Study of Compton suppression capability in a triple-layer phoswich detector

A triple layer phoswich detector was designed and assembled in the advanced radiation instrumentation lab at Oregon State University. The detector had three scintillation layers: the first one was a BC-400 for beta and conversion electron detection, the second layer was a CsI(Tl) for x-ray and gamma detection, and the third layer was BGO for shielding the CsI(Tl) crystal from background radiation and identifying scattered photons from the CsI(Tl) layer. Digital pulse processing was utilized to analyze pulses at a 200 MHz sampling rate. Pulses were analyzed according to their light decay time. The detector was able to suppress Compton events in low energy spectrum through pulse shape analysis. Suppression factors were calculated at the 90 keV and 250 keV regions in the ¹³⁷Cs gamma ray spectrum. Compton suppression capability reduced the Compton continuum at 90 keV region, and at 250 keV region by a factor of 56.5%, and 68.3%, respectively

Small Prototype Gamma Spectrometer Using CsI(Tl) Scintillator Coupled to a Solid-State Photomultiplier

Small solid-state photomultipliers (SSPMs) are an alternative scintillator light-detection technology to traditional photomultiplier tubes that offer advantages such as lower bias voltages and insensitivity to magnetic fields. A digital spectrometer using a commercially available SSPM was constructed and characterized at Oregon State University as a prototype for small, highly-mobile, low-power, robust spectroscopy devices. The SSPM has over 19,000 microcells in a photo-sensitive area of 6.32 x 6.32 mm and was coupled to 6 x 6 x 10 mm reflectively-coated CsI(Tl) crystals. The rest of the spectrometer consists of a fast preamplifier and 200 MHz, 12-bit digital pulse processor based around a field-programmable gate array (FPGA). The efficiency, resolution, linearity, and peak-to-Compton ratio of the system were characterized.This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by IEEE-Institute of Electrical and Electronics Engineers and can be found at: http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=23. (c) 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.Keywords: scintillation, gamma radiation detection, digital pulse processing, solid-state photomultiplierKeywords: scintillation, gamma radiation detection, digital pulse processing, solid-state photomultiplie

A review on preparation and characterization of silver/nickel oxide nanostructures and their applications

Nickel oxide and silver oxide nanoparticles have wonderful properties that could be employed in numerous applications. Thus, synthesis of nickel silver oxide nanostructures with different characteristics is of great interest. In this review, many synthesis methods were reported such as: electrodeposition, electrochemical method, simple immersion process and subsequent RFsputtering deposition, chemical oxidative polymerization, followed by acidic sol–gel process, flame-based process, liquidphase reduction technique, sol–gel, hydrothermal method, co-precipitation method, simple precipitation method, thermal decomposition, chemical wet synthesis, low and high-temperature reduction, high-pressure autoclave, thermal treatment method, and laser-liquid–solid interaction technique. Reporting all methods employed for the fabrication of NiO and Ag2O nanostructures is useful to produce and develop novel nanomaterials with enhanced properties and applications. Studying the factors that tuned their properties: particle size, shape, and capping agents as well as solution pH is highly recommended in future works. Also, further research studies should be conducted for finding another/other facile and effective synthesis method/methods

The Spectral Measurement of Scattered Radiation From a Clinical Linear Accelerator Using a CZT Detector

The study of the induced radioactivity following radiotherapy with high energy X-rays from medical linear accelerator. Patient equivalent phantom made of Polymethyl methacrylate (PMMA) of 30x30x27 cm size irradiated with 15 MV X-rays from Versa HD medical linear accelerator form Elekta. Induced radioactive and ambient dose rates were measured at 0.25, 0.5 and 1 m from beam center using GR1® spectrometry with Cadmium Zinc Telluride (CZT) detectors having energy resolution less than 2%. Spectrum analysis was performed using MultiSpect software. The measured spectrum showed 511 keV annihilation photons possibly as a result of positron emitter of which most likely candidates are 62Cu(T1/2: 9.7 min), 64Cu (T1/2: 12.7 h )  and 57Ni  (T1/2:  35.6 h) and a  peak at ≈ 1780 keV that could be attributed 28Al and 214Bi radioisotope. Ambient photon dose rates post radiotherapy treatment ranged 660 µGyh-1at o.5 m to 41 µGyh-1at 1 m. These values agree well with the results presented in the literature. Keywords: Radiotherapy; Activation Products; Gamma spectrometry; Occupational exposure; Medical Linear Accelerator. DOI: 10.7176/ALST/83-05 Publication date: November 30th 2020

Binary nickel and silver oxides by thermal route: preparation and characterization

Many studies have concentrated on exploring behaviors of nickel silver oxide nanoparticles using various routes of fabrication. Thermal treatment technique has never been utilized to fabricate nickel oxide silver oxide nanoparticles. In this research, binary (NiO)0.4 (Ag2O)0.6 nanoparticles were synthesized using the thermal treatment method due to its attractive advantages such as low cost, eco-friendly, and purity of nanoparticles. The structural, morphological, and optical behaviors of these nanoparticles were investigated at different calcined temperatures. X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectroscopy (UV–Vis), and photoluminescence (PL) were the techniques used to characterize the synthesized nanoparticles. XRD was conducted at different calcined temperatures. The crystallite size was increased from 25.4 nm to 37.0 nm as the calcined temperature increased from 500 °C to 800 °C. Also, TEM results verified that the mean particle size was enlarged as the calcined temperatures increased. Two band gaps were found for each temperature, which were decreased from (3.05, 2.45) to (2.70, 1.95) eV as the temperature varied from 500 to 800 °C, respectively. Broadbands were observed by PL spectra, and the intensity of two emission peaks was also increased at higher temperatures. The results approved the successful formation of binary (NiO)0.4 (Ag2O)0.6 nanoparticles by a novel facile synthesis route. These nanoparticles are likely to have various applications, especially optical applications due to the formation of two band gaps

The effect of precursor concentration on the particle size, crystal size, and optical energy gap of CexSn1â’xO2 nanofabrication

In the present work, a thermal treatment technique is applied for the synthesis of CexSn1−xO2 nanoparticles. Using this method has developed understanding of how lower and higher precursor values affect the morphology, structure, and optical properties of CexSn1−xO2 nanoparticles. CexSn1−xO2 nanoparticle synthesis involves a reaction between cerium and tin sources, namely, cerium nitrate hexahydrate and tin (II) chloride dihydrate, respectively, and the capping agent, polyvinylpyrrolidone (PVP). The findings indicate that lower x values yield smaller particle size with a higher energy band gap, while higher x values yield a larger particle size with a smaller energy band gap. Thus, products with lower x values may be suitable for antibacterial activity applications as smaller particles can diffuse through the cell wall faster, while products with higher x values may be suitable for solar cell energy applications as more electrons can be generated at larger particle sizes. The synthesized samples were profiled via a number of methods, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). As revealed by the XRD pattern analysis, the CexSn1−xO2 nanoparticles formed after calcination reflect the cubic fluorite structure and cassiterite-type tetragonal structure of CexSn1−xO2 nanoparticles. Meanwhile, using FT-IR analysis, Ce-O and Sn-O were confirmed as the primary bonds of ready CexSn1−xO2 nanoparticle samples, whilst TEM analysis highlighted that the average particle size was in the range 6−21 nm as the precursor concentration (Ce(NO3)3·6H2O) increased from 0.00 to 1.00. Moreover, the diffuse UV-visible reflectance spectra used to determine the optical band gap based on the Kubelka–Munk equation showed that an increase in x value has caused a decrease in the energy band gap and vice versa

Development of a CZT-Silicon Detection System in Support of the Comprehensive Nuclear-Test-Ban Treaty

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear explosion tests for military or civilian purposes. The International Monitoring System (IMS) was established to verify compliance with the treaty. It consists of several monitoring stations that detect: seismic activities, hydrocoustic activities, infrasound waves, and radionuclide particles and noble gases. Radioxenon detection provides the most robust evidence of a nuclear weapon test. There are four radioxenon isotopes of interest: 131mXe (t1 2 = 11.93 days), 133mXe (t1 2 = 2.19 days), 133Xe (t1 2 = 5.25 days) and 135Xe (t1 2 = 0.38 days). All of these radioxenons emit beta and gamma radiation in coincidence or conversion electrons and X-rays in coincidence during their decay process. In this research, a new radioxenon detection system was developed based on Si and CZT detectors. The system is made of the “PIPSBox” silicon gas cell recently developed by Canberra to detect beta and conversion electrons, and two coplanar CZT detectors to detect X-rays and gamma rays. The PIPSBox silicon gas cell offers many advantages such as: (1) increasing the frequency of air sampling at IMS stations because memory effect does not affect the PIPSBox gas cell like it does with plastic gas cells currently used at IMS stations, (2) reducing the Minimum Detectable Concentration (MDC) for radioxenons due to better energy resolution of silicon, and minimal background interference from previous measurements. The detection system was simulated using MCNP6 and was characterized by 131mXe to determine optimum operating voltages, proper gain, and the length of the coincidence window.Pulse waveforms of the silicon and CZT detectors were analyzed using two digital pulse processors: DPP2 and DPP8. DPP2 is a two-channel digital pulse processor with a 200 MHz sampling frequency and a 12-bit ADC resolution. DPP8 is an 8-channel, 125 MHz digital signal processor with a 14-bit ADC resolution. A coincidence firmware was implemented in the on-board FPGA to identify specific coincidences events between silicon and CZT detectors to generate 2D spectra for the four radioxenons of interest. The resolution of the 129 keV conversion electron was measured to be 16.66% in silicon1 and 16.87% in silicon2. These resolutions are the best-known values reported from other radioxenon detection systems that were included in the literature review of this research. The minimum detectable concentration (MDC) of PIPSBox CZT detection system four all radioxenons of interest was measured to be less than the 1 mBq m3 IMS requirement. Specifically, 0.25 mBq m3 for 131mXe, 0.26 mBq m3 for 133mXe, 0.39 mBq m3 for 133Xe, and 0.72 mBq m3 for 135Xe

Kerf characteristics during CO2 laser cutting of polymeric materials: Experimental investigation and machine learning-based prediction

This study uses advanced machine learning approaches to predict the kerf open deviation (KOD) when a CO2 laser is used to cut polymeric materials. Four polymeric materials, namely polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), and polyvinyl chloride (PVC), were cut under the same conditions. The process control factors were the power of the laser beam (80–140 W) and cutting speed (1–6 mm/s), while sheet thickness, standoff distance, and gas pressure were kept constant during experiments. KOD between the upper and lower opens of the kerf was the process response. KOD was predicted using three machine learning models, namely a conventional artificial neural network (ANN), a hybrid neural network–humpback whale optimizer (HWO-ANN), and a hybrid neural network–particle swarm optimizer (PSO-ANN). Experimental data for all polymeric materials were employed to train and test all models. The hybrid neural network–humpback whale optimizer model outperformed other models to predict KOD for all cut materials. The root-mean-square error between predicted and experimental data was 0.349–0.627 µm, 0.085–0.242 µm, and 0.023–0.079 µm for conventional neural network, neural network–particle swarm model, and neural network–humpback whale model, respectively

Utilization of an energy-resolving detection system for mammography applications : a preliminary study

Breast cancer remains one of the major causes of mortality among female cancer patients. This fact caused a spark in the medical field, which in turn helped to improve the diagnostic and treatment of breast cancer patients over the years making this field always active with new ideas and innovative methods. In our study, a new method was explored using an energy-resolving detection system made from a NaI (Tl) scintillation detector to detect the gamma photons from an Am-241 radiation source to try and construct an image by scanning the American College of Radiology (ACR) mammography phantom. In addition to the experimental work, a Geant4 Application for Tomographic Emission (GATE) toolkit was used to investigate more complex options to improve the image quality of mammographic systems, which is limited by the experimental setup. From the experimental setup, the researchers were able to construct an image using the 26.3 keV and the 59.5 keV energy photons, to show the largest size tumour (12 mm) in the ACR phantom. With an improved setup in the simulation environment, the majority of the ACR phantom tumours was visible using both energy windows from the 26.3 keV and the 59.5 keV, where the 26.3 keV yielded better quality images showing four tumours compared to three when using 59.5 keV. The simulation results were promising; however, several improvements need to be incorporated into the experimental work so that the system can generate high-resolution mammographic images similar to the ones obtained by the GATE simulation setup