As a radiation detection material, CdZnTe (CZT) exhibits excellent performance at room temperature. With the development of CZT detectors, unipolar charge sensitive technology has effectively reduced the influence of incomplete hole collection on the energy resolution. In order to achieve high-resolution and high efficiency for MeV gamma-ray astronomy observation, a capacitive Frisch-grid CZT detector with dimensions of 5 & times;5 & times;20 mm3 has been fabricated and systematically tested. Its leakage current is 3.6 nA at 3000 V, and the energy resolution (FWHM) is 1.20% at 662 keV (2800 V). Additionally, the electron mobility lifetime product ((& micro;z)e) has been evaluated. The comparison of simulation and experimental results suggest that the (& micro;z)e is close to 1.0 & times; 10-1 cm2/V, which is significantly higher than the value obtained using the Hecht equation and the optimized direct measurement method.
This paper presents a novel digital cusp-flat-top shaping algorithm aimed at improving both the counting rate and the imaging quality of capacitive anode detectors. The method is developed as an enhancement of conventional cusp shaping, combining the advantage of cusp filtering in approximating an infinite impulse response with the noise-suppression capability of trapezoidal shaping. Compared with conventional trapezoidal shaping, the proposed algorithm effectively mitigates pulse pile-up, thereby satisfying detection requirements under high counting-rate conditions. The algorithm was implemented on a field-programmable gate array (FPGA) using the System Generator and Vivado platforms, and its performance was validated through software simulation, FPGA-based verification, and a benchtop imaging experiment using a capacitive anode detector with a low-pressure mercury lamp as the input light source and a dense pinhole-array mask as the test target. The results demonstrate that the algorithm achieves significant suppression of electronic noise and effective reduction of pulse pile-up. A minimum resolvable pulse interval of 0.4 mu s was obtained, corresponding to a maximum counting rate of 2500 kcps, while the reconstructed images achieved an averaged spatial resolution of 17.62 +/- 1.73 line pairs per millimeter. These findings indicate that the proposed algorithm offers a practical and efficient solution for digital signal processing in high-performance capacitive anode detectors.
The design of the compact gantry is critical for reducing the footprint and construction costs of proton therapy facilities. In this study, a compact gantry using FeCo-alloy magnets was designed with a short source-to-axis distance (SAD). A downstream scanning layout is implemented, with the beam optics optimized and verified through error analysis and orbit correction. A hybrid lamination strategy, combining FeCo pole tips with silicon steel yoke, was implemented to reduce the material costs of dipole magnets. This approach achieved a maximum magnetic field of 1.72 T and a reduced bending radius of 1.35 m, while maintaining an integrated field uniformity of +/- 3.8 & times; 10-4. The beam quality was validated through Monte Carlo simulations using BDSIM, which incorporated a detailed beamline model and a realistic nozzle with helium-filled chamber. Despite the emittance growth induced by beam-material scattering in the nozzle, the transverse beam spot size increase at the isocenter was limited to be less than 60% for 70 MeV protons. Furthermore, the beamline maintained a transmission efficiency above 94% across the entire 70-230 MeV energy range. With an estimated total weight of approximately 80 tons and a length of 8 m, this gantry design provides a reference for the development of compact proton therapy systems.
Accurate neutron spectrum measurement is vital for nuclear energy and nuclear medicine applications. While iterative unfolding methods are favored for their efficiency and accuracy, their precision critically depends on the initial guess spectrum. Without prior information of the measured field, a non-informative "all-ones flat spectrum" is typically used, limiting further accuracy improvements. This paper proposes a method to construct preset spectra based on analytical neutron spectrum models (Watt, Maxwell-Boltzmann, moderation, evaporation spectra), incorporating physical characteristics to provide more instructive initial values for iterative unfolding. Numerical validation using IAEA-403's PTB multi-sphere response functions and 251 radiation-protection scenario spectra shows that the moderation-model-based preset spectrum reduces average relative deviation by similar to 20% compared to the flat preset spectrum, achieving superior accuracy in 80.1% of scenarios and comparable accuracy in 17.1%. The method also suppresses spurious structures from uneven energy-group division, enhancing spectral restoration. Cf-252 neutron source experiments confirmed a 26.4% reduction in deviation and improved restoration using the moderation preset spectrum. The proposed method offers a clear, versatile approach compatible with various unfolding algorithms, supporting high-accuracy broad-energy neutron spectrometry. (c) 2001 Elsevier Science. All rights reserved.
Ce3+-doped lutetium yttrium oxyorthosilicate (LYSO:Ce) crystal is a category of widely-used and significant scintillator that has been employed in a large number of international scientific projects and cutting-edge medical imaging equipment. However, its light yield non-proportionality and energy resolution performances have not been systematically investigated in the whole hybrid concentration of x from 0 to 1 in Lu2-2xY2xSiO5:Ce (x = 0, 0.1, 0.2, 0.3, 0.5, 0.6, 0.7, 0.9, 1). In this work, a versatile method has been developed to quantitatively describe and compare the above-mentioned two performances of a series of as-prepared Lu2-2xY2xSiO5:Ce single crystals. The results indicate that the two performances are improved substantially with the introduction of Y. In particular, light yield non-proportionality has a steady platform within x = 0.3-0.7 and then tends to be better with further addition of Y within x = 0.7-1. The energy resolution of Lu2-2xY2xSiO5:Ce at the energy range of 32.2 keV to 1.3 MeV is a nearly linear improvement with the doping of Y elements. The greatest degree of light yield non-proportionality and the most remarkable improvement of intrinsic resolution are observed at x = 0.1. Meanwhile, the influence of crystal quality on both performances is also discussed here. Combining our previous work about intrinsic radioactivity, time response, afterglow, structure, energy transfer, and traps in Lu2-2xY2xSiO5:Ce crystals, the current work provides non-proportionality of the light yield and energy resolution varying with the incident energies for further perfecting the comprehensive performance of LSO-YSO:Ce solid solution system.
A compact digital pulse processing Multi-Channel Analyzer based on the STM32F407 Discovery Board is presented for alpha-spectroscopy. The system implements real-time recursive trapezoidal shaping with pole-zero cancellation using the on-chip analog-to-digital converter and circular Direct-Memory-Access buffering. Linearity was first evaluated using an exponential decay signal from waveform generator with an constant matched to a charge-sensitive preamplifier, followed by detector-based measurements using a 226Ra alpha source. A highly linear energy response was observed over the 4-8 MeV range. Benchmark measurements performed with the FASTER data acquisition system showed comparable energy resolutions in physical units. The results demonstrate the suitability of microcontroller-based MCA for low-cost nuclear spectroscopy applications.
This study introduces a neutron optical scheme for small-angle neutron scattering based on compact neutron sources by combining the neutron focusing supermirror with a post-collimation system. A multi-layer nested neutron-focusing supermirror is employed to enhance the neutron current at sample. However, it inevitably introduces additional noise, which evidently deteriorates the resolution. To achieve better performance, we propose a post-collimation system, composed of several aperture blades, in addition to the focusing mirror. Using simulation, we determine the optimal configuration of the system. Its tolerance to installation deviations is also examined. It is shown that the post-collimation system significantly suppresses the stray neutrons and improves the resolution. Such effectiveness has also been demonstrated by neutron experiments.
Displacement damage in silicon photomultipliers (SiPMs) increases dark current and dark count rate (DCR), leading to baseline elevation, increased pulse pile-up, and reduced sensitivity to weak signals. An evaluation chain based on irradiation experiments that links proton fluence to waveform degradation is presented for the JSP-TN3050-SMT SiPM. Using a 10 MeV proton irradiation campaign, dependence of dark current on fluence and bias is parameterized and, combined with device level electric field enhancement and avalanche triggering probability, a KD approximate to 1.8 & times; 105 Hz/MeV g- 1 cm- 3 is extracted for the tested device, following the universal dark current damage factor formalism for silicon depleted regions. The resulting degradation law is integrated into a pixel level waveform simulator that explicitly models triggering and recovery and outputs baseline and optical response metrics defined in fixed time windows consistent with the readout format. At the highest fluence, agreement between simulation and measurement is achieved only when voltage drop and self-heating are included; omitting them distorts the simulated waveform. Across multiple fluence points, the simulated light window integrated charge matches measurements within 7%, demonstrating the utility of the proposed chain for lifetime extrapolation and readout parameter planning.
The crab-waist (CW) collision scheme has become a key ingredient of modern circular e+e- colliders, owing to its ability to suppress beam-beam-driven betatron resonances and to enable operation at very high luminosity. Nevertheless, resonance-related beam blowup and luminosity degradation can still appear in simulations and machine operation. In this paper, we revisit beam-beam-driven resonances in CW colliders within a weak-strong analytical framework, following the formulation of Pestrikov and Dikansky. The resonance-driving terms of the ideal CW transformation are re-examined in detail, with emphasis on their physical interpretation. The analysis confirms that the ideal CW transformation strongly suppresses ordinary betatron resonances, especially those with odd horizontal indices, whereas synchrobetatron resonances are not fully eliminated. Horizontal, vertical, and three-dimensional synchrobetatron resonances may therefore remain relevant constraints on the working point and luminosity performance of CW colliders. Representative machine imperfections are also discussed qualitatively to illustrate how the ideal resonance-suppression mechanism may be modified in realistic machines. The results organize known resonance effects into a coherent analytical picture and provide guidance for interpreting beam-beam limitations in CW colliders.
Gas-gain calibration is essential for achieving good energy resolution in large-area, pixelated detectors used in active-target time projection chambers. In this work, a fast gain calibration method based on least-squares minimization is applied to TPC calibration. The method simultaneously extracts all pixel gains by solving a global least-squares problem that models the shared charge response from each 55Fe X-ray event. Compared with conventional pixel-by-pixel X-ray spectrum fitting, the proposed method requires significantly fewer calibration data while providing stable and accurate gain determination. The method is validated using a multi-component alpha source, and an energy resolution of 2.1% at 6.35 MeV is achieved after calibration. This approach offers an efficient solution for gain calibration in large-area, pixel-readout TPC systems.
We have been promoting various hardware developments on pulsed magnets by using non-linear characteristics of materials since 2008. Among them, the experiments by using the high-field fast-rise magnet by operating the return yoke over the saturation of the magnetic flux density were successfully completed in the beam handling of high-energy protons. The experimental results are described in this article. Based on the favorable experimental results, we are discussing some possibilities of the precise investigation on a field performance and the applications to a handling of a high-energy small beam theoretically, and then are planning to perform a precise measurement of the magnetic field performance by using small high-energy electrons at the KEK-ATF accelerator as the next step. If a stable flattop can be confirmed in the experiment, the result itself indicates the possibility of more stable delivery of high-energy electrons at the view point of a transverse emittance growth due to a perturbation like a jitter or a droop from a power supply. It is important to know more precise information on the working kicker systems for the small beam experiment, and then the detailed simulations on a performance on the working kicker systems and a problem on the beam induced field are also discussed in this article. On the other hand, the fast-rise and strong magnetic field is capable of an induction of higher-voltage in a magnet gap and larger-current induced in the case of an additional loop-coil to be inserted in the magnet gap. Higher magnetic flux density can be excited around the surface of the loop-coil in the case of a thin coil because it is reversely proportionate to the coil radius theoretically. A new beam handling method can be expected by a combination of such a thin loop-coil and the SY-kicker system. An example of such application plans is also described.
Photon-counting computed tomography (PCCT) has recently emerged as the next-generation CT technology, offering multi-energy and low-dose imaging. In particular, PCCT systems using CdTe-based semiconductor detectors have already entered clinical use. However, several practical limitations remain, such as the low detection efficiency for high-energy photons due to the difficulty of fabricating thick semiconductor layers. To address the issues, we propose a novel PCCT system employing a dual-layer scintillator detector. Our design features a thin front layer optimized for low-energy photon detection and a thicker rear layer for high-energy photons. Moreover, we introduce sub-pixel shifts between the two layers to enhance spatial resolution via super-resolution techniques. We constructed a prototype dual-layer detector and conducted imaging experiments using contrast agent and resolution phantoms. The results demonstrated improved image quality across a wide energy range and enhanced spatial resolution compared with a single-layer system. This study highlights the potential of dual-layer scintillator-based PCCT as a practical, low-cost alternative to CdTe-based systems, providing enhanced spectral performance, particularly for K-edge imaging, and spatial resolution compared with a single-layer system.
A higher-order-mode (HOM) damped spoke cavity has been proposed in which a C-shaped waveguide (CSWG) is embedded inside the spoke to selectively extract HOMs while keeping the accelerating mode confined within the cavity. The integration of a 90 degrees bend and a 180 degrees folded structure provide sufficient attenuation length for the fundamental mode, while the optimized connection-plate geometry ensures that only HOMs propagate above the designed cutoff frequency. Measurements using aluminum CSWG models confirmed that the intended RF characteristics are preserved despite the geometric complexity. A prototype HOM-spoke was then fabricated using press-formed copper components and evaluated within a two-spoke cavity model. Experimental measurements of external Q values demonstrated effective HOM damping above cutoff, in good agreement with numerical simulations. These results validate the practical feasibility of the HOM-spoke concept for HOM suppression in spoke cavities. Furthermore, an evaluation of fabrication tolerances of the CSWG revealed that elliptical deformation has only a minor impact on the cutoff frequency when the average circumference is preserved, whereas concentricity errors significantly shift the cutoff frequency.
Proton irradiation induced single-event transients (SETs) in CMOS image sensors (CIS) can produce bright spots and bright lines that degrade imaging performance in radiation environments. This work combines 70 MeV proton irradiation experiments (flux 2.5 & times; 108 p/(cm2 & sdot;s)) with TCAD-Geant4 simulations to systematically investigate the mechanisms and energy dependence of SETs. The experimental sample is a 130 nm 5T high-dynamic-range CIS, in which three types of bright spots and bright lines are observed. In simulation, a full 3-D 5T pixel and a 2 & times;4 micro-array are first constructed in Sentaurus TCAD to analyze proton direct ionization, secondary heavy-ion ionization, bright-spot formation, and charge collection efficiency. The TCAD model is then imported into Geant4 to establish a 220 & times;220-pixel array for simulating secondary-particle transport under 1-300 MeV proton irradiation. The simulation successfully reproduces the experimentally observed SET features: secondary ions with high deposited energy, such as Si, Al, and Mg, produce large bright spots, and single-pixel, low-output spots mainly result from proton direct ionization. Bright-spot size and occurrence probability follow Weibull-type dependence on proton energy. Bright lines are primarily induced by secondary protons, alpha particles, and deuterons, and both their track length and the number of affected pixels also exhibit Weibull-type growth. These results provide a quantitative and physically consistent understanding of proton-induced SETs in CIS.
To enhance the detection sensitivity for weakly ionizing radiation, charge multiplication and avalanches have been utilized in the development of various detector structures based on different semiconductor materials. However, in the case of diamond, the charge multiplication process has not yet been leveraged for this purpose, primarily because of the extreme electric fields required to induce charge multiplication. In addition, performing reliable measurements of charge-carrier-initiated impact ionization, which results in charge multiplication, is challenging. Therefore, in this study, we explored the responses of two different electrode arrangements deposited on single-crystal diamond membranes using the ion-beam-induced charge technique. Electric fields of up to 1 MV/cm were applied on the membranes with thickness of 3.5 and 6.1 & micro;m. Charge multiplication was observed for heavy ions (C and O), with MeV-scale energies. By contrast, for light ions such as Li, He, and H, the thresholds for charge multiplication were higher. For these light ions, the electric-field crowding effect, along the edge of one of the electrodes, was used to reach the threshold for charge multiplication. In addition, the need for further investigation of the impact ionization and possible application areas are discussed herein.
We report on the development and characterization of a novel implantation detector based on a segmented 139La-GPS (Gd,La)2Si2O7:Ce scintillator for /1-decay spectroscopy at fragmentation facilities. The new detector aims at an improved /1-implant correlation owing to the high density (5.2 g/cm3) and effective atomic number (Z approximate to 51) of La-GPS, as well as the required time resolution for time-of-flight neutron measurements. To mitigate intrinsic radioactivity of 138La, crystals were synthesized with A = 139 enriched La2O3 powder and its radioactivity was evaluated using ultra-low background HPGe detector setup. The detector consists of a 32 & times; 32 array of 1.5 mm & times; 1.5 mm pixels coupled to a multi-anode PMT with Anger logic for spatial reconstruction. Performance evaluations demonstrated acceptable internal radioactivity (2.04(5) Bq for the entire array), a timing resolution of 1161(15) ps in FWHM, and clear pixel-resolved position imaging with a 60Co source. These results establish 139La-GPS as a promising candidate for next-generation active stoppers in advanced /1-delayed neutron spectroscopy experiments.
Independent measurements are essential during nuclear safeguards inspections to verify operators' declarations and ensure accurate nuclear material accountancy. Determination of the 235U enrichment is a key task in this process. However, the limited availability of suitable radioactive standards for detector calibration in field measurements often requires the use of alternative analytical calibration approaches. In this work, uranium isotopic verification was carried out using experimental gamma-ray spectrometry supported by mathematical efficiency calibration. A set of Standard Nuclear Material (SNM) samples with cylindrical geometry and different enrichment levels has been measured using both high-purity germanium (HPGe) and NaI(Tl) detectors. Detector efficiency has been obtained using ISOCSTM software based on detector specifications and sample geometry. The isotopic masses of 235U and 238U have been calculated from the measured count rates, and uranium enrichment has subsequently been derived. In addition, MGAU software was applied to estimate the isotopic fractions from the measured spectra. The enrichment values obtained using the different analytical methods were compared. They were also compared with the certified reference values of the SNM samples. The results demonstrated good agreement, with relative deviations ranging from -2.81% to +1.82% for the HPGe detector and -6.33% to +5.49% for the NaI(Tl) detector. These findings confirm the reliability of the proposed approach for nondestructive uranium verification.
Based on the data from beam position monitors (BPMs) using a high-speed oscilloscope, the transverse position and arrival time, equivalent to the longitudinal phase, of beam bunches, including the injected bunch have been measured and analyzed on a bunch-by-bunch basis. We present the results of applying this method to study the injection process at the High Energy Photon Source (HEPS). The beam transfer and injection in different areas, e.g., from the linear accelerator (LINAC) to the booster, from the booster to the storage ring (SR), and from the storage ring back to the booster—were analyzed using the oscilloscope. Valuable information, such as amplitude and frequency of the oscillation of the injected bunch, as well as the damping time are presented. This method exhibits the high sensitivity required for the detection of the longitudinal phase, allowing unambiguous identification of the longitudinal tune even after damping and decoherence. The longitudinal tune was measured at different energy points throughout the booster's energy ramping process, showing excellent agreement with theoretical values with a relative error of less than 5%. Furthermore, we used this method to analyze the energy and phase stability of the LINAC. The initial phase of the first turn demonstrated that the timing jitter of the LINAC beam is below 1.6 ps, and the oscillation amplitude confirmed that the energy stability of the LINAC beam is better than 0.02%. The methodology based on the oscilloscope has been successfully implemented at HEPS, highlighting its broad applicability across different types of electron accelerators, with a broad analysis potential.
Photocathodes are extensively utilized in electron injectors for accelerator-based applications, with their performance substantially impacting electron beam quality. Cesium telluride is a commonly used semiconductor material for photocathodes, conventionally fabricated through sequential or co-deposition methods. In this study, we propose a new multilayer deposition technique in which tellurium and cesium are alternately deposited. This approach enables the precise determination of the ideal tellurium-to-cesium ratio, offering an effective alternative to sequential and co-deposition methods. Our experimental results demonstrate that cathodes prepared using multilayer deposition exhibit high quantum efficiency and reproducibility.
The Electron-Proton/Ion Collider Experiment (ePIC) will be a large, multi-purpose detector to be installed at the Electron-Ion Collider (EIC) being built at Brookhaven National Laboratory. As robust particle identification (PID) capabilities are essential for fully realizing the EIC science program, ePIC contains several PID subsystems spanning different angular ranges. PID capability in the electron-going endcap is provided by a proximityfocusing Ring Imaging Cherenkov detector (pfRICH) designed to deliver at least 3 separation between pions and kaons for momenta up to 7 GeV/c. It will also aid with electron-hadron discrimination at low momentum and assist in the determination of the collision time (t(0)). This contribution will summarize the design of the pfRICH as well as ongoing fabrication and component testing efforts. geant-based performance simulations will also be discussed.
