arXiv subjects

Rui Qiu

Publications and source records attributed to Rui Qiu.

21 records · Page 2Linked to original sources

arXiv2016

Improved Algorithms and Coupled Neutron-Photon Transport for Auto-Importance Sampling Method

The Auto-Importance Sampling (AIS) method is a Monte Carlo variance reduction technique proposed for deep penetration problems, which can significantly improve computational efficiency without pre-calculations for importance distribution. However, the AIS method is only validated with several simple examples, and cannot be used for coupled neutron-photon transport. This paper presents the improved algorithms for the AIS method, including particle transport, fictitious particles creation and adjustment, fictitious surface geometry, random number allocation and calculation of the estimated relative error. These improvements allow the AIS method to be applicable to complicated deep penetration problems with complex geometry and multiple materials. A coupled Neutron-Photon Auto-Importance Sampling (NP-AIS) method is proposed to solve the deep penetration problems of coupled neutron-photon transport using the improved algorithms. The NUREG/CR-6115 PWR benchmark was calculated by using the methods of NP-AIS, geometry splitting with Russian roulette and the analog Monte Carlo, respectively. The calculation results of NP-AIS were in good agreement with those of geometry splitting with Russian roulette and the benchmark solutions. The computational efficiency of NP-AIS for both neutron and photon was much better than that of geometry splitting with Russian roulette in most cases, and increased by several orders of magnitude compared with that of the analog Monte Carlo.

nucl-th↗

arXiv2016

Characterization study of a broad-energy germanium detector at CJPL

The ability of background discrimination using pulse shape discrimination (PSD) in broad-energy germanium (BEGe) detectors makes them as competitive candidates for neutrinoless double beta decay (0ν\b{eta}\b{eta}) experiments. The measurements of key parameters for detector modeling in a commercial p-type BEGe detector are presented in this paper. Point-like sources were used to investigate the energy resolution and linearity of the detector. A cylindrical volume source was used for the efficiency calibration. With an assembled device for source positioning, a collimated 133Ba point-like source was used to scan the detector and investigate the active volume. A point-like source of 241Am was used to measure the dead layer thicknesses, which are approximately 0.17 mm on the front and 1.18 mm on the side. The described characterization method will play an important role in the 0ν\b{eta}\b{eta} experiments with BEGe detectors at China JinPing underground Laboratory (CJPL) in the future.

physics.ins-det↗

arXiv2015

Dose conversion coefficients for Chinese reference adult male and female voxel phantoms from idealized neutron exposures

A new set of fluence-to-dose conversion coefficients based on the Chinese reference adult voxel phantoms CRAM and CRAF are presented for six idealized external neutron exposures from 10-8 MeV to 20 MeV. The voxel phantoms CRAM and CRAF were adjusted from the previous phantoms CNMAN and CNWM respectively, and the masses of individual organs have been adjusted to the Chinese reference data. The calculation of organ-absorbed doses and effective doses were performed with the Monte Carlo transport code MCNPX. The resulting dose conversion coefficients were compared with those published in ICRP Publication 116, which represents the reference Caucasian. The organ-absorbed dose conversion coefficients of most organs are in good agreement with the results in ICRP Publication 116, however, obvious discrepancies are observed for some organs and certain geometries. For neutrons with energies above 2 MeV, the effective dose conversion coefficients of Chinese reference adult are almost identical to those of ICRP Publication 116 in AP, PA, ROT and ISO geometries. When energies range from 10-8 MeV to 1 MeV, differences are within 10% in AP (5%), PA (8%) and ROT (-4%) geometries. However, relatively large discrepancies are shown in lateral and ISO geometries when energies are below 1 MeV, with differences of -15% for LLAT, -20% for RLAT and -12% for ISO, respectively.

physics.med-ph↗