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Irradiation effect of yttria-stabilized zirconia by high dose dual ion beam irradiation

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Chinese Physics B 2014年第6期23卷 417-421页

作者：张艳文王绪刘士毅唐美雄赵子强张鹏王宝义曹兴忠 State key laboratory of nuclear Physics and Technology Institute of Heavy Ion Physics Peking University Key Laboratory of Nuclear Analysis Techniques Institute of High Energy Physics Chinese Academy of Sciences

Yttria-stabilized zirconia （YSZ） is irradiated with 2.0-MeV Au2＋ ions and 30-keV He＋ ions. Three types of He, Au, Au ＋ He （successively） ion irradiation are performed. The maximum damage level of a sequential dual ion beam implanted sample is smaller than single Au ion implanted sample. A comparable volume swelling is found in a sequential dual ion beam irradiated sample and it is also found in a single Au ion implanted sample. Both effects can be explained by the partial reorganization of the dislocation network into weakly damaged regions in the dual ion beam implanted YSZ. A vacancy-assisted helium trapping/diffusion mechanism in the dual ion beam irradiated condition is discussed. No phase transformation or amorphization behavior happens in all types of ion irradiated YSZ.

关键词： irradiation damage swelling helium diffusion

Design of data acquisition system and algorithm research for omnidirectional gamma-ray positioning equipment

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Chinese Physics C 2014年第1期38卷 89-93页

作者：胡婷婷帅磊王培林丰宝桐张译文孙芸华李晓辉魏书军单保慈魏龙 Key Laboratory of Nuclear Analysis Techniques Institute of High Energy PhysicsChinese Academy of Sciences Beijing Engineering Research Center of Radiographic techniques and Equipment

This article introduces the design and performance of the data acquisition system used in an omnidi- rectional gamma-ray positioning system, along with a new method used in this system to obtain the position of radiation sources in a large field. This data acquisition system has various built-in interfaces collecting, in real time, information from the radiation detector, the video camera and the GPS positioning module. Experiments show that the data acquisition system is capable of carrying out the proposed quantitative analysis to derive the position of radioactive sources, which also satisfies the requirements of high stability and reliability.

关键词： gamma-ray positioning data acquisition FPGA

A Monte Carlo simulation and setup optimization of output ef f iciency to PGNAA thermal neutron using ^(252)Cf neutrons

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Chinese Physics C 2014年第7期38卷 139-143页

作者：张金钊庹先国 Applied nuclear techniques in Geoscience key laboratory Chengdu University of Technology

We present the design and optimization of a prompt T-ray neutron activation analysis （PGNAA） thermal neutron output setup based on Monte Carlo simulations using MCNP5 computer code. In these simulations, the moderator materials, reflective materials, and structure of the PCNAA 2526f neutrons of thermal neutron output setup are optimized. The simulation results reveal that the thin layer paraffin and the thick layer of heavy water moderating effect work best for the 252Cf neutron spectrum. Our new design shows a significantly improved per- formance of the thermal neutron flux and flux rate, that are increased by 3.02 times and 3.27 times, respectively, compared with the conventional neutron source design.

关键词： PGNAA neutron source thermal neutron moderation reflection

Respiratory motion correction with an improved demons algorithm for PET images

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Chinese Physics C 2012年第10期36卷 1025-1030页

作者：高娟柴培贠明凯刘双全单保慈魏龙 Key Laboratory of Nuclear Analysis Techniques Institute of High Energy Physics Chinese Academy of Sciences Graduate University of Chinese Academy of Sciences

Respiratory motion is a major factor that affects the quality of PET images of the thoracic area. The diaphragm moves about 15–20 mm due to respiratory motion, which substantially degrades the effective spatial resolution of PET. In this paper, a gated acquisition method is used to correct the motion effects. In this method, an improved demons algorithm is proposed to align the gated images. The experimental results show that the quality of PET images is significantly improved when using our improved method and the proposed method has a faster convergence rate than the original demons algorithm.

关键词： motion correction demons algorithm discontinuity PET

Preliminary Measurement of the K-Shell Ionization Cross Sections of Ti by Positron Impact in the Low Energy Region

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Plasma Science and Technology 2012年第5期14卷 434-437页

作者：田丽霞刘慢天朱敬军安竹王宝义秦秀波 key laboratory of Radiation Physics and Technology of Ministry of Education Institute of Nuclear Science and TechnologySichuan University East China Institute of Technology Key Laboratory of Nuclear Analysis Techniques Institute of High Energy PhysicsCAS

Measurements were performed of K-shell ionization cross sections of Ti element by 10～30 keV positron impact using the thick-target method. The effects of multiple scattering of incident positron and from bremsstrahlung photons and annihilation photons with the thick-target method are discussed with the Monte Carlo code PENELOPE. Meanwhile, the Monte Carlo method is also applied to determine the detection efficiencies of X- and γ-ray detectors. Our experimental K-shell ionization cross sections for Ti element are compared with the distorted-wave Born approximation （DWBA） theoretical predictions, and it is found that the agreement of the experimental data and theoretical values is good and this indicates that the experimental method adopted in this study is applicable.

关键词： positron impact ionization cross sections thick-target method Monte Carlosimulation

Investigation of scatter from out of the field of view and multiple scatter in PET using Monte Carlo simulations

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Chinese Physics C 2011年第12期35卷 1166-1171页

作者：叶婷柴培高娟贠明凯刘双全单保慈魏龙 Key Laboratory of Nuclear Analysis Techniques Institute of High Energy Physics Chinese Academy of Sciences Graduate University of Chinese Academy of Sciences

In fully three-dimensional （3D） positron emission tomography （PET） imaging, the scatter fraction （SF） is about 40% 60%, which may degrade the imaging quality severely. Scatter correction is important for high quality image reconstruction. Model-based scatter correction has been proved to be accurate and available in clinical PET. However, it does not correct the scatter from out of the field of view （OFOV） and multiple scatters. In this study, we demonstrate the radial and axial distribution of scatters from OFOV when the source is located in different radial positions. In order to apply the above conclusions to different PET systems, we characterize the scatters from OFOV as a function of the ratio of the scanner diameter to the length of the axial field of view （AFOV） by modeling several typical whole-body and micro PET systems. The proportions of true events （S0-0）, single scatter of one photon （S1-0）, single scatter of both photons （S1-1）, double scatter of one photon （S2-0） and multiple scatter （Sm） are also calculated and compared. Here the 3D-PET Monte Carlo simulations are performed with the Geant4 Application for Tomography Emission （GATE）. In summary, the scatters from OFOV tend to be recorded on the lines of response （LOR） far away from the source. They have a much more serious impact on whole-body PET than micro PET depending on the ratio of scanner diameter to the length of AFOV. In whole-body PET, twice scatters including single scatter of both photons （S1-1） and double scatter of one photon （S2-0） add up to about 12% so that twice scatter correction must be taken into account to acquire a high quality reconstruction image.

关键词： PET Monte Carlo simulation GATE scattering

Attenuation correction for dedicated breast PET using only emission data based on consistency conditions

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Chinese Physics C 2013年第1期37卷 138-143页

作者：王璐柴培武丽伟贠明凯周小林刘双全张玉包单保慈魏龙 Key Laboratory of Nuclear Analysis Techniques Institute of High Energy PhysicsChinese Academy of Sciences Graduate University of Chinese Academy of Sciences Beijing Engineering Research Center of Radiographic techniques and Equipment

Accurate attenuation correction is required in dedicated breast PET imaging systems for image artifact removal and quantitative studies. In this study, a method using only emission data based on consistency conditions is proposed for attenuation correction in breast PET imaging systems. The consistency conditions are exploited to evaluate the accuracy of the estimated attenuation distribution and find the appropriate parameters that yield the most consistent attenuation distribution with the measured emission data. We have proved the validity of the method with experimental investigations and single-patient studies using a dedicated breast PET. The results show that the method is capable of accurately estimating the attenuation distribution of a uniform attenuator from the experimental data with various relatively low activities. The results also show that in single-patient studies, the method is robust for the irregular boundary of breast tissue and provides a distinct improvement in image quality.

关键词： attenuation correction breast PET consistency conditions

Positronium annihilation in silica aerogel studied by a positron age-momentum correlation technique

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Chinese Physics C 2009年第1期33卷 81-84页

作者：王丹妮张兰芝王宝义于润升章志明李道武魏龙 Key Laboratory of Nuclear Analysis Techniques Institute of High Energy PhysicsCAS Graduate University of Chinese Academy of Sciences

A high-performance positron age-momentum correlation （AMOC） spectrometer was newly developed. The counting rate is increased up to 200 cps much larger than the value 20 cps reported by other international groups. And at the same time, the time resolution still keeps at the international level of 220 ps. Furthermore, positronium （Ps） annihilation in silica aerogel was investigated by AMOC, which indicates：（1） Ps annihilation between the grains dominantly undergoes pick-off process and spin conversion from o-Ps to p-Ps; （2） Annealing below 400 ℃ changes the grain surface conditions, i. e. the desorption of hydrogen and the decrease of the defect centers concentration.

关键词： positron age-momentum correlation positronium formation positron states silica aerogel

A compact positron annihilation lifetime spectrometer

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Chinese Physics C 2011年第1期35卷 100-103页

作者：李道武刘军辉章志明王宝义张天保魏龙 key-laboratory of nuclear analysis techniques Institute of High Energy PhysicsChinese Academy of Sciences Graduate University of Chinese Academy of Sciences

Using LYSO scintillator coupled on HAMAMATSU R9800 （a fast photomultiplier） to form the small size γ-ray detectors, a compact lifetime spectrometer has been built for the positron annihilation experiments. The system time resolution FWHM=193 ps and the coincidence counting rate -8 cps/p.Ci were achieved. A lifetime value of 219±1 ps of positron annihilation in well annealed Si was tested, which is in agreement with the typical values published in the previous lectures.

关键词： compact PLS LYSO positron annihilation