Application of CMOS charge-sensitive preamplifier in triple-GEM detector

1 Introduction With novel materials and advanced technique of printed circuit board (PCB) and micro-electronics be- ing used in MPGD, over the past two decades, great progress has been made in MPGD[1], and as a new type of MPGD, the GEM[2] detector was developed during the late 1990s. Standard GEM from CERN is a thin, two-side copper-coated Kapton foil, perforated with a high density of holes etched using a photolitho- graphic process. The diameter of these holes is about 70 μm (ext…     

Design and test results of a low-noise readout integrated circuit for high-energy particle detectors

A low-noise readout integrated circuit for high-energy particle detector is presented.The noise of charge sensitive amplifier was suppressed by using single-side amplifier and resistors as source degeneration.Continuous-time semi-Gaussian filter is chosen to avoid switch noise.The peaking time of pulse shaper and the gain can be programmed to satisfy multi-application.The readout integrated circuit has been designed and fabricated using a 0.35 μm double-poly triple-metal CMOS technology.Test results show the functions of the readout integrated circuit are correct.The equivalent noise charge with no detector connected is 500–700 e in the typical mode,the gain is tunable within 13–130 mV/fC and the peaking time varies from 0.7 to 1.6 μs,in which the average gain is about 20.5 mV/fC,and the linearity reaches 99.2%.     

Application of a 6LiF Small Neutron Detector with an Optical Fiber to Tritium Production Rate Measurement in D-T Neutron Fields

⁶LiF small neutron detectors with an optical fiber have been used to measure ⁶Li(n,α)T reaction rate distributions at thermal research reactors and accelerator facilities. In the present study, we developed an experimental method for the measurement of tritium production rate (TPR) of ⁶Li using this small detector in deuterium-tritium (D-T) neutron fields. Reaction rate measurements with the detector were conducted in the D-T neutron fields at the Fusion Neutronics Source (FNS) facility. From the results, we determined that this detector can be used to measure the TPR distribution in soft neutron spectrum fields such as in a Be assembly. It is difficult to obtain ⁶Li(n,α)T reaction rate separately in hard neutron spectrum fields such as in a Li₂O assembly, because many kinds of charged particle production reactions need to be taken into consideration. However, a time-dependent reaction rate measurement method combined with the ⁶LiF detector and the ZnS detector is effective to separate the ⁶Li(n,α)T reaction from other reactions even in a hard spectrum field, and it can be applied to the measurement of the TPR distribution accurately.     

10 cm×10 cm Bulk Micromegas探测器的研制

Bulk Micromegas探测器是一种新型微结构气体探测器。利用光蚀刻技术制作了有效面积为10 cm×10 cm的多通道Bulk Micromegas探测器。对探测器的各通道进行了电容测试，显示探测器具有较好的均匀性。在Ar+10%CO₂气体中，使用⁵⁵Fe放射源和自主研制的基于APV25前端卡的数字化电子学，对制作的有效面积为10 cm×10 cm的探测器进行了测试，其结果显示探测器性能良好，能得到清晰的二维事件分布图。该探测器目前全部工艺国产化，并能进行批量生产，成品率接近100%。     

A new glass GEM with a single-sided guard-ring structure

The gas electron multiplier (GEM) is a gaseous detector that is widely used in many applications. Our glass GEM (G-GEM) comprises a photo-etchable glass (PEG3, HOYA Corporation, Japan). Our research indicated that it shows superior performance compared with other gas detectors. In this article, a new type of G-GEM is introduced. It has a guard-ring structure around the holes in order to improve the spark tolerance by reducing the total capacitance of each hole structure. A measured gas gain of approximately 7500 is attained for this new G-GEM with a single-sided guard-ring structure using a gas mixture of Ar (90%) and CH₄ (10%) in the gas flow mode. An energy resolution of 17.3% (FWHM) is also achieved with a collimated 6 keV X-ray beam. The results of a 10 to 12 hour gas gain stability measurements are also shown.     

Simple preparation of thin CR-39 detectors for alpha-particle radiobiological experiments

Alpha-particle radiobiological experiments involve irradiating cells with alpha particles and require accurate positions where the alpha particles hit the cells. In the present work, we prepared thin CR-39 detectors from commercially available CR-39 SSNTDs with a thickness of 100 μm by etching them in 1 N NaOH/ethanol at 40 °C to below 20 μm. The desired final thickness was achieved within ∼8 h. Such etching conditions can provide relatively small roughness of the detector as revealed by atomic force microscope, and thus provide transparent detectors for radiobiological experiments. UV radiation was employed to shorten track formation time on these thin CR-39 detectors. After exposure to UV light (UVA + B radiation) for 2-3 h with doses from 259 to 389 W/cm², 5 MeV alpha-particle tracks can be seen to develop on these CR-39 detectors clearly under the optical microscope within 2 h in 14 N KOH at 37 °C. As an example for practical use, custom-made petri dishes, with a hole drilled at the bottom and covered with a thin CR-39 detector, were used for culturing HeLa cells. The feasibility of using these thin CR-39 detectors is demonstrated by taking photographs of the cells and alpha-particle tracks together under the optical microscope, which can allow the hit positions on the cells by the alpha particles to be determined accurately.     

Portable spectroscopic fast neutron probe and 3He detector dead-time measurements

This paper presents dead-time calculations for the Portable Spectroscopic Fast Neutron Probe (N-Probe) using a combination of the attenuation law, MCNP (Monte Carlo N-particle Code) simulations and the assumption of ideal paralyzing and non-paralyzing dead-time models. The N-Probe contains an NE-213 liquid scintillator detector and a spherical ³He detector. For the fast neutron probe, non-paralyzing dead-time values were higher than paralyzing dead-time values, as expected. Paralyzing dead-time was calculated to be 37.6 μs and non-paralyzing dead-time was calculated to be 43.7 μs for the N-Probe liquid scintillator detector. Dead-time value for Canberra ³He neutron detector (0.5NH1/1K) was also estimated using a combination of subcritical assembly measurements and MCNP simulations. The paralyzing dead-time was estimated to be 14.5 μs, and the non-paralyzing dead-time was estimated to be 16.4 μs for ³He gas filled detector. These results are consistent with the dead-time values reported for helium detectors.     

Effect of O<Subscript>2</Subscript>/Ar Mixture on the Structural and Optical Properties of ZnO Thin Films Fabricated by DC Cylindrical Magnetron Sputtering

Direct Current Cylindrical Magnetron Sputtering Setup was used to deposit ZnO thin films on BK7 substrates. The effects of changing O₂/Ar reactive gas mixtures on the structural and optical properties of films were studied. Crystallinity and structure of films were obtained by X-ray diffraction (XRD). Preferential crystalline growth orientation of ZnO films detected by XRD was always along the (002) orientation. The thickness of films was measured by surface profilometer which showed thickness increasing from 68.7 to 80.8 nm for 3–6% O₂ amount respectively. The morphology and roughness of the films were investigated by Atomic Force Microscopy (AFM). As oxygen gas amount was increased, the roughness and the grain size were decreased and the deposition rate was increased. The optical transmittance of ZnO films are obviously affected by the changing of O₂/Ar reactive gas mixtures. All films exhibit a transmittance higher than 70% in the visible region. The optical band gap of films was measured by Tauc’s method. The results show that by increasing the amount of O₂ in reactive gas mixture, the optical band gap of deposited films increases.     

改善CeF_3闪烁探测器输出特性的方法研究

常用的CeF3闪烁探测器,由于闪烁体发光与光电器件光谱响应不完全匹配,使得探测器的主要输出特性——输出幅度和脉冲波形形状发生明显变化,较难依据相似性通过探测器输出复原得到辐射源的真实特征。本工作针对这种不完全匹配情况,分析比较了几种改善闪烁探测器输出的方法,提出了在CeF3无机闪烁体与光电器件光阴极之间加移波膜片耦合的方法。原理分析和实验测量结果表明:采取移波膜片耦合方法可使传统CeF3闪烁探测器输出特性得到明显改善,输出幅度增加50%以上,脉冲时间响应前沿由传统方式的12ns变化到移波方式的约3ns。     

Tests for “cold fusion” in the Pd-D2 and Ti-D2 systems at 40–380 MPa and −196-27°C

Experiments have been conducted on the Pd-D₂ and Ti-D₂ systems at 40–380 MPa and −196-27°C to investigate the possibility that “cold fusion” occurs in palladium and titanium deuterides generated by reaction with high-pressure D₂ gas. The experiments were performed using a 4.8 mm i.d. stainless steel pressure vessel that can be operated routinely at pressures as high as 400 MPa. In experiments completed to date, reactions between high-purity Pd or Ti and D₂ were monitored with: (1) an array of three BF₃ neutron detectors, (2) an internal, type-K sample thermocouple, and (3) an internal, type-K reference thermocouple located approximately 10 cm above the sample thermocouple. Using a²⁵²Cf source, the efficiency of the BF₃ detector array was determined to be approximately 6%. During experimentation, the three neutron detectors were immersed in a water bath thermostated at 27°C. The neutron count rate, D₂ pressure, sample and reference thermocouple readings, and bath temperature were recorded continuously at time intervals ranging from 6 seconds to 10 minutes. Experimental results obtained so far range from negative to potentially significant. No sustained heat production has been observed in any experiment. Thermal pulses that persist briefly after pressurizing Pd with D₂ gas are attributable to small amounts of chemical heat released when Pd and D₂ react to form palladium deuteride. No sustained neutron flux above background was observed in any Pd-D₂ experiment. On the other hand, in a Ti-D₂ experiment just completed, potentially significant results were obtained. During this experiment, there was a period of 5 consecutive hours when count rates rose to approximately 60 counts/hour above the average background rate. This detector count rate corresponds nominally to 1000 neutrons/hour emitted from the Ti-D₂ sample. However, due to several deficiencies in our neutron detection methods and equipment, we cannot demonstrate conclusively that our experimental data are valid. Consequently, we are upgrading our neutron detection equipment in preparation for a second, improved Ti-D₂ experiment.     

一种新型气体探测器的研制

加速器质谱(accelerator mass spectrometry,AMS)技术因探测对象不同,探测器也应根据需要进行选择。为建立低能量重离子加速器质谱测量技术,本文设计制作一台新型气体探测器并调试应用。该探测器采用厚度50 nm,膜面积8 mm×8 mm的氮化硅膜作为入射窗。采用5.48 MeV的241Am源的α粒子对探测器进行调试,调试后将该探测器安装于中国原子能科学研究院的300 kV小型AMS系统上进行129I粒子测量。经模拟计算以及对探测器的调试、应用,证明该探测器具有较高的能量分辨率,可以很好的实现不同粒子的鉴别,同时测量灵敏度可达到10^-13国际水平,满足低能量重离子的测量要求。     

Monte Carlo simulations of response functions for gas filled and scintillator detectors with MCNPX code

Monte Carlo simulation of a detector response function presents a very challenging problem. The detector response functions have been calculated for different neutron and gamma detectors: ³He gas filled proportional counter, NE213 organic scintillator, BrillanCe 350 or LaCl₃(Tl), and an ionization chamber with mixed gas composition. MCNPX code was used for simulations. The simulations were done with different neutron and gamma energies. The effects of neutron scattering, wall effects, recoil continua and contribution from charged particles have been included. The detector response function for the NE213 organic scintillator was obtained with consideration of light output curves of different products of neutron reactions with materials of the scintillator. The simulated data has been compared with experiments.     

Effect of O2 in O2/Ar Gas Mixture on Morphological and Optical Properties of TiO2 Thin Films Deposited by DC Cylindrical Magnetron Sputtering

TiO₂ films have been deposited on BK7 substrates by DC cylindrical magnetron sputtering setup in ambient temperature. The samples were fabricated at various O₂/Ar reactive gas mixtures. The effects of changing O₂ amount in O₂/Ar reactive gas mixture on structural, morphological and optical properties of films were studied. The thickness of films was measured by surface profile meter. Thickness of films decreases with increasing the O₂ amount in gas mixture. XRD studies shows that the films are amorphous. Atomic Force Microscopy was used to evaluate and compare the surface roughness and morphologies. The optical properties (transmission and reflection) of the samples were measured by UV–Vis–NIR spectrophotometer. Results show that increasing the O₂ amount in O₂/Ar mixture changes the surface morphologies and optical properties of films. All films exhibit a transmittance higher than 65 % in the visible region. The band gap of films was calculated from the optical measurements. The band gap of TiO₂ thin films increases from 3.471 to 3.526 for different O₂/Ar amounts.     

Hydrogenated Amorphous Silicon Sensor Deposited on Integrated Circuit for Radiation Detection

Radiation detectors based on the deposition of a 10 to 30 mum thick hydrogenated amorphous silicon (a-Si:H) sensor directly on top of integrated circuits have been developed. The performance of this detector technology has been assessed for the first time in the context of particle detectors. Three different circuits were designed in a quarter micron CMOS technology for these studies. The so-called TFA (Thin-Film on ASIC) detectors obtained after deposition of a-Si:H sensors on the developed circuits are presented. High internal electric fields (10⁴ to 10⁵ V/cm) can be built in the a-Si:H sensor and overcome the low mobility of electrons and holes in this amorphous material. However, the deposited sensor's leakage current at such fields turns out to be an important parameter which limits the performance of a TFA detector. Its detailed study is presented as well as the detector's pixel segmentation. Signal induction by generated free carrier motion in the a-Si:H sensor has been characterized using a 660 nm pulsed laser. Results obtained with a TFA detector based on an ASIC integrating 5 ns peaking time pre-amplifiers are presented. Direct detection of 10 to 50 keV electrons and 5.9 keV X-rays with the detectors are then shown to understand the potential and the limitations of this technology for radiation detection.     

Upgrading of X-ray CT technology for analyses of irradiated FBR MOX fuel

The X-ray CT technology previously developed by JAEA was upgraded. The shape of the X-ray source beam was changed from a circular shape to an elliptical one and the collimator slit width was decreased from 0.3 to 0.1 mm. The X-ray detector was improved by changing a CdWO₄ scintillator to a highly sensitive silicon semiconductor detector. The analysis code of X-ray CT image was revised with respect to the number of points by using two kinds of experimental results and taking into account the effects of crack existence and deviation of the central void position from the radial center of a fuel pellet. As a result, high resolution X-ray CT images could be obtained on the transverse cross section of irradiated fuel assemblies. The error of the dimensional measurement was improved from ±0.1 to ±0.03 mm by upgrading the instrument and revising the analysis code of X-ray CT image. The discriminating accuracy of density difference could be increased, and the low density region (undisturbed region) and high density region (equi-axial and columnar regions) in the X-ray CT image on the cross section of irradiated fuel could be discriminated from each other. The reliability of fuel performance analysis improves because a large number of PIE data can be collected, compared with the conventional destructive PIE.     

The Effect of Substrate Temperature on the Structure and Morphology of Titanium Nitride Compounds Grown by DC Magnetron Sputtering

The TiN thin films were deposited on p-type silicon (100) substrates using reactive planar DC magnetron sputtering system. The target was 99.99% pure Ti. The reactive sputter gas was a mixture of Ar (99.999%) and N₂ (99.999%) with the ratio Ar (97%) and N₂ (3%) by volume. Structural characterization of the coating was done using X-ray diffraction (XRD). The surface roughness of the coating was determined using an Atomic Force Microscope (AFM). The reflectivity of thin films was investigated by a spectrophotometer system. The X-ray diffraction measurements showed that by increasing the substrate temperature during the growth, change in crystalline structure will occur. The crystallite size of the films determined by Scherrer’s equation, and the crystallite size measured by AFM also increased by increasing the substrate growth temperature. The surface reflectivity measurements indicate that by increasing the substrate growth temperature, the optical properties of the films changes. The change in optical properties and crystalline structure of the films indicate that substrate growth temperature plays an important role in structure and morphology of the grown layers.     

Two-phase Flow Patterns in a Four by Four Rod Bundle

Air-water two-phase flow patterns in a four by four square lattice rod bundle consisting of an acrylic channel box of 68mm in width and transparent rods of 12mm in diameter were observed by utilizing a high speed video camera, FEP (fluorinated ethylene propylene) tubes for rods, and a fiberscope inserted in a rod. The FEP possesses the same refractive index as water, and thereby, whole flow patterns in the bundle and local flow patterns in subchannels were successfully visualized with little optical distortion. The ranges of gas and liquid volume fluxes, {J_G} and {J_L}, in the present experiments were 0:1 ? {J_L} < 2:0 m/s and 0:06 < {J_G} < 8:85 m/s, which covered typical two-phase flow patterns appearing in a fuel bundle of a boiling water nuclear reactor. As a result, the following conclusions were obtained: (1) the region of slug flow in the {J_G}-{J_L} flow pattern diagram is so narrow that it can be regarded as a boundary between bubbly and churn flows, (2) the boundary between bubbly and churn flows is close to the boundary between bubbly and slug flows of the Mishima and Ishii's flow pattern transition model, and (3) the boundary between churn and annular flows is close to the Mishima and Ishii's model.     

Gas Chromatographic Measurements of Hydrogen Isotopes Mixture by Using Catalytic Oxidation Type Detector

A new type of gas chromatograph for quantitative measurements of hydrogen isotopes mixture has been developed through the adoption of catalytic oxidation type detector. Experiments using He as the carrier gas were successfully performed for the separation of D₂-HD and H₂-HD-D₂ mixtures. The minimum detection limits were 0.4–0.9 μl-STP for these components. The linear calibration curves were obtained in the range of 10 μl-STP–20 ml-STP. The sensitivities for H₂, HD and D₂ were 843, 774 and 654 (μl-STP)^?1, respectively. The maximum time needed for the analysis was about 16 min.     

Linux real-time framework for fusion devices

A new framework for the development and execution of real-time codes is currently being developed and commissioned at JET. The foundations of the system are Linux, the Real Time Application Interface (RTAI) and a wise exploitation of the new i386 multi-core processors technology.The driving motivation was the need to find a real-time operating system for the i386 platform able to satisfy JET Vertical Stabilisation Enhancement project requirements: 50 μs cycle time. Even if the initial choice was the VxWorks operating system, it was decided to explore an open source alternative, mostly because of the costs involved in the commercial product.The work started with the definition of a precise set of requirements and milestones to achieve: Linux distribution and kernel versions to be used for the real-time operating system; complete characterization of the Linux/RTAI real-time capabilities; exploitation of the multi-core technology; implementation of all the required and missing features; commissioning of the system.Latency and jitter measurements were compared for Linux and RTAI in both user and kernel-space. The best results were attained using the RTAI kernel solution where the time to reschedule a real-time task after an external interrupt is of 2.35 ± 0.35 μs. In order to run the real-time codes in the kernel-space, a solution to provide user-space functionalities to the kernel modules had to be designed. This novel work provided the most common functions from the standard C library and transparent interaction with files and sockets to the kernel real-time modules. Kernel C++ support was also tested, further developed and integrated in the framework.The work has produced very convincing results so far: complete isolation of the processors assigned to real-time from the Linux non real-time activities, high level of stability over several days of benchmarking operations and values well below 3 μs for task rescheduling after external interrupt. From being the alternative option, RTAI has been finally chosen as the platform for the project. A first stable version of the framework has been integrated on the JET system and is already being commissioned. It will be soon be used on the Vertical Stabilisation Enhancement for the Plasma Control Upgrade (PCU) project at JET.