolution data of both detectors exhibit 1/√E γ dependence.

The voltage optimization of a four-element lens used on a hemispherical spectrograph with virtual entry for highest energy resolution

The methodology and results of a detailed four-element lens optimization analysis based on electron trajectory numerical simulations are presented for a hemispherical deflector analyzer (HDA), whose entry aperture size is determined by the injection lens itself and is therefore virtual. Trajectory calculations were performed using both the boundary-element method (BEM) and the finite-difference method (FDM) and results from these two different approaches were benchmarked against each other, to probe and confirm the accuracy of our results. Since the first and last electrode are held at fixed potentials, the two intermediate adjustable lens electrode voltages were varied over the entire available voltage space in a direct, systematic, brute-force approach, while minima in beam spot size on the 2-D position sensitive detector (PSD) at the exit of the HDA were investigated using a beam shaping approach. Lens voltages demonstrating improved energy resolution for the combined lens/HDA/PSD spectrograph system were sought with and without pre-retardation. The optimal voltages were then tested experimentally on the modeled HDA system using a hot-wire electron gun. The measured energy resolution was found to be in good overall agreement with our simulations, particularly at the highest resolution (∼0.05%) working conditions. These simulations also provide a detailed insight to the distinctive trajectory optics and positions of the first and second image planes, when the PSD has to be placed some distance away from the HDA exit plane, and is therefore not at the ideal optics conjugate image position. The substantial time savings afforded over usual trial-and-error experimentation should make this type of make-do simulation approach attractive to experimentalists.

LUMINEU: a search for neutrinoless double beta decay based on ZnMoO4 scintillating bolometers

The LUMINEU is designed to investigate the possibility to search for neutrinoless double beta decay in 100 Mo by means of a large array of scintillating bolometers based on ZnMoO4 crystals enriched in 100 Mo. High energy resolution and relatively fast detectors, which are able to measure both the light and the heat generated upon the interaction of a particle in a crystal, are very promising for the recognition and rejection of background events. We present the LUMINEU concepts and the experimental results achieved aboveground and underground with large-mass natural and enriched crystals. The measured energy resolution, the α/β discrimination power and the radioactive internal contamination are all within the specifications for the projected final LUMINEU sensitivity. Simulations and preliminary results confirm that the LUMINEU technology can reach zero background in the region of interest (around 3 MeV) with exposures of the order of hundreds kgxyears, setting the bases for a next generation 0v2β decay experiment capable to explore the inverted hierarchy region of the neutrino mass pattern.