Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense

Beijing, China

Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense

Beijing, China

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Li J.-L.,Tsinghua University | Li J.-L.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | Li C.-Y.,Nuctech Company Ltd | Qiu R.,Tsinghua University | And 8 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2013

In order to study the influence of inelastic cross sections on the simulation of direct DNA strand breaks induced by low energy electrons, six different sets of inelastic cross section data were calculated and loaded into the Geant4-DNA code to calculate the DNA strand break yields under the same conditions. The six sets of the inelastic cross sections were calculated by applying the dielectric function method of Emfietzoglou's optical-data treatments, with two different optical datasets and three different dispersion models, using the same Born corrections. Results show that the inelastic cross sections have a notable influence on the direct DNA strand break yields. The yields simulated with the inelastic cross sections based on Hayashi's optical data are greater than those based on Heller's optical data. The discrepancies are about 30-45% for the single strand break yields and 45-80% for the double strand break yields. Among the yields simulated with cross sections of the three different dispersion models, generally the greatest are those of the extended-Drude dispersion model, the second are those of the extended-oscillator-Drude dispersion model, and the last are those of the Ashley's δ-oscillator dispersion model. For the single strand break yields, the differences between the first two are very little and the differences between the last two are about 6-57%. For the double strand break yields, the biggest difference between the first two can be about 90% and the differences between the last two are about 17-70%. © 2013 Elsevier B.V. All rights reserved.


Xie W.,Tsinghua University | Xie W.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | Li J.,Tsinghua University | Li J.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | And 7 more authors.
Radiation Protection Dosimetry | Year: 2013

In Monte Carlo simulation of DNA damage, the geometric model of DNA is of great importance. To study the influence of DNA model on the simulation of DNA damage, three DNA models were utilised in this paper. They were a volume model and two atomic models with different parameters. A direct DNA strand break induced by low-energy electrons was simulated, respectively, with the three models. The results show that most of the energy depositions in the DNA segments do not lead to strand breaks. The simple single-strand break (SSB) tends to be the predominant damage type, and the contribution of complex double-strand break (DSB) to the total DSB cannot be neglected. Among the yields of all the three DNA target models applied here, the yields of the volume model are the highest, the yields of the atomic model with double van der Waals radii (r) take the second place, whereas the yields of the atomic model with single r come last. On average, the ratios of SSB yields are approximately equivalent to the corresponding ratios of the models' volume. However, there seems to be no clear relationship between the DSB yields and the models' volume. © The Author 2013. Published by Oxford University Press. All rights reserved.


Ma H.,Tsinghua University | Ma H.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | Zeng Z.,Tsinghua University | Zeng Z.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | And 7 more authors.
Acta Oceanologica Sinica | Year: 2011

234Th was utilized as a tracer of particulate organic carbon (POC) export in the northwestern South China Sea (SCS) on the basis of the data collected at four stations during a spring cruise. Depth profiles of dissolved and particulate 234Th activities were measured in the upper 60 m, showing a significant deficit relative to 238U over the investigated stations. A stratified structure of 234Th- 238U disequilibrium was in general observed in the upper 60 m water column, indicating that the euphotic zone of the northwestern SCS in this reason can be divided into two layers, an upper and lower layer, with different export rates. POC export fluxes were estimated from a one-dimensional steady state model of 234Th fluxes in combination with the measurement of POC/ 234Th ratios on suspended particles. The POC export in this region ranged from 8.2 to 20.0 mmol/(m 2•d), with an average of 16.0 mmol/(m 2•d), and was slightly higher than those previously reported in the southern SCS. © 2011 The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg.


Sheng X.H.,Tsinghua University | Sheng X.H.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | Hui H.W.,Tsinghua University | Hui H.W.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense
Science China: Physics, Mechanics and Astronomy | Year: 2011

In this article, we present the design of the beam transport line and injection system of the compact storage ring for the Tsinghua Thomson scattering X-ray (TTX) source. The layout of the beam transport line fits in with the limited available space. The injection system is simplified, consisting of only one single kicker; the stray field on the reference orbit is also reduced without the septum magnet. We choose a travelling wave kicker and present both 2D and 3D simulations for the structure design. © Science China Press and Springer-Verlag Berlin Heidelberg 2011.


Huo Z.-X.,Tsinghua University | Huo Z.-X.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | Zhou J.-F.,Tsinghua University | Zhou J.-F.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense
Research in Astronomy and Astrophysics | Year: 2013

The hard X-ray modulation telescope (HXMT) mission is mainly devoted to performing an all-sky survey at 1-250 keV with both high sensitivity and high spatial resolution. The observed data reduction as well as the image reconstruction for HXMT can be achieved by using the direct demodulation method (DDM). However the original DDM is too computationally expensive for multi-dimensional data with high resolution to be employed for HXMT data. We propose an accelerated direct demodulation method especially adapted for data from HXMT. Simulations are also presented to demonstrate this method. © 2013 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd.


Du Y.-C.,Tsinghua University | Du Y.-C.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | Huang W.-H.,Tsinghua University | Huang W.-H.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | And 2 more authors.
Chinese Physics C | Year: 2012

We propose and analyze a scheme to produce comb bunches, i.e. a bunch consisting of micro-bunch trains, with tunable subpicosecond spacing. In the scheme, the electron beam is first deflected by a deflecting cavity which introduces a longitudinal-dependent linear transverse kick to the particles. After passing through a drift space, the transverse beam size is linearly coupled to the longitudinal position of the particle inside the beam, and a mask is placed there to tailor the beam, then the mask distribution is imprinted on the beam's longitudinal distribution. A quadrupole magnet and another deflecting cavity are used in the beam line to compensate the transverse angle due to the first deflecting cavity. Analysis shows that the number, length, and spacing of the trains can be controlled through the parameters of the deflecting cavity and the mask. Such electron bunch trains can be applied to an infrared free electron laser, a plasma-wakefield accelerator and a supper-radiance THz source. © 2012 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.


Li X.,Tsinghua University | Li X.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | Zheng S.-X.,Tsinghua University | Zheng S.-X.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense
Chinese Physics C | Year: 2011

The waveguide to coaxial cable adapter is very important to the cavity beam position monitor (CBPM) because it determines how much of the energy in the cavity could be coupled outside. In this paper, the waveguide to coaxial cable adapter of a CBPM is designed and experiments are conducted. The curve shapes of experiments and simulations are very similar and the difference in reflection is less than 0.1. This progress provides a reliable method for designing the adapter. © 2011 Chinese Physical Society.


Huo Z.-X.,Tsinghua University | Huo Z.-X.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | Zhou J.-F.,Tsinghua University | Zhou J.-F.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2012

We present in this article the use of probabilistic background constraints in astronomical image deconvolution to approach a solution as an interval estimate. We elaborate our objective-the interval estimate of the unknown object from observed data and our approach-Monte Carlo experiment and analysis of marginal distributions of image values. One-dimensional observation and deconvolution using the proposed approach are simulated. Confidence intervals revealing the uncertainties due to the background constraint are calculated and significance levels for sources retrieved from restored images are provided. © 2012 Optical Society of America.


Qiu R.,Tsinghua University | Qiu R.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | Li J.,Tsinghua University | Li J.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | And 3 more authors.
Journal of Nuclear Science and Technology | Year: 2012

A group of Monte Carlo simulations has been performed for external neutron dosimetry calculation based on a whole-body mathematical model. The Chinese mathematical phantom (CMP) is a mathematical human body model developed based on methods of ORNL (Oak ridge National Laboratory) mathematical phantom series (OMPS), and data from Chinese reference man and reference Asian man. Fluence-to-absorbed dose conversion coefficients of 24 organs and tissues for monoenergetic neutron beams ranging from 10 -9 to 10 2 MeV were calculated using the Monte Carlo code MCNPX. Irradiation conditions include anterior-posterior, posterior-anterior, right lateral, left lateral, rotational, and isotropic geometries. Results for the different organs are compared with those recommended in International Commission of Radiological Protection (ICRP) publication 74 and results obtained based on the visible Chinese human (VCH) phantom. Overall the consistency among the three sets of data was observed, but significant deviations up to 30-50% were also found in the AP, PA and lateral irradiation conditions. Since CMP represents the Chinese population, this work is helpful as a reference to investigate the difference of the neutron induced organ doses due to the anatomical variation between the Chinese and the Caucasians, and that between the average population and an individual. © 2012 Atomic Energy Society of Japan. All rights reserved.


Su G.,Tsinghua University | Su G.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | Zeng Z.,Tsinghua University | Zeng Z.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | And 2 more authors.
Radiation Protection Dosimetry | Year: 2011

Monte Carlo simulation of energy-response functions of gamma rays from natural/artificial radionuclides in seawater and simulation of energy spectrum due to self-activity in LaBr crystal were carried out using MCNPX codes and MATLAB programs for the in situ LaBr gamma-ray spectrometer immersed in homogeneous seawater. The effective detection distance, the detection efficiency and the minimum detectable activity concentration (MDAC) for artificial radionuclides 137Cs were worked out as an instance. Similar researches for NaI detector was also implemented for comparison. The results indicate that the self-activity in LaBr deteriorates the MDAC to merely several times of that of NaI detector. The LaBr detector is possible to be used as in situ gamma-ray spectrometer for monitoring of artificial radionuclides in seawater. © The Author 2011. Published by Oxford University Press. All rights reserved.

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