Pulse Height Research Articles

Characterisation of Sm2+-doped CsYbBr3, CsYbI3 and YbCl2 for near-infrared scintillator application

Fast energy transfer from Yb2+ to Sm2+ is a requirement when using Yb2+ as a sensitiser for Sm2+ emission for near-infrared scintillator applications. This cannot be achieved through dipole-dipole interactions due to the spin-forbidden nature of the involved Yb2+ transition, making the rate of energy transfer too slow for application. This work explores whether exploiting the exchange interaction by increasing the Yb2+ concentration to 99% is an effective way to increase the rate at which energy is transferred from Yb2+ to Sm2+. The scintillation characteristics of CsYbBr3:1%Sm, CsYbI3:1%Sm and YbCl2:1%Sm single crystals were studied through 137Cs excited pulse height spectra, X-ray excited decay and X-ray excited luminescence spectra. An energy resolution of 7% and a light yield of 30,000 ph/MeV was achieved with CsYbI3:1%Sm. Photoluminescence spectroscopy and decay studies were performed to study the band structure and relaxation dynamics.

Efficient liquid scintillator loaded with a light-emitting conjugated oligomer for beta- and gamma-ray spectroscopic measurements

Liquid scintillation (LS) counting is a common way to detect and measure radioactivity because it has a better time resolution and can discriminate between neutrons and gamma rays. We show how to make a promising liquid scintillator with a light-emitting conjugated oligomer: 9,9,9′,9′,9″,9″-hexakis(octyl)-2,7′,2′,7″-trifluorene (ADS038FO or 9HOTF). A container with a LS blend coupled with a photomultiplier detector setup showed enhanced scintillation for different radioactive sources. The gamma and beta radiation responses of LS were studied under various radiation sources: 137Cs, 60Co, and 22Na as gamma rays and 90Sr as a beta source. We observed a scintillation count increase with an increase in the percentage of 9HOTF. Further studies were performed to evaluate the characteristics of the fabricated liquid scintillator, such as emission wavelength, absorption, Compton edge (CE), and count rate. CE spectra were used to calibrate the energy, and the pulse height spectra were measured for the prepared LSs. The energy linearity was investigated, and the fabricated LSs showed more than 99% energy linearity. According to the results, the CE determined was more than 90% of the theoretical values for the 137Cs, 60Co, and 22Na sources. For the 90Sr/90Y beta source, the pulse height spectrum's lower energy (90Sr) and the higher energy (90Y) were distinguishable. The comparison between POPOP and 9HOTF-based LS proved that the performance of 9HOTF was marginally better than that of POPOP.

On the Energy Dependence of Galactic Cosmic Ray Anisotropies in the Very Local Interstellar Medium

We report on the energy dependence of Galactic cosmic rays (GCRs) in the very local interstellar medium (VLISM) as measured by the Low Energy Charged Particle (LECP) instrument on the Voyager 1 spacecraft. The LECP instrument includes a dual-ended solid-state detector particle telescope mechanically scanning through 360° across eight equally spaced angular sectors. As reported previously, LECP measurements showed a dramatic increase in GCR intensities for all sectors of the ≥211 MeV count rate (CH31) at the Voyager 1 heliopause (HP) crossing in 2012; however, since then the count rate data have demonstrated systematic episodes of intensity decrease for particles around 90° pitch angle. To shed light on the energy dependence of these GCR anisotropies over a wide range of energies, we use Voyager 1 LECP count rate and pulse height analyzer (PHA) data from ≥211 MeV channel together with lower-energy LECP channels. Our analysis shows that, while GCR anisotropies are present over a wide range of energies, there is a decreasing trend in the amplitude of second-order anisotropy with increasing energy during anisotropy episodes. A stronger pitch angle scattering at higher velocities is argued as a potential cause for this energy dependence. A possible cause for this velocity dependence arising from weak rigidity dependence of the scattering mean free path and resulting velocity-dominated scattering rate is discussed. This interpretation is consistent with a recently reported lack of corresponding GCR electron anisotropies.

Crystal growth and scintillation properties of Tm3+ doped LaCl3 single crystal for radiation detection

Single crystal of Tm-doped LaCl3 (LaCl3:Tm3+) with the dimension of diameter 7 mm and length 55 mm was successfully grown using an in-house-developed Bridgman furnace. The grown crystal has the self-trapped exciton (STE) emission in the range of 300–500 nm along with the characteristic emissions corresponding to the 4f-4f transition of Tm3+ ions under X-ray excitation. The scintillation characterizations of the grown crystal were performed by pulse height spectra, scintillation decay time, as well as pulse shape discrimination studies under γ-ray and α-particle excitation sources. The LaCl3:Tm3+ crystal was found to have a high light yield (42,000 ± 4,200 ph/MeV) with 4.2% energy resolution under γ-rays excitation. Moreover, the pulse shape discrimination was studied using 137Cs and 241Am as the radiation sources with a good FOM value. The results conclude the LaCl3:Tm3+ single crystal to be a promising candidate for X-ray and γ-ray detection purposes.

Recent Trends in Elpasolite Single Crystal Scintillators for Radiation Detection

Scintillation detection has attracted great interest in nuclear medicine, nuclear radiation detection, high-energy physics, and non-destructive inspection. The elpasolite crystals with Ce3+ dopants are promising for these endeavors due to their modest light yield and extremely good proportionality when excited by the gamma ray. Moreover, the 6Li and 35Cl isotopes in elpasolite crystals endow them with excellent neutron detection capability. These features allow not only a high energy resolution but also a high detection sensitivity. The elpasolite scintillators also enable the precisely dual detection of gamma/neutron signals through pulse height discrimination (PHD) or pulse shape discrimination (PSD). In this work, we review recent investigations on using the typical elpasolite scintillators, including Ce3+-doped Cs2LiYCl6 (CLYC), Cs2LiLaCl6 (CLLC), and Cs2LiLaBr6 (CLLB), for the monitoring of gamma rays and neutrons. The scintillation properties, detection mechanism, and elpasolite crystal structure are also discussed with the aim of improving high-energy ray detection ability.

Luminescence and scintillation properties of Ce-doped calcium hafnate perovskite single crystals

Hafnium-based materials are attractive for a scintillator owing to their high density and effective atomic number. In this study, single crystals of Ce-doped calcium hafnate perovskite (Ce:CaHfO3) were synthesized from a Ca-rich composition, and photoluminescence (PL) and scintillation properties were investigated. The X-ray diffraction patterns revealed that the synthesized single crystals were a single phase of CaHfO3. The Ce:CaHfO3 exhibited blue luminescence at 430 nm and fast decay due to the 5d–4f transition of Ce3+ in both PL and scintillation. From the measurement of pulse height spectra under 137Cs irradiation, the highest light yield of 7800 photons/MeV was observed in the 3% Ce:CaHfO3.

Charge collection efficiency of scCVD diamond detectors at low temperatures

The charge collection efficiency (CCE) in electronic grade, single crystal chemical vapor deposition (scCVD) diamond detector was studied using different ions of the MeV energy range from room temperature down to 47 K. The measurements were performed by using the ion beam induced charge (IBIC) technique, with 0.8 MeV H+, 3 MeV He2+, 5.6 MeV Li2+, and 12.8 MeV C4+ ion beams. The total accumulated charge as a function of temperature was extracted from the measured pulse height spectra. A similar decreasing trend of the detector CCE with temperature was observed for all ion species. A plateau was observed from room temperature to 145 K followed by a sharp, step like, decrease in the temperature range of 65 K < T < 145 K. Below 65 K, the CCE reaches another plateau with small variations down to 47 K. The decrease in collected charge was observed in the same temperature window for each ion. However, the level of the CCE decrease varied. For He, Li and C, the CCE decreased to 24.7 ± 0.4 %, 23.6 ± 1.3 %, 25.9 ± 0.8 % respectively while 39.3 ± 0.8 % for H. The reduction of the CCE is in agreement with earlier reported results obtained by alpha particles which was associated with the changes in lifetime of excitons in diamond.

Overcoming the quantum mechanics measurement problem by experiment and theory

The unknown mechanism of wave-function collapse is called the measurement problem. The problem is best portrayed by a beam-split coincidence test, usually performed with visible light. The notion that energy conservation requires quantization is challenged by considering new beam-split tests and a threshold model (TM). An analysis of pulse heights in detectors for visible light concludes that their pulse height distribution is too broad to make the quantum/threshold distinction. This is because TM recognizes a preloaded state, understood in the loading theories of Planck, Debye, and Millikan, but usually unrecognized. The narrow pulse height distribution of gamma-ray detectors overcomes this detector problem. In addition, a source of singly emitted radiation is required for these beam-split tests. To assure a singly emitted source, the well-known true-coincidence test from nuclear physics is far more reliable than any test with visible light. One of my many successful beam-split coincidence tests with gamma-rays is described revealing the failure of quantum mechanics. After plotting the times between photoelectric effect pulses from the two detectors and comparing to accidental chance, I report a seemingly two-for-one effect that contradicts a photon kind of energy conservation. My similar tests performed with alpha-rays also contradict quantum mechanics. To explain how matter can load up, I hypothesize that our electron constants h, e, and m are maxima. Simple conserved ratios of these constants h/m, e/m, h/e, seen in equations involving electron beams, can explain how charge waves can spread, yet accumulate to measurable threshold values h, e, m, upon absorption to convey particle-like effects.

Pulse Height Analyzer with Coincidence Correction

A pulse height analyzer (PHA) is used to measure the frequency distribution of the signal output height of an event detector. However, the typical PHA algorithm has limitations in measurement; it cannot distinguish multiplet due to coincidence and singlet pulse. Coincidences will pile up the signals that make the pulse height value higher than it should be. Therefore, this study has developed a simple algorithm to calculate pulse height distribution with coincidence correction (PHA-CC). The developed algorithm firstly identified the coincidence pulse by considering its pulse width. The result shows that the developed algorithm could successfully distinguish multiplet and singlet pulses. The significance of pulse height distribution measured by the PHA-CC compared to regular PHA was also discussed in this paper.

1093-P: Vascular Health across the Lifespan in Women with and without Type 1 Diabetes (TID)

Introduction: Cardiovascular disease (CVD) is the leading cause of death in people with T1D, and women with T1D are disproportionately affected. However, few studies have examined how T1D affects vascular health in women across the lifespan. Methods: Women ages 18-79 with (N=309) and without T1D (n=351) were examined cross-sectionally for markers of CVD: pulse wave velocity (PWV) , augmentation index (AiX) , pulse height (PH) , brachial artery distensibility (BrachD) , subendocardial viability index (SVI) , and carotid intima thickness (cIMT) . Menopausal status was self-reported. Body composition was measured by Dual Xray Absorptiometry. CVD markers were examined by diabetes status and age using linear regression models adjusted for menopausal status. Results: Age did not differ in women with and without diabetes (49 ± 12 vs. 50±14 years, p=0.32) . Women with T1D had higher systolic blood pressure (SBP) , cIMT, PWV and PH, and lower BrachD and SVI than non-diabetic women (Table 1) . Changes in blood pressure, cIMT, AiX, and SVI with age differed by diabetes status, as demonstrated by a significant interaction. While SBP and Aix were increased more in women with T1D at younger ages, cIMT and SVI worsened with age to a greater extent in T1D. Conclusions: Women with T1D have worse CVD markers than women without diabetes across the lifespan, with more arterial stiffness at younger ages and more atherosclerosis and lower SVI later in life. Disclosure C.J.Chartier-logan: None. A.C.Alman: None. V.Shah: Advisory Panel; Medscape, Sanofi, Consultant; Dexcom, Inc., Research Support; Dexcom, Inc., Eli Lilly and Company, Insulet Corporation, Novo Nordisk. J.K.Snell-bergeon: Stock/Shareholder; GlaxoSmithKline plc.

439-P: Disparate Effects of Menopause on Cardiovascular Risk in Women with Type 1 Diabetes

Introduction: Women with type 1 diabetes (T1D) are at increased risk for cardiovascular disease (CVD) , and menopause increases CVD risk. However, little is known about menopause and CVD risk in T1D. Methods: Women with (N=64) and without T1D (n=63) ages 47-55 years were examined for CVD risk factors and surrogate CVD markers: pulse wave velocity (PWV) , augmentation pressure (AP) and pulse height (PH) , brachial artery distensibility (BrachD) , and subendocardial viability index (SVI) . Body composition was measured by Dual Xray Absorptiometry. Menopausal status was determined by self-report. CVD markers were examined by diabetes and menopausal status using linear regression models adjusted for age. Results: Mean ± SD age was 51±2.5 years in women with T1D and 51 ± 2.4 years in women without diabetes (p=0.32) . The percentage postmenopausal did not differ (30% vs. 32%, p=0.8) between T1D and nondiabetes women. As shown in the table, women with T1D had higher systolic blood pressure and measures of arterial stiffness (PWV, AP, PH, and BrachD) and lower SVI than women without diabetes. Menopause was associated with a greater loss in fat free mass and a greater increase in PWV and AP among women with T1D compared to women without diabetes. Conclusions: Women with T1D have worse CVD markers, and menopause is associated with greater increases in arterial stiffness and loss in lean body mass than in nondiabetes women, independent of age. Disclosure H.K.Wise: None. E.Malecha: None. C.J.Chartier-logan: None. L.Pyle: None. A.Keshawarz: None. J.K.Snell-bergeon: Stock/Shareholder; GlaxoSmithKline plc. Funding American Diabetes Association (7-13-CD-10)

Deep Learning-Based Pulse Height Estimation for Separation of Pile-Up Pulses From NaI(Tl) Detector

Deep Learning-Based Pulse Height Estimation for Separation of Pile-Up Pulses From NaI(Tl) Detector

Heading for brighter and faster β-Ga2O3 scintillator crystals

Czochralski-grown β-Ga2O3 and β-Ga2O3:Si crystals with the free electron concentrations between 2.5·1016 and 4.3·1018 cm−3 have been characterized by means of pulse height and scintillation time profile measurements in order to assess their basic scintillation properties. At room temperature, with increasing free electron concentration in the studied range, the scintillation yields decrease from 8920 to 1930 ph/MeV, while the mean scintillation decay times pare down from 989 to 61 ns. However, when the brightest β-Ga2O3 sample is cooled down below 100 K, its scintillation yield exceeds 20000 ph/MeV.

Development of personal neutron dosimeter with energy resolution ability

The prototype neutron personal dosimeter consists of three passive implanted planar silicon detectors. Polyethylene, B4C-containing polyethylene, and 6LiF act as neutron moderators, absorbers, and converters in front of each detector. This personal dosimeter has two modes of operation: real-time mode and unfolding mode. In real-time mode, it shows three neutron personal dose equivalent values, which represent the personal neutron equivalent of high energy (1–15 MeV), intermediate energy (1 × 10−3 MeV –1MeV), and low-energy (2.53 × 10−8 MeV −1 × 10−3 MeV), respectively. Unfolding method based on Genetic Algorithm was used to deduce neutron spectra from pulse height spectra of recoil proton. The dosimeter was calibrated in monoenergetic neutron fields and was tested in an 241Am–Be neutron field.

Bandgap engineering of [formula omitted

CdZnTe (CZT) detectors with more than 10% zinc content did not show any remarkable improvement in the detector performance due to the additional defects introduced by the higher zinc content. However, recent research showed that the formation of defects was suppressed effectively by adding a small amount of selenium (at. 2%) in CZT. On this basis, we attempted to enhance the detector performance through the bandgap engineering by increasing the zinc content up to 25%, while adding 2% of selenium. Multiple CdZnTeSe (CZTS) ingots with Zn = 10, 12.5, 15, and 20%, while keeping the Se contents at 2%, were grown by the Bridgman method. The bandgap of CZTS for the different Zn and Se contents was analyzed and then introduced modified equation for predicting more accurately the bandgap of other alloy compositions. Also, the crystallinity of CZTS was evaluated by photoluminescence measurements. The pulse height spectra for Am-241 and Co-57 sources were used to evaluate the detector performance for the CZTS samples.

New experimental measurement of natSe(n, γ) cross section between 1 eV to 1 keV at the CSNS Back-n facility

The 74Se is one of 35 p-nuclei, and 82Se is a r-process only nucleus, and their (n, γ) cross sections are vital input parameters for nuclear astrophysics reaction network calculations. The neutron capture cross section in the resonance range of isotopes and even natural selenium samples has not been measured. Prompt γ-rays originating from neutron-induced capture events were detected by four C6D6 liquid scintillator detectors at the Back-n facility of China Spallation Neutron Source (CSNS). The pulse height weighting technique (PHWT) was used to analyze the data in the 1 eV to 100 keV region. The deduced neutron capture cross section was compared with ENDF/B-VIII.0, JEFF-3.2, and JENDL-4.0, and some differences were found. Resonance parameters were extracted by the R-matrix code SAMMY in the 1 eV–1 keV region. All the cross sections of natSe and resonance parameters are given in the datasets. The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00019.

Electron probe microanalysis of light elements: Improvements in the measurement and signal extraction methods

AbstractQuantitative electron probe microanalysis (EPMA) by wavelength dispersive spectrometry of light elements is a significant challenge due to difficulties of signal extraction for low intensities. Therefore, a good choice of measurement parameters and a suitable signal treatment, accurate background description and interference correction are crucial. For light elements, peak to background ratios (P/B) can easily approach unity and special care needs to be paid to the setting of the pulse height analyser (PHA) to avoid noise contribution to the emission peak. Furthermore, the background may have a high curvature and the classical approach of a linear background fit is no longer valid. This work investigates the EPMA of light elements from Be to F with the aim to determine the best experimentation parameters (dispersive element, accelerating voltage, PHA). It also provides detailed information about peak shifts, peak broadening and the influence of different background fits on quantification. In total, 25 samples containing light elements were analysed and Monte Carlo simulations were carried out. These simulations show that the X‐ray intensity of the light element's characteristic line can be increased by working with low accelerating voltages around 5 kV. PHA should be used in automatic differential or integral mode. Our work also shows that a third degree linear polynomial describes the background better than an exponential or linear function. Consequently overestimation of P/B values leading to large quantification errors can be avoided. This paper provides a large database containing peak position and peak shifts, peak full width at half maximum, as well as P/B ratios and information about peak enlargement for different materials of various compositions.

Investigation on the performance of a thick ceramic gas electron multiplier

We report the performance of a THick Gas Electron Multiplier (THGEM) fabricated by drilling holes in a gold-clad ceramic substrate using the standard PCB (Printed Circuit Board) technology and etching rims. The THGEM has a total thickness of 200μm with a hole diameter and rim size of 200μm and 80μm, respectively. In order to carry out a performance study, a detector was assembled by putting the THGEM inside a versatile chamber and irradiating it with a 55Fe X-ray source (5.9 keV). An Ar/CO2 gas mixture was flushed inside the chamber at a pressure of about 1 atm, with volume ratios varying between 70/30 and 90/10. Pulse height spectra of the detector were recorded by a multichannel analyzer to investigate the gain and energy resolution at different drift and induction electric fields. The variations in the gain and energy resolution were also interpreted using simulations. The gain and resolution data of the THGEM were compared with those of a standard GEM which was measured using the same experimental setup.

Impulsive feedback control of birhythmicity: Theory and experiment

We study the dynamic control of birhythmicity under an impulsive feedback control scheme where the feedback is made ON for a certain rather small period of time and for the rest of the time, it is kept OFF. We show that, depending on the height and width of the feedback pulse, the system can be brought to any of the desired limit cycles of the original birhythmic oscillation. We derive a rigorous analytical condition of controlling birhythmicity using the harmonic decomposition and energy balance methods. The efficacy of the control scheme is investigated through numerical analysis in the parameter space. We demonstrate the robustness of the control scheme in a birhythmic electronic circuit where the presence of noise and parameter fluctuations are inevitable. Finally, we demonstrate the applicability of the control scheme in controlling birhythmicity in diverse engineering and biochemical systems and processes, such as an energy harvesting system, a glycolysis process, and a p53-mdm2 network.

Ce concentration dependence on scintillation properties of Ce-doped yttrium pyrosilicate single crystal

Yttrium pyrosilicate (Y2Si2O7) single crystals are successfully grown by the floating-zone method with 0.5–10.0% of Ce-doping concentration. X-ray diffraction patterns indicate a single phase of Y2Si2O7 without the impurity phase. The series photoluminescence (PL) and scintillation properties are systematically explored in this study, including PL emission, PL decay time, X-ray induced scintillation spectra, X-ray induced scintillation decay time, afterglow profile, and pulse height spectra. Ce-doped Y2Si2O7 is presented interesting properties including the intense emission band at 390 nm from Ce3+ 5d-4f transition on both PL emission contour maps as well as X-ray-induced scintillation spectra in all samples. The afterglow level at 20 ms after X-ray irradiation of the Ce-doped YPS is comparable with commercial scintillators such as CdWO4 and Tl-doped CsI. Under 137Cs (662 keV) γ-ray irradiation 137Cs (662 keV), the highest scintillation light yield of Ce-doped Y2Si2O7 is reach up to 17,200 ph/MeV for 2.0% Ce-doped sample.