Real-time wide-range neutron flux monitor for thorium-based molten salt reactor

A novel full-digital real-time neutron flux monitor(NFM) has been developed for thorium-based molten salt reactor(TMSR).The system is based on the highspeed,parallel,and pipeline processing of the field programmable gate array as well as the high-stability controller area network platform.A measurement range of 10~8 counts per second is achieved with a single fission chamber by utilizing the normalization of the count and Campbell algorithms.With the advantages of using the measurement range,system integrity,and real-time performance,digital NFM has been tested in the Xi'an pulsed reactor fission experiments and was found to exhibit superior experimental performance.     

ITER中子通量监测器的优化计算

中子通量监测器(NFM)可实现ITER实时的中子通量测定,转化得到聚变功率,功率密度,等离子体温度等。获得NFM探测效率对能量的相对平坦响应对准确诊断十分必要。论文针对特定的NFM裂变室结构,运用MCNP—4C对裂变室包裹层慢化剂/屏蔽材料种类及厚度进行了优化计算。这些工作对探测器裂变室结构的优化设计实验标定及定型具有重要意义。     

数字化多通道宽量程ITER中子通量密度测量系统研制

针对国际热核聚变实验堆(ITER)对中子通量密度测量宽量程、高集成度、实时性的要求,设计了一套基于PXI架构的多通道中子通量密度测量系统。该系统包括新研制的电流灵敏前置放大器及基于高速模数转换器(ADC)和可编程逻辑器件(FPGA)的主电子学插件。通过全数字化信号处理技术衔接脉冲计数和坎贝尔两种测量模式,大幅拓展了测量量程和提高了系统集成度。该系统通过使用脉冲堆积率估算算法,实现了测量模式的精确自动切换。实验结果表明,该系统具备单一裂变室大于1.7×10~(10)cm~(-2)·s~(-1)中子通量密度实时测量能力,全量程相对误差低于7.1%。     

A digital wide range neutron flux measuring system for HL-2A

To achieve wide-range, high-integration, and real-time performance on the neutron flux measurement on the HL-2A tokamak, a digital neutron flux measuring(DNFM) system based on the peripheral component interconnection(PCI) e Xtension for Instrumentation express(PXIe) bus was designed.This system comprises a charge-sensitive preamplifier and a field programmable gate array(FPGA)-based main electronics plug-in. The DNFM totally covers source-range and intermediate-range neutron flux measurements, and increases system integration by a large margin through joining the pulse-counting mode and Campbell mode. Meanwhile, the neutron flux estimation method based on pulse piling proportions is able to choose and switch measuring modes in accordance with current flux, and this ensures the accuracy of measurements when the neutron flux changes suddenly. It has been demonstrated by simulated signals that the DNFM enhances the full-scale measuring range up to 1.9?×?10~8cm~(-2)s~(-1), with relative error below 6.1%. The DNFM has been verified to provide a high temporal sensitivity at 10 ms time intervals on a single fission chamber on HL-2A.     

A study of beryllium moderator thickness for a fission chamber with fast neutron measurements

The detection efficiency of the fission chamber(FC) is very important for studying the neutron flux measurement(NFM) system in ITER. In this article, we mainly focus our attention on the influence of the moderator. With the Monte Carlo particle transport simulation tool named Geant4, we make a simulation of FC detection efficiency with different levels of thickness of a beryllium moderator.Two manufactured FCs for ITER-NFM systems are then used to test the parameters and performance. The test results agree well with our simulation.     

基于3层硅探测器的主动式中子个人剂量计研制

研制了一种具有能量分辨能力的中子个人剂量计。该个人剂量计由3层硅探测器组成，硅探测器周围装有⁶LiF、聚乙烯和含硼聚乙烯作为转化体、慢化体和吸收体。个人剂量计有直读和解谱两种工作模式。直读模式将中子能区划分为低能、中能和快中子3个能区，可实时测量。解谱模式可获得快中子能区的中子能量分布。利用GEANT4程序模拟了7 MeV γ射线的能量沉积谱，设置适当的甄别域以降低γ射线的影响。采用GEANT4程序模拟了个人剂量计对不同能量入射中子的个人剂量当量率响应。在加速器单能中子参考辐射场中完成了单能中子剂量响应的实验校准，对模拟计算的响应函数进行了实验修正，并得出了不同能区的平均中子个人剂量当量率响应。     

Counting and Integrating Readout for Direct Conversion X-ray Imaging: Concept, Realization and First Prototype Measurements

A novel signal processing concept for X-ray imaging with directly converting pixelated semiconductor sensors is presented. The novelty of this approach compared to existing concepts is the combination of charge integration and photon counting in every single pixel. Simultaneous operation of both signal processing chains extends the dynamic range beyond the limits of the individual schemes and allows determination of the mean photon energy. Medical applications such as X-ray computed tomography can benefit from this additional spectral information through improved contrast and the ability to determine the hardening of the tube spectrum due to attenuation by the scanned object. A prototype chip in 0.35-micrometer technology has been successfully tested. The pixel electronics are designed using a low-swing differential current mode logic. Key element is a configurable feedback circuit for the charge sensitive amplifier which provides continuous reset, leakage current compensation and replicates the input signal for the integrator. This paper will discuss measurement results of the prototype structures and give details on the circuit design     

大体积低能β量热装置研制

为了实现大体积样品放射性活度的非破坏性测量．研制了大体积低能β量热装置。该装置采用工作于伺服控制方式的等温型量热计原理．测量腔体积约3200cm3，热功率测量范豳30-2000mW.装置的实验验证表明：当热功率为300mW时，测量结果的扩展不确定度好于0．4％，平均测量时间小于3．5h。本文描述了装置的测量原理、系统组成、校准方法、性能测试及测量不确定度分析等。     

便携式2π粒子发射率测量系统研制

为满足现场测量需求,研制了便携式2π粒子发射率测量系统。系统基于流气式多丝正比计数器,设计了多道脉冲幅度分析处理模块,编制了上位机能谱测量软件,实现α、β平面源能谱的实时显示和能谱数据的离线分析处理,方便了β外推中的应用。实验结果表明:系统工作性能稳定,α能谱能量线性较好,实测发射率与标准值能够在不确定度范围内一致,结果偏差小于1%,能够满足2πα、2πβ粒子表面发射率准确测量的需求,为现场粒子发射率量值传递装置的建立奠定了基础。     

A precision control method for plasma electron density and Faraday rotation angle measurement on HL-2A

The precision of plasma electron density and Faraday rotation angle measurement is a key indicator for far-infrared laser interferometer/polarimeter plasma diagnosis.To improve the precision,a new multi-channel high signal-to-noise ratio HCOOH interferometer/polarimeter has been developed on the HL-2A tokamak.It has a higher level requirement for phase demodulation precision.This paper introduces an improved real-time fast Fourier transform algorithm based on the field programmable gate array,which significantly improves the precision.We also apply a real-time error monitoring module (REMM) and a stable error inhibiting module (SEIM) for precision control to deal with the weak signal.We test the interferometer/polarimeter system with this improved precision control method in plasma discharge experiments and simulation experiments.The experimental results confirm that the plasma electron density precision is better than 1/3600 fringe and the Faraday rotation angle measurement precision is better than 1/900 fringe,while the temporal resolution is 80 ns.This performance can fully meet the requirements of HL-2A.     

The upgraded laser in vessel viewing system (IVVS) for ITER

A prototype of a laser in vessel viewing and ranging system was developed at ENEA laboratories in Frascati, it uses the amplitude modulated laser radar concept and it is conceived to withstand the severe ITER conditions. The in vessel viewing system (IVVS) probe has been designed and built to perform sub-millimetric three-dimensional images inside ITER; it is based on an intrinsically radiation resistant concept and architecture. A first characterization of the IVVS probe under room conditions was made at Frascati Labs on a full-scale mock-up of the ITER first wall panel (FWP) and of the divertor vertical target. The first characterization demonstrated that an upgrade of the IVVS performances was necessary especially to cope with divertor surfaces made of carbon material, which is highly absorbent from optical point of view.The paper describes the new developments of IVVS prototype to increase range measurement performances that was obtained increasing the modulation frequency, the optical efficiency of the probe optics and the laser power. A new test campaign has been carried out on the upgraded IVVS and a compact characteristic curve describing its performances has been found both in mathematical and graphical form. As far as viewing is concerned, the system has confirmed the sub-millimetric viewing resolution, reaching in the worst cases ～1 mm of resolution. The image quality was excellent in almost all the cases. The range measurement performance of IVVS system has been strongly upgraded reducing the standard deviation of range measure of a factor varying from 6 to 12. The increased performance allows measuring surface shapes and erosion on first wall tiles and divertor also for inclination angles completely outside the previous IVVS characteristics.     

99Mo-99mTc发生器平衡活度测量系统

为满足^99Mo-^99mTc发生器批量生产的要求，研究了^99Mo-^99mTc发生器平衡活度测量系统。实现了放射性活度的实时在线测量。本文介绍了该系统的功能特点，系统配置及其性能，实验证明，该系统具有操作简便，测量快速准确等特点，测量的重复性及稳定性均优于0．5％，扩展不确定度＜5％。     

Real-Time Detection for Magnetic Island of Neoclassical Tearing Mode in EAST Plasma Control System

Accurate detection of a magnetic island in real time is one of the important issues for the tearing mode(TM) and neoclassical tearing mode(NTM) control.This paper presents a real-time detection system for the magnetic island of NTM control in the EAST Plasma Control System(PCS).Diagnosis is based on magnetic periodic perturbation and electron temperature fluctuation caused by the magnetic island.Therefore,a Mirnov measurement has been selected to calculate the island's parameters,such as island width,frequency of island rotation,and toroidal number.The electron cyclotron emission(ECE) system can detect the island position,which is calculated by two fast detection algorithms called correlation analysis and Hilbert transform.For future NTM control,real-time equilibrium reconstruction(rt-EFIT) is needed to locate the rational q-surface where the island is detected.This fast detection system is able to detect an island within 3 ms.It can be integrated into PCS to provide effective parameters of the island for NTM control by using EC resonance heating(ECRH) in the next experiment of EAST.     

Real-time fibre optic radiation dosimeters for nuclear environment monitoring around thermonuclear reactors

The ability of fibre optic sensors to operate in hazardous nuclear environments and their intrinsic immunity to electro-magnetic interference make fibre optic sensing a very promising technology for the future ITER thermonuclear fusion reactor. In this paper, we evaluate fibre optic sensing technology for monitoring radiation dose in the vicinity of ITER during its operation and during the maintenance periods.First, the performance of an OSL dosimeter interrogated remotely using radiation tolerant optical fibres is evaluated both for real-time and integrating measurements for doses exceeding 100 Gy. We demonstrate its satisfactory operation in a mixed gamma neutron field. Second, we discuss the successful calibration of a new scintillating fibre optic radiation probe based on CsI(TI) crystals for operation in the dose-rate range 0.3-3000 mGy/h. The CsI(TI) crystal scintillator is mounted at the end of a 10-m long multimode fibre transceiver link to allow for remote deployment. The probes can detect and measure gamma dose rates ranging from 1 to 1000 mGy/h. Finally, we investigate the possible use of commercially available PMMA plastic optical fibres as on-line dosimeters up to 34 kGy. The dose measurement is derived from the radiation-induced attenuation in the optical fibre itself. A novel interrogation scheme based on a ratiometric technique is proposed for real-time dosimetry.     

Estimation of precursor concentration in a research reactor by using second order sliding mode observer

The paper pertains to novel higher order sliding mode observer (SMO) design for estimating precursor concentration of a nuclear research reactor. The linear and nonlinear models of Pakistan Research Reactor-1 (PARR-1) have been tuned and validated with experimental data. These models are subsequently used for higher order sliding mode observer design and performance evaluation. In thermal reactors, precursor concentration is a very important reactor variable because it is responsible for delayed neutron production and finally for reactor control. Linear observers have been used in the past to estimate precursor concentration, but the bandwidth is much limited and performance degraded as the operating point is changed. The nonlinear observer can cater for this problem in a much efficient manner. In this paper a robust nonlinear observer for estimating precursor concentration has been developed by using second order sliding mode technique. The higher order sliding mode observer is efficient and has the main advantage of reduced chattering. The observer estimates the precursor concentration with the measurement of neutron flux only and the estimated value is in close agreement with the theoretically calculated value.     

TAM-Ⅱ型空气中氚监测仪的研制

介绍了TAM－Ⅱ型实时连续氚监测仪的研制。仪器的探测器由4个对称放 置的有效体积为2L丝壁电离室构成,使电离室对被监测氚产生的记忆效应减到最小,对γ本底的补偿,在几乎所有方向好于97％。该探测器配备一台工作在微电流积分模式的场效应管静电计,氚监测仪的测量过程由一个单片机自动控制,如自动转换量程,数据显示、储存与处理。该 监测仪的测量范围为6－10^6Bq/L,特别适用于氚设施和实验室手套箱或烟囱排出氚的连续自动监测。     

The Real-Time,High Precision Phase Difference Measurement of Electron Density in HL-2A Tokamak

This paper introduces a real-time high precision measurement of phase difference based on Field Programmable Gate Array (FPGA) technology, which has been successfully applied to laser grating interference measurement and real-time feedback of plasma electron density in HL-2A tokamak. It can track the changes of electron density while setting the starting point of the density curve to zero. In a laboratory test, the measuring accuracy of phase difference is less than 0.1?, the time resolution is 80 ns, and the feedback delay is 180 μs.     

A data acquisition system for real-time magnetic equilibrium reconstruction on ASDEX Upgrade and its application to NTM stabilization experiments

The pre-emptive stabilization of a neoclassical tearing mode, NTM, requires the calculation of the tokamak magnetic equilibrium in real-time. A launcher mirror is positioned to deposit electron cyclotron current drive on the rational surface where the NTM should appear. A real-time Grad–Shafranov solver using constraints from magnetic probe, flux loop and Motional Stark Effect measurements has been developed to locate these rational surfaces and deliver this information to the mirror controller in real-time. A novel algorithm significantly reduces the number of operations required in the first and second step of the solver. Contour integrals are carried out to calculate the q profile as a function of normalized radius and the rational surfaces are found by spline interpolation. A cycle time of 0.6 ms for calculating two tokamak equilibria in parallel using four current basis functions with magnetic constraints only and using six current basis functions with magnetic and MSE constraints has been achieved. Using these tools, pre-emptive stabilization of a m/n = 3/2 NTM mode in ASDEX Upgrade could be demonstrated.     

Subcriticality Measurement by Neutron Source Multiplication Method with a Fundamental Mode Extraction

A new neutron multiplication method has been proposed for an accurate measurement of subcriticality. The proposed method consists of two correction processes for (1) extraction of the fundamental mode from measuring data of a neutron detector that contains higher modes as well as the fundamental mode feeding from an external neutron source and (2) spatial corrections for perturbations induced by a reactivity addition in the distributions of the fundamental mode and a neutron importance field. Feasibility of the proposed method has been verified from a numerical study, although under some limitations such that the neutron multiplying system to be analyzed is small-sized and a reactivity change takes place homogeneously in a fuel loaded region. With extraction of the fundamental mode and the spatial corrections, the subcriticality can be estimated accurately even with measuring data highly contaminated with higher modes due to a detector position near to an external point neutron source. For a future application to measurement of control rod bank worth of a nuclear power plant from measuring data during a reactor physical testing, some useful guidelines have been obtained.     

高性能微电流集成放大器的设计

介绍了用ICL7650运算放大器设计高性能微电流集成放大器的方法,阐述了电路的工作原理和提高放大器性能的措施,给出了实际应用的实验结果。该放大器测量范围10^-9～10^-12A,自换量程,自动校零,测量准确,工作稳定。