Dynamic linear calibration method for a wide range neutron flux monitor system in ITER

As a key part of the diagnosis system in the International Thermonuclear Experimental Reactor(ITER),the neutron flux monitor(NFM),which measures the neutron intensity of the fusion reaction,is a Counting-Campbelling system with a large dynamic counting range.A dynamic linear calibration method is proposed in this paper to solve the problem of cross-over between the different counting and Campbelling channels,and improve the accuracy of the cross-calibration for long-term operation.The experimental results show that the NFM system with the dynamic linear calibration system can obtain the neutron flux of the fusion reactor in real time and realize the seamless measurement area connection between the two channels.

Determination of spatial resolution of plastic scintillation fiber array with a simple method

The spatial resolution of a position sensitive gamma-ray detector configuration based on plastic scintillation fiber array was measured using a Monte Carlo simulation method. Both point spread function and modulation transfer function (MTF) were presented. The factors that influence the spatial resolution were also discussed. The results of the simulation showed that the intrinsic spatial resolution was consistent with the size of the physical pixels and a few centimeters spatial resolution could be obtained under certain circumstances.

An automatic gain adjustment Campbell integrator for neutron flux detection in ITER

Neutron Flux Monitor, a key diagnostic system in International Thermonuclear Experimental Reactor, may provide for reading a series of important parameters in fusion reaction process. We designed an important part of its main electronic system - Automatic Gain Adjustment Campbell Integrator (AGACI), expanding the detecting neutron counting rate of 104-108 cps (counts per second). The total gain of AGACI in five files is divided into 1, 10, 100, 1000, and 10 000 times, and can be automatically adjusted. The linear correlation coefficient (R) is more than 0.9999 in AGACI working range.

Simulation study of BGO array for characteristic gamma rays from neutron-stimulated elements

Characteristic gamma rays of 100 keV to about 6 MeV from different elements stimulated by neutrons have been applied to diagnosis biological imaging.In this paper,BGO detectors are used for the spectrum simulation. Signals from a single crystal and after correction are both obtained,and the energy spectrum summing adjacent signals seems possible to achieve excellent energy resolution for such high-energy photons.Some ideal suppositions are in- troduced and some other information,such as spatial resolution and difficult electronics,should be considered after this correction.

Simulation and calibration of the response function of multi-sphere neutron spectrometer

In order to realize the on-line real-time measurement of neutron spectrum of ITER fusion,this paper presents a multi-sphere spectrometer system which consists of eight thermal neutron detectors,namely SP9 3He proportional counter,embedded in eight different diameter polyethylene spheres.The response function of eight polyethylene spheres of multi-sphere neutron spectrometer was calculated after the simulation of the neutron transport processes in multi-sphere spectrometer by adopting software Geant4.The peak of the response function is in the low energy region for smaller diameter polyethylene sphere.As the polyethylene sphere diameter increased,the peak of the response function moves to the high energy region.The experimental calibration adopts 241Am-Be neutron source.The relative error between normalized data of experiment 4πsolid angle counts and normalized data of simulated detection efficiency of 4in to 8in polyethylene sphere is from 1.152%to 12.222%.The experimental results verify the response function of the simulation.All these results provide a theoretical and experimental basis for solving the on-line real-time neutron spectrum of ITER fusion.

Some characteristics of X-ray imaging for energy region of over 100 keV using plastic scintillation fiber array

In this work, characteristics of using PSFs (plastic scintillation fibers) coupled with CCD (charge-coupled devices ) to build area detectors for high energy X-ray imaging are studied with a Monte Carlo simulation, which cover an energy range of a few hundred keV to about 20 MeV. It was found that the efficiency of PSF in detecting X-ray with energy above a few hundred keV is low. We can use large incident flux to increase the output signal to noise ratio (SNR). The performance can also be improved by coating PSF with X-ray absorption layers and the MTF of the system is presented. By optimizing the absorption layer thickness, the crosstalk of the area detector built with PSF decreases.