最新刊期
      卷 0 ， 期 0 ， 2020
      • Issue 6, (2000)
        摘要：The fatigue of aluminum and steel samples was studied by using positronarmihilation technique(PAT) and ultrasonic decay method, respectively. When thenumber of fatigue cycle is small, some of positron parameters increase with theincrement of fatigue cycles because of the extreme sensitivity of positron to verysmall vacancies. But some structural transformation might happen when the numberof fatigUe cycle is large enough. For example some vacancies might aggregate andform vacancy clusters. Some dislocations might annex or tangle. These kinds oftransformation in structure will reduce the density of vacancies and dislocations,which is responsible for the decreasing trend of the curve after the average lifetimeof positron achieves its maximum. The result of ultrasonic decay constantmeasurement also shows similar trend.  
        关键词：Positron annihilation;Ultrasonic decay method;Fatigue   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：The radiation defects and damage in N-type GaP irradiated by 85MeV 19F ionsat fluences of 2.4 ×10 15/cm2 and 2.2× 1016/cm2 as a function of annealing temperaturefrom 300K to 1023K were investigated by positron annihilation lifetime technique.Monovacancies were created in the irradiated N-type GaP, and the concentration ofmonovacancies was proportional to the irradiation fluence. Defects more complicatedthan di-vacancies in the high fluence irradiated GaP and di-vacancies in lowfluence irradiated GaP were observed during annealing process, respectively. Thecomplete annealing temperature of the defects for low fluence irradiated GaP was250K lower than that for high fluence irradiated GaP.  
        关键词：GaP;19F ions;Radiation damage;Annealing effect;Positron annihilation   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：The CoFe2O4 ferrofluid was studied by positron annihilation technique. Theexperimental results showed that there were three kinds of lif e-time stateτ1= 151.0ps, τ2 = 457.9ps and τ3 = 2325.6ps in the positron annihilation spectrum. Itindicated that there were a large number of vacancy and vacancy cluster in thesurface layer of the CoFe2O4 nanoparticles.  
        关键词：Ferrofluid;Positron annihilation;CoFe2O4 nanoparticle;Vacancy;Vacancy cluster   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：A structure of InP(InGaAsP)/InP was grown by He Plasma Assisted MolecularBeam Epitaxy (PAMBE). The epitaxy layer had a high resistivity and very fast lightresponse. The results of positron annihilation spectrum showed that those electricand optical characteristics were linked with the defects and its evolution created byPAMBE.  
        关键词：Low energy positron annihilation;He plasma;Molecular beam epitaxy   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：An investigation of positron lifetime spectrum for ZnO varistor cera-micsfabricated by Sol-gel route was carried out. The relationship between lifetimeparameters and the densitification and nonlinear coefficient a was given. Thedependence of electrical properties on sintering temperature and duration wasdiscussed.  
        关键词：ZnO varistor ceramics;Sol-gel route;Positron lifetime spectrum   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：In this report, the porous silicon formed by anodization of crystal silicon wasstudied by positron annihilation technique (PAT) and scanning electron microscopy(SEM). The PAT experiments showed that the mean life and vacancy defectsincreased with the increasing anodization time. While the intensities of the longestlifetime, several ns~tens ns (orth- positronium) droped down. Small single-crystal Sispheres with mean radius of a few μm were observed by SEM after anodization. Pitswith mean radius of a few U m from the divorcement of single-crystal spheres werealso observed after further anodization. The increases of vacancy defects might bethat the extension of structures of porous silicon towards inner layer withanodization tAne and caused more vacancy defects in inner layer. Our SEMobservation presented another possibility of the increase of density of vacancy defectsin surface layer induced by the change of structures.  
        关键词：Positron annihilation;Scanning electron microscopy;Porous silicon   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：The microstructures of vacancy-type defect in HgCdTe (MCT) samples grownunder micro-gravity condition were studied by positron lifetime measurements. Theresults showed that, the defect concentrations in the samples grown under spacendcro-gravity were lower than those grown under earth gravity on the ground. Thedistribution of defect concentration along the axial in the samples grown under spacemicro-gravity were more uniform than that grown under earth gravity on theground.  
        关键词：Microgravity;Defect;HgCdTe   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：The reaction mechanism of irradiation induced grafting co-polymerization offluoride polymer is investigated by positron annihilation lifetAne technique. Theresults indicated that γ-irradiation induced grafting changed the structure ofcondensed state of polymer. With increasing irradiation dose, graft rate raised andthe long lifetime of positron annihilation changed significantly. It show thatirradiation- grafted reaction is mainly localized in non- crystflllite as well as interfacebetween non-crystallite and crystallite.  
        关键词：Positron annihilation lifetime;Irradiation;Irradiation induced grafting   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：Polyvinyl chloride (PVC) blended material which was filled with ACR toughenparticles was studied by positron annihilation technique (PAT). The result showedthat, with the increasing proportion of ACR particles in the material, the stroryelecbegativity of chloride atom in PVC decreased, and the dimension and quantityof free volume defects in the main- chain of PVC increased.  
        关键词：Positron annihilation;Polyvinyl chloride;Modification;Free volume   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：In this article, positron annihilation technique was used to study the free volumeof PTFE, nylon and PBT after fretting, the result indicated that fretting caused thesize of average free volume to increase and made polymer wear out and invalid.  
        关键词：Positron annihilation;Polymer;Fretting;Free volume   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：Monte-Carlo method was applied to calculate the annihilation probabilities ofpositrons from 22Na in Mylar and Ni films with different thickness. Results ofsubstrate effects of Mylar films with different thickness for sample of Si, Fe, PE andPP were obtained. The results showed that the substrate effects for samples PE andPP were stronger than those for Si and Fe. Therefore it is feasible for usingMonte-Carlo method to calculate substrate effect.  
        关键词：Monte-Carlo simulation;Positron annihilation lifetime spectrum;Substrate effect   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：Image plate can be used as a two-dimension positioncasensitive detector forpositrons. In the sodium-22 source experiment, a linear relation between the positronfluence f(e+ ) and output signal intensity f(p) was obtained, written as f(p)=bf (e+ ), b= 1.38×10-5. Since the pixel size of the image plate was 25 μ m × 25 μm forthe analyzer, we used it on our slow positron beam line and gained a meaningfulpicture, the slow positron beam spot and corresponding intensity could be shown atthe same timc. This two dimensional positiontalsensitive detector is a extremelyuseful tool for detecting slow positron.  
        关键词：Image plate;Positron;Slow positron beam line   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：A Monte-Carlo simulation about the positron source used on the BEPC andBFEL LINAC-based slow positron beam lines was reviewed. The results showed thatwhen the BEPC LINAC was operated under parasitic condition, the fast positronyield of BEPC LINAC-based Slow Positron Beam Line were 1.84 ×1010e+ /s for Tatarget, the slow positron yield was about 106 to 107e+/s. When the BFEL LINAC wasoperated under parasitic condition, the fast positron yield was 3.9 × 1011e+/s and theslow positron yield was about 107 to 10°e+/s.  
        关键词：EGS4;Electron linear accelerator;Slow positron beam line   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：The updated analysis program CONTIN(PALS2) based on the Laplace inversionof positron anniliilation spectra has been studied comprehensively. The principle andutilisation of the program have been explained exhaustively- Three auxiliaryprograms have been made to help the transportation of data and adjustment of thedata’s pattern. Four experiments have been made, the results computed by programCoNTIN(PALS2) have been analyzed, and compared with those by POSIREONFITprogram  
        关键词：Positron lifetime spectrum program;CONTIN(PALS2)   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：Experimental results obtained by PIXE technique on some fake Ming- ChenghuaBlue-and-White porcelains made in the early period of Ching dynasty were reportedin this paper. The chemical composition of both body and glaze were measured, andby choosing a set of proper parameters, we can distinguish the fake ones from theoriginal Chenghua Blue- and-White porcelains.  
        关键词：PIXE;Ancient fake porcelain;Blue-and-White porcelain;Body;Glaze   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：The research progress of positron, antimatter and antihydrogen in the past threeyears is reviewed  
        关键词：Antimatter;Antiparticle;Positron;Antihydrogen   
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        发布时间：2021-03-12
      • Issue 6, (2000)
        摘要：The development of radiation vulcanized rubber and its applications,characteristics of the technique, the domestic progress in radiation rubber curing andindustrialization scale of radiation processing abroad were reviewed.  
        关键词：Radiation curing of rubber;Radiation precuring of rubber;Tire manufacture;Tire component;Radiation vulcanization   
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        发布时间：2021-03-12
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