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EFFECT OF IRRADIATION WITH SLOW NEUTRONS OF LOW fluence ON YBCO-SYSTEM SUPERCONDUCTORS

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Chinese Science Bulletin 1992年第23期37卷 1963-1966页

作者：金继荣金新张贻瞳鹿牧吉和林姚希贤 Department of Physics and State Key Laboratory of Solid State Microstructures Nanjing University Nanjing 210008 PRC

Ⅰ. INTRODUCTION Critical current density J_c varies with structural imperfections in non-ideal type-Ⅱ superconductors, and it is sensitive to the defect concentration. Neutron irradiation has been established as a useful tool to increase the defect concentration in superconducting materials. Many experiments have shown that neutron irradiation at a suitable fluence would

关键词： slow neutron of low fluence high- T_e superconductors irradiation-induced defects pinning centers dislocation loops

ACCURATE DETERMINATION OF NEUTRON fluence IN FISSION TRACK DATING

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Chinese Science Bulletin 1990年第12期35卷 983-987页

作者：赵云龙 Beijing Geology Research Institute of Nuclear Industry Beijing 100013 PRC

Age determination using the fission track technique depends upon the accurate neutron fluence and the fission cross section value of 235U. The neutron fluence determined commonly by Au and Co monitors or the B value（ψ=BPd, ψ=thermal fluence; pd=induced fission track density in uranium standard dosimetric glass after neutron irradiation）of

关键词： neutron fluence fission track dating B value.

An Automatic Approach for Satisfying Dose-Volume Constraints in Linear fluence Map Optimization for IMPT

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Journal of Cancer Therapy 2014年第2期5卷 198-207页

作者： Maryam Zaghian Gino Lim Wei Liu Radhe Mohan Department of Industrial Engineering University of Houston Houston USA Department of Radiation Oncology Mayo Clinic Phoenix USA Department of Radiation Physics The University of Texas MD Anderson Cancer Center Houston USA

Prescriptions for radiation therapy are given in terms of dose-volume constraints (DVCs). Solving the fluence map optimization (FMO) problem while satisfying DVCs often requires a tedious trial-and-error for selecting appropriate dose control parameters on various organs. In this paper, we propose an iterative approach to satisfy DVCs using a multi-objective linear programming (LP) model for solving beamlet intensities. This algorithm, starting from arbitrary initial parameter values, gradually updates the values through an iterative solution process toward optimal solution. This method finds appropriate parameter values through the trade-off between OAR sparing and target coverage to improve the solution. We compared the plan quality and the satisfaction of the DVCs by the proposed algorithm with two nonlinear approaches: a nonlinear FMO model solved by using the L-BFGS algorithm and another approach solved by a commercial treatment planning system (Eclipse 8.9). We retrospectively selected from our institutional database five patients with lung cancer and one patient with prostate cancer for this study. Numerical results show that our approach successfully improved target coverage to meet the DVCs, while trying to keep corresponding OAR DVCs satisfied. The LBFGS algorithm for solving the nonlinear FMO model successfully satisfied the DVCs in three out of five test cases. However, there is no recourse in the nonlinear FMO model for correcting unsatisfied DVCs other than manually changing some parameter values through trial and error to derive a solution that more closely meets the DVC requirements. The LP-based heuristic algorithm outperformed the current treatment planning system in terms of DVC satisfaction. A major strength of the LP-based heuristic approach is that it is not sensitive to the starting condition.

关键词： fluence Map Optimization (FMO) Linear Programming (LP) Nonlinear Programming (NLP) Dose-Volume Constraint (DVC) Intensity-Modulated Proton Therapy (IMPT)

Bragg accelerator optimization

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High Power Laser Science and Engineering 2014年第3期2卷 37-45页

作者： Adi Hanuka Levi Schchter Department of Electrical Engineering Technion–Israel Institute of Technology

We present the first steps of a design of the optimal parameters for a full Bragg X-Ray free electron laser(BX-FEL).Aiming towards a future source of coherent X-ray radiation,operating in the strong Compton regime,we envisage the system to be the seed for an advanced light source or compact medical X-ray source.Here we focus on the design of the accelerator parameters: maximum gradient,optimal accelerated charge,maximum efficiency,and ‘wake coefficient',which relates to the decelerating electric field generated due to the motion of a charged-line or train of charged-lines.Specifically,we demonstrate that the maximum efficiency has optimal value and given the fluence of the materials,the maximum accelerated charge in the train is constant.These two results might be important in any future design.

关键词： Bragg wake-field Compton scattering energy conversion efficiency fluence light source medical accelerator

Search for electron-antineutrinos associated with gravitational-wave events GW150914,GW151012,GW151226,GW170104,GW170608,GW170814,and GW170817 at Daya Bay

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Chinese Physics C 2021年第5期45卷 190-201页

作者： F.P.An A.B.Balantekin H.R.Band M.Bishai S.Blyth G.F.Cao J.Cao J.F.Chang Y.Chang H.S.Chen S.M.Chen Y.Chen Y.X.Chen J.Cheng Z.K.Cheng J.J.Cherwinka M.C.Chu J.P.Cummings O.Dalager F.S.Deng Y.Y.Ding M.V.Diwan T.Dohnal J.Dove M.Dvorak D.A.Dwyer J.P.Gallo M.Gonchar G.H.Gong H.Gong W.Q.Gu J.Y.Guo L.Guo X.H.Guo Y.H.Guo Z.Guo R.W.Hackenburg S.Hans M.He K.M.Heeger Y.K.Heng A.Higuera Y.K.Hor Y.B.Hsiung B.Z.Hu J.R.Hu T.Hu Z.J.Hu H.X.Huang X.T.Huang Y.B.Huang P.Huber D.E.Jaffe K.L.Jen X.L.Ji X.P.Ji R.A.Johnson D.Jones L.Kang S.H.Kettell S.Kohn M.Kramer T.J.Langford J.Lee J.H.C.Lee R.T.Lei R.Leitner J.K.C.Leung F.Li J.J.Li Q.J.Li S.Li S.C.Li W.D.Li X.N.Li X.Q.Li Y.F.Li Z.B.Li H.Liang C.J.Lin G.L.Lin S.Lin J.J.Ling J.M.Link L.Littenberg B.R.Littlejohn J.C.Liu J.L.Liu C.Lu H.Q.Lu J.S.Lu K.B.Luk X.B.Ma X.Y.Ma Y.Q.Ma C.Marshall D.A.Martinez Caicedo K.T.MeDonald R.D.McKeown Y.Meng J.Napolitano D.Naumov E.Naumova J.P.Ochoa-Ricoux A.OIshevskiy H.-R.Pan J.Park S.Patton J.C.Peng C.S.J.Pun F.Z.Qi M.Qi X.Qian N.Raper J.Ren C.Morales Reveco R.Rosero B.Roskovec X.C.Ruan H.Steiner J.L.Sun T.Tmej K.Treskov W.-H.Tse C.E.Tull B.Viren V.Vorobel C.H.Wang J.Wang M.Wang N.Y.Wang R.G.Wang W.Wang W.Wang X.Wang Y.Wang Y.F.Wang Z.Wang Z.Wang Z.M.Wang H.Y.Wei L.H.Wei L.J.Wen K.Whisnant C.G.White H.L.H.Wong E.Worcester D.R.Wu F.L.Wu Q.Wu W.J.Wu D.M.Xia Z.Q.Xie Z.Z.Xing J.L.Xu T.Xu T.Xue C.G.Yang L.Yang Y.Z.Yang H.F.Yao M.Ye M.Yeh B.L.Young H.Z.Yu Z.Y.Yu B.B.Yue S.Zeng Y.Zeng L.Zhan C.Zhang F.Y.Zhang H.H.Zhang J.W.Zhang Q.M.Zhang X.T.Zhang Y.M.Zhang Y.X.Zhang Y.Y.Zhang Z.J.Zhang Z.P.Zhang Z.Y.Zhang J.Zhao L.Zhou H.L.Zhuang J.H.Zou Instiute of Modern Physics East China University of Science and TechnologyShanghai 200237 University of Wisconsin MadisonWisconsin 53706 Wright Laboratory and Department of Physics Yale UniversityNew HavenConnecticut 06520 Brookhaven National Laboratory UptonNew York 11973 Department of Physics National Taiwan UniversityTaipei Institute of High Energy Physics Beijing 100049 National United University Miao-Li Department of Engineering Physics Tsinghua UniversityBejing 100084 Shenzhen University Shenzhen 518060 Sun Yat-Sen(Zhongshan)University Guangzhou North China Electric Power University Bejjing 102206 Chinese University of Hong Kong Hong Kong 999077 Siena College LoudonvilleNew York 12211 Department of Physics and Astronomy University of CaliforniaIrvineCaliformia 92697 University of Science and Technology of China Hefei 230026 Charles University Faculty of Mathematics and PhysicsPrague Department of Physics University of llinois at Urbana-ChampaignUrbanaIlinois 61801 Lawrence Berkeley National Laboratory BerkeleyCalifornia 94720 Department of Physics Illinois Institute of TechnologyChicagoIllinois 60616 Joint Institute for Nuclear Research DubnaMoscow Region Beijing Normal University Beijing 100875 Department of Nuclear Science and Technology School of Energy and Power EngineeringXi'an Jiaotong UniversityXi'an 710049 Department of Physics University of HoustonHoustonTexas 77204 China Institute of Atomic Energy Beijing 102413 Shandong University Jinan 250100 Guangxi University Nanning 530004 Center for Neutrino Physics Virginia TechBlacksburgVirginia 24061 Institute of Physics National Chiao-Tung UniversityHsinchu Department of Physics University of CincinnatiCincinnatiOhio 45221 Department of Physies Collge of Science and TechnologyTemple UniversityPhiladelphiaPennsylvania 19122 Dongguan University of Technology Dongguan 523808 Department of Physics University of CaliforniaBerkeleyCalifornia 94720 Department of Physics The University of Hong KongPokfulamHong Kong 999077 School

The establishment of a possible connection between neutrino emission and gravitational-wave(GW)bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge.In the Daya Bay experiment,using the data collected from December 2011 to August 2017,a search was per-formed for electron-antineutrino signals that coincided with detected GW events,including GW150914,GW151012,GW151226,GW170104,GW170608,GW 170814,and GW 170817.We used three time windows of±10,±500,and±1000 s relative to the occurrence of the GW events and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates.The detected electron-antineutrino candidates were consistent with the expected background rates for all the three time windows.Assuming monochromatic spectra,we found upper limits(90%confidence level)of the electron-antineutrino fluence of(1.13-2.44)×10^(11)cm^(-2)at 5 MeV to 8.0×10^(7)cm^(-2)at 100 MeV for the three time w indows.Under the assumption of a Fermi-Dirac spectrum,the upper limits were found to be(5.4-7.0)×10^(9)cm^(2)for the three time windows.

关键词： grav itational waves electron-antineutrinos fluence upper limit

Parameters measurement for the thermal neutron beam in the thermal column hole of Xi'an pulse reactor

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Science China(Technological Sciences) 2010年第5期53卷 1220-1224页

作者： ShuHuan Liu XinBiao Jiang YunHong Zhong QingYu Yu WenShou Zhang Kai Wang Jun Yang YingLin Wang School of Nuclear Science & Technology Xi’an Jiaotong University Xi’an China Northwest Institute of Nuclear Technology Xi’an China

The distribution of the neutron spectra in the thermal column hole of Xi'an pulse reactor was measured with the time-of-flight method.Compared with the thermal Maxwellian theory neutron spectra,the thermal neutron spectra measured is a little softer,and the average neutron energy of the experimental spectra is about 0.042±0.01 eV.The thermal neutron fluence rate at the front end of thermal column hole,measured with gold foil activation techniques,is about 1.18×105 cm-2 s-1.The standard uncertainty of the measured thermal neutron fluence is about 3%.The spectra-averaged cross section of 197Au(n,γ) determined by the experimental thermal neutron spectra is(92.8±0.93) ×10-24 cm2.

关键词： thermal neutron spectra time-of-flight method neutron fluence reactor

An Algorithm for the Reconstruction of Entrance Beam fluence from Virtual Patient Exit Electronic Portal Images

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2015年第2期4卷 177-183页

作者： Nicholas N. Sperling E. Ishmael Parsai Department of Radiation Oncology University of Toledo Medical Center Toledo USA

The problem of determining the in vivo dosimetry for patients undergoing radiation treatment has been an area of interest since the development of the field. More recent methods of measurement employ Electronic Portal Image Devices (EPID), or dosimeter arrays, for entrance or exit fluence determination. The more recent methods of in vivo dosimetry make use of detector arrays and reconstruction techniques to determine dose throughout the patient volume. One method uses an array of ion chambers located upstream of the patient. This requires a special hardware device and places an additional attenuator in the beam path, which may not be desirable. An alternative to this approach is to use the existing EPID, which is part of most modern linear accelerators, to image the patient using the treatment beam. Methods exist to deconvolve the detector function of the EPID using a series of weighted exponentials [1]. Additionally, this method has been extended to the deconvolution of the patient scatter in order to determine in vivo dosimetry. The method developed here intends to use EPID images and an iterative deconvolution algorithm to reconstruct the impinging primary fluence on the patient. This primary fluence may then be employed, using treatment time volumetric imaging, to determine dose through the entire patient volume. Presented in this paper is the initial discussion of the algorithm, and a theoretical evaluation of its efficacy using montecarlo derived virtual fluence measurements. The results presented here indicate an agreement of 1% dose difference within 95% the field area receiving 10% of the entrance fluence for a set of sample highly modulated fields. These results warrant continued investigation in applying this algorithm to clinical patient treatments.

关键词： Beam fluence EPID Images In-Vivo Dosimetry Monte Carlo Algorithm Dose Reconstruction

Hierarchical microstructures with high spatial frequency laser induced periodic surface structures possessing different orientations created by femtosecond laser ablation of silicon in liquids

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Opto-Electronic Advances 2019年第3期2卷 1-18页

作者： Dongshi Zhang Koji Sugioka RIKEN Center for Advanced Photonics WakoSaitama 351-0198Japan

High spatial frequency laser induced periodic surface structures(HSFLs)on silicon substrates are often developed on flat surfaces at low fluences near ablation threshold of 0.1 J/cm2,seldom on microstructures or microgrooves at relatively higher fluences above 1 J/cm^2.This work aims to enrich the variety of HSFLs-containing hierarchical microstructures,by femtosecond laser(pulse duration:457 fs,wavelength:1045 nm,and repetition rate:100 kHz)in liquids(water and acetone)at laser fluence of 1.7 J/cm^2.The period of Si-HSFLs in the range of 110–200 nm is independent of the scanning speeds(0.1,0.5,1 and 2 mm/s),line intervals(5,15 and 20μm)of scanning lines and scanning directions(perpendicular or parallel to light polarization direction).It is interestingly found that besides normal HSFLs whose orientations are perpendicular to the direction of light polarization,both clockwise or anticlockwise randomly tilted HSFLs with a maximal deviation angle of 50°as compared to those of normal HSFLSs are found on the microstructures with height gradients.Raman spectra and SEM characterization jointly clarify that surface melting and nanocapillary waves play important roles in the formation of Si-HSFLs.The fact that no HSFLs are produced by laser ablation in air indicates that moderate melting facilitated with ultrafast liquid cooling is beneficial for the formation of HSFLs by LALs.On the basis of our findings and previous reports,a synergistic formation mechanism for HSFLs at high fluence was proposed and discussed,including thermal melting with the concomitance of ultrafast cooling in liquids,transformation of the molten layers into ripples and nanotips by surface plasmon polaritons(SPP)and second-harmonic generation(SHG),and modulation of Si-HSFLs direction by both nanocapillary waves and the localized electric field coming from the excited large Si particles.

关键词： high spatial frequency laser induced periodic surface structures silicon laser ablation in liquids hierarchical microstructures femtosecond laser high fluence formation mechanism surface melting nanocapillary wave surface plasmon polaritons second-harmonic generation

Nanoscale Track Diameter and Hydrogen Yield: Dependence upon Charge State of Incident Ion on Polystyrene

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World Journal of Condensed Matter Physics 2013年第1期3卷 95-101页

作者： D. P. Gupta R. S. Chauhan Shyam Kumar P. K. Diwan S. A. Khan Ambuj Tripathi Santanu Ghosh V. K. Mittal Department of Applied Sciences Chitkara Institute of Engineering and Technology Chandigarh India Department of Physics Indian Institute of Technology New Delhi India Department of Physics Kurukshetra University Kurukshetra India Department of Physics Punjabi University Patiala India Department of Physics RBS College Agra India Inter University Accelerator Centre New Delhi India

The study of radiation damage of high- molecular weight substances due to MeV ion interactions is of interest for engineering and scientific applications. In the present study polystyrene (PS) was irradiated with 107Ag ions of three different charge states (q) 11+, 14+ and 25+ and of 130 MeV energy. The emission of hydrogen from PS was monitored as a function of the incident ion fluence. The experimental results showed that the hydrogen depletion per incident ion from PS varies as qn, where n was found to be 2.1 as compared to the value 2.7 to 3.0 reported in the literature. Radii of the nanometric damaged zones or ion tracks formed were analyzed from the slope of the hydrogen depletion versus ion fluence curves as a function of charge state of incident ion. These have values between 3.2 - 6.8 nm. These radii were found to depend upon the charge state of the incident ion and vary as qm, where m has the value 0.9.

关键词： Polystyrene Heavy Ions Ion fluence Hydrogen Depletion Cross-Section Track Radius