共查询到20条相似文献,搜索用时 234 毫秒
1.
2.
3.
由28个多气隙电阻板室(MRPC)模块组成的探测阵列-STAR/TOFr, 在相对论重离子对撞机(RHIC)实验上获得了大量的数据. 利用质心能量62.4GeV Au+Au对撞的实验数据, 分析了MRPC探测不同带电粒子(K介子、π介子、质子等)时的输出信号与气体中的电离能损(dE/dx)之间的关系, 给出了MRPC的气体电离和雪崩放大一些新的实验结果. 为了进一步解释实验结果, 针对工作条件下MRPC输出信号的特点, 对MRPC的气体电离和雪崩过程进行Monte Carlo模拟, 深入探讨了影响MRPC输出信号幅度的原因. 相似文献
4.
5.
6.
7.
8.
研制的由28个多气隙电阻板室(MRPC)模块构成飞行时间探测系统, 从2003年以来在RHIC-STAR实验上成功运行并获得了大量的实验数据. 为了深入了解MRPC实际运行中的性能,采用质心能量200GeV的Au-Au对撞的实验数据, 对MRPC-TOF的刻度方法进行了深入研究, 主要包括: (1) 对现有的刻度方法做了进一步的改进;
(2) 对粒子入射角度等因素进行了修正; (3) STAR径迹重建的位置分辨率对MRPC时间分辨率影响. 用改进后的刻度和修正方法, 计算得到MRPC的本征时间分辨率为大约60ps, 与束流实验结果相近. 相似文献
9.
Multi-gap Resistive Plate Chamber (MRPC) is a new generation of gas detector with good timing and spacial resolution, whose technique is widely applied in some recent high energy (nuclear) physics experiments. In this letter, we report a long-strip two-end readout MRPC and its test beam performance. The measurements show that the long-strip performs a transmission line characteristic and the impedance is independent of the length of strip. The MRPC module we developed is presented to gain a timing resolution of -80 ps and a spacial resolution of -6.4 mm. The possible application of the MRPC is also discussed. 相似文献
10.
11.
12.
13.
S. Hunsmann K. Wunderle S. Wagner U. Rascher U. Schurr V. Ebert 《Applied physics. B, Lasers and optics》2008,92(3):393-401
A new sampling-free and calibration-free multi-channel hygrometer using near infrared (NIR) tunable diode laser absorption
spectroscopy (TDLAS) at 1.37 μm was developed and used to determine absolute transpiration rates of single plant leafs. Four
8×6× 4 cm3, fiber-coupled absorption cells are used to simultaneously measure absolute water vapor concentrations with an absolute accuracy
of about 5% and a temporal resolution of about 2 s. Two chambers (BOTTOM, TOP) are directly attached to the leaf surface,
while two chambers (IN, OUT) analyze the purge gas supplied to the plant leaf and the total outflow of the leaf chambers.
The BOTTOM–TOP comparison provided a direct, leaf-side resolved ratio of stomatal conductance and–by taking into account the
purge gas flow and the leaf area exposed–leaf side resolved water transpiration rates. The OUT–IN-difference yielded the total
leaf transpiration rate with 2 μmol/m2/s resolution. The new multi-point hygrometer was validated by monitoring of the transpiration dynamics of a plant of the
species Epipremnum pinnatum (L.) Engl. during diurnal variation of the leaf irradiation. During these experiments the differential H2O concentration resolution between two chambers was determined to be better than 3 ppm at Δt= 2 s (i.e. better than 711 ppb m Hz1/2). This performance was verified by an Allan analysis over a 30 min time period using CH4 as a surrogate absorber and yielded an average optimum optical resolution of 4.9×10-6 for 83 s measurement time, i.e. a CH4 resolution of 892 ppb, which corresponds to the optical resolution needed for a water sensitivity of 454 ppb m Hz1/2.
PACS 07.57.Ty; 42.62.Fi; 42.62.Be; 42.55.Px; 82.80.Gk 相似文献
14.
B. Zh. Zalikhanov 《Physics of Particles and Nuclei Letters》2006,3(2):118-130
The results of studying an electron avalanche in narrow-gap wire chambers in the region of avalanche-to-streamer transition are described. The amplitude and temporal characteristics of the chambers in the high gas multiplication mode (≥107) are given. Due to specific features of the electric field distribution in narrow-gap chambers and the application of a CF4-based working gas, previously unknown processes taking place in a shower and more clearly reflecting the dynamics of avalanche development were discovered—electron velocity distribution, electrostatic oscillations of the avalanche as a whole, decrease in the anode signal duration, increase in the delay time of charge induction on the cathode by the avalanche development time, and, finally, varying shapes of the anode and cathode signal amplitude distributions. The observed processes can be explained if a completed avalanche is represented in the form of a double charged layer. The basis for such a representation is the specific features of a high-current avalanche mentioned above. The model under consideration is simple, provides answers to questions related to streamer formation and growth, and reflects the structure of an ionized channel and its stability mechanism. 相似文献
15.
16.
The performance of a 1m×1m drift chamber system have been measured with on-line microcomputer using comic rays. The time resolution is 4.26 ns. The spatial resolution is 132 μm and the efficiency is above 96%. The experimental set-up include five 1m×1m adjustable field drift chambers, scintillation counter trigger system, readout electronics and a TRS-80 microcomputer. The data acquisition and processing have been done with on-line microcomputer and off-line data analysis. 相似文献
17.
The average amplitude of the vertical electric field strength in the atmospheric surface layer at the frequencies of lunisolar
tides has been estimated. The special feature of the problem of estimation of the amplitude Ez at the frequencies of tides is related to the necessity of using a long time series of experimental data which is related
to the frequency range of tidal variations and to the necessary frequency resolution. The signal amplitude at the frequencies
of tides has been estimated by using the radio engineering method of quadrature correlation receiver. Experimental data on
the electric field in the atmospheric surface layer over the range of lunisolar tides obtained at different stations of Hydrometeorological
Service have been analyzed.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 69–73, August, 2007. 相似文献
18.
Noninvasive in vivo functional optical imaging of the intact retina is demonstrated by using high-speed, ultrahigh-resolution optical coherence tomography (OCT). Imaging was performed with 2.8 microm resolution at a rate of 24,000 axial scans per second. A white-light stimulus was applied to the dark-adapted rat retina, and the average reflectivities from different intraretinal layers were monitored as a function of time. A 10%-15% increase in the average amplitude reflectance of the photoreceptor outer segments was observed in response to the stimulus. The spatial distribution of the change in the OCT signal is consistent with an increase in backscatter from the photoreceptor outer segments. To our knowledge, this is the first in vivo demonstration of OCT functional imaging in the intact retina. 相似文献
19.
在低计数率背景下X射线谱的高精度测量受X射线流的统计涨落影响,统计涨落决定了给定探测器能量分辨率的理论极限,而其他因素的影响则可以通过适当的噪声滤除和电子技术来降低。以往关于能量分辨率的研究大多利用谱反卷积对获取到的能谱进行后处理,从而降低特征峰的半高宽(FWHM)。这些后处理方法是基于将获取到的能谱建模为输入能谱和探测器响应函数这两个随机变量的函数,往往计算量极大,执行效率低。针对上述问题,提出一种多脉冲局部平均(MPLA)算法对X射线光谱数据处理平台进行优化,MPLA算法是一种在线实时处理的谱获取方法,该方法在动态窗口内对脉冲幅度值进行了平均。MPLA算法涉及两项可变参数,一是平均窗口的大小r,另一项参数则是每一次平均的脉冲幅度数量n。该算法的执行流程包含以下几个步骤,首先读取第一个脉冲幅度并定位一个平均窗口,读取成功后更新当前平均窗口的脉冲幅度和脉冲个数;第二步,读取下一个脉冲幅度,每次更新后即对平均窗口内的脉冲个数进行判断,当其小于预设的参数n时继续执行第三步,反之则执行第四步;第三步,继续读取下一个脉冲幅度;第四步,对相应平均窗口内的脉冲幅度进行平均,得出的平均数即为需要更新计数的道址,然后再对取平均值的窗口内脉冲幅度和脉冲个数进行清零。本文在理论推导部分研究了应用MPLA过程时原始概率密度函数(PDF)的转换,推导了应用MPLA后得到的概率密度函数的解析表达式,证明了MPLA概率密度转换后具有以下特征:(1)对称分布,MPLA保留了均值和对称性。(2)对于单峰对称分布,MPLA减少方差,锐化分布峰。在实验环节中,以铁矿样品为测量对象,将采用MPLA算法处理后的结果与传统的成谱方法得到的结果进行对比,结果表明在具有正态分布PDF的频谱峰值的典型情况下,即使仅对两个脉冲高度进行平均,变换后峰的FWHM也变窄。 相似文献
20.
A new technique to instantaneously measure microwave frequency and amplitude is presented and experimentally demonstrated. The architecture described is based on a single sideband modulation with suppressed carrier (SSB-SC) and the measurement of the Stokes parameters at the output of a birefringent medium. The results show errors below 50 MHz in the 59% of measurements carried out in a range from 1 to 11 GHz and an average power error of 0.34 dB. The technique shows the potential to increase the resolution and the range by increasing the differential time delay of the birefringent medium. 相似文献