In-situ energy calibration of SSRF macromolecular crystallography beamline using powder diffraction

<正>For X-ray powder diffraction spectra collected by an area detector of MarCCD on macromolecular crystallography beamline of SSRF,an energy calibration method was developed using LaB_6(660a) powder diffraction for in-situ rapid energy calibration of the X-rays without changing the experimental conditions.The intensity of each diffraction ring was integrated,and the accurate peak positions were fitted by Pseudo-Voigt function model.The sample's interplanar spacing for XRD analysis and the calibrated energy were obtained by the PCPDFWIN code and by fitting all the energies with the least-square method.The exposure time and the sample-to-detector distance were found no effect on accuracy of the energy calibration,and the in-situ energy calibration could be done with an accuracy of better than 0.4‰in 7-18 keV.This method is applicable to other X-ray beamlines.     

Studies on absorption coefficients of dual-energy γ-rays and measuring error correction for multiphase fraction determination

In tiffs article, principle and mathematical method of determining the phasc fractions of multiphase flows by using a dual-energy γ-ray system have been described. The dual-energy γ-ray device is composed of radioactive isotopes of ^241Am and ^137Cs with γ-ray energies of 59.5 and 662 keV, respectively. A rational method to calibrate the absorption coefficient was introduced in detail. The modified arithmetic is beneficial to removing the extra Compton scattering from the measured value. The result shows that the dual-energy γ-ray technique can be used in thrce-phase flow with average accuracy greater than 95%, which enables us to determine phase fractions almost independent of the flow regime. Improvement has been achicved on measurement accuracy of phase fractions.     

New Soft x-ray PHA Diagnostic in the HT-7 Tokamak

A soft x-ray Pulse Height Analysis (PHA) diagnostic with the recently introduced Silicon Drift Detector (SDD) and a new MCA system has been installed in HT-7 for the measure-ments of electron temperature. With the SDD detector, the x-ray emission can be detected in the energy range from 1 keV up to 20 keV. The extremely low anode capacity of SDD allows very high counting rates of x-ray above 200 kHz and short shaping times below 0.25μs to be measurede. In routine operation a counting rate of 120 kHz has been normally obtained with an energy resolution of better than 180 eV at 5.9 keV. The assembly is equipped with six SDD detectors measuring the soft x-ray emission integrated along six chords of the upper half plasma cross section. The preliminary results from the new soft x-ray PHA diagnostic are also presented in this paper.     

Simulation study of energy resolution with changing pixel size for radon monitor based on Topmetal-Ⅱ~- TPC

In this paper, we study how pixel size influences energy resolution for a proposed pixelated detector—a high sensitivity, low cost, and real-time radon monitor based on a Topmetal-Ⅱ~- time projection chamber(TPC). This monitor was designed to improve spatial resolution for detecting radon alpha particles using Topmetal-Ⅱ~- sensors assembled by a 0.35 lm CMOS integrated circuit process.Owing to concerns that small pixel size might have the side effect of worsening energy resolution due to lower signalto-noise ratio, a Geant4-based simulation was used to investigate the dependence of energy resolution on pixel sizes ranging from 60 to 600 lm. A non-monotonic trend in this region shows the combined effect of pixel size and threshold on pixels, analyzed by introducing an empirical expression. Pixel noise contributes 50 keV full-width at half-maximum energy resolution for 400 lm pixel size at 1–4σ threshold that is comparable to the energy resolution caused by energy fluctuations in the TPC ionization process( ~20 keV). The total energy resolution after combining both factors is estimated to be 54 keV for a pixel size of 400 lm at 1–4σ threshold. The analysis presented in this paper would help choosing suitable pixel size for future pixelated detectors.     

Some characteristics of X-ray imaging for energy region of over 100 keV using plastic scintillation fiber array

In this work, characteristics of using PSFs （plastic scintillation fibers） coupled with CCD （charge-coupled devices ） to build area detectors for high energy X-ray imaging are studied with a Monte Carlo simulation, which cover an energy range of a few hundred keV to about 20 MeV. It was found that the efficiency of PSF in detecting X-ray with energy above a few hundred keV is low. We can use large incident flux to increase the output signal to noise ratio （SNR）. The performance can also be improved by coating PSF with X-ray absorption layers and the MTF of the system is presented. By optimizing the absorption layer thickness, the crosstalk of the area detector built with PSF decreases.     

Generation of Alfvén wave energy during magnetic reconnection in Hall MHD

The effect of the reconnection rate on the generation of Alfvén wave energy is systematically investigated using Hall magnetohydrodynamics(MHD). It is well known that a decrease in magnetic energy is proportional to the reconnection rate. It is found that an instantaneous increase in Alfvén wave energy in unit Alfvén time is the square dependence on the reconnection rate. The converted Alfvén wave energy is strongly enhanced due to the large increase in the reconnection rate in Hall MHD. For solar-terrestrial plasmas, the maximum converted Alfvén wave energy in unit Alfvén time with the Hall effect can be over 50 times higher than that without the Hall effect during magnetic reconnection.     

GEANT4 simulation of water volume fraction measurement in dehydrated crude oil

Online measurement of water volume fraction (WVF) in dehydrated crude oil is a difficult task due to very little water in dehydrated crude oil and high precision requirements. We presents a method to measure water volume fraction in dehydrated crude oil with γ-ray densitometry. The Monte Carlo computer simulation packet GEANT4 was used to analyze the WVF measuring sensitivity of the γ-ray densitometry at different γ-ray energies, and effects of temperature, pressure, salinity and oil components on WVF measurement. The results show that the γ-ray densitome-try has high sensitivity in γ-ray energy ranges of 16～25 keV, and it can distinguish WVF changes of 0.0005. The calculated WVF decreases about 0.0002 with 1 ℃ of temperature increase and they have approximately linear relation with temperature when water volume fraction remains the same. Effects of pressure, salinity and oil components on water volume fraction can be neglected. Experiments were done to analyze sensitivity of the γ-ray densitometry. The results, as compared with simulations, demonstrate that simulation method is reliable and it is feasible to gauge low water volume fraction using low energy γ-rays.     

Preliminary results of a Compton camera based on a single 3D position-sensitive CZT detector

A Compton camera prototype has been developed using a pixelated CZT detector with 4-by-4 pixels.Signals of the detector are read out by a VASTAT ASIC that is controlled by a self-developed DAQ board. The DAQ software is developed using LabVIEW, and the offline Compton imaging codes are written in C++. The prototype has been successfully calibrated, and its capabilities for source detection, spectroscopy, and Compton imaging have been demonstrated using a Cs-137 source.The angular resolution of the 662 keV line is 36° FWHM for the simple back-projection method and 9.6° FWHM for the MLEM reconstruction method. The system is ready to be extended to 11-by-11 pixels in the future, and a better imaging quality can be expected due to the better relative position resolution.     

Application of electric field for measuring Rn

A new method for the measurement of radon is described in this paper. The characteristic that initial RaA carries positive charges was used to make it possible to drift RaA onto the surface of the barrier detector in an oppropiate electric field. The activity of RaA on the detector surface can be measured in high efficiency and the concentration of radon can also be calculated. The new method is distinct from the conventional one using semiconductor device. The Detector acts not only as a signal monitor but also as an ion collection electrode. The sensitivity for one litre measurement chamber is nearly two order higher than that of the conventional instrument with barrier detector for measuring radon.     

Numerical Simulation of the Self-Heating Effect Induced by Electron Beam Plasma in Atmosphere

For exploiting advantages of electron beam air plasma in some unusual applications,a Monte Carlo(MC) model coupled with heat transfer model is established to simulate the characteristics of electron beam air plasma by considering the self-heating effect.Based on the model,the electron beam induced temperature field and the related plasma properties are investigated.The results indicate that a nonuniform temperature field is formed in the electron beam plasma region and the average temperature is of the order of 600 K.Moreover,much larger volume pear-shaped electron beam plasma is produced in hot state rather than in cold state.The beam ranges can,with beam energies of 75 keV and 80 keV,exceed 1.0 m and 1.2 m in air at pressure of 100 torr,respectively.Finally,a well verified formula is obtained for calculating the range of high energy electron beam in atmosphere.     

QXT-full Automatic Saccharify Instrument

QXT is a full automatic saccharify instrument of eight holes . The instrument use process control technology of micro-computer. It can realize automatic of saccharify full process correctly. Due to adapt control mode of high precision expert PID and digit automatic calibration technology of fill micro computer, not only ensure precision of linear raising temperature region (1 ℃ /min) and constant temperature region (temperature error ±0.2 ℃), but also overcome the disturbance     

Optimized energy thresholds in a spectral computed tomography scan for contrast agent imaging

Spectral computed tomography(CT) based on photon counting detectors(PCDs) is a well-researched topic in the field of X-ray imaging. When PCD is applied in a spectral CT system, the PCD energy thresholds must be carefully selected, especially for K-edge imaging, which is an important spectral CT application. This paper presents a threshold selection method that yields better-quality images in K-edge imaging. The main idea is to optimize the energy thresholds ray-by-ray according to the targeted component coefficients, followed by obtaining an overall optimal energy threshold by frequency voting. A low-dose pre-scan is used in practical implementations to estimate the line integrals of the component coefficients for the basis functions. The variance of the decomposed component coefficients is then minimized using the Cramer–Rao lower bound method with respect to the energy thresholds. The optimal energy thresholds are then used to take a full scan and gain better image reconstruction with less noise than would be given by a full scan using the non-optimal energy thresholds. Simulations and practical experiments on imaging iodine and gadolinium solutions, which are commonly used as contrast agents in medical applications, were used to validate the method. The noise was significantly reduced with the same dose relative to the non-optimal energy thresholds in both simulations and in practical experiments.     

Experiment of Mechanism of Gas Entrainment in Pool Tank

<正>The experiment aims to gain the main parameter of gas entrainment on pool tank and research the influence of scale and flow to the gas entraiment.The device can satisfy the demand.When the liquid level is high,the liquid flows intensively in the tank.The vortex is formed on the free surface.It leads to the generation of gas     

Energy calibration of laterally segmented electromagnetic calorimeters based on neutral pion detection

This paper describes a method for energy calibration of laterally segmented electromagnetic calorimeters based on the detection of two-photon decays of π~0 mesons.The calibration procedure performs a X~2 function minimization between the measured π~0 energy in the calorimeter and its expected energy deduced from the π~0 momentum direction. The performance of this technique is demonstrated with a Monte Carlo simulation of an experimental case where biased calibration coefficients are employed. The real calibration coefficients are restored with less than 1% relative accuracy when a sufficient number of π~0 is detected. This technique is applied to monitor daily the calibration coefficients of the calorimeter used in the Jefferson Lab Hall A DVCS experiments.     

High-resolution pixelated CdZnTe detector prototype system for solar hard X-ray imager

A multichannel low-noise electronic prototype system was designed for a pixelated CdZnTe detector. This system is the result of preliminary work on a solar hard X-ray imager, which is one of the three payloads for future solar observations satellite-Advanced Space-based Solar Observatory(ASO-S). A new charge-sensitive amplifier application-specific integrated circuit, VATA450.3, with an on-chip analog-to-digital converter, is used to read out 8×8 anode pixel signals. Two CdZnTe detectors with a thickness of 2 mm and 5 mm were tested. The 2-mm-thick detector achieved energy resolution better than 5%(fullwidth at half-maximum, FWHM) at 59.5 keV, and the 5-mm-thick detector had better resolution than 1.2%(FWHM) at 662 keV. The design and test results of the prototype system are discussed in this paper.     

Measure Fly off Velocity of the Ion by Time of Flight Method

Primary detector is the charge collector, i.e. Faraday cup to measure fly off velocity of the ion by time of flight method. It is simple and applied set up,When it irradiates on the solid plane targets that laser beam of high power is focused, a thin layer of the high temperature and tight density plasma is produced on the target surface. As this plasma expands in the vacuum, it has of its energy in from of directed kinetic energy of the ion. The ion current signals observed by the charge collector at a large distance will correspond to high     

Simulation and calibration of the response function of multi-sphere neutron spectrometer

In order to realize the on-line real-time measurement of neutron specmnn of ITER fusion, this paper presents a multi-sphere spectrometer system which consists of eight thermal neutron detectors, namely SP9 3He proportional counter, embedded in eight different diameter polyethylene spheres. The response function of eight polyethylene spheres of rnulti-sphere neutron spectrometer was calculated after the simulation of the neutron transport processes in multi-sphere spectrometer by adopting software Geant4. The peak of the response function is in the low energy region for smaller diameter polyethylene sphere. As the polyethylene sphere diameter increased, the peak of the response function moves to the high energy region. The experimental calibration adopts 241Am-Be neutron source. The relative error between normalized data of experiment 47t solid angle counts and normalized data of simulated detection efficiency of 4in to 8in polyethylene sphere is from 1.152% to 12.222%.The experimental results verify the response function of the simulation. All these results provide a theoretical and experimental basis for solving the on-line real-time neutron spectrum of ITER fusion.     

Analysis of the Variability of the L-H Transition Power Threshold in a Helium-4 Discharge

In this paper, a mechanism about the variability of the L-H transition power thresh- old PL-H is proposed which is based on the ion orbit losses. Only in the edge where there are enough ion orbit losses and the negative radial electric field Er is high enough can the H-mode be triggered. The ion orbit losses are determined by the ion in the loss region under certain edge conditions. For different mass A and different charge Z, the critical loss energy E Z2/A in the loss region. In H and D charges, because the D＋ loss region is larger than H＋, it can be deduced that the PL-H of H is larger than that of D. In a 4He discharge, experiment finds there exist a considerable number of 4He1＋ in the plasma edge. The actual ion orbit losses are determined by the mixing ratio of a He1＋ and 4He2＋. The 4He1＋ loss region is larger than that of 4He2＋, and the loss region of D＋ interposes between 4He1＋ and 4He2＋. Different 4He1＋ content can cause the edge ion losses in a 4He discharge to be greater than, less than or equal to that in a D discharge. So a 4He discharge can exhibit multiple experimental phenomena in the PL-H.     

Preliminary Results of Ion Beam Extraction Tests on EAST Neutral Beam Injector

The neutral beam injection (NBI) system is one of the most important auxiliary plasma heating and current driving methods for fusion device.A high power ion beam of 3MW with 80keV beam energy in 0.5s beam duration and a long pulse ion beam of 4s with 50keV beam energy ion beam extraction were achieved on the EAST neutral beam injector on the test-stand.The preliminary results show that the EAST-NBI system was developed successfully on schedule.     

Use of sampling based correction for non-radioactivity X-ray energy calibration

As the requirement of non-radioactivity measurement has increased in recent years, various energy calibration methods applied in portable X-ray fluorescence (XRF) spectrometers have been developed. In this paper, a sampling based correction energy calibration has been discussed. In this method both history information and current state of the instrument are considered and relative high precision and reliability can be obtained.