Radiation shielding design of the CFETR polarimeter interferometer and CO_(2) dispersion interferometer

A three-wave based laser polarimeter/interferometer and a CO_(2)laser dispersion interferometer are used to determine the electron and current density profiles on a Chinese fusion engineering test reactor(CFETR).Radiation shielding is designed for the combination of polarimeter/interferometer and CO_(2)dispersion interferometer.Furthermore,neutronics models of the two systems are developed based on the engineering-integrated design of CFETR polarimeter/interferometer and CO_(2)dispersion interferometer and the major material components of CFETR.The polarimeter/interferometer and CO_(2)dispersion interferometer's neutron and photon transport simulations were performed using the Monte Carlo neutral transport code to determine the energy deposition and neutron energy spectrum of the optical mirrors.The energy depositions of the first mirrors on the polarimeter/interferometer are reduced by three orders with the whole shielding.Since the mirrors of CO_(2)dispersion interferometer are very close to the diagnostic first wall,shielding space is limited and the CO_(2)dispersion interferometer energy deposition is higher than that of the polarimeter/interferometer.The dose rate after shutdown106s in the back-drawer structure has been estimated to be 83μSv h^(-1)when the radiation shield is filled in the diagnostic shielding modules,which is below the design threshold of 100μSv h^(-1).Radiation shielding design plays a key role in successfully applying polarimeter/interferometer and CO_(2)dispersive interferometer in CFETR.

Study of shielding design for SANS at CSNS

The small angle neutron scattering （SANS） instrument is presently being constructed at Chinese Spal- lation Neutron Source （CSNS） in China, and the biological shielding design is needed to prevent the instrument from causing excessive dose rates in accessible locations. In this paper, the study of shielding design for SANS that relies on Monte Carlo simulation is introduced. Beam line shielding calculations are performed considering both scenarios of closed versus open TO chopper. The basic design scheme of the beam stop is discussed. The size of the TO chopper rotor is also estimated.

High Magnetic Field Shielding for Sensitive Devices Relevant to ITER

High magnetic field shielding has been increasingly important for engineering design in recent years. In this report, a cylindric shield made from soft iron is studied using FEM （finite element method） analysis and COlnpared with experiments. The residual fields inside the shield are calculated and measured in both parallel and perpendicular fields up to 2000 Gs. The calculated results are compared with the experiments, and the input B-H curve is modified for a better conformity. The results indicate that the covers could greatly improve the shielding performance of the cylindric shield in our research. The comparison result shows that a proper B-H curve, which can well describe the material properties, is very important in FEM analysis and should be selected carefully.

Radiation protection designs of the linac for the HEPS

Purpose The high-energy photon source(HEPS)is the first fourth-generation light source under construction in China.It is designed to operate at an average current of 200 mA stored beam current with a top-up model at 6 GeV energy.Considering the linac radiation shielding design,a suitable beam loss scenario,optimized thickness for the bulk shielding and detailed structure design for dumps should be proposed.In this paper,the beam loss scenarios were determined and categorized as normal;the dose limits were presented;using these scenarios and the dose limits,the thickness of the linac tunnel was calculated and detailed designs of the main beam dumps were established.The material selection and size setting of the low-power electron beam dump were discussed.Method The Monte Carlo code is a good choice to simulate the radiation analysis.And the iSHIELD11 was used to verify the simulation calculations.Result and conclusion The designs of the linac bulk shield and dumps satisfied the requirements of radiation protection.

Study on the radiation problem caused by electron beam loss in accelerator tubes

The beam dynamic code PARMELA was used to simulate the transportation process of accelerating electrons in S-band SW linacs with different energies of 2.5, 6 and 20 MeV. The results indicated that in the ideal condition, the percentage of electron beam loss was 50% in accelerator tubes. Also we calculated the spectrum, the location and angular distribution of the lost electrons. Calculation performed by Monte Carlo code MCNP demonstrated that the radiation distribution of lost electrons was nearly uniform along the tube axis, the angular distributions of the radiation dose rates of the three tubes were similar, and the highest leaking dose was at the angle of 160° with respect to the axis. The lower the energy of the accelerator, the higher the radiation relative leakage. For the 2.5 MeV accelerator, the maximum dose rate reached 5% of the main dose and the one on the head of the electron gun was 1%, both of which did not meet the eligible protection requirement for accelerators. We adopted different shielding designs for different accelerators. The simulated result showed that the shielded radiation leaking dose rates fulfilled the requirement.