Photomultiplier Tube Detector Research Articles

Light Scattering Measurements of KCl Particles as an Exoplanet Cloud Analog

Salt clouds are predicted to be common on warm exoplanets, but their optical properties are uncertain. The Exoplanet Cloud Ensemble Scattering System (ExCESS), a new apparatus to measure the scattering intensity and degree of linear polarization for an ensemble of particles, is introduced here and used to study the light scattering properties of KCl cloud analogs. ExCESS illuminates particles with a polarized laser beam (532 nm) and uses a photomultiplier tube detector to sweep the plane of illumination. Scattering measurements for KCl particles were collected for three size distributions representative of modeled clouds for the warm exoplanet GJ 1214b. Our measurements show that Lorenz–Mie calculations, commonly used to estimate the light scattering properties of assumedly spherical cloud particles, offer an inaccurate depiction of cubic and cuboid KCl particles. All of our measurements indicate that Lorenz–Mie scattering overestimates the backscattering intensity of our cloud analogs and incorrectly predicts the scattering at mid-phase angles (∼90°) and the preferential polarization state of KCl scattered light. Our results align with the general scattering properties of nonspherical particles and underscore the importance of further understanding the effects that such particles will have on radiative transfer models of exoplanet atmospheres and reflected light observations of exoplanets by the upcoming Nancy Grace Roman Space Telescope and Habitable Worlds Observatory.

Weak signal detection based on pulse width counting method for underwater wireless optical communication with an analog mode PMT detector

This work proposes a weak signal detection method based on pulse width counting (PWC) for the on-off keying (OOK) underwater wireless optical communication (UWOC) system with an analog mode photomultiplier tube (PMT) detector. The signal output model of the analog mode PMT in weak light communication and the influence of pulse overlap are investigated. We experimentally evaluate the proposed algorithm under different sampling rates, detection thresholds, data rates as well as received optical powers (ROPs), and compare the performance of the proposed approach with that of pulse amplitude detection and pulse peak counting. A 10-Mbps OOK UWOC link is realized with a sensitivity of -71.5 dBm in a 7-meter tank, which is 1.1-dB and 3.8-dB lower than that of pulse peak counting (PPC) and pulse amplitude detection (PAD) methods, respectively, and the total link attenuation is 94.8 dB. This system utilizes the analog mode PMT with larger dynamic range than photon-counting mode PMT to achieve weak light signal detection, which benefits design long-range UWOC systems.

Broadband Cavity-Enhanced Absorption Spectroscopy (BBCEAS) Coupled with an Interferometer for On-Band and Off-Band Detection of Glyoxal.

Glyoxal (CHOCHO) is a trace gas in the atmosphere, often used as an indicator of biogenic emissions. It is frequently compared to formaldehyde concentrations, which serve as indicators of anthropogenic emissions, to gain insights into the characteristics of the environmental source. This study employed broadband cavity-enhanced absorption spectroscopy to detect gaseous CHOCHO, methylglyoxal, and NO2. Two different detection methods are compared. Spectrograph and CCD Detection: This approach involves coupling the system to a spectrograph with a charge-coupled device (CCD) detector. It achieved a 1 min 1-σ detection limit of 2.5 × 108 molecules/cm3, or 10 parts per trillion (ppt). Methylglyoxal and NO2 achieved 1 min 1-σ detection limits of 34 ppt and 22 ppt, respectively. Interferometer and PMT Detection: In this method, an interferometer is used in conjunction with a photomultiplier tube (PMT) detector. It resulted in a 2 min 1-σ detection limit of 1.5 × 1010 molecules/cm3, or 600 ppt. The NO2 2 min 1-σ detection limit was determined to be 900 ppt. Concentrations of methylglyoxal were difficult to determine using this method, as they appeared to be below the detection limit of the instrument. This study discusses the advantages and limitations of each of these detection methods.

Cosmic muons as PMT and SiPM detector background signals

Photomultiplier tube (PMT) and Silicon Photo Multiplier (SiPM) are often used for detecting small number of photons or very weak radiations. A light guide usually connects these photodetectors to the test space. In this article, we investigate the effect of background signals caused by cosmic muons scintillation or interactions with PMT and SiPM, their light guide or input window materials. We study such interactions by making simulations using GATE software package and undertaking experiments using detector circuits developed as in [1]. The background cosmic muons can generate photons which will lead to errors in low radiation and single photon detection experiments especially if standard scintillators are not used. For such experiments, we conclude that the most useful method for cutting down the cosmic muons background should be by conducting the experiments deep underground or inside tunnels with several tens of meters of materials above it.

Auto-Lectin Dotcoding by Two Octopuses: Rapid Analysis of Fluorescence-Labeled Glycoproteins by an 8-channel Fully-Automatic Bead Array Scanner with a Rolling-Circle Detector.

Protein glycosylation is a crucial factor that must be evaluated in biological pharmaceuticals. The glycoform profile of a protein can vary depending on the conditions of the cultivation, purification process, and the selection of a host cell. Lectin microarrays are reliable bioanalytical methods used in the early phases of bioprocesses for the detection of glycosylation. The concept of a fully automated glycan detection with a bead array has been previously reported; however, no simple system has been constructed on fluorescence-based detection using a microarray. Here, we present a fully automated detection system equipped with a novel fluorescence detector for a 13-lectin bead array with a single tip. The lattice-like arrangement of a set of fibers proximate to the tip of the light emitting diode and photomultiplier tube detector minimized the noise caused by the reflection of incident light on the plastic capillary tip and bead. A unique rolling-circle fiber unit with quadruple lattices stacked in two layers realizes the 8-parallel automeasurement with a drastic reduction in scanning time and machine size. The 8-glycan profiles obtained automatically within 25 min were identical with those obtained with the conventional lectin microarray after overnight incubation. The signals obtained were represented as lectin dotcodes. Therefore, autolectin dotcoding assisted by the twin 8 legs named as "detection and irradiation octopuses" may be a rapid glyco-evaluation system during the production and development of biopharmaceuticals.

Wide dynamic range signal detection for underwater optical wireless communication using a PMT detector.

In the underwater optical wireless communication (UOWC) scenario, a photomultiplier tube (PMT) with higher sensitivity, lower noise, and a larger receiver area is employed as the photon detector to further extend the transmission distance. Due to the complex underwater environment, the high directionality of the light beam, and the vibration of a transceiver, the incident optical power usually spans a very wide dynamic range, and the PMT may operate in any one of the three regimes: pulse, transition, and waveform. While it is difficult to obtain the analytical characterization of the output electric signals across these regimes, this paper resorts to experimental measurements of the upsampled discrete samples within a training symbol duration. Among different statistical distribution fitting options, generalized extreme value (GEV) distribution is found to show excellent performance in fitting the probability density function (PDF) of either multiple samples or the superimposition of all samples within a symbol duration. Then joint sample distribution (JSD) based and superimposed sample distribution (SSD) based symbol detection methods are proposed by adopting the GEV distribution and log-likelihood ratio (LLR) testing criterion. The proposed methods are experimentally evaluated under different received signal optical powers, data rates, and sampling rates. They are shown to outperform the Poisson and Gaussian based maximum likelihood detection methods which are employed for the pulse regime and waveform regime respectively. Furthermore, the effectiveness of the proposed methods in alleviating strong ambient radiation is experimentally verified.

Measurement system for ultraviolet channel modeling and communications.

There has been an increasing interest in ultraviolet (UV) communications as a promising technology for non-line-of-sight (NLOS) networking by exploiting atmospheric scattering at UV wavelengths that enables a unique NLOS UV communication channel. While there has been significant theoretical and simulation-based investigation of the UV channel characteristics, there is limited work in terms of experimental research and validation of the analytical models. In this paper, we present a flexible experimental system for precise UV channel and communications measurements. Specifically, a transceiver system is developed that consists of a gimbal, UV light-emitting-diode array, and photomultiplier tube detector, node synchronization, and LabVIEW-based data acquisition subsystems. Novel techniques to precisely characterize the UV LED array radiation pattern, absolute transmit power, and field of view of the detector are also presented. The utility of the developed system is then demonstrated by performing a variety of experiments including UV channel model validation and steering optimization for UV communication links where the results were in very good agreement with theory and simulation.

Early detection and warning of standoff bio-threats using ultraviolet laser wavelengths

The paper presents the results of detection experiments conducted to detect bio-aerosol from a standoff distance of nearly 2 km using laser scattering and ultraviolet laser induced fluorescence (UV-LIF) LiDAR in the presence of potential interfering molecules (molecules having spectrum overlapping with the biological warfare agents). The presence of interfering molecules can make the detection of bio-aerosol difficult. Therefore, conduction of detection experiments in the presence of interfering molecules is a must to develop a system such as to keep the false signal at bay. The software for synchronized spectrum acquisition (gated mode) of UV-LIF signatures of bio-aerosol has been developed and integrated into the system. The detection algorithm on data discrimination has been implemented. Standoff experiments using the developed software have been carried out with the samples consisting of bio-aerosols and interfering molecules. The wavelengths used in the experiments are 266 and 355 nm as the fluorescence quantum yield of two prominent bio-markers is high at these excitation wavelengths. Spectra were acquired with the developed system and analyzed by the developed software. The bio-agents were detected and discriminated from the interfering molecules successfully. In addition to this, the scattering method is also utilized to make distinction between bio and non-bio-molecules using two identical photomultiplier tube detectors based on the depolarization method.

An optical system for suppression of laser echo energy from the water surface on single-band bathymetric LiDAR

When a bathymetric LiDAR (Laser Detection And Ranging) onboard unmanned ship is close to the water surface less than 50 cm, the laser echo energy from the water surface is much higher than that from the water bottom. This phenomenon causes a large dynamic range of echo signals that is output from the PMT (Photomultiplier Tube) detector, resulting in that the echo signal from the water bottom cannot correctly be detected in shallow water. For this reason, this paper proposes an optics system to suppress the amplitude of the echo signal from water surface through suppressing the laser echo energy. A two-channel receiving optical system, which receives echo signals from shallow water and deep water is designed and implemented, and then a polarized optical system is designed to embedded inside to suppress the laser echo energy from the water surface. The verifications are carried out through three sets of indoors experiments, and three sets of outdoors experiments. The experimental results demonstrate that the proposed system can effectively suppress 80.7% of the amplitude of the echo signal from the water surface when the voltage control of PMT detector is 0.40 V, which can largely improve the detection ability of the echo signals from water bottom in shallow water.

PMT gain self-adjustment system for high-accuracy echo signal detection

ABSTRACT The intensity difference between the echo signals from the water surface and bottom during bathymetry LiDAR operation requires a photomultiplier tube (PMT) gain self-adjustment. Otherwise, noise echo signals are collected, while weak and useful signals are not. For this reason, this paper proposes a PMT gain self-adjustment system for the high-accuracy detection of LiDAR echo signals. The developed system uses a field programmable gate array (FPGA) collector as a feedback signal generator, an STM32 controller as the PMT gain and voltage control signal generator and a DA module as the PMT gain voltage conversion circuit. The system controls the PMT gain voltage by judging the feedback signal to achieve PMT gain self-adjustment. The system was verified in an indoor tank, building roof, and outdoor pond experiments. By comparing the experiments, the developed system is shown to detect laser energy intensity with a sensitivity of at least 2.26 times stronger than the traditional system, and can measure water depth at least 2.5 times deeper than the traditional system. Therefore, it can be concluded that the proposed PMT gain self-adjusting system can effectively adapt to the changes in laser energy, improve the measurement of water depth, control the amplitude of the echo signals, increase the accuracy of water depth detection, reduce the saturation of the PMT detector, and protect PMT from damages.

Modeling electron transport and multiplication in photomultiplier tubes using COMSOL Multiphysics®

Combining stochastic and finite element methods, a modeling approach was executed that will inform new photomultiplier tube and scintillation detector designs. Time-dependent signal formation within a commercially available photomultiplier tube was modeled including the release and transport of electrons from the photocathode through the dynode stages. An ET Enterprises 9214B photomultiplier tube was digitally reproduced using Computed Tomography, X-ray radiography, and SolidWorks solid-modeling software. Simulations were executed with COMSOL Multiphysics® finite element solving package. Stochastic models of electron emission from the photocathode and dynodes were integrated within the COMSOL framework. Photoelectron emission energy was modeled by combining NaI(Tl) spectral emission characteristics and K2CsSb photocathode quantum efficiency. Secondary electron emission yields were produced to follow nominal photomultiplier gain, while secondary electron energies were sampled from the Chung-Everhart distribution. Electron emission trajectories were sampled according to Lambert's cosine law. Coupling stochastic and finite element models, simulation reproduced signal formation for the commercial photomultiplier tube including timing characteristics within 9.5% and gain within 3% over a voltage range of 900–1250 V.

Development of a Lightweight Single-Band Bathymetric LiDAR

Traditional bathymetry LiDAR (light detection and ranging) onboard manned and/or unmanned airborne systems cannot operate in the context of narrow rivers in urban areas with high buildings and in mountainous areas with high peaks. Therefore, this study presents a prototype of a lightweight bathymetry LiDAR onboard an unmanned shipborne vehicle (called “GQ-Cor 19”). The GQ-Cor 19 system primarily includes an emitting optical module, a receiving optical module, control module, detection module, high-speed A/D sampling module, and data processing system. Considering that the “GQ-Cor 19” is extremely close to the water surface, various new technical challenges are encountered, such as significant laser scattering energy from the surface of the water, which saturates signals received by the photomultiplier tube detector. Therefore, this study presents various new technical solutions, including (1) an improved Bresenham algorithm, (2) a small and lightweight receiving optical system with a split-field method, and (3) a data acquisition module with a high-speech A/D collector. Following a series of different experimental verifications, the results demonstrate that the new generation of single-band LiDAR onboard an unmanned shipborne vehicle can swiftly measure the underwater depth, and the maximum measurement depth is more than 25 m. The measurement accuracy is better than 30 cm and the weight is less than 12 kg.

Evaluation of optical transmission across the ITER hard x-ray monitor system designed for the first plasma scenarios.

Hard x-ray (HXR) spectroscopy is applied for diagnostics of runaway electrons in nuclear fusion reactors. The scintillation counter is one of the most commonly used types of detectors for HXR spectroscopy. It consists of a detector that emits light when excited by HXR radiation (scintillator) directly coupled to a PMT (Photomultiplier Tube) that converts light pulses into an electrical signal. This type of detector is commonly used in existing tokamaks, such as Joint European Torus (JET),Experimental Advanced Superconducting Tokamak (EAST),Compact Assembly (COMPASS), andAxially Symmetric Divertor Experiment (ASDEX-U). In all these cases, the scintillator is directly coupled to the PMT to provide the best possible light transmission efficiency. The Hard X-ray Monitor (HXRM) is one among the first plasma diagnostic systems at ITER that provides information about the energy distribution of runaway electrons inside a tokamak by HXR spectroscopy. This system also uses a scintillator and a PMT as a detector. Due to the heavy shielding of the blanket modules, vacuum vessel, and port-plugs, it is not possible to assemble the scintillator outside the tokamak vacuum vessel. The PMT detector cannot be installed in the close vicinity of the tokamak due to either the significant magnetic field or temperature. A possible solution is to decouple the scintillator from the PMT and place the PMT inside the port-cell. Light pulses will be transmitted to the PMT via a 12m long optical fiber bundle. Evaluation of the optical transmission was carried out to assess the performance of the HXR monitor and verify possible problems related to the PMT pulse discrimination under low light conditions.

Influence of impulse magnetic fields of extremely low frequencies on H2O2- and Fe2+-induced free radical lipid oxidation in liposomal suspensions

Background: For a long time, special attention in experimental biology and medicine is paid to free radical processes involving reactive oxygen species. In electromagnetic biology, the interest in free radical oxidation in biological membranes has increased significantly due to the discovery of spin mechanisms of magnetic fields on free radical processes. In the present day, these mechanisms are considered to be key in the processes of magnetoreception in living organisms. Liposomes, as the simplest models of biological membranes, are often used to study the primary mechanisms of action of different factors on the structural and functional properties of membranes. However, the influence of ecological significant extremely low-frequency magnetic fields on free radical oxidation in liposomal suspensions has not been studied enough. Objectives: The elucidation of the peculiarities of the influence of the extremely low frequency pulsed magnetic fields (ELF PMF) on H2O2- and Fe2+-induced peroxidation of natural phospholipids in liposomal suspensions. Materials and methods: The liposomal suspensions in phosphate buffer pH=7.4 were used. According to the literature and own results on light scattering the average diameter of liposomes was about 500Å. Ultra-weak chemiluminescence of liposomal suspensions was recorded using a device that operated in the mode of single photons counting. It consisted of a light-insulated cuvette unit where the test samples were placed, as well as a temperature sensor and a solenoid, which was used to create the PMF. Optical contact of the test samples with the photoelectron multiplier was carried out using a light guide. The recording system consisted of a broadband photomultiplier tube detector — FEU-130, which was at a temperature of –20°C. The pulse analyzer AI-256 was used to separate the useful signal that corresponded to the registration of single chemiluminescence light quanta. The voltage on the photomultiplier tube detector was applied in the range of current-voltage characteristics of this detector, in which a random voltage fluctuation had a minimal effect on the measurement of the useful signal. The number of light quanta that were recorded for defined time intervals characterized the overall intensity of the process of free radical oxidation of lipids in the experimental samples. The pulsed magnetic field was created using a solenoid coil located in the cuvette part. PMF was created using a serial generator G6-28. The magnetic field pulses were rectangular in shape with variable polarity for a period of oscillations. The induction of PMF was monitored using microteslameter G-79. The series of extremely low frequencies (5–80 Hz) and induction (5–500 μT) of PMF was chosen due to their environmental and physiological significance. Results: PMF of different frequencies with induction of 5 and 50 μT did not affect (p>0.05) H2O2- and Fe2+-induced lipid oxidation in liposomal suspensions. Statistically significant changes (p<0.05) were revealed only when liposomal suspensions were exposed to PMF with induction of 500 μT. It was found that the action of PMF with the frequency of 8 Hz 500 μT significantly inhibited H2O2-induced and enhanced Fe2+-induced chemiluminescence. This effect is associated with inhibition of the decomposition and with the accumulation of phospholipid hydroperoxides, which decompose and recombine in the presence of Fe2+ ions, which is accompanied by stronger chemiluminescence. The study of the dependence of the dynamics of the chemiluminescence intensity on the frequency of the PMF indicates the presence of a certain dependence of the effects in the range of up to 30 Hz. However, the inhibitory effect of PMF for the H2O2-induced oxidation phase is not always accompanied by a statistically significant increase in the amplitude of Fe2+-dependent light flash of chemiluminescence that indicates the general inhibitory effect of PMF at a certain frequency. Conclusions: PMF of extremely low frequencies statistically significantly affects the free radical oxidation in liposomal suspensions only at inductions exceeding several hundred microteslas. This indicates the effect of PMF on free radical processes for the conditions of the selected membrane model is realized mainly through spin interactions that determine the recombination of free radicals. The decrease of induction by one or two orders of magnitude, as well as increasing in frequency of the PMF above 50 Hz, leads to a decrease in the effectiveness of the influence of this physical factor on the intensity of lipid-free radical oxidation in liposomal suspensions. The most sensitive to the influence of ELF PMF is the phase of H2O2-induced free radical oxidation of lipids.

Space-resolved vacuum-ultraviolet spectroscopy for measuring impurity emission from divertor region of EAST tokamak

The measurement of impurity distribution in the divertor region of tokamaks is key to studying edge impurity transport. Therefore, a space-resolved vacuum-ultraviolet (VUV) spectrometer is designed to measure impurity emission in the divertor region on EAST. For good spectral resolution, an eagle-type VUV spectrometer with 1 m long focal length with spherical holograph grating is used in the system. For light collection, a collimating mirror is installed between the EAST plasma and the VUV spectrometer to extend the observing range to cover the upper divertor region. Two types of detectors, i.e. a back-illuminated charge-coupled device detector and a photomultiplier-tube detector, are adopted for the spectral measurement and high-frequency intensity measurement for feedback control, respectively. The angle between the entrance and exit optical axis is fixed at 15°. The detector can be moved along the exit axis to maintain a good focusing position when the wavelength is scanned by rotating the grating. The profile of impurity emissions is projected through the space-resolved slit, which is set horizontally. The spectrometer is equipped with two gratings with 2400 grooves/mm and 2160 grooves/mm, respectively. The overall aberration of the system is reduced by accurate detector positioning. As a result, the total spectral broadening can be reduced to about 0.013 nm. The simulated performance of the system is found to satisfy the requirement of measurement of impurity emissions from the divertor area of the EAST tokamak.

Label-free image-encoded microfluidic cell sorter with a scanning Bessel beam.

The microfluidic-based, label-free image-guided cell sorter offers a low-cost, high information content, and disposable solution that overcomes many limitations in conventional cell sorters. However, flow confinement for most microfluidic devices is generally only one-dimensional using sheath flow. As a result, the equilibrium distribution of cells spreads beyond the focal plane of commonly used Gaussian laser excitation beams, resulting in a large number of blurred images that hinder subsequent cell sorting based on cell image features. To address this issue, we present a Bessel–Gaussian beam image-guided cell sorter with an ultra-long depth of focus, enabling focused images of >85% of passing cells. This system features label-free sorting capabilities based on features extracted from the output temporal waveform of a photomultiplier tube (PMT) detector. For the sorting of polystyrene beads, SKNO1 leukemia cells, and Scenedesmus green algae, our results indicate a sorting purity of 97%, 97%, and 98%, respectively, showing that the temporal waveforms from the PMT outputs have strong correlations with cell image features. These correlations are also confirmed by off-line reconstructed cell images from a temporal–spatial transformation algorithm tailored to the scanning Bessel–Gaussian beam.

Detector-specific issues in Satellite Laser Ranging to Swarm-A/B/C satellites

Satellite Laser Ranging (SLR) to Low Earth Orbiters (LEOs) is traditionally used to validate orbits derived by microwave techniques, e.g., Global Positioning System (GPS). For most LEOs, SLR is the only possibility to independently assess the GPS orbit quality, to calibrate onboard instruments, and to reveal otherwise unnoticed systematic errors. However, the detector-specific errors in SLR measurements may corrupt the SLR observations and derived parameters. We found that the stations employing Compensated Single-Photon Avalanche Diode (CSPAD) detectors are characterized by the lowest, 15 and 21 mm root-mean-square residuals for reduced-dynamic and kinematic orbits, respectively, and show almost no dependency on the satellite nadir angle nor the observation acquisition time, as opposed to stations with Multi-Channel Plates (MCP) and Photomultiplier Tube (PMT) detectors. SLR observations to Swarm-A/B/C can also be used for the determination of SLR station coordinates characterized by 27, 15, 18 mm interquartile range repeatability for the Up, North, and East components, respectively.

Design of fast response Doppler spectroscopy system for HUST field-reversed configuration device.

A fast response Doppler spectroscopy system with high throughput and high resolution is under development for studying the drifting velocity, rotation velocity, and ion temperature on the HUST field-reversed configuration (HFRC) device. The system has been designed to observe the spectral line of oxygen V (O V) ion emission at 278.1nm (1s22s3p → 1s22s3s) over the lifetime (∼0.5ms) of the FRC plasma. A high throughput Czerny-Turner monochromator with 3600 g/mm grating and 670mm focal length is applied to achieve high spectral resolution; a 32-channel multi-anode photomultiplier tube (PMT) detector is utilized to achieve the high-speed response of up to 1MHz; a 1D magnification optics combined with a cylindrical lens assembly and a fiber optic expansion is developed to magnify the spectral dispersion fitting the PMT channel interval. Through the ray-tracing analysis, the system's final spectral resolution is evaluated to be ∼0.03nm. Taking into account the system sensitivity and O V line emissivity in HFRC plasma, the system is expected to be workable with the temporal response of 1 µs.

A comparison of PMT-based and CCD-based sensors for electrochemiluminescence detection of sunset yellow in soft drinks

The use of artificial colorants in food is highly regulated due to their potential to harm human health. Thus, it is crucial to detect these substances effectively to ensure conformance with industrial standards. In this work, we prepared a photomultiplier tube (PMT)-based electrochemiluminescence (ECL) sensor and a charged coupled device (CCD)-based ECL sensor and compared their merits in the detection of sunset yellow (SY) dye. The sensors used C,N quantum dot-embedded g-C3N4 nanosheets (QDs@NSs) as the ECL agent and K2S2O8 as the coreactant. SY was analyzed on the basis of amplification in the QDs@NHs-K2S2O8 ECL system. The PMT-based sensor realized ultrasensitive detection using a single electrode, especially at low concentrations of SY. A CCD-based sensor imaged the ECL phenomenon of an electrode array and provided the advantages of high throughput and time savings. Under optimized conditions, both sensors exhibited high specificity, reproducibility and stability; detection limits of 20 nM with PMT detection and 5 μM with CCD detection were determined for SY, with detection ranging over at least two decades. The practical feasibilities of these systems were confirmed by satisfactory detection of SY in real drink samples.

Application of Gallium Nitride Technology in Particle Therapy Imaging

A transimpedance amplifier (TIA) is an essential electronic circuit in prompt gamma detection. To improve the performance and reliability of the electronics, we designed a TIA using GaN high electron mobility transistor (HEMT) as it is more radiation-hardened when compared to its silicon counterpart and it has lower noise. Our circuit is designed using GaN HEMT from efficient power conversion (EPC) and has a 3-dB frequency of 21 MHz and 45 dB Ω of transimpedance gain. Its total output rms noise voltage is 3.1 mV. Its functionality is verified using a Lu-176 radiation source, and experimental result shows that the current generated from the H12700 position-sensitive photomultiplier tube (PSPMT) detector when the gamma radiation hits the scintillator crystal is successfully converted into voltage with the gain in agreement with our simulation result. Comparison of this GaN-based TIA with the reported silicon-based TIA shows superior performances for particle therapy imaging. The circuit is also tested under 100-MeV proton radiation with a fluence of 1.6×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> cm $^{-2}$ and flux of 1.14×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , and negligible variations in the linearity and gain in the postradiation measurements are observed.