圆柱形涂硼正比计数管的性能参数研究

为了确定涂硼正比计数管的最优性能参数,运用Diethorn公式,对4种不同设计的涂硼圆柱正比计数管的倍增系数、阴阳极尺寸、电场强度分布、气体压强和最小工作电压这些参数进行了研究。结果表明:电子倍增发生在阳极附近几十μm的范围内,阳极丝直径的减小可导致周围电场强度加大,最小工作电压随阴阳极直径增加而提升,充气压力的降低也会使倍增系数变大。确定涂硼正比计数管的最优设计方案为:阳极为半径6μm镀金钨丝、阴极为半径30 mm不锈钢合金、工作电压为1 000 V、填充气体为0.6×105Pa的95%Ar+5%CH4(P5)。     

球形含氢正比计数管的气体放大

设计和使用供中子能谱测量用的球形含氢正比计数管,要求了解气体放大倍数M,工作电压V、气体压力p和球阴极内半径d等参数之间的相互关系。关于圆柱形正比计数管的气体放大,可以用很多经验公式来描述,其中以Diethorn关系式最为常用。但这关系式适用的范围是:充气压力应小于1个大气压,气体放大倍数10—10~5之间。随着快中子能谱仪的发展和应用,为得到好的能量分辨率,正比计数管的工作条件是:阴极     

2π流气正比计数器装置——标定大面积α-板源和β-板源

中国计量科学研究院放射性室于1971年建成2π流气正比计数器装置,该装置用于标定10~2—10~6粒子/分·2π的α-板源及(10~4—10~6)粒子/分·2π的β-板源,给出结果的不确定度±2％,所允许测量的放射源最大活性面积为180×120毫米。 该装置最明显的特点是计数管的几何尺寸大,计数管阴极外壳呈长方盒形(220×160×36毫米),是不锈钢材料制做的。盒高中部沿计数管长轴方向平行地安置五根拉紧的阳极丝(鏮铜丝,直径0.05毫米),丝与丝之间距离30毫米,两侧丝距阴极壳内壁20毫米。待标定     

三氟化硼正比计数管

三氟化硼(BF_3)正比计数管是应用十分广泛的慢中子探测器之一,1939年可尔夫(Korff)首先制成了这种计数管,后来经过各国有关研究工作者进一步改进和提高,目前可作出阴极直径10厘米的BF_3计数管(充气到一大气压左右),目前,它仍然在继续发展中,BF_3气体正比计数管对于固体和液体的慢中子探测器来说有它的优点:在技术上较简单;生产成本低;使用方便;对γ射线的分辨能力高等,并且可获得较高的探测效率。所以,BF_3正比计数管在探测     

有机计数管

工作原理当带电粒子进入计数管时,使管内气体产生电离。电子在电场的作用下向阳极加速并获得能量。当其能量达到管内气体的电离电位时,便产生电离碰撞,结果阳极附近的电子数急剧倍增,形成电子“雪崩”。放电沿整个阳极丝传播,直到正离子鞘形成,降低了阳极附近的电场,以致不能产生碰撞电离时,放电才终止,电子全部到达阳极,正离子的质量远远大于电子质量,运动较慢.在电场的作用下正离子向阴极移动,迭时阳极的电压相应发生变化,形成一个电压脉冲,被电子学仪器记录下来。由此可探测辐射的强度。     

采用多丝正比室读出的屏栅电离室能量分辨研究

搭建了一个基于多丝正比室读出的屏栅电离室探测器,使其保留屏栅电离室屏蔽特性的同时具备雪崩放大功能,通过在探测器内部对原初电离信号进行预放大,以提高信噪比,改善探测器的能量分辨率。利用²⁴¹Am源详细测试了探测器在不同气压、沉积能量、阳极丝径时能量分辨率及增益随阳极电压的变化关系。探测器最佳能量分辨对应的工作电压与入射粒子在漂移区中沉积的能量有关,能量沉积越小,对应的最佳工作电压越高,探测器的增益越大。对于5.486 MeV的²⁴¹Am α粒子源的能量分辨率可达1.45%。     

环氧封接铍窗正比计数管的寿命

有人认为:环氧类粘结剂封接铍窗正比计数管,由于有机类环氧放气和封接处慢漏现象,管子存放寿命不长。但我们的工作已经表明,只要封接工艺好,环氧树脂E-7胶封接铍窗计数管的存放寿命可达10年以上,使用寿命可达6年以上。 74型环氧树脂封接铍窗正比计数管是1974年3月试制成的。管子阴极内径为36mm的无氧铜圆筒,阳极为经烧氢处理的φ50μm的钨丝,内充73.33kPa的4％N_2 96％Kr混合气。E-7胶是上海合成树脂研究所生产的,其中~#5计数管经一年多使用后存放9年,于1984年7月在与以前相近的实验条件下测试了其主要性能。     

共轴对称组合中子探测器灵敏度研究

在某些应用场合,要求中子计数管具有快收集时间、高中子灵敏度、低工作电压等特性,但是单一只中子正比管无法满足全部的要求,这时需要使用多支中子计数管组合的方式来实现测量目的。本文通过对三种常用中子正比计数管类型进行三支中子正比计数管共轴对称组合,并对其进行实验,得出了其在组合后的对中子灵敏度等特性的影响。     

中子正比计数管内径与充气压力对中子灵敏度影响

中子正比计数管内径和充气压力在不同程度上影响其中子灵敏度、电子收集时间、工作电压等指标,根据多年的实际运行数据和试验数据对中子正比计数管内径和充气压力对中子正比计数管性能的影响进行了定量分析。在实际运用过程中,可根据实际需要,选择一个权衡点,作为生产探测器的参数,以达到预期的效果。     

矩形管的气体放大

不少实验中需要采用知形结构正比管。例如西欧核子中心的L3中的强子量能器的基个单元——正比管的阴极截面就是矩形的。又如一般大型磁谱仪上配用的单丝位置灵敏正比管的阴极也常常选用矩形结构。因而从设计和使用的角度,我们需要对这类计数管的几何参数和气体放大间的关系作定量的了解。通常,圆柱形正比管的几何参数与气体放大间的关系遵循Diethorn公式,即     

密封中子管氘-氘产额及二次电子抑制

中子管的工作参数是影响中子产额的重要因素.为了更准确地调控D-D中子管的中子产额,对中子管的工作参数与产额关系进行了研究,同时为了提高中子管束流品质及寿命,对中子管的二次电子抑制进行实验.采用控制参数变量的方法分别研究了D-D中子管的热子电流、阳极高压、靶极高压对中子产额的影响,以及二次电子抑制电阻阻值与靶极电流之间的...     

一种基于SiPM的具有高能量分辨率的紧凑型溴化镧γ谱仪

基于光电倍增管(photomultiplier tube,简称PMT)的LaBr₃:Ce γ谱仪具有比NaI(Tl)γ谱仪更高的能量分辨率,但具有体积大、对磁场敏感、需要高电压等缺点。硅光电倍增管(Silicon photomultiplier tube,简称SiPM)具有与PMT相近的增益和效率,同时具有诸如高定时分辨率、抗磁场能力强、低偏压和紧凑尺寸等优良特性。本文将LaBr₃:Ce晶体与SiPM阵列耦合,设计研制基于SiPM的紧凑型LaBr₃:Ce γ谱仪,通过降噪、优化工作电压等措施改善SiPM的缺点对γ谱仪性能的影响。工作电压的噪声会导致能量分辨率发生恶化,通过设计无源滤波电路CLC π型滤波器,利用其对直/交流阻抗的不同特性,滤除高频纹波,工作电压的信噪比从未降噪前的62.6 dB提高到74.64 dB;能量分辨率最优值对应于表示暗噪声、串扰、光电探测效率和SiPM增益之间折衷的最佳工作电压。通过实验给出不同工作电压下的能量分辨率,确定最佳工作电压为54.8 V,该电压下的能量分辨率为3.06%(@662 keV),结果与使用光电倍增管(PMT)测量的2.89％非常接近。     

Modification of the Charpak Chamber with Foil Supported Conductors

A conductive film supports the anode wires of a multi-wire proportional type counter and a bias voltage applied through this film controls the electric field concentration around the anode wires. Because the critical operating voltage is applied through the film one has increased freedom in the mechanical design of these chambers . Two coordinates of spacial information are available with this technique. The first coordinate is the anode wire signals. The second is obtained by a grid of ribbons on the back of the anode supporting film which picks up an induced signal from the primary discharge. Spacial resolution of 1.6 mm fwhm has been measured using the induced readout ribbon grid along with 3.3 mm fwhm on the anode grid. We expect this to improve.     

Simulation of Secondary Electron and Backscattered Electron Emission in A6 Relativistic Magnetron Driven by Different Cathode

Prticle-in-cell(PIC) simulations demonstrated that,when the relativistic magnetron with diffraction output(MDO) is applied with a 410 kV voltage pulse,or when the relativistic magnetron with radial output is applied with a 350 kV voltage pulse,electrons emitted from the cathode with high energy will strike the anode block wall.The emitted secondary electrons and backscattered electrons affect the interaction between electrons and RF fields induced by the operating modes,which decreases the output power in the radial output relativistic magnetron by about 15%(10%for the axial output relativistic magnetron),decreases the anode current by about 5%(5%for the axial output relativistic magnetron),and leads to a decrease of electronic efficiency by 8%(6%for the axial output relativistic magnetron).The peak value of the current formed by secondary and backscattered current equals nearly half of the amplitude of the anode current,which may help the growth of parasitic modes when the applied magnetic field is near the critical magnetic field separating neighboring modes.Thus,mode competition becomes more serious.     

Resolving power of multisection geiger counters, proportional and corona counters

Calculations are made of the resolving power of multisection Geiger counters with independently operating sections and of single-section proportional and corona neutron counters. Account is taken of the influence of the number of sections in the device, the dead time of an individual section, the duration of the output voltage pulse, and the dead time of the recording apparatus. it is shown that proportional and corona neutron counters filled with a working gas at high pressure (several atmospheres) behave as multisection counters having an, equivalent number of sections and the same ratio of the anode length to the average, mean free path of the charged particles formed in the radiator under the action of the neutrons. VNIITFA. Translated from Atomnaya énergiya, Vol. 86, No. 6, pp. 460–465, June, 1999.     

Study of the pulsed working characteristics of the penning ion source for neutron tubes

The pulsed working characteristics of the neutron tube ion source were studied experimentally.The principle and method of selecting the gas pressure and anode voltage were determined.     

The Effect of Working Gas Admixture,Applied Voltage and Pressure on Focusing Time Parameter in the APF Plasma Focus Device

In the present research the effects of key parameters, applied voltage, working gas composition and pressure, on the focusing time in the APF plasma focus device are investigated. Pure nitrogen (N₂) and three volumetric ratios (90:10), (75:25), and (50:50) of (N₂:Ne) admixture gases were used as the filling gas in a range of four applied voltage between 10 and 13 kV and seven operating pressure of 1.5–4.5 torr. It was found that with addition of 1 kV in the charging voltage, a decrease of around 50–75 ns happens in the focusing time while with increase of 0.5 torr in operating pressure, an increment of around 100–150 ns occurs in the focusing time. Also it was observed that the focusing time decreases around 50–75 ns with addition of 10% neon (Ne) in volumetric ratio of admixture working gas at all applied voltage and operating pressure.     

X-Ray Measurement and Enhancement of SBUPF1 Plasma Focus Device in Different Ar Pressures and Operating Voltages

In this paper, best condition of filling gas pressure and operating voltage for SBUPF1 plasma focus device to have maximum intensity of hard and soft X-ray emission has been reported. For time resolved X-ray detection, PIN detector and fast plastic Scintillator detector with appropriate filters have been used and for time integrated X-ray emission measurement, radiography films with appropriate filter masks have been used. Rogowski coil has been used for pinch detection. The highest hard X-ray emission has been observed at the pressure of 0.45 mbar of Argon and discharge voltage about 23.5 kV. The highest Soft X-ray emission has been observed at the pressure of 0.35 mbar of Argon and discharge voltage about 23.5 kV. For enhancement of hard X-ray emission intensity, lead disk was placed in copper anode tip and measurements were repeated. Results have shown that hard X-ray emission has been enhanced about 23% and soft X-ray emission has been enhanced about 33% with inserting a high atomic number metal disk like lead. Results from integral X-ray measurement have shown presence of dominant peaks in ranges 13.2–15, 21–21.9 and 23.4–24.3 keV with significant spectral components in the range of 0–50 keV. Pinch size has measured with pin hole camera and it is about 0.6 mm × 2.12 mm. Captured images with SBUPF1 have confirmed that it is a suitable source for introspective imaging with capability of showing very fine details.     

Experimental Study of the Variation of Neutron Emission Anisotropy in a Filippov-type Plasma Focus Facility

This paper presents the results of experimental studies of the variation of spatial anisotropy in neutron emission with working conditions in a 90 kJ Filippov-type plasma focus device. The working gases are D₂ and D₂ + 1%Kr. The results of our experiments have shown that the anisotropy factor decreases with increasing the initial pressure and/or discharge energy. Furthermore, it has been observed that by using D₂ + 1%Kr as working gas, the variation in anisotropy factor with initial pressure and/or discharge energy is relatively high, but by using D₂ it changes slowly. The highest neutron yield has been achieved by using D₂ + 1%Kr and a conic insert anode. Thus, we have studied the correlation between neutron yield and anisotropy factor for this case at fixed working conditions from shot to shot. At 16 kV discharge voltage and pressures around optimum, the behavior of anisotropy factor is generally increasing with neutron yield, whereas at low and high pressures, the anisotropy factor does not change significantly with yield.     

PIC/MCC Simulation of Radio Frequency Hollow Cathode Discharge in Nitrogen

A two-dimensional PIC/MCC model is developed to simulate the nitrogen radio frequency hollow cathode discharge (rf-HCD).It is found that both the sheath oscillation heating and the secondary electron heating together play a role to maintain the rf-HCD under the simulated conditions.The mean energy of ions (N2+,N+) in the negative glow region is greater than the thermal kinetic energy of the molecular gas (N2),which is an important characteristic of rf-HCD.During the negative portion of the hollow electrode voltage cycle,electrons mainly follow pendulum movement and produce a large number of ionization collisions in the plasma region.During the positive voltage of the rf cycle,the axial electric field becomes stronger and its direction is pointing to the anode (substrate),therefore the ions move toward the anode (substrate) via the axial electric field acceleration.Compared with dc-HCD,rf-HCD is more suitable for serving as a plasma jet nozzle at low pressure.