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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.


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.


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.


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.


Li J.-L.,Tsinghua University | Li J.-L.,Key Laboratory of High Energy Radiation Imaging Fundamental Science for National Defense | Li C.-Y.,NUCTECH Co. | 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.

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