Effect of oriented crystalline converter temperature on spectrometer response

Cooling of a 1-mm crystalline tungsten converter oriented along the ??111?? axis situated in front of an electromagnetic spectrometer of thickness 25X ₀, recording showers of 28-GeV electrons, to a temperature of 77 K results in a decrease of the crystal radiation length by ??30%, shifts the cascade curve of the shower development in the spectrometer by ??7%, and improves the spectrometer energy resolution by ??5% in comparison with similar parameters of the spectrometer at a crystal temperature of 293 K.     

Orientation dependences of the response of an electromagnetic spectrometer with oriented crystal converter

The experimental results of the study of orientation dependences of the response of a composite Cherenkov shower spectrometer with a converter made of a 1-mm tungsten crystal oriented along the 〈111〉 axis at an electron energy of 28 GeV and two converter temperatures, 293 and 77 K, are presented. The parameters of the cascade curve of the shower development are varied depending on the orientation angle and crystal temperature. It is found that there is a point S in the cascade curve of the shower development in the spectrometer, at which all cascade curves intersect at any converter orientation. The position of this point in the spectrometer depth depends on the converter temperature.     

Estimation of the parameters of the cascade curve of electromagnetic shower development in a spectrometer with oriented crystal converter

Based on the experimental results on the development of electromagnetic showers from 26-GeV electrons in misoriented and oriented along the 〈111〉 axis tungsten crystals 2.7, 5.8, 8.4mm thick and then in a composite Cherenkov shower spectrometer, the parameters of the cascade curve of shower development in a spectrometer with 1-mm tungsten crystal converter were estimated.     

Energy dependence of the response of an electromagnetic spectrometer with oriented crystal converter

The experimental results of the study of the dependence of the response of a composite Cherenkov shower spectrometer with a converter made of 〈111〉 tungsten crystal 1 mm thick on the electron energy of 26, 28, and 31 GeV are presented. It is found that the cascade curve maximum position and the energy release at the maximum of the cascade curve of shower development in the spectrometer with both oriented or misoriented converters have the logarithmic and proportional dependences on electron energy.     

Detection of high-energy electrons by a directional spectrometer

A method for the detection of 26- and 28-GeV electrons by a directional spectrometer based on oriented tungsten, tungstate, and garnet crystals has been reported. In spite of an anomalous character of the development of an electromagnetic shower at the initial stage in a crystal oriented along the 〈111〉 axis, the relative energy release of the shower in the spectrometer behind the crystal at the final stage is described by the standard dependence of the development of the electromagnetic shower.     

Critical energy of anomalous electron-induced showers

The results of experimental studies of anomalous electromagnetic showers caused by electrons with energies of tens of GeV, emerging from oriented tungsten crystals and detected by an electromagnetic spectrometer, are presented. An approximately twofold increase in the critical energy ? _c of the anomalous shower development in comparison with the similar quantity in the case of the standard shower development is detected. Its behavior is studied as a function of the crystal orientation, thickness, temperature, and the electron energy.     

Electromagnetic showers in crystals at high energies

The development of an electromagnetic shower in crystals at high energies has been studied. It is shown that coherence effects in radiation and e⁺e^--pair production can make the shower develop in a crystal over an appreciably shorter length than in an amorphous medium. The possibility of photon shower development in a crystal has been demonstrated.     

An apparatus of the NBC type and the physics results obtained

A nonbubble chamber (NBC) setup, especially designed to perform a series of experiments, is described. The setup consists of a neutron missing-mass spectrometer coupled with a system of large electromagnetic shower detectors. In spite of its large dimensions (the sensitive surface and volume are 2.16 × 10⁴ cm² and 7.8 × 10⁵ cm³, respectively), the neutron spectrometer has a time resolution of ±0.70 nsec FWHM, with ∼25% detection efficiency in the range (70–390 MeV) neutron kinetic energy. The time equalization between the various components of the neutron spectrometer has been established to within ±0.1 nsec. At present this is the most powerful and the most accurate high-energy neutron detector. The electromagnetic shower detector is based on the principle of simultaneous measurements of the spatial development of the electromagnetic cascade and of its energy release. This is obtained with nine elements of lead foil — spark chamber — plastic scintillator, all sandwiched together. The sensitive surface and volume of the electromagnetic shower detector are 1.45 × 10⁴ cm² and 7.2 × 10⁵ cm³, respectively.     

Estimates of the transverse development of anomalous electromagnetic showers

Estimates of the transverse development of anomalous electromagnetic showers induced by 26-GeV electrons and oriented along the 〈111〉 axis in tungsten, tungstate, and garnet crystals show the differences of shower development profiles from similar profiles of standard shower development. The Moliere length estimates are ～8X ₀, ～7.5X ₀, and ～6X ₀ or ～28 mm, ～67 mm, and 87 mm, respectively.     

Elektron-Photon-Kaskaden in Blei bei Primärenergien von 100, 200 und 400 MeV

Electron initiated showers in compact lead plates at primary energies of 100, 200 and 400 MeV have been measured by means of a propane bubble chamber. Cut-offenergies of the shower electrons were measured from 1.5 to 7.5 MeV by the range in propane. The wide-spread range distribution was related to energy by a Monte-Carlocalculation. The results are compared with shower calculations of Nagel. The electron numbers show good agreement at depths between 2 and 15 rad. length. Radial and angular distributions agree also but cannot be measured with the same precision as the numbers.     

A study of hadronic shower development in the ECAL of the alpha magnetic spectrometer Ⅱ

In this paper, we studied the development of hadronic shower in an electromagnetic calorimeter of Alpha Magnetic Spectrometer Ⅱ. Two parametrized empirical formulae were proposed to describe the hadronic shower shape in calorimeter. Using 100 GeV proton beam incident on the center of the ECAL, detailed plots of lateral and longitudinal hadronic shower behavior were given and we found the formulae can describe the development of the hadronic shower with the test beam data. The possible application of the parametrized formulae including e^±-π^± discrimination and tau jet reconstruction was discussed.     

Baseline effect on the forward-scatter radar reflections from meteor trains

Summary The influence of the baseline orientation on the rate of recorded meteor echoes has been shown from the observations carried out during the Lyrid meteor shower periods in 1992 and 1993 with receivers rectangularly displaced from the transmitting station in Bologna with a baseline length of about 700 km. It is shown that the maximum echo rate precedes or occurs later than the shower radiant culminates (at heights of 80°), favouring the 45° radiant elevation and similar angle between the radiant and the beam axis. The consequences of the measured effect on the meteor flux within the shower and sporadic radiant distribution is discussed.     

Energy loss of electron-induced showers in oriented tungsten crystals

The development of the shower induced by 26- and 28-GeV electrons in the oriented tungsten crystal results in strong absorption of the shower energy by the crystal and an increase in the energy fraction of shower particles scattered between the crystal and detector. The ratios of total shower energy losses in oriented tungsten crystals to total losses in misoriented crystals 1, 2.7, 5.8, and 8.4 mm thick were 3.9, 2.6, 2.1, and 1.9, respectively.     

一种用于冶金炉前快速分析的新仪器——激光诱导击穿光谱仪

冶金炼钢要求快速分析冶金炉前样品来及时掌握冶炼过程。文章介绍了自主研制的一种新型的光谱仪——激光诱导击穿光谱仪,该仪器采用ns级脉宽的Nd∶YAG激光器作为样品离子化光源,激光聚焦样品表面激发产生的等离子体光谱依次经帕邢-龙格光学系统进行分光、光电倍增管探测、门控积分器积分、模拟数字转换器转换后获得的最终结果输入计算机进行数据处理。和目前冶金炉前样品分析常用的光谱仪相比,该仪器无需样品预处理,分析速度快(1 min或更少),准确灵敏度高,非常适用于冶金炉前样品的快速分析。近年来随着光纤技术的迅速发展,使用该仪器进行钢液实时在线分析和动态控制冶金工艺必将成为现实。     

A study of hadronic shower development in the ECAL of the alpha magnetic spectrometer Ⅱ

In this paper, we studied the development of hadronic shower in an electromagnetic calorimeter of Alpha Magnetic Spectrometer Ⅱ. Two parametrized empirical formulae were proposed to describe the hadronic shower shape in calorimeter. Using 100 GeV proton beam incident on the center of the ECAL, detailed plots of lateral and longitudinal hadronic shower behavior were given and we found the formulae can describe the development of the hadronic shower with the test beam data. The possible application of the parametrized formulae including e^±-π^± discrimination and tau jet reconstruction was discussed.     

Effect of an oriented crystalline converter on the electromagnetic spectrometer response

The results of the experimental studies of the response of an electromagnetic spectrometer with a converter made of 〈111〉 tungsten crystal at electron energies of 26, 28, and 31 GeV are presented. It is found that the ratio of the difference between positions of the cascade curve maximum for misoriented and oriented converter to the difference between energy releases at the cascade curve maximumis a constant value at a given electron energy, converter type and thickness, and is independent of the converter temperature.     

THE DESIGN AND CONSTRUCTION OF THE BARREL SHOWER COUNTER FOR BES

The design and construction details of the barrel shower counter for BES are discussed.The barrel shower counter is cylinderical,of 2.5m inner diameter,3.4m outer diameter and 3.85m length,constructed on an aluminum spool of 2.5m diameter,3 cm thickness and 4.23m length.There are 23 layers of lead (0.5r.l. as an absorber) and 24 layers of selfquenching streamer (SQS) tubes.The total weight of the counter is 40,000kg and 80% of 4π sr soild angle coverage.     

TE01-TE11模式转换器的带宽特性

针对模式转换器设计中在相同的中心频点转换效率下模式转换器越短带宽越宽的传统观点,研究发现了最佳长度的存在,即当结构长度大于最佳长度时,带宽随着结构长度增加而减小,当结构长度小于最佳长度时,带宽随着结构长度增加而增加。通过对中心频率35 GHz、半径13.6 mm的TE01-TE11模式转换器进行的验证发现,最佳长度为550 mm,此时带宽达到最大值6.28%。     

ALICE光子谱仪光子判别能力模拟研究

光子判别能力是ALICE光子谱仪PHOS的重要性能指标之一. 利用ALIROOT软件包对0.5—100 GeV能量范围随机分布的7种粒子n, p,π+, K+和γ入射到PHOS上时光子判别的效率和纯度进行模拟研究. 在簇射形状分析中, 采用主成分分析方法将7参数分析问题约简为2参数, 并与7参数拓扑分析结果进行了比较. 给出了不同能区中光子判别效率与纯度的关系.The photon discrimination power of the ALICE photon spectrometer is simulated for incident particles n, p,π+, K+and γ with random energy distribution in the range from 0.5 to 100 GeV. The pricipale component analysis method is used to reduce the number of parameters in the shower shape analysis, and the results are compared with that from the seven parameter topology analysis.The efficiency dependence of purity for the photon discrimination is obtained for the deposited energy range 0.5—10, 10—20, 20—50 and 50—100 GeV.