A DRIFT CHAMBER WITH UNIFORM ELECTRIC FIELD AND MEASUREMENTS OF THE ELECTRON DRIFT VELOCITY

The measurements of the electron drift velocity as a function of the electric field have been made in a small drift chamber with uniform electric field for Ar/CH₄, Ar/i-C₄H₁₀, Ar/CO₂ and SQS gas mixtures. The values of the electric field range from obout 0.3 to 2.5kV/cm. The results of the measurements are discussed.     

PRELIMINARY TEST FOR AGEING EFFECT OF DRIFT CHAMBERS

The degradation of some performances of the drift chambers irradiated with 5 MeV electron beam has been tested. The gas mixtures filled were Ar/CO₂, Ar/CH₄ and C₄H₁₀ in proportion.
The dark current, the pulse height, the energy resolution and the counting rate plateau have been measured during the irradiation.     

DELAY LINE READ OUT FOR A TWO-DIMENSIONAL DRIFT CHAMBER

Tests on the read out of the second coordinate (along the anode wire) of the MIT-Harward-type drift chamber by using a Naples type flat solenoieal delay line were conducted. Spatial resolution of 2～5mm and linearity better than 1% were obtained along the delay line of 80cm in length with the gas mixture of P9 or Ar/CH₄=70/30.     

液氮与液态一氧化碳混合物的冲击压缩特性研究

 利用二级轻气炮研究了等体积的液态一氧化碳（LCO）与液氮（LN₂）混合物的冲击压缩特性，在10～25 GPa压力范围内获得了5个Hugoniot数据点。混合物冲击绝热线位于单质一氧化碳和液氮Hugoniot拟合线之间，并靠近前者。这意味着混合物的冲击压缩特性不是其中各单质行为的简单平均。     

PERFORMANCE INVESTIGATION OF MULTISTEP AVALANCHE CHAMBER

We have designed and operated a test module of multistep avalanche chamber with effective detection area of 9 by 9 cm². Argon-acetone mixture gas is provided by a simple gas mixing system, and mixture ratio can be modulated by gas flow. The performance of the chamber has been investigated by use of ⁵⁵Fe 5.9 keV X-ray source at acetone concentration in argon of 2.7％, and the effect of acetone concentration to the chamber has been measured.     

THE STUDY AND PRODUCTION OF PWC'S FOR THE FIRST MODULE OF L3 HADRON CALORIMETER

This paper reports the study and production and the performance of 60 PWC's which were the first module of L3 hadron calorimeter.125 Volts plateau and 3.4%/100V plateau slope were obtained with the gas mixture of Ar:CO₂=80:20.We also checked the dark current of some chambers and found that the dark current could be reduced by "cooking".The chambers worked well when they were assembled in a calorimeter module and tested by the beam of SPS at CERN.     

THE COLLECTIVE MOTION OF THE BAG AND THE NUCLEON STRUCTURE FUNCTIONS

Using the hypothesis of the bag-quarks' wave-function with the property of transla-tion invariance, and introducing a Lorentz-invariant effective Lagrangian, we have cal-culated the nucleon deep -inelastic structure functions In our calculation the4-momentum conservation is satisfied automatically, while the resultant structurefunctions are positive-definite and vanish when x>1. Furthermore, using the assumptionof the asymptotic freedom, we obtain explicitly the Bjorken scaling, the approximateexpession F₁ (x～1)∝(1--x)⁴, and by the way, a new counting rule Computercalculation gives the F₂(x) curve which seems to be consistent with the data in therange of 0.4<x<1.     

Experimental studies of micromegas detectors with different micro-meshes

The structure of micromegas (micro-mesh gaseous structure) detectors with different micro-meshes of stainless steel wire woven netting and Ni foil has been presented. The counting rates, energy resolution, gain, discharge probability and time resolution have been measured. Wider counter plateaus and gain for the developed detector were obtained. Excellent energy resolution of the micromegas detector, 17% (FWHM) based on Ni foil micro-mesh and 25% (FWHM) based on stainless steel wire woven netting micro-mesh, has been obtained for the 5.9 keV photon peak of the 55Fe X-ray source in an Ar/CO2(10%) gas mixture. The best time resolution at -620 V micro-mesh voltage and -870 V drift voltage is 14.8 ns for cosmic rays in an Ar/CO2 (10%) gas mixture. These results satisfy the basic demand of the micromegas detector preliminary design.     

CONSTRUCTION AND PERFORMANCE OF TWO-DIMENSIONAL DRIFT CHAMBER

The two dimensional drift chamber was formed by gluing a delay-line in a MIT-Harvard type drift chamber. An average drift velocity about 3.34cm/μs was obtained when the chamber was operated at plateau region and filled with P-9 gas. Its average space resolution is 570μm. The output signal amplitude of the chamber being changed when alter the incident particle's (both β^－ and X-ray) position was observed.     

Developments of a 2D position sensitiveneutron detector

China Spallation Neutron Source (CSNS), one project of the 12^th Five-Year-Plan scheme of China, is under construction in Guangdong province. Three neutron spectrometers will be installed during the first phase of the project, and two-dimensional position sensitive thermal neutron detectors are required. Before the construction of the neutron detectors, a prototype of a two-dimensional 200 mm×200 mm Multi-wire Proportional Chamber (MWPC) with Ar/CO₂ (90/10) flowing gas has been constructed. In 2009, the prototype was tested with the ⁵⁵Fe X-ray using part of the electronics, and performed well.
Following the test in 2009, the neutron detector was constructed with the complete electronics and filled with the 6 atm. ³He+2.5 atm. C₃H₈ gas mixture in 2010. The neutron detector has been primarily tested with an Am-Be source. In this paper, new developments of the neutron detector including the design of the high pressure chamber, the optimization of the gas purifying system and the gas filling process will be reported. The results and discussion are also presented in this paper.     

高压低温条件下固态氩和4∶1甲醇-乙醇混合物传压介质的传压特性

 在高压低温（77 K）条件下，利用红宝石荧光测压方法，系统地研究了金刚石对顶砧装置中固态氩和4∶1甲醇-乙醇混合物的传压特性。通过测量不同位置上红宝石荧光R₁线的频移，确定了样品室内的压力分布。实验结果表明：在0~16 GPa的压力范围内，固态氩介质中反映介质非均匀性程度的|Δp/p|<3%、σ_p/p<2%，均在室温静水压条件下所允许的范围之内。红宝石荧光R线除随压力变宽外，与常压的很相似，表明固态氩在高压低温条件下是良好的传压介质。与之相比，4∶1甲醇-乙醇介质在77 K低温下的传压特性明显差于固态氩，已不适合作传压介质。     

THE PROTOTYPE OF THE TIME EXPANSION CHAMBER

The prototype of the time expansion chamber, one kind of drift chambers, inwhich the drift region and amplification region is well separated, is described. Its prin-ciple, characteristic, construction and some experimental results are given in detail, Theseresulte are: signals of ionization process along a single charged particle track; the driftvelocities of the electrons in several gases; and the counts distribution of the ionizationclusters in the unit track of a beta particle. And some possible improvements of theseexperiments and the possible applications of this chamber are discussed.     

90 GPa（准）静水压力的产生及压力分布的测量

 本文使用固态氩做传压介质，在自制的Mao-Bell型金刚石对顶砧装置中获得了90 GPa的准静水压。通过测量样品室内不同位置上红宝石荧光R₁线的频移来确定压力分布。实验结果表明在80 GPa以下，样品室内不同位置上的压力与平均压力（p）的差Δp很小，最大的Δp/p不超过1.5%。在90 GPa时，红宝石的荧光R线与常压的很相似。这表明利用固态氩做传压介质可以获得接近100 GPa的准静水压。此外，对红宝石荧光光谱中位置在14 938 cm^-1和14 431 cm^-1两条谱线随压力的变化情况也作了讨论，并由此得出结论，14 938 cm^-1这条线也可用来标定压力。     

RESEARCH ON SOME CHARACTERISTICS AND IMPROVEMENTS OF A 70cm STREAMER CHAMBER

In this paper the influence of various proportion of Ne-He gases and the time delay on the quality of streamer tracks has been studied. The diameterand density of streamers under these mixed-gas conditions have been measured.
The time resolution of this streamer chamber was determined to be 2.1μs in 69% Ne+31% He+8×10^－8 SF₆, and as 177μs in pure neon by using the exponentially decreasing relation of streamer desity with delay time. The spatial resolution was determined to be 0.32mm in Ne+3×10^－8 SF₆ by measuring the streamer diameters, and the method of track standard deviation was also used.
Some results show that the diameter and brightness increase with increasing high voltage, but become rather even when high voltage continues increasing.
Photographs were taken with domestically produced special film (32 DIN, 60 lines/mm), being similar to Kodak SO-143.
A special designed central electrode of the streamer chamber with its wires inlaid in lucite plate is successful for preventing gas from breakdown near wires. Besides, delay time has been reduced to 1.3μs, mainly by the Marx generator and its trigger system the parameters of which have been chosen by a series of experiments.     

高温高压下CeTbO3合成过程中电阻的动态测试研究

 在0.5 GPa、4.0 GPa的压力下，从室温到800 ℃的温度范围内测量了氧化物CeTbO₃、单稀土氧化物Tb₄O₇、CeO₂和摩尔比维4∶1配比的混合物CeO₂+Tb₄O₇等的电阻随温度变化关系。对这四种物质均反映出电阻随温度增加而减小的半导体特征。在压力维0.5 GPa，温度高于600 ℃时发现了混合物CeO₂+Tb₄O₇、氧化物Tb₄O₇中电阻变化的起伏。X射线衍射谱表明，对应这一电阻变化，在结构上出现了变化。结果分析表明，这一变化与Tb⁴⁺→Tb³⁺的价态变化密切相联。     

BaCO3和TiO2粉末混合物冲击压缩性和BaTiO3冲击合成的实验研究

 利用高能炸药爆轰驱动冲击波、狭缝扫描闪光隙高速照相技术和阻抗匹配解原理，在10~100 GPa压力范围内，测量了BaCO₃和TiO₂粉末混合物的冲击绝热数据。同时，利用轴对称柱面和平面爆轰装置，进行了该混合物样品的冲击后回收实验和回收样品的X射线衍射分析，考察BaTiO₃的冲击合成。测量出的冲击绝热数据，以冲击波压力和比容平面上的结果为例，在约30和45 GPa两个压力值时，比容发生明显跃变。冲击绝热数据与回收样品X射线衍射分析结果相结合，判断出，这两个跃变分别对应于TiO₂从锐钛矿相转变到高压β-TiO₂相，BaCO₃与TiO₂开始急剧化学反应合成出BaTiO₃并放出CO₂。此外，在压力为10 GPa左右作回收实验，其回收样品的X射线衍射分析表明TiO₂由锐钛矿相完全转变为金红石相。     

Aging effect in the BESIII drift chamber

As the main tracking detector of BESIII, the drift chamber provides accurate measurements of the position and the momentum of the charged particles produced in e+e-collisions at BEPCII. After six years of operation, the drift chamber is suffering from aging problems due to huge beam-related background. The gains of the cells in the first ten layers show an obvious decrease, reaching a maximum decrease of about 29% for the first layer cells. Two calculation methods for the gain change(Bhabha events and accumulated charges with 0.3% aging ratio for inner chamber cells) give almost the same results. For the Malter effect encountered by the inner drift chamber in January 2012, about 0.2% water vapor was added to the MDC gas mixture to solve this cathode aging problem.These results provide an important reference for MDC operating high voltage settings and the upgrade of the inner drift chamber.     

直流等离子体炬放电特性研究

对于磁约束直流等离子体炬,用氩－氢等离子体的放电体系,研究了等离子体炬几何结构、真空室气压、弧电流、外磁场与比变化等对等离子体炬放电特性的影响。得到了影响等离子体炬宏观和微观参数变化的一些基本规律。     

液态水、苯和壬基乳化剂混合物冲击压缩特性的实验研究

 利用二级轻气炮在3.75~57.87 GPa 压力范围内,对体积比为10∶10∶1的液态水-苯-壬基酚聚氧乙烯醚混合体系进行了动高压加载实验,获得了10个Hugoniot数据。拟合结果表明,该混合体系的D-u关系可近似用直线方程D=1.407+1.503u_p描述,拟合精度约为0.102。混合体系H₂O-C₆H₆-C₃₅H₆₄O₁₁的冲击压缩实验结果基本符合体积相加原理,而在给定的实验压力区间内,冲击绝热曲线发生多次拐折的事实意味着该系统可能在6 GPa、10 GPa和30 GPa压力点附近发生了多次结构性相变。另外,还讨论了Lawrence-Berthlot混合规则中修正因子对高密度条件下指数-6型相互作用势排斥部分的影响。     

A 70cm STREAMER CHAMBER SYSTEM

In this paper, the design, construction and characteristics of a 70cm streamerchamber system are deseribed. A very fast pulse with rise time 2 ns and duration 10ns has been successfullyobtained by using a four-spark-gap cylindrical Blumlein line with a 25 stage Marxgenerator (up to 600kV) connected to it. The output pulse of the Blumlein line isthen fed to the chamber, via heteromorphic transmission line with pulse shapeminimum distortion. The system are triggered by three-fold large area scintillation counter telescopeto pick up particle of the cosmic ray traversing the sensitive volume of the chamber.The coincidence-counting rate is ～5 particles/min., the resolving time is 10ns, andthe ratio of the true-accidental coincidence is more than 700. The chamber has two 15 cm gaps and is 70 cm long, 50 cm wide, with 30Ω ofcharacteristic impedence. In order to photograph through the electrodes, the central and the ground electrodes towards the cameras are made of 0.2mm diameter beryl-lium-copper wire stands spaced 2 mm apart, with transparency～90%. Pure neon and mixtures of neon-helium gas were used to fill the chamber, oneatmosphere, and a cycling and purifier system were designed to maintain its purity.The gas is passed through type 5A and 13x molecular sieve operated at room andliquid -nitrogen temperature to remove CO₂, H₂O and O₂, N₂, respectively. The im-purities of the chamber gas can be reduced to 0.2% within 2hr., at the gas flow rate500 1/hr. All photographs are taken with one or two oscilloscope cameras on 35mm film of28 DIN. A demagnification 30x and a resolution 30 line pairs/mm at the maximumaperture (f/2) are used. The sizes of the visual streamers were estimated about3 to 4 mm in diameter (view along the E field), and 10 to 15 mm long (view perpen-dicular to the E field). The delay time between the penetration of charged particle and the supply of thehigh voltage pulse on the chamber was ～3.5μs. The system was suggested in June1975. The whole facility began to mount and adjust in January 1979, and the strea-mer tracks were seen on July 26, 1979. We plan to make the performance tests, to reduce the delay time of the system,and to improve the chamber suitable for use in high energy accelerator and cosmic-ray experiments in the near future.