Performance simulation and structure design of Binode CdZnTe gamma-ray detector

A new electrode structure CdZnTe(Cadmium Zinc Telluride) detector named Binode CdZnTe has been proposed in this paper.Together with the softwares of MAXWELL,GEANT4,and ROOT,the charge collection process and its gamma spectrum of the detector have been simulated and the detector structure has been optimized.In order to improve its performance further,Compton scattering effect correction has been used.The simulation results demonstrate that with refined design and Compton scattering effect correction,Binode CdZnTe detectors is capable of achieving 3.92%FWHM at 122 keV,and 1.27%FWHM at 662 keV.Compared with other single-polarity(electron-only) detector configurations,Binode CdZnTe detector offers a cost effective and simple structure alternative with comparable energy resolution.

Analysis and optimization of energy resolution of neutron-TPC

Neutron-TPC(n TPC)is a fast neutron spectrometer based on GEM-TPC(Gas Electron Multiplier-Time Projection Chamber)and expected to be used in nuclear physics,nuclear reactor operation monitoring,and thermonuclear fusion plasma diagnostics.By measuring the recoiled proton energy and slopes of the proton tracks,the incident neutron energy can be deduced.It has higher n/γseparation ability and higher detection efficiency than conventional neutron spectrometers.In this paper,neutron energy resolution of n TPC is studied using the analytical method.It is found that the neutron energy resolution is determined by 1)the proton energy resolution(σEp/Ep),and 2)standard deviation of slopes of the proton tracks caused by multiple Coulomb scattering(σk(scattering))and by the track fitting accuracy(σk(fit)).Suggestions are made for optimizing energy resolution of n TPC.Proper choices of the cut parameters of reconstructed proton scattering angles(θcut),the number of fitting track points(N),and the working gas help to improve the neutron energy resolution.

An ART iterative reconstruction algorithm for computed tomography of diffraction enhanced imaging

X-ray diffraction enhanced imaging （DEI） has extremely high sensitivity for weakly absorbing low- Z samples in medical and biological fields. In this paper, we propose an Algebra Reconstruction Technique （ART） iterative reconstruction algorithm for computed tomography of diffraction enhanced imaging （DEI-CT）. An Ordered Subsets （OS） technique is used to accelerate the ART reconstruction. Few-view reconstruction is also studied, and a partial differential equation （PDE） type filter which has the ability of edge-preserving and denoising is used to improve the image quality and eliminate the artifacts. The proposed algorithm is validated with both the numerical simulations and the experiment at the Beijing synchrotron radiation facility （BSRF）.

Bunch evolution study in optimization of MeV ultrafast electron diffraction

Megaelectronvolt ultrafast electron diffraction（UED） is a promising detection tool for ultrafast processes.The quality of diffraction image is determined by the transverse evolution of the probe bunch. In this paper, we study the contributing terms of the emittance and space charge effects to the bunch evolution in the MeV UED scheme, employing a mean-field model with an ellipsoidal distribution as well as particle tracking simulation. The small transverse dimension of the drive laser is found to be critical to improve the reciprocal resolution, exploiting both smaller emittance and larger transverse bunch size before the solenoid. The degradation of the reciprocal spatial resolution caused by the space charge effects should be carefully controlled.

Polynomial curve fitting method for refraction-angle extraction in diffraction enhanced imaging

X-ray diffraction sorbing low-Z sample. How enhanced imaging （DEI） is applied to extract phase information from to inspect internal structures of weakly abraw images measured in different positions of rocking curve is the key problem of DEI. In this paper, we present an effective extraction method called polynomial curve fitting method, in order to extract accurate information angular in a fast speed. It is compared with the existing methods such as multiple-images statistical method and Gaussian curve fitting method. The experiments results on a plastic cylinder and a black ant at the Beijing Synchrotron Radiation Facility prove that the polynomial curve fitting method can obtain most approximate refraction-angle values and its computation speed is 10 times faster than the Gaussian curve fitting method.