Detection Of Alpha Particles Research Articles

Investigation of the Operation of a Fast Photomultiplier in a Scintillation Alpha-Particle Detector

Investigation of the Operation of a Fast Photomultiplier in a Scintillation Alpha-Particle Detector

Correction method of the coloration in fluorescent nuclear track detector

A fluorescent nuclear track detector (FNTD) is a single crystal of aluminum oxide doped with carbon and magnesium (Al2O3:C,Mg). We report calibration method of difference in the fluorescence intensity depending on the color center concentration (coloration) using a confocal microscope. The fluorescence intensity ratio of 510–530 nm due to the excitation at 488 nm to the reflection intensity of 483–493 nm is used for the coloration correction. The fluorescence track intensity of alpha particles increases monotonically with the color center concentration. From the relation between values of coloration concentration and the fluorescence track intensity of alpha particles, we have made a correction function. Consequently, the standard deviation of the detection of alpha particles with the coloration correction becomes six times smaller than without it. Additionally, the track response curve is properly made in a wide LET range from 1 to 200 keV/μm.

A Methodology for the Discrimination of Alpha Particles from Other Ions in Laser-Driven Proton-Boron Reactions Using CR-39 Detectors Coupled in a Thomson Parabola Spectrometer

Solid-state nuclear track detectors (CR-39 type) are frequently used for the detection of ions accelerated by laser-plasma interaction because they are sensitive to each single particle. To the present day, CR-39 detectors are the main diagnostics in experiments focused on laser-driven proton-boron (p11B) fusion reactions to detect alpha particles, which are the main products of such a nuclear reaction, and to reconstruct their energy distribution. However, the acceleration of multispecies ions in the laser-generated plasma makes this spectroscopic method complex and often does not allow to unambiguously discriminate the alpha particles generated from p11B fusion events from the laser-driven ions. In this experimental work, performed at the PALS laser facility (600 J, 300 ps, laser intensity 1016 W/cm2), CR-39 detectors were used as main detectors for the angular distribution of the produced alpha particles during a p11B fusion dedicated experimental campaign. Additionally, a CR-39 detector was set inside a Thomson Parabola (TP) spectrometer with the aim to calibrate the CR-39 response for low energetic laser-driven ions originating from the plasma in the given experimental conditions. The detected ion energies were ranging from hundreds of keV to a few MeV, and the ion track diameters were measured for etching times up to 9 hours. The goal of the test was the evaluation of the detectors’ ability to discriminate the alpha particles from the aforementioned ions. Within this study, the calibration curves for protons and silicon low energy ions are accomplished, the overlapping of the proton tracks and alpha particles is verified, and a methodology to avoid this problem is realized.

A phoswich alpha/beta detector for monitoring in the site of Fukushima Daiichi Nuclear Power Station

Alpha contamination and high concentrations of beta contamination can be found inside the reactor buildings at the Fukushima Daiichi Nuclear Power Station (FDNPS). This study proposes a newly developed phoswich alpha/beta detector that can discriminate alpha and beta particles emitted from the alpha and beta contaminations in the FDNPS site. The phoswich alpha/beta detector is made up of two layers of scintillators that detect alpha and beta particles. The first layer is an octagonal, 50 mm diameter, 40-μm-thick plastic scintillator that measures alpha particles, while the second layer is an octagonal, 50 mm diameter, 50-μm-thick Gd₂Si₂O₇ (GPS) scintillator that measures beta particles. The combination of the two scintillators improves the ability to distinguish between alpha and beta particles. The two layers of scintillators were optically coupled to an 8 × 8 multianode photomultiplier tube (MA-PMT) with 50 mm × 50 mm through a 3-mm-thick light guide (glass plate). An eight-channel 14-bit 500 MS/s digitizer was fed with four output signals. Python programming was used to analyze the collected voltage waveforms. The pulse shape discrimination (PSD) method was used to detect alpha particles in high beta particle and high gamma-ray (comparable to gamma-ray dose rate near the FDNPS reactor building) environments. Due to a 23.3% full width at half maximum (FWHM) energy resolution for alpha particles, the detector can be used to distinguish between nuclear fuel materials such as plutonium and its radon progeny (Po-214). Moreover, the detector could distinguish alpha particles from 137Cs gamma rays with a dose rate background up to 9.0 mSv/h. It is the first to demonstrate that the developed phoswich detector can be used to discriminate and measure alpha and beta particles of the actual contaminated FDNPS samples. As a result, this detector will be effective as an air monitoring device for alpha and beta radionuclide contamination measurement in real time.

Gamma ray, beta and alpha particles as a sources and detection

The aim of this experiment is to study various features and components in the detection of gamma ray, beta and alpha particles. For gamma ray detection, cesium-137 and cobalt-60 were used. Varies of fine gain and course gain were used too. The count rate for that varied between fine gain and course gain was then recorded and analysed. Moreover, Monazite ore, Strontium-90, and Americium-241 were used for beta and alpha rays' detection. The procedure was done to check the efficiency of the alpha counter. As a result, the best fine gain in this experiment was fine gain 2. When the course gain is increased, the photopeak of the graph will shift to the right. From this procedure, it confirms that the time also influenced the count rate reading as it increased with increasing time. Others, like Monazite ore, Strontium-90, and Americium-241, were used for beta and alpha rays’ detection. The procedure was done to check the efficiency of the alpha counter. Furthermore, it shows that course gain, fine gain, and time used influence the count readings. The count rate was proportional to the amplifier setting. Increasing the course gain and fine gain contributes to the increase in count rate. The absolute efficiency for the scintillation alpha counter was 1.35%, and the count rate of Monazite ore is nearly proportional to the weight of Monazite ore. Thus, it can be concluded that when the weight increased, the reading of the count rate also increased.

Development of a wide-field EMCCD camera-based alpha-particle imaging system

We demonstrate a wide-field alpha-particle imaging system based on the detection of alpha-induced scintillation light from ZnS:Ag screen using an EMCCD camera. We develop an efficient image processing algorithm to remove cosmic and thermal noise and to locate alpha particle interactions in EMCCD images. This algorithm is particularly suited to imaging low-activity samples where long image acquisition periods entail a large number of frames with no detected alpha particle. Our system has a relative counting efficiency of ∼50 % compared to a PMT-based alpha counter. It can detect alpha particles at a resolution of <480 µm over an imaging area of ∼45 × 45 mm. We demonstrate the performance of this system by imaging a granite sample. Correlation between the resulting alpha image and the micro XRF-determined element map demonstrates that most of the alpha activity in our sample is held in dark-coloured Ba-rich veins and inclusions at mineral grain boundaries.

Direct Detection of Alpha Particles with Solid-State Electronics

Alpha-particle sources are widely used in industrial and medical applications. Such applications include smoke detectors, static charge eliminators, and radiation therapy. This paper is concerned with the detection of alpha particles. A number of techniques are known for the detection of alpha particles. Those techniques include the Geiger–Müller tube, the ZnS scintillator, the air-filled ionization chamber, and the spark chamber. All the techniques that are currently known are based on the interaction of the ionizing radiation with matter. Charged particles, such as alpha particles, upon entering a medium (such as air), encounter many collisions with bound electrons and lose kinetic energy in the process. The atoms of the medium also become ionized, and a large number of free electrons are released inside the medium. The theory describing the interaction of ionizing radiation with matter is well known and includes formulas such as the Bethe-Bloch formula for the stopping power of matter and formulas for calculating the range of the ionizing radiation in matter. Essentially, all the known techniques for the detection of alpha particles are based on detecting the presence of free electrons inside the medium. This paper presents a new technique for the detection of alpha particles that does not depend on the theory of the interaction of alpha particles with matter. Instead, the technique is based on the direct detection of the positive charge that is carried by the alpha particles. Furthermore, it is the objective of this paper to demonstrate that the direct detection of the charge carried by alpha particles can be done with a tiny and inexpensive component: a metal–oxide–semiconductor field-effect transistor (MOSFET).

Spectroscopic performance of Ni/4H-SiC and Ti/4H-SiC Schottky barrier diode alpha particle detectors

Advancement in the growth of 4H-SiC with low micropipe densities (∼ 0.11 cm-2) in achieving high pure epitaxial layers, enabled the development of high-resolution 4H-SiC alpha particle Schottky radiation detectors for harsh environments. In particular, the study considers two types of 4H-SiC radiation detectors having Ni and Ti as Schottky contacts. They are fabricated by depositing Ni and Ti on 25 μm thick n-type 4H-SiC by epitaxially growing on 350 μm thick conducting SiC substrates. Electrical characterization and alpha spectral measurements performed on Ni/4H-SiC and Ti/4H-SiC SBDs are reported in this work. The spectral measurements were carried out using 241Am alpha emitting radioactive source. Ni/ 4H-SiC Schottky detector showed a better spectral response with 22.87 keV FWHM (∼ 0.416%) at a reverse bias of 150 V for 5.48 MeV alpha particles while Ti/4H-SiC Schottky detector achieved a resolution of 38.25 keV FWHM (∼ 0.697%) at 170 V reverse bias. This work presented spectral broadening analysis to understand the various factors affecting the energy resolution of the detectors. The extracted charge collection efficiencies (CCEs) are approximately 99% in both the detectors. In addition, polarization effects are not noticed in any of the fabricated detectors. The diffusion length of minority carriers (Lp ) is computed based on the drift-diffusion model by fitting the CCE curve as a function of applied bias, and the values are close to 9 μm and 7 μm for Ni/4H-SiC SBD and Ti/4H-SiC SBD detectors, respectively. Annealing at 400°C for 5 minutes in N2 ambient resulted in resolution of 23.98 keV FWHM (∼ 0.436%) for Ni/4H-SiC SBD detector at -170 V and 36.21 keV FWHM (∼ 0.661%) for Ti/4H-SiC SBD detector at -150 V. Overall Ni/4H-SiC SBD detectors showed superior spectral characteristics and superior resolution when compared to Ti/4H-SiC SBD detectors. However, the Ti/4H-SiC SBD detector fabricated in this work performed better than the previously reported work on a similar device structure. Hence, future work aimed at improving resolution of radiation detectors could also consider Ti/4H-SiC SBDs along with Ni/4H-SiC SBDs.

The microdosimetic one-hit detector model for calculating the alpha particles detection efficiency of polycarbonate SSNTD

In this work, a polycarbonate (PC) detector with 250μm thickness and 2 cm × 2 cm dimension exposed to alpha particles of an 241Am source is simulated by Geant4 toolkit. Different energies of alpha particles ranging from 0.2 to 5.0 MeV are considered. Spheres with 2μm diameter randomly positioned within the etching layer of the PC are considered as the sensitive volumes. Considering the threshold of 240 keV μm−1 for forming the tracks, specific energy distribution for any alpha energy is computed. Finally, the number of tracks and the detection efficiency are calculated applying the microdosimetric one-hit detector formulation. It is found that the obtained efficiencies differ at most 10% and 12% from the previous simulation and the measurements (adapted with the two different etchings), respectively.

Calculation of alpha particles detection efficiency for polycarbonate detector using Geant4 toolkit

In the present work, alpha particles detection efficiency of polycarbonate detector (PC) is calculated using Geant4 simulation toolkit. A PC detector with 250 µm thickness and dimension of 2.5 × 2.5 cm2 is considered. Assuming the passage of alpha particles of an 241Am source through brass collimators with different lengths, various alpha energies ranging from 0.2 to 2.5 MeV are modeled. Also, an etching layer of 6 µm related to a given electrochemical etching process as well as a threshold stopping power of 240 keV µm-1 required for forming the tracks are used as the input data. The detection efficiency is determined as the ratio of registered tracks per unit area to the number of alpha particles reaching the PC detector surface. To validate the simulation, the results are compared with the experimental data reported in the literature. It is found that the both results agree well within a maximum variation of 10%.

The high energy resolution of Pt/Si alpha particle detector with Al2O3 passivation layer

Schottky type detectors (STDs) are normally used to detect high-energy particles due to their excellent properties, such as simple fabrication technique, linearity, and fast-rising time. Conventional STDs cannot obtain high energy resolution due to the large leakage current working at the reverse bias condition, which is ascribed to the high interface states between metal and substrate. In this study, a thin layer of Al2O3 (<6 nm) is innovatively inserted between metal Pt and silicon substrate to fabricate the Al2O3 passivated Schottky type detectors. In comparison to Pt/Si, it was found that the interface states of Pt/Al2O3/Si could be remarkably suppressed from 1014 eV−1 cm−2 to 1012 eV−1 cm−2. Thus, the lower leakage current of 5 nA was obtained with the reverse bias of 100 V, as compared to the 70 nA without the Al2O3 passivation layer, which greatly reduced the detection noise. The α particles of 239Pu, 241Am, and 244Cm are successfully detected with an energy resolution of 0.56% due to the suppression of interface states.

Lead Halide perovskite based plastic scintillators for alpha particle detection

Solid-state synthesis of perovskites has recently drawn attraction in the fabrication of high purity lead halide perovskites with high throughput, ease in fabrication and cost-effective manner. In this study, we synthesized CsPbBr3 perovskites by manually grinding the constituent salts and fabricated their corresponding polystyrene-CsPbBr3 composite films with concentrations ranging from 5% to 50% (w/w) at room temperature by solvent casting. The perovskite phase was confirmed from the XRD studies. The bandgap from absorption spectra was estimated to be 2.26 eV, close to the corresponding PL emission ~ 550 nm. These composite films were evaluated for their alpha radiation response. Films with 25% perovskite loading exhibit 28% detection efficiency and minimum detection activity of 0.29 Bq. We report an excellent alpha response from the lead halide perovskite-based scintillator prepared through the facile solid-state synthesis technique.

Development and characterization of a novel alpha particle SOI pixel sensor for neutron detection

Semiconductor sensors for neutron detection have been initially proposed as direct replacement of 3He detectors but have recently raised interest in imaging systems. We have developed a monolithic sensor with high spatial granularity in SOIPIX technology for the detection of alpha particles of energy compatible with the reaction products of neutrons with typical converter materials. The chipset is composed by the main pixel matrix and the test structures needed for a better understanding of the chip functionality and for studying the electronic tuning strategies. The fabricated prototypes have been recently delivered and the first tests under alpha source have been performed. In this paper we will present the proposed devices and the results of the experimental characterization.

Particles Detection System with CR-39 Based on Deep Learning

We present a novel method that we call FAINE, fast artificial intelligence neutron detection system. FAINE automatically classifies tracks of fast neutrons on CR-39 detectors using a deep learning model. This method was demonstrated using a LANDAUER Neutrak® fast neutron dosimetry system, which is installed in the External Dosimetry Laboratory (EDL) at Soreq Nuclear Research Center (SNRC). In modern fast neutron dosimetry systems, after the preliminary stages of etching and imaging of the CR-39 detectors, the third stage uses various types of computer vision systems combined with a manual revision to count the CR-39 tracks and then convert them to a dose in mSv units. Our method enhances these modern systems by introducing an innovative algorithm, which uses deep learning to classify all CR-39 tracks as either real neutron tracks or any other sign such as dirt, scratches, or even cleaning remainders. This new algorithm makes the third stage of manual CR-39 tracks revision superfluous and provides a completely repeatable and accurate way of measuring either neutrons flux or dose. The experimental results show a total accuracy rate of 96.7% for the true positive tracks and true negative tracks detected by our new algorithm against the current method, which uses computer vision followed by manual revision. This algorithm is now in the process of calibration for both alpha-particles detection and fast neutron spectrometry classification and is expected to be very useful in analyzing results of proton-boron11 fusion experiments. Being fully automatic, the new algorithm will enhance the quality assurance and effectiveness of external dosimetry, will lower the uncertainty for the reported dose measurements, and might also enable lowering the system’s detection threshold.

Investigating the impact of alpha particles energy level on the DNA- Schottky diode behavior

In this work, the influence of the alpha energy level on the Al/DNA/Al Schottky diode was examined through J-V curve. The diodes were exposed to alpha radiation energy ranging from 0.625 MeV to 5.485 MeV under the same irradiation time. Diode parameters, such as series and shunt resistance, were determined by using a conventional method. The current density and electrical conductivity were also tested. From the results, it is observed that the series resistance for the irradiated samples is found to be higher than the non-radiated one, and its behavior is approximately equivalent to the hypersensitivity phenomena. The current density, for all samples, increases with increasing the electric field. Furthermore, the electrical conductivity of the non-radiated sample was higher than the alpha irradiated samples at a voltage of 6.0 V. These results highlight the significance of using this device as a detector for alpha particles’ radiation in bioelectronics applications.

GEANT4 modeling of alpha particles detection efficiency for polycarbonate SSNTD

In this paper, a simple model based on the GEANT4 simulation toolkit is presented to determine the detection efficiency of polycarbonate detectors. Different alpha energies obtained by traveling of 241Am source alpha particles through different air columns are considered. Experimental measurement are also carried out using two different solutions and electrochemical etching conditions. The thicknesses of the bulk and the electrochemical etching layers extracted from the etching process are assumed as the key parameters. When the vertical range of an alpha particle corresponding to a linear energy transfer above the threshold required for forming the tracks lies between the two above thicknesses, the model counts a track. Fitting the modeled and the experimental efficiencies in the energy range 0.2 to 5 MeV shows that the threshold for forming the tracks in polycarbonate is 240 keV μm−1. Finally, the linear energy transfer threshold as well as the model for track formation presented here can be utilized for future investigations on the polycarbonate detector.

Development of a phoswich detector composed of ZnS(Ag) and YAP(Ce) for astatine-211 imaging

For the research on alpha emitters used for targeted alpha particle therapy such as astatine-211 (211At), alpha particle as well as X-ray imaging are required for autoradiography and phantom imaging or in vivo imaging of small animals. Consequently, two imaging detectors for different types of radiations are required in such research. However, preparing two types of imaging detectors needs cost and space. If a single imaging detector could image alpha particles as well as X-rays for 211At, it would be an advance in the imaging research for targeted alpha particle therapy. Consequently, we developed a detector that can be used for both alpha particle and X-ray imaging. The developed imaging detector is a phoswich type made of a ZnS(Ag) sheet and a cerium doped YAlO3 (YAP(Ce)) plate optically coupled to each other with a 1-mm-thick light guide between scintillators. These scintillators were optically coupled to a 1-inch-square position-sensitive photomultiplier tube (PSPMT) to form an imaging detector. The ZnS(Ag) sheet detects alpha particles while the YAP(Ce) plate detects X-rays from 211At. Due to the pulse height difference between alpha particles and X-rays, a different high voltage was supplied to the PSPMT for alpha particle and low-energy X-ray detection. Discrimination between alpha particles and X-rays were conducted by pulse height as well as pulse shapes of ZnS(Ag) and YAP(Ce). The intrinsic spatial resolution for 5.5-MeV alpha particles was better than 0.6 mm the full width at half maximum (FWHM), while that for 60-keV gamma photons was ∼1.2 mm FWHM. Energy resolution for 5.5-MeV alpha particles was 60% FWHM, while that for 60-keV gamma photons was 25% FWHM. With a 4-mm-thick, 0.6-mm-diameter parallel hole collimator mounted on the detector, the system spatial resolution for 60-keV gamma photons was ∼2 mm FWHM within 5 mm from the collimator surface, and its sensitivity was 0.5%. An image of the 211At alpha particle distribution of a sliced kidney as well as an X-ray image of a paper soaked with 211At solution could be obtained. We conclude that the developed detector is promising for single-detector imaging of alpha particles as well as X-rays from 211At.

Alpha emitter detection systems using a UV light detector.

To visualize alpha contamination, an alpha-particle detection system has been developed that is capable of detecting alpha-induced UV lights from a few meters distance in dark environments. It detects UV lights from ionized nitrogen with a photomultiplier tube. To identify the contaminated spot quickly, large diameter lenses were designed and tested.

Detection efficiency of alpha particles using CR-39 nuclear detector- etched with BSW

In this study a new etchingsolution has been used to register alpha particles. The etching characteristics for the detection of alpha particles in CR-39 nuclear track detector using a new etching solution have been investigated. Several important parameters that control the track formation such as, the bulk etch rate, the track etching rate, and the critical angle have been measured. The dependence of etching efficiency and sensitivity upon the volume of 1- Butanol and temperature has been studied. The effect of etching time, the volume of 1-Butanol and the temperature upon the etching parameters have been investigated. Also, the enhancement in the etching efficiency with the decrease in the volume of 1-Butanol is more pronounced. The new etching solution has been demonstrated to be a fast etching solution. Results of irradiation of CR-39 detector with alpha particles and the etching characteristics, along with recording alpha particles tracks in the detector are also addressed and thoroughly discussed.

Evaluation of Alpha Particle Emission Rate Due to the p-11B Fusion Reaction in the Large Helical Device

A numerical study of the alpha particle emission rate due to the p-11B fusion reaction based on the respectively obtained Large Helical Device (LHD) plasma parameters in an experiment is performed. First, the total alpha particle emission rate is estimated by employing the beam ion distribution calculation code FIT3D and the fusion reaction rate calculation code FBURN based on the classic confinement of beam ions. Then, the calculation is performed using hydrogen-beam-heated hydrogen plasma parameters and the radial boron density profile obtained from boron drop discharge. The result shows that the total alpha particle emission rate reaches approximately 1014 s−1. Then, based on the radial profile of the alpha particle emission calculated by the FBURN code, the distribution of the first orbit loss of5.78-MeV alpha particles created by the p-11B reaction on the vacuum vessel and the divertor plate is calculated by the collisionless Lorentz orbit code LORBIT. Although most of the alpha particles are lost to the divertor plate, some of the alpha particles are lost on the vacuum vessel. Finally, a feasibility study of alpha particle detection by the existing manipulators and fast ion loss detector position is performed. The number of particles as a function of position shows that a substantial number of alpha particles can be detected. Alpha particles with a pitch angle of ~130 deg can reach manipulator positions. In contrast, particles with pitch angles of ~50 and ~110 deg can reach the fast ion loss detector position. The calculation shows that measurement of alpha particles due to p-11B is thought to be possible using charged particle detectors.