Detection Of Alpha Particles Research Articles

Optical fiber-based ZnS(Ag) detector for selectively detecting alpha particles

In alpha radionuclide therapy, an optical fiber-based alpha particle detector is a new tool that could possibly be employed for the direct detection of alpha particles in subjects. Thus, in the present study, we developed an optical fiber-based alpha particle detector. The alpha particle detector was made of a 1mm diameter, 10 cm long plastic double clad optical fiber drilled a 0.7 mm diameter, 2 mm depth open space at the one end of the fiber. Silver-doped zinc sulfide (ZnS (Ag)) was painted inside this open space to form a ZnS(Ag) small scintillation chamber. To conduct performance comparisons, we also developed a fiber detector using the same fiber in which a Ce-doped Lu1.8Y0·2SiO5 (LYSO(Ce)) scintillator with dimensions of 0.32 mm × 0.5 mm × 5 mm was inserted. Both fiber detectors were wrapped in aluminized Mylar and optically coupled to a position sensitive photomultiplier tube, before calculating the two-dimensional distributions, energy, and pulse shape spectra. For 5.5-MeV alpha particles, the ZnS(Ag) fiber detector produced ~ 5 times larger pulse heights and the count rate was ~2 times higher compared with those using the LYSO(Ce) fiber detector. For the maximum energy 2.28-MeV beta particles and 0.66-MeV gamma photons, the ZnS(Ag) fiber detector produced no counts, but it yielded small counts from natural alpha particles. Our results confirmed that the ZnS(Ag) fiber detector developed in this study could selectively detect alpha particles and it was insensitive to beta particles and gamma photons.

Characterization of Makrofol[formula omitted] DE 1-1 (bisphenol-A polycarbonate) as SSNTD and its application in the alpha particle detection

Makrofol® DE 1-1 (bisphenol-A polycarbonate) was characterized as a solid state nuclear track detector (SSNTD) as well as for alpha particle detection. The bulk etch rate of the Makrofol® DE 1-1, at different etchant concentrations and temperatures, was found to be homogenous. The visible light absorbance measurements of the etched Makrofol® DE 1-1 at different etching conditions indicated that the lowest visible light absorbance occurs at the etching conditions of 75% 6 N KOH+25% C2H5OH and a temperature of 50∘C. The bulk etch rate activation energy EB increased from (0.59±0.05) eV to (0.76±0.05) eV for Makrofol® DE 1-1 etched in KOH and 25% 6 N KOH+75% C2H5OH, respectively. Before alpha particle tracks overlapping, the alpha track density in Makrofol® DE 1-1 is linearly correlated with the exposure time to alpha particles. The alpha particles track diameter was found to be a non-monotonic function of the alpha particle energy. The range of alpha particles in Makrofol® DE 1-1, which is a monotonic function of alpha particle energy, was determined using the over-etched track technique. The range-energy relationship of a perpendicularly incident alpha particle in a Makrofol® DE 1-1 detector can be used for the determination of the alpha particle energy over a wider energy range than with the etch pit diameter-energy relationship.

Comparison of light outputs, decay times, and imaging performance of a ZnS(Ag) scintillator for alpha particles, beta particles, and gamma photons

ZnS(Ag) is a scintillator mainly used for alpha particle detection because of the high light output for alpha particles. However, the light output and decay times of ZnS(Ag) for beta particles or gamma photons are not obvious. We therefore measured and compared the light outputs and decay times of ZnS(Ag) for beta particles or gamma photons with that for alpha particles. We measured the pulse height distribution and decay times of ZnS(Ag) for Am-241 alpha particles (5.5 MeV), St-Y-90 beta particles (2.28-MeV maximum energy), and Cs-137 gamma photons (0.66 MeV). The relative light output/MeV for the beta particles and gamma photons was ~2%–~5% of that for alpha particles. Decay time for the beta particles and gamma photons was 2.7 ns–2.8 ns, while that for alpha particles was 61 ns. With the different decay times, pulse shape discrimination of the alpha and beta particles was possible for the ZnS(Ag) radiation-imaging detector. We confirmed that ZnS(Ag) is a suitable scintillator for the detection of alpha particles using energy discrimination as well as pulse shape discrimination.

Standoff UV-C imaging of alpha particle emitters

Alpha particles are proven to be very useful in many areas of medicine, technology and science. Yet, they represent the biggest risk to soft biological tissues compared to all nuclear decay products when ingested or inhaled, implying thus stringent radiation protection measures in the management and monitoring of samples that emit them. In this paper we present a standoff optical imaging approach that enables sensing of a radiological threat items at facilities where alpha-emitting material is manufactured, handled, used and stored, at safe distances without putting personnel at risk or contaminating equipment. The optical imaging of alpha-emitting samples is based on the radiation induced air luminescence (radioluminescence) in the UV-C (solar-blind) spectral region which enables detection of alpha particles even under bright light conditions. We show that by adding trace amounts of nitric oxide into the nitrogen atmosphere surrounding the sample, alpha sources with specific activities as low as 1.5 Bq/cm2 can be remotely imaged. This work provides a proof-of-concept implementation of a novel imaging approach that not only enhances capabilities of a state to take actions which effectively mitigate consequences of an radiological emergency for the society, health, environment and economy, but also benefits nuclear industry in decommissioning efforts.

Electron, Neutron, and Proton Irradiation Effects on SiC Radiation Detectors

Owing to their low dark current, high transparency, high thermal conductivity, and potential radiation hardness, there is a special interest in silicon carbide (SiC) devices for radiation monitoring in radiation harsh environments and with elevated temperatures and, especially, for the plasma diagnostic systems in future nuclear fusion reactors. In this work, four-quadrant p-n junction diodes produced on epitaxial 4H-SiC substrates are studied. The impact of electron, neutron, and proton irradiations (up to fluences of $1 \times 10^{16}$ electrons (e)/cm2, $2 \times 10^{15}$ neutrons (n)/cm2, and $2.5\times 10^{15}$ protons (p)/cm2, respectively) on the electrical characteristics is studied by means of current–voltage ( $I$ – $V$ ) and capacitance–voltage ( $C$ – $V$ ) techniques. Regardless of the particle type and applied fluences, the results show similar low reverse currents for irradiated SiC devices, which are at least about four orders of magnitude lower than comparable Si devices. The effects of irradiation on interquadrant resistance and charge build-up in the interquadrant isolation are assessed. Furthermore, device performance as a radiation detector is investigated upon exposure to a collimated 239Pu–241Am–244Cm tri-alpha source. The performance at room temperature is preserved even for the highest irradiation fluences, despite the fact that the rectification character in electrical characteristics is lost. From the results, advantages of using SiC devices in alpha particle detection in harsh environments can be envisaged.

Study on ZnS(Ag) for alpha spectrometer using silicon based photo sensor

The measuring of alpha particles is essential in many research fields such as radiation safety, health science, high energy, and nuclear physics. One of the most hazardous background radiation sources, radon, emits alpha particles, and damages lungs. Thus, the measurement of alpha particles in air correlates with the amount of radon and indicates when to ventilate the air. To detect alpha particles decayed from radon, a silicon photon multiplier (SiPM) in the shape of a multipixel photon counter (MPPC) and a scintillator optimized for zinc sulfide phosphor [ZnS(Ag)] alpha measurement were used. In this study, a dedicated amplifier was designed. The change in the pulse shape owing to operational amplifier, feedback resistor, and capacitor affect were studied and compared to that of a photo multiplier tube (PMT).

Radiation detection using fully depleted 50 μm thick Ni/n-4H-SiC epitaxial layer Schottky diodes with ultra-low concentration of Z1/2 and EH6/7 deep defects

Recent advances in the development of thick 4H-SiC epitaxial layers for the fabrication of surface barrier radiation detectors have been paving the way for their use in highly penetrating radiation detection. Challenges still exist to achieve full depletion all the way to the epilayer width, while maintaining a low leakage current at high reverse bias conditions. We report the fabrication of high-resolution and low leakage current Schottky barrier alpha particle detectors with a large active area of 11 mm2 on 50 μm thick n-type 4H-SiC epitaxial layers, which can be fully depleted. The detectors were cut out of large substrates of 100 mm diameter with a micropipe density <1 cm−2 in the epilayers. Mott–Schottky plots obtained from the capacitance–voltage measurements revealed an effective doping concentration of 1.9×1014cm−3. A parallel plate capacitor model implied that a reverse bias of ∼440 V was needed to achieve a full-depletion width (50 μm). The current–voltage characteristics demonstrated a very low leakage current of 0.45 nA at a reverse bias of −450 V, which is low enough for the detector to be operated at full-depletion bias. In fact, pulse height spectroscopy using a 241Am alpha source, with the detector biased at −120 V, exhibited a well-resolved alpha spectrum with an energy resolution of 0.8% for the alpha peak corresponding to 5486 keV. This energy resolution was maintained consistently up to a full-depletion bias of −440 V. The ultra-stable performance of the detector has been attributed to the remarkably low concentration of carrier lifetime affecting deep-level defects like Z1/2 and EH6/7, which were found to be of the order of 1012cm−3 or less using capacitance mode deep-level transient spectroscopy measurements.

Enhanced extraction via surface asperities of light generated around the boundary plane in poly (ethylene naphthalate)

Applications of poly (ethylene naphthalate) (PEN) in radiation safety are attractive. However, for worker safety at nuclear power reactors, further enhancements of undoped scintillation materials are required for alpha particle detection. Here, we show that restrictions on the maximum light extraction from PEN can be lifted by controlling its surface conditions. Specifically, 1 mm-thick PEN plates with various degrees of surface asperities were examined. Emission and transmission spectra indicated little effect on the emission wavelengths of the generated light, but large effect on the propagation directions. These features resulted in excellent instrument efficiency for short-range alpha particles in radioactive contamination inspection devices that incorporated PEN having several tens of μm deep surface scratches. We modelled the relationship between surface asperities and instrument efficiencies for alpha particles by imaging the surface conditions with scanning electron microscopy. Surface asperities led to a quasi-decrease in the critical angle of the light generated around the surface boundary plane, which then resulted in an increase in total internal reflections at the plane. This knowledge should initiate general interest in PEN for radiological management devices.

IBIC analysis of SiC detectors developed for fusion applications

In this work, we consider a 4H-SiC detector as a plasma diagnostic system for the detection of fusion-born alpha particles in future nuclear fusion reactors. A nuclear microprobe was used to locally irradiate micrometer-sized regions of the detector with 3.5 MeV He ions to fluences from 5 × 109 to 5 × 1011 cm-2. Ion Beam Induced Charge (IBIC) microscopy was employed to study its degradation in Charge Collection Efficiency (CCE) and energy resolution after irradiation. At high reverse-bias voltages, both parameters remain practically unaffected for fluences up to 1 × 1011 cm-2, while a significant deterioration of the spectroscopic performance was observed above 3 × 1011 cm-2. A theoretical drift-diffusion model, in combination with Shockley-Read-Hall recombination statistics, was used to obtain the holes lifetime from the fitting of the experimental CCE values measured at different reverse voltages. Holes lifetime was found to strongly decrease with increasing particle fluence, changing from 57 ns in pristine detectors to 0.2 ns after irradiation with a fluence of 1 × 1011 cm-2.

Determination and analysis of ionization/excitation distributions for alpha particles in silicon detectors

As known, the detector response function in the detection of alpha particles is characterized by the following distributions: electronic excitation and ionization, electron–hole pair statistics, and electronic noise contribution. The distribution due to the ionization–excitation process is of particular relevance, because it is not Gaussian and contributes essentially to the asymmetry of the alpha lines. For this work, we adapted the well-known code SRIM, to obtain and analyze the ionization/excitation distributions for alpha-particles in silicon, in a wide range of energies from 0.5 to 10 MeV. These curves were later well-fitted to a function corresponding to the convolution of a Gaussian with exponentials truncated in the low-energy zone of the distribution. A detailed study about the dependence of all the fitting parameters on energy was performed. The parametrization carried out in this work can also be an useful tool to generate the corresponding ionization–excitation curves required in the task of reproducing real alpha-particle spectra.

Alpha particle detection by Makrofol® DE1-1 and CR-39 NTDs: A comparative study

In this present study, a color contrast approach was proposed to find a method for quantify uncertainty in alpha particle spectroscopy using nuclear track detectors (NTDs). According to this method, this color contrast approach was applied to NTDs as an alpha particle spectrometer. A comparison between the registration of 4.0 MeV alpha particles by Makrofol®DE1-1 and CR-39 NTDs using a color contrast method was carried out in alpha spectroscopy. The contrast of the alpha tracks of each single color channel whether red, green and blue resulting from split RGB image was determined. The measurements were proved that green color channel produced the highest contrast of the alpha tracks of about 85%, in both Makrofol® DE1-1 and CR-39 NTDs. The results of 4.0 MeV alpha particle etch-pits diameters in Makrofol® DE1-1 didn't show homogenous diameters for short etching time. The standard deviation of 4.0 MeV alpha-track diameters in Makrofol® DE1-1 went up to a maximum value of 2.23 μm at a removal thickness of 12.25 μm. When increasing the etching time, they decreased sharply to about 1.18 ± 0.02 μm at a ratio of change 0.047 that was less than 6%. The standard deviation of 4.0 MeV alpha particle etch-pit diameters in CR-39 detector was linearly correlated with the removal thickness at a ratio of change of 0.02 which was less than 5%. Results revealed that the etch-pit diameter in Makrofol® DE1-1detector, in alpha particle spectrometry was best measured around the end of the alpha particle range. Results of this study are discussed within the frame work of nuclear track formation theories and etching mechanism in nuclear track detectors (NTDs).

Detection of alpha and 7Li particles from 10B(n, α)7Li reactions using a combination of CR-39 nuclear track detector and potassium hydroxide-ethanol-water solution in accelerator-based neutron fields

We investigated the optimum etching condition for potassium hydroxide-ethanol–water solution (PEW) to detect only alpha and 7Li particles from 10B(n, α)7Li reactions registered in a CR-39 plastic nuclear track detector. The background recoil protons, which are induced by fast neutrons with energies of <2 MeV produced by 9Be(p, n)9B reactions in accelerator-based neutron sources, were discriminated by the desensitization effect with PEW. We found that an ethanol concentration of ≥15 wt% in a PEW solution discriminated recoil proton tracks with energies of <2 MeV. The optimized conditions will be applicable for evaluating dose distribution in tissue in accelerator-based boron neutron capture therapy.

MAPbBr3−xIx Crystals Improved by Accurate Solution-Grown Procedure for Alpha Particle Detection

High quality organic-inorganic halide perovskite brings an opportunity for ideal nuclear radiation detection due to its large carrier mobility, lifetime and heavy atoms. However, the relatively low bulk resistivity restricts its development for alpha particles and X/γ-ray detector. Here, we report on the MAPbBr3-xIx (MPB:I) perovskite crystals grown by the modified inverse temperature crystallization method. Based on the measured supersolubility and solubility curves, the heating procedure was accurately designed to control the nucleation and growth rate. The resulting MPB:I single crystals exhibit higher bulk resistivity of 1.4×109 Ω·cm, which is 10 times than that obtained from the traditional ITC method. Finally, An uncollimated 0.8 μCi 241Am @5.48 MeV alpha particles source was adopted to evaluate the MPB:I single crystals at room temperature condition. The electron mobility (μe) and mobility-lifetime product (μτ)e of (264.6 ± 6.5) cm2 V-1 s-1 and (2.6 ± 0.3) × 10-3 cm2/V, respectively, were obtained.

Preliminary Study on Improving Resolution of D-T Neutron Radiography based on Associated Alpha and Coded Source Imaging Methods

Limitations of fast neutron radiography include low detection efficiency and poor spatial resolution. D-T neutron radiography is one compact fast neutron radiography method. Based on D-T associated alpha particle method and coded source imaging method, we indicate one new method to improve resolution of D-T neutron radiography. This method could get distribution of D-T neutrons by detecting alpha particles. Without real coded mask, the D-T radiography structure is considered as coded source imaging of fast neutrons. With reconstruction method, the real object could be reconstructed from projections. One prospect setup of D-T associated alpha neutron source has been carried out with Monte-Carlo simulation. The projection images of two different situations are collected and reconstruction results show that it’s possible to improve image quality of D-T neutron radiography.

Simple Alpha Particle Detector with an Air Ionization Chamber

In this paper, we discuss the theory of the operation and some practical considerations for the construction of an air ionization chamber, which can be used as a very simple detector of alpha particles. These detectors have several benefits compared to spinthariscopes and spark detectors. Classical experiments with ionization chamber detectors are presented. Ionization chambers equipped with a recording device, such as Arduino, are sensitive enough to evaluate the activity of lantern mantle alpha particle sources and uranium glass beads. Weak emitters are placed directly inside the chamber, which is then sealed with a shielding cap.

Measurement of the streamer intensities in the self quenching streamer mode for TGEM structure

In this study, two geometries of Thick Gas Electron Multipliers (TGEM) were employed for alpha particle detection in the Self-Quenching Streamer mode (SQS mode). This mode was followed by the appearance of streamers in the range of the visible light spectrum. The streamer intensities were measured by an Ambient Light Sensor (ALS) and these streamers appeared with intensities around the same illuminance at different input voltages. After the appearance of the primary streamers, an increment observed in the streamer intensities versus the voltage difference between TGEM electrodes. There is demonstrated that in the presence of the sources with different activity and a TGEM with the high accuracy in the geometry, the detector entered to the SQS mode in the different applied input voltages.

Response of Superheated Emulsion Detectors to low energy alpha irradiation

Superheated Emulsion Detectors (SED) are traditionally employed in the detection of neutrons. In this work the focus is on the detection of alpha particles for an eventual alpha spectrometer using C2ClF5 as the target liquid. The alpha-droplet interaction is examined via computational studies, and a geometric model developed to describe the anticipated detector response. Experiments with alpha-emitting uranium- and samarium-doped SEDs at temperatures of 5-12 ºC confirm that the event rate is related to the size of the droplets, and are in model agreement for temperatures below 8 ºC; above this temperature, the acoustic sensitivity is reduced by signal attenuation as a result of the increasing bubble population, for which the addition of an attenuation coefficient restores the agreement with experiment. The results suggest an SED-based alpha spectrometer.

Development of an alpha-particle imaging detector based on a low radioactivity micro-time-projection chamber

An important issue for rare-event-search experiments, such as the search for dark matter or neutrinoless double beta decay, is to reduce radioactivity of the detector materials and the experimental environment. The selection of materials with low radioactive impurities, such as isotopes of the uranium and thorium chains, requires a precise measurement of surface and bulk radioactivity. Focused on the first one, an alpha-particle detector has been developed based on a gaseous micro-time-projection chamber. A low-αμ-PIC with reduced alpha-emission background was installed in the detector. The detector offers the advantage of position sensitivity, which allows the alpha-particle contamination of the sample to be imaged and the background to be measured at the same time. The detector performance was measured by using an alpha-particle source. The measurement with a sample was also demonstrated and the sensitivity is discussed.

Characterization of n-GaN / p-GaAs NP heterojunctions

Abstract n-GaN/p-GaAs heterojunctions were fabricated by plasma-assisted molecular beam epitaxy (PA-MBE). The fabrication was carried out by the growth of n-type cubic GaN on p-type GaAs(100) substrates, followed by Ohmic contact deposition using conventional e-beam and rapid thermal annealing. With the n-GaN/p-GaAs heterojunction we have obtained photovoltaic effect and demonstrated that this effect strongly depends of the GaN nucleating layer on the GaAs surface. Likewise, we found that the decrease of hexagonal-stable phase and planar defects inclusions in the cubic-metastable GaN decreases the leakage current, and therefore, increases the open circuit voltage (Voc). Furthermore, the increase in crystal quality also increases the External quantum efficiency (EQE) at longer wavelengths due to the reduction of surface recombination velocity at the GaN/GaAs interface. In addition, the heterojunctions were tested as radiation detectors, demonstrating that they could be a candidate for alpha particle detectors if the thickness of the absorber layer is increased.

Optimization of airborne alpha beta detection system modeling using MCNP simulation

Abstract An airborne alpha beta detection system using passivated implanted planar silicon (PIPS) detector was modeled with the MCNP6 code and its resolution and detection efficiency were analyzed. Simulation of the resolution performed using the Gaussian energy broadening (GEB) function showed that the full width at half maximum (FWHM) of 35.214 keV for alpha particles was within 34–38 KeV, which is the FWHM range of the actual detector, and the FWHM of 15.1 keV for beta particles was constructed with a similar model to 17 keV, which is the FWHM range of an actual detector. In addition, the detection efficiency and the resolution were simulated according to the distance between the detector and the air filter. When the distance was decreased to 0.2 cm from 0.8 cm, the efficiency of the alpha and beta particles detection decreased from 5.33% to 4.89% and from 5.64% to 4.27%, respectively, and the FWHM of the alpha and beta particles improved from 40.9 KeV to 29.84 keV and 25.76 keV–13.27 keV, respectively.