Performance evaluation of a parallel-hole collimated detector module for animal SPECT imaging

We have built and investigated a detector module for animal SPECT imaging, especially for use in large field of view (FOV) conditions. The module consists of a PMT-based detector and a parallel-hole collimator with an effective area of 80 mm × 80 mm. The detector is composed of a NaI scintillation crystal array coupled to four H8500 position sensitive photomultiplier tubes (PS-PMT). The intrinsic energy resolution of the detector is 11.5% at 140 keV on average. The planar spatial resolution of the module changes from 2.2 mm to 5.1 mm at different source-to-collimator distances with an unchanged sensitivity of about 34cps/MBq. Additionally, the SPECT Micro Deluxe Phantom imaging was performed with a radius of rotation (ROR) of 40 mm. Using the FBP reconstruction algorithm, a high performance image was obtained, indicating the feasibility of this detector module.     

A future project at tibet： the large high altitude air shower observatory （LHAASO）

Gamma ray source detection above 30 TeV is an encouraging approach for finding galactic cosmic ray sources. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100 GeV. In order to target those goals, a large air shower particle detector array of 1 km^2 （the LHAASO project） at 4300 m a.s.l, is proposed, By adding two MagicⅡ- type telescopes in the array as proposed, LHAASO will be enhanced in source morphologic investigation power. The proposed array will be utilized also for energy spectrum measurement for individual cosmic ray species above 30 TeV. By re-configuring the wide field of view telescopes into fluorescence light detector array, the aperture of the detector array can be enlarged to cover an energy region above 100 PeV where the second knee is located. Cosmic ray spectrum and composition will be measured in order to transfer an energy scale to ultra high energy cosmic ray experiments.     

Design and development of compact readout electronics with silicon photomultiplier array for a compact imaging detector

This work aims at developing compact readout electronics for a compact imaging detector module with silicon photomultiplier (SPM) array. The detector module consists of a LYSO crystal array coupling with a SensL's 4×4 SPM array. A compact multiplexed readout based on a discretized positioning circuit (DPC) was developed to reduce the readout channels from 16 to 4 outputs. Different LYSO crystal arrays of 4×4, 8×8 and 12×12 with pixel sizes of 3.2, 1.6 and 1.0 mm respectively, have been tested with the compact readout board using a ¹³⁷Cs source. The initial results show that the compact imaging detector module with the compact multiplexed readout could clearly resolve 1 mm× 1 mm× 10 mm LYSO scintillation crystal array except those at the edges. The detector's intrinsic spatial resolution up to 1 mm can be achieved with the 3 mm×3 mm size SPMArray4 through light sharing and compact multiplexed readout. Our results indicate that this detector module is feasible for the development of high-resolution compact PET.     

Study of the characteristics of a scintillation array and single pixels for nuclear medicine imaging applications

By using a pixelized Nal（T1） crystal array coupled to a R2486 PSPMT, the characteristics of the array and of a single pixel, such as the light output, energy resolution, peak-to-valley ratio （P/V） and imaging performance of the detector were studied. The pixel size of the NaI（TI） scintillation pixel array is 2 mm×2 mm×5 mm. There are in total 484 pixels in a 22×22 matrix. In the pixel spectrum an average peak-to-valley ratio （P/V） of 16 was obtained. In the image of all the pixels, good values for the Peak-to- Valley ratios could be achieved, namely a mean of 17, a maximum of 45 and the average peak FWHM （the average value of intrinsic spatial resolution） of 2.3 mm. However, the PSPMT non-uniform response and the scintillation pixels array inhomogeneities degrade the imaging performance of the detector.     

Centrality Dependence of Flow in High—Energy Nucleus—Nucleus Collisions

Directed flow and elliptic flow of final state particles in high-energy nucleus-nucleus collisions in the EMU01 experiment have been studied.The dependences of directed flow and elliptic flow on incident energy and impact centrality of outgoing particles are presented.The results exhibit strong dependence of flow on centrality and energy.We also suggest a more reliable way to determine the event plane resolution here.     

Performance testing of a long-strip two-end readout multi-gap resistive plate chamber

Multi-gap Resistive Plate Chamber （MRPC） is a new generation of gas detector with good timing and spacial resolution, whose technique is widely applied in some recent high energy （nuclear） physics experiments. In this letter, we report a long-strip two-end readout MRPC and its test beam performance. The measurements show that the long-strip performs a transmission line characteristic and the impedance is independent of the length of strip. The MRPC module we developed is presented to gain a timing resolution of -80 ps and a spacial resolution of -6.4 mm. The possible application of the MRPC is also discussed.     

Monitoring the energy variation of an electron linac using a Cerenkov detector

A new method to monitor the energy variation of a multi-energy electron linac by combining a Cerenkov detector and a CsI（Tl） detector is reported. The signals in the Cerenkov detector show an appreciable but different dependence on the energy of the electron linac from the traditional CsI（Tl） detector due to the particular response of the former to charged electrons with high velocity above threshold. The method is more convenient than the HVL （half-value layer） method which is commonly employed to calibrate the energy of an electron linac for real time monitoring. The preliminary validity of the method is verified in a dual-energy electron linac with 6 MeV and 3 MeV gears. Moreover, the method combining the Cerenkov detector and the CsI（Tl） detector is applicable to probe the X-ray spectrum hardened by the inspected material and may serve as a novel tool for material discrimination with effective atomic number in radiation imaging.     

Characteristics of the sampling paddle modules of neutron wall from the cosmic ray test

In the construction of a large area neutron detector （neutron wall） that is used to detect neutrons at GeV energies, the performances of all the sampling paddle modules prepared for the neutron wall are investigated with a specially designed test bench. Tested by cosmic rays, an average intrinsic time resolution of 222.5 ps is achieved at the center of the modules. The light attenuation length and the effective speed of the light in the module are also investigated.     

Design of Multi-unit Control System of High Voltage Power Supply for LASCAR Scintillator Detector Array

The power voltages of Photomultipliers (PMTs) at RIBLL LASCAR scintillator detector array are distributed between 900 V and 1 800 V irregularly. 392 CC123 modules are employed to supply high voltage for the PMT array. The CC123 module serves as PMT interface groupware package, and it can transform 12 V DC input voltage to ranges of 0～-2200 V for the PMT power supply corresponding to 0～ 5 V output voltage from the control board crate. The relation of PMT power supply with the output voltage of the control crate is shown in Fig.1.     

Study on gamma response function of E J301 organic liquid scintillator with GEANT4 and FLUKA

The gamma response function is required for energy calibration of EJ301 （5 cm in diameter and 20 cm in height） organic liquid scintillator detector by means of gamma sources. The GEANT4 and FLUKA Monte Carlo simulation packages were used to simulate the response function of the detector for standard 22Na, 60Co, 137Cs gamma sources. The simulated results showed a good agreement with experimental data by incorporating the energy resolution function to simulation codes. The energy resolution and the position of the maximum Compton electron energy were obtained by comparing measured light output distribution with simulated one. The energy resolution of the detector varied from 21.2% to 12.4% for electrons in the energy region from 0.341 MeV to 1.12 MeV. The accurate position of the maximum Compton electron energy was determined at the position 81% of maximum height of Compton edges distribution. In addition, the relation of the electron energy calibration and the effective neutron detection thresholds were described in detail. The present results indicated that both packages were suited for studying the gamma response function of EJ301 detector.     

Study of the e+ e－ to hadrons via ISR at BABAR

Experimental data from the PEP-II B-factory at 10.6 GeV center-of-mass （c.m.） energy, obtained via initial-state radiation （ISR） with the BABAR detector, are presented. The cross sections for many hadronic processes have been measured from the production threshold to 4-5 GeV of the e^＋e^- c.m. energy. The obtained data allow to study a number of intermediate states and determine the parameters of known resonances and their branching fractions. The exclusive cross section for some number of hadronic sub-processes are presented.     

Upgrade of beam energy measurement system at BEPC-Ⅱ

The beam energy measurement system is of great importance for both BEPC-Ⅱ accelerator and BES-III detector. The system is based on measuring the energies of Compton back-scattered photons. In order to meet the requirements of data taking and improve the measurement accuracy, the system has continued to be upgraded, which involves the updating of laser and optics subsystems, replacement of a view-port of the laser to the vacuum insertion subsystem, the use of an electric cooling system for a high purity germanium detector, and improvement of the data acquisition and processing subsystem. The upgrade system guarantees the smooth and efficient measurement of beam energy at BEPC-II and enables accurate offline energy values for further physics analysis at BES-Ⅲ.     

Fast calibration methods using cosmic rays for a neutron detection array

An overall irradiation and calibration technique was introduced and applied to a test scintillation detector array. An integral conversion method was used to reduce the nonlinearity of the time difference spectrum, and to improve the position determination especially for positions close to the two ends of a long scintillation bar. An overall position resolution of about 3.0 cm (FWHM) was extracted from the residual analysis method and verified by a direct measurement. Energy calibration was also realized by selecting cosmic rays at different incident angles. The bulk light attenuation lengths for the four test bars were also determined. It is demonstrated that these methods are especially efficient for calibrating large and complex detector arrays.     

Performance of superconducting nanowire single-photon detector with the fan coupling antenna array

The performance of superconducting nanowire single-photon detector （SNSPD） involving niobium nitride with the fan coupling antenna array is analyzed. The SNSPD has a high detection efficiency and counting rate. Hydrogen silsesquioxane and niobium nitride are filled in the gold grating deposited on the substrate in which the fan coupling antenna arrays are embedded. By changing the position of the fan coupling antenna array, the maximum area of optical intensity is obtained and the photon collection efficiency is increased by 26.5 times. The detection efficiency of SNSPD is improved without changing the detection speed. These parameters are important for designing a practical single-photon detector,     

Effects due to a Pu-C source on a HPGe detector and the corresponding neutron shielding

A gamma spectrum of a Pu-C source is measured using a p-type HPGe detector, whose three peaks (full energy, single-escape and double-escape peak) can be used as a calibration source for the beam energy measurement system of BEPCII. The effect of fast neutron damage on the energy resolution of the HPGe detector is studied, which indicates that the energy resolution begins to deteriorate when the detector is subject to 2×10⁷ n/cm² fastneutrons. The neutron damage mechanism and detector repair methods are reviewed. The Monte Carlo simulation technique is utilized to study the shielding of the HPGe detector from the fast neutron radiation damage, which is of great significance for the future commissioning of the beam energy measurement system.     

Online charge calibration of LHAASO-WCDA——a study with the engineering array

LHAASO-WCDA is a large ground-based water Cherenkov detector array planned to be built at ShangriLa, Yunnan Province, China. As a major component of the LHAASO project, the main purpose of LHAASO-WCDA is to survey the northern sky for very-high-energy（above 100 GeV） gamma ray sources and measure the spectrum. To gain full knowledge of the water Cherenkov technique and to investigate the engineering issues, a 9-cell detector array has been built at the Yang-Ba-Jing site, neighboring the ARGO-YBJ experiment. With the array, charge calibration methods for both low and high ranges of the PMT readout are studied, whose result shows that a precision at several percentages can be reached, which can satisfy the requirement of the detector array. During the long term operation, the charge calibration stability and environmental afection are studied; in this paper, the results are discussed. These calibration methods are proposed to be applied in the future LHAASO-WCDA project.     

Testing technology of vacuum ultraviolet spectral radiance北大核心CSCD

The spectral radiance of vacuum ultraviolet (UV) target is of crucial significance to plenty of researches including deep space exploration and spacecraft damage test. Two types of test systems and methods for vacuum UV light sources were studied. Through the research of test method for vacuum UV spectral radiance, a corresponding test system was developed, which included vacuum UV standard light source, optical imaging system, light splitting module, vacuum UV detector module, vacuum chamber and data processing system. According to the direct measurement method and the comparative method, the spectral radiance of deuterium lamps was tested and analyzed, the influencing factors and the relative index error of vacuum UV spectral radiance were discussed, and the accurate measurement of vacuum UV spectral radiance in the five wavelength ranges of 121.2 nm, 135.6 nm, 160 nm, 180 nm, 200 nm at 0.01 μW/cm2·nm·sr~1 μW/ cm2·nm·sr was realized. The repeatability of the measurement is 0.001 34, which shows that the proposed test system can realize the test of vacuum UV signal. © 2022 Editorial office of Journal of Applied Optics. All rights reserved.     

A cosmic ray test platform based on high time resolution MRPC technology

In order to test the performance of detector prototypes in a laboratory environment, we design and build a large area (90 cm×52 cm) test platform for cosmic rays based on a well-designed Multi-gap Resistive Plate Chamber (MRPC) with excellent time resolution and a high detection efficiency for minimum ionizing particles. The time resolution of the MRPC module used is tested to be ～80 ps, and the position resolution along the strip is ～5 mm, while the position resolution perpendicular to the strip is ～12.7 mm. The platform constructed by four MRPC modules can be used for tracking cosmic rays with a spatial resolution of ～6.3 mm, and provide a reference time ～40 ps.     

Performance of a double sided silicon strip detector as a transmission detector for heavy ions

The performance of a double sided silicon strip detector （DSSSD）, which is used for the position and energy detection of heavy ions, is reported. The analysis shows that although the incomplete charge collection （ICC） and charge sharing （CS） effects of the DSSSD give rise to a loss of energy resolution, the position information is recorded without ambiguity. Representations of ICC/CS events in the energy spectra are shown and their origins are confirmed by correlation analysis of the spectra from both the junction side and ohmic side of the DSSSD.