RETGEM探测器的初步测试

研制了一种新型的带有阻抗性电极的TGEM——RETGEM(Thick GEM with Resistive Electrodes)探测器, 阻抗性电极可以有效地保护探测器和前端电子学免于偶尔放电的损伤。 对RETGEM探测器进行了初步测试, 其中包括计数率、能量分辨、增益以及打火率。 结果表明, 探测器达到了设计的基本要求。 In this study we present preliminary results from a new detector: a thick gaseous electron multiplier(GEM) with resistive electrodes. The resistive electrodes protect the detector and the front end electronics from damage by occasional discharges. In different gas mixtures, we test Thick GEM with Resistive Electrodes(RETGEM) detector for the first time, including counting rate, energy resolution, effective gain, and discharge probability. The results can satisfy the basic demand of RETGEM detector design.     

Investigation of the energy resolution with a RETGEM detector

A novel Micro-pattern gaseous detector （MPGD）, thick GEM with electrodes made of a resistive material （RETGEM） is presented. In this paper we mainly investigate the energy resolution of a RETGEM in Ar＋CO2 with different gas mixtures. The results indicate that an energy resolution 30% in single and double mode can be obtained. The existence of an optimum energy resolution is discussed.     

Investigation of the energy resolution with a RETGEM detector

A novel Micro-pattern gaseous detector (MPGD), thick GEM with electrodes made of a resistive material (RETGEM) is presented. In this paper we mainly investigate the energy resolution of a RETGEM in Ar+CO_2 with different gas mixtures. The results indicate that an energy resolution 30% in single and double mode can be obtained. The existence of an optimum energy resolution is discussed.     

Atmospheric-Pressure Glow Discharge Sustained by a Resonant Power Supply

This paper illustrates an atmospheric-pressure glow discharge sustained by a resonant power supply. The power supply can provide an ac current with a constant peak value, while the load of resistive character is varied by many orders of magnitude. Gas discharges between pin-to-plate electrodes are observed. The electrical characteristics and photo of the glow discharge have been obtained. Influence factors on the stability of the discharge, such as the gap clearance and the shape of electrodes, are discussed.      

Experimental study on the performance of a single-THGEM gas detector

A kind of thick GEM-like gaseous electron multiplier （THGEM）, which is mechanically an expansion of the GEM with its various dimensions being enlarged, is studied. The leak current of THGEM plates is measured. The effective gain and energy resolution of a single THGEM are studied with a source of 55Fe, and the effective gain of the single THGEM versus the electric field strength in the induction region is investigated. The results show that the leak current of THGEM plates is less than 200 pA. In an atmospheric-pressure standard gas mixture, 8×103 effective gain and about 32% energy resolution can be reached for the single-THGEM detector.     

Experimental study on the performance of a single-THGEM gas detector

A kind of thick GEM-like gaseous electron multiplier (THGEM), which is mechanically an expansion of the GEM with its various dimensions being enlarged, is studied. The leak current of THGEM plates is measured. The effective gain and energy resolution of a single THGEM are studied with a source of 55Fe, and the effective gain of the single THGEM versus the electric field strength in the induction region is investigated. The results show that the leak current of THGEM plates is less than 200 pA. In an atmospheric-pressure standard gas mixture, 8×103 effective gain and about 32% energy resolution can be reached for the single-THGEM detector.     

Study of the THGEM detector with a reflective CsI photocathode

The THGEM detector without and with a CsI has been tested successfully. The optimal parame- ters of THGEM have been determined from eight samples. The UV photoelectric effect of the CsI photocathode is observed. The changing tendency related to the extraction efficiency (ε<,extr>) versus the extraction electric field is measured, and several electric fields influencing the anode current are adjusted to adapt to the THGEM detector with a reflective CsI photocathode.     

Study of a nTHGEM-based thermal neutron detector

With new generation neutron sources, traditional neutron detectors cannot satisfy the demands of the applications, especially under high flux. Furthermore, facing the global crisis in ~3He gas supply, research on new types of neutron detector as an alternative to ~3He is a research hotspot in the field of particle detection. GEM(Gaseous Electron Multiplier) neutron detectors have high counting rate, good spatial and time resolution, and could be one future direction of the development of neutron detectors. In this paper, the physical process of neutron detection is simulated with Geant 4 code, studying the relations between thermal conversion efficiency, boron thickness and number of boron layers. Due to the special characteristics of neutron detection, we have developed a novel type of special ceramic n THGEM(neutron THick GEM) for neutron detection. The performance of the n THGEM working in different Ar/CO_2 mixtures is presented, including measurements of the gain and the count rate plateau using a copper target X-ray source. A detector with a single n THGEM has been tested for 2-D imaging using a ~(252)Cf neutron source. The key parameters of the performance of the n THGEM detector have been obtained, providing necessary experimental data as a reference for further research on this detector.     

Experimental studies of THGEM in different Ar/CO_2 mixtures

In this paper, the performance of a type of domestic THGEM (THick Gaseous Electron Multiplier) working in Ar/CO₂ mixtures is reported in detail. This kind of single THGEM can provide a gain range from 100 to 1000, which is very suitable for application in neutron detection. In order to study its basic characteristics as a reference for the development of a THGEM based neutron detector, the counting rate plateau, the energy resolution and the gain of the THGEM have been measured in different Ar/CO₂ mixtures with a variety of electrical fields. For the Ar/CO₂(90%/10%) gas mixture, a wide counting rate plateau is achieved from 720 V to 770 V, with a plateau slope of 2.4%/100 V, and an excellent energy resolution of about 22% is obtained at the 5.9 keV full energy peak of the ⁵⁵Fe X-ray source.     

Influence of Surface Contaminations on Cathode Processes of Vacuum Discharges

The influence of surface contaminations on the ignition and maintenance of vacuum discharges is discussed qualitatively. Surface analysis of the electrodes and gas analysis during the discharges demonstrate that fresh electrodes contain always impurities within the upper surface layers, which affect the behaviour of vacuum arcs and vacuum breakdowns. The most effective way for cleaning the surfaces are the discharges themselves, if they burn in UHV. During that cleaning the following variations have been found: Are cathodes spots change from rapid moving ones with small erosion (type 1) to slow ones with strong erosion (type 2). The ignition of nanosecond discharges needs higher field strength and field emission current density. Polishing effects by short discharges (< 5 ns) become more pronounced. Erosion craters in nanosecond discharges increase.     

Formation of ac Discharges Between Glass Insulated Electrodes in Ne + 1% N2 Mixtures. I. Experiments and Analysis

Ac plasma displays make use of medium pressure ac discharges in Penning mixtures between insulated electrodes. Discharges in Ne + 1% N₂ with glazed electrodes are a suitable experimental model showing the characteristic pulse and continous discharge modes. The axial optical space time structure of sinus wave sustained model discharges are measured with a scanning device, obtaining characteristic phases of discharge formation. Application of luminous flux method for stationary and dynamic Townsend discharges yields the first Townsend ionization coefficient α, and the comparison of the optical structure of ac discharges with that of dc discharges allows to explain the axial structure and to estimate the space charge effects.     

两级同轴Blumlein线理论及其模拟分析

利用拉普拉斯变换求解两级同轴Blumlein线对负载的放电过程,得到了纯电阻负载上理想输出电压的解析表达式。分析了开关电感、负载电感及回路电感对负载主脉冲的影响。对PSpice模拟的结果与推测的负载电压表达式进行对比,两者符合得较好。分析结果表明:脉冲的前沿主要是由开关电感决定,而平顶幅值的变化趋势主要是由回路电感决定;开关电感越小,上升沿越小,回路电感越大;脉冲输出电压和能量传输效率越高。     

Bipolar resistive switching in BiFe_(0.95)Zn_(0.05)O_3 films

Bipolar resistive switching is studied in BiFe0.95Zn0.05O3 films prepared by pulsed laser deposition on （001） SrTiO3 substrate, with LaNiO3 as the bottom electrode, and Pt as the top electrode. Multiple steps of resistance change are ob- served in the resistive switching process with a slow voltage sweep, indicating the formation/rupture of multiple conductive filaments. A resistive ratio of the high resistance state （HRS） to the low resistance state （LRS） of over three orders of mag- nitude is observed. Furthermore, the conduction mechanism is confirmed to be space-charge-limited conduction with the Schottky emission at the interface with the top Pt electrodes in the HRS, and Ohmic in the LRS. Impedance spectroscopy demonstrates a conductive ferroelectric/interfacial dielectric 2-layer structure, and the formation/rupture of the conductive filaments mainly occurs at the interfacial dielectric layer close to the top Pt electrodes.     

Effect of the plasma location on the deflagration-to-detonation transition of a hydrogen–air flame enhanced by nanosecond repetitively pulsed discharges

This work presents a method for using nanosecond repetitively pulsed (NRP) plasma discharges for accelerating a propagating flame such that the deflagration-to-detonation transition occurs. A strategy is developed for bringing the location of the plasma near the tube wall and, thus, reducing the presence of the electrodes in the combustion tube as well as presenting a configuration in which cooling of the electrodes is viable for practical applications. Time-of-flight measurements were used in combination with energy deposition measurements and high-speed OH*-chemiluminescence imagery to investigate the flame acceleration process. For stoichiometric hydrogen–air flames, successful transition to detonation was achieved by applying a burst of 110 pulses at 100 kHz, with energies as low as 10 mJ per pulse. This was also achieved when plasma discharges were applied in the vicinity of the wall. Two enhancement mechanisms for flame acceleration were identified. The essential role of shock–flame interaction was established as being the main mechanism for flame acceleration when the discharges are located near the wall. This work presents an effective alternative that allows for NRP discharges to be applied near the wall while successfully maintaining a promising success rate for detonation transition.     

Design,development and performance study of six-gap glass MRPC detectors

The multigap resistive plate chambers (MRPCs) are gas ionization detectors with multiple gas sub-gaps made of resistive electrodes. The high voltage (HV) is applied on the outer surfaces of outermost resistive plates only, while the interior plates are left electrically floating. The presence of multiple narrow sub-gaps with high electric field results in faster signals on the outer electrodes, thus improving the detector’s time resolution. Due to their excellent performance and relatively low cost, the MRPC detector has found potential application in time-of-flight (TOF) systems. Here we present the design, fabrication, optimization of the operating parameters such as the HV, the gas mixture composition, and, performance of six-gap glass MRPC detectors of area 27 cm \(\times \) 27 cm, which are developed in order to find application as trigger detectors, in TOF measurement etc. The design has been optimized with unique spacers and blockers to ensure a proper gas flow through the narrow sub-gaps, which are 250 \(\upmu \)m wide. The gas mixture consisting of R134A, Isobutane and SF\(_{6}\), and the fraction of each constituting gases has been optimized after studying the MRPC performance for a set of different concentrations. The counting efficiency of the MRPC is about 95% at 17.9 kV. At the same operating voltage, the time resolution, after correcting for the walk effect, is found to be about 219 ps.     

Study of a sealed high gas pressure THGEM detector and response of alpha particle spectra

A sealed high gas pressure detector working in pure argon is assembled.It consists of a 5 cm x 5 cm PCB THGEM(THick Gaseous Electron Multiplier).The detector structure and experimental setup are described.The performance under high pressure(2 atm) is examined,selecting optimal voltages for the ionization region and induction region.The dependence of the shape of alpha particle spectra measured with relative gas gain on gas pressure(1.3-2.0 atm) has been studied.Eight data sets of relative gas gain versus working voltage of THGEM,expressed by weighting field E/P,are normalized,consistent with theory.The results show that the air tightness of the chamber is good,measured by a sensitive barometer and checked with gas gain.The experimental results are compared with Monte Carlo simulation of energy deposition without gas gain involved.     

Analysis of time-dependent characteristics for a pseudosparkdischarge in air

The time-dependent resistive voltage and resistance of a pseudospark discharge in air are obtained by solving the equivalent circuit equation using the measured values of the discharge current and breakdown voltage. Pulsed, underdamped discharge currents ranging from about 30 to 100 A are investigated experimentally. The gas pressures range from 0.005-0.1 torr. The discharges can be characterized by three phases: initial, quasi-stationary, and relaxation. The quasi-stationary phase occurs near the time of the current maximum. The variations of the resistive pseudospark voltage are similar to those observed in a spark discharge, which can explain the sparklike behavior of a pseudospark discharge. Details of the current-voltage characteristics and resistance are presented     

多间隙气体开关电感

介绍了一种用于快脉冲直线变压器的低电感多间隙气体开关。专门构造了多种形式的单通道放电实验,测量了在不同形态单通道放电时的开关电感,研究发现:单通道放电时开关电感除了受到角向电流的影响,还与电弧通道引起的放电回路面积变化有关,开关电感理论计算值与单通道放电时的实测结果最接近;开关在自放电和触发时,均形成了多通道放电,电感明显降低,触发时开关电感最小约为49 nH,电极角向电流的影响可以忽略。     

Experimental study of a THGEM detector with mini-rims

The gas gain and energy resolution of single and double THGEM detectors (5 cm×5 cm effective area) with mini-rims (rim less than 10 μm) were studied. The maximum gain was found to reach 5×10³ and 2×10⁵ for single and double THGEMs respectively, while the energy resolution for 5.9 keV X-rays varied from 18% to 28% for both single and double THGEM detectors of different hole sizes and thicknesses. Different combinations were also investigated of noble gases (argon, neon) mixed with a quantity of other gases (isobutane, methane) at atmospheric pressure.     

A simulation study of the e~+/e~- sensitivity of a low resistive phosphate glass electrode in a RPC using GEANT MC

The resistivity of conventional glass is quite high and is unacceptable in a high rate environment. Low resistive glass-electrodes could be a solution for this problem. The present study reports the e+/e-simulation results of an RPC detector made from low resistive phosphate glass electrodes. The detailed geometrical configuration of the content materials which are the essential components of the glass of the RPC detector have been created with the GEANT4 simulation code. Two different types of particle sou...