Simulation and prototype testing of multi-wire drift chamber arrays for the CEE

The building of a large-scale external-target experiment, abbreviated as CEE, in the cooling storage ring at the Heavy Ion Research Facility in Lanzhou has been planned. The CEE is a multi-purpose spectrometer that will be used for various studies on heavy-ion collisions. A multi-wire drift chamber(MWDC) array is the forward tracking detector of the CEE. In this work, GEANT4 simulations were performed for the MWDC forward tracking array with a focus on the track reconstruction algorithm. Combined with the time of flight information,particle identification is achieved. The residue is about 30 μm, while the tracking efficiency is higher than 90%with the current redundancy. In addition, a prototype of the forward tracking system using three MWDCs was assembled and tested using a high-energy proton beam. The firing efficiency of the detector and the reconstruction accuracy of the prototype were derived. The track residue for the protons at about 400 MeV/c is better than 300 μm, meeting the requirements of the CEE. Suggestions for improving the performance of the forward tracking system are given.

Construction and cosmic-ray test of the new inner drift chamber for BESIII

A new inner drift chamber has been built which can replace the aged part of the BESIII drift chamber when needed. The design of the new inner drift chamber can minimize the ineffective area in the very forward and backward region and hence reduce the background event rate. With this design, the new inner drift chamber is expected to have a longer lifetime and improved performance due to the lower occupancy. The endplates and the cylinder were machined with high precision. Wire stringing was performed after the mechanical structure was assembled, and good quality of wire stringing was ensured by measurement of the tension and leakage current of the wires. After completion of the physical construction of the new chamber, a cosmic-ray test was carried out to test its performance. The results of the cosmic-ray test show that the new inner chamber achieves a spatial resolution of127 μm and a d E/dx resolution of 6.4%, which satisfies the design specifications.

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.

Low transverse momentum track reconstruction based on the Hough transform for the BESIII drift chamber

Background The multilayer drift chamber(MDC)is one of the key detectors at the BESIII,which is mainly responsible for the precise measurement of charged particles.High reconstruction efficiency of charged particles with a wide range of momentums is a basic requirement for the MDC reconstruction software.Purpose The purpose is to improve the tracking efficiency at the low transverse momentum region.Methods The Hough transform is a mathematical method that can map hits in a detector to parameter space to find tracks globally.In this paper,we have used it as the basis for developing a new tracking algorithm to find tracks in MDC.In addition,the drift distances of hits are considered when implementing Hough transform.Results This tracking algorithm is implemented in the BESIII offline software system,and its performance is checked using both Monte Carlo and data.The results show that this tracking method improves reconstruction efficiency at the low transverse momentum region.Conclusions The tracking algorithm based on Hough transform is proved to be beneficial for the MDC low transverse momentum tracking,and has been used in BESIII offline data reconstruction .

A study of the calibration of wire positions for the BESⅢ drift chamber using physics data without magnetic field

A method to determine precisely three-dimensional wire positions in the BESⅢ drift chamber using physics events is introduced. In part the proposed technique takes advantage of the possibility that the magnetic field can be turned off, thereby providing a huge sample of straight tracks for which effects due to multiple scattering, energy loss and non-uniformity of the magnetic field are minimized during the calibration process. A toy Monte Carlo study is performed to demonstrate the viability of the method. As a result of the calibration process, the rms of the distribution of wire position deviation is reduced from 35 μm to 10 μm.

Calibration study of the X-T relation for the BES drift chamber

Offiine calibration plays an important role in BESⅢ offiine data processing. In order to achieve good spatial and momentum resolution, it is necessary to implement high precision offline calibration for the BESⅢ drift chamber. This paper studies the time-to-distance relations, which are important calibration constants for track reconstruction. The parameterization of the time-to-distance relation, studies of left-right asymmetry and studies of variation with entrance angle are performed. The impact of dead channels on the time-to-distance relation is given special attention in order to reduce the shift in measured momentum for tracks passing near dead cells. Finally we present the resolutions for barrel Bhabha events （｜cosθ｜ 〈0.8） from a J/ψ data set taken in 2012. The average spatial resolution is 123 μm and the momentum resolution for 1.548 GeV/c Bhabha tracks is 11.9 MeV/c.

Improvement of main drift chamber Monte-Carlo tuning model at BESⅢ

Based on real data, a new parameterized model of the main drift chamber response is proposed. In this model, we tune the ratio of good hits and the residual distribution separately. By data quality checking, the diference between simulation and data in track reconstruction efciency reduces from 1% to 0.5% averagely for the pion in J/ψ→π＋π π0, and the momentum resolution agreement improves significantly for the proton in J/ψ→ppˉ.

A Flash-ADC data acquisition system developed for a drift chamber array and a digital filter algorithm for signal processing

A Flash-ADC data acquisition （DAQ） system has been developed for the drift chamber array designed for the External-Target-Experiment at the Cooling Storage Ring at the Heavy Ion Research Facility, Lanzhou. The simplified readout electronics system has been developed using the Flash-ADC modules and the whole waveform in the sampling window is obtained, with which the time and energy information can be deduced with an offiine processing. A digital filter algorithm has been developed to discriminate the noise and the useful signal. With the digital filtering process, the signal to noise ratio （SNR） is increased and a better time and energy resolution can be obtained.

Design and implementation of the detector control system for the BESⅢ drift chamber cosmic ray test

After the construction of the BESⅢ drift chamber, a long period of cosmic rays test is necessary to verify its performance. This also provides a good opportunity to integrate the detector readout electronics and Detector Control System （DCS） into a unified working system. The goal of the DCS is to guarantee reliable physics data quality and the safe operation of the detector. It monitors and controls the HV, gas, VME crates and the environmental variables. The upper-level system is mainly developed from LabVIEW and the lower-level system mainly uses MCU and PLC technology. The system is designed to be highly flexible and scalable so that it can be applied to other detectors with little or no change. In the immediate future, it will be integrated into the entire BESⅢ Slow Control System.

Tuning of the cosmic-ray test system of the BESⅢ drift chamber

The BESⅢ drift chamber and its subsystems need a cosmic-ray test after the chamber construction to check the chamber construction quality,testing the joint operation of the whole system and the performance of the chamber.The noise performance,drift time and charge measurements,and the scanning of channels were examined specifically.The preliminary results of the test indicate that the whole system works well.

Installation and cosmic ray test of the high voltage system of the BESⅢ drift chamber

After examination of the designed high voltage power supply system of the BESⅢ drift chamber in the beam test of the full length prototype of drift chamber, a full system covering all the channels of high voltage was installed. The system＇s training and the high voltage value adjustment were carried out in the cosmic ray test of the BESⅢ drift chamber. The cosmic ray test for the full system and its final installation on the BESⅢ drift chamber were reported. The full system of high voltage power supply works stably and reliably.

Software alignment of the BESⅢ main drift chamber using the Kalman Filter method

Software alignment is quite important for a tracking detector to reach its ultimate position accuracy and momentum resolution. We developed a new alignment algorithm for the BESⅢ Main Drift Chamber using the Kalman Filter method. Two different types of data which are helix tracks and straight tracks are used to test this algorithm, and the results show that the design and implementation is successful.

小单元多丝漂移室探测器系统研制

为精确测量CSR外靶终端靶前入射粒子的径迹,研制了多套小单元多丝漂移室探测器,该探测器灵敏面积为80 mm×80 mm,每套探测器包括x、x′、y、y′4个探测电极面,每个电极面引出16个阳极丝信号。前端电子学采用基于SFE16芯片的放大器,数据读出系统采用基于HPTDC芯片的数据采集卡。采用两套小单元多丝漂移室对400 MeV/u的^(16)O束流位置进行了测试,探测器的工作气体为Ar(80%)+CO_(2)(20%),阳极丝电压为+900 V,场丝与阴极丝均接地,拟合得到的单层电极的位置分辨(拟合残差)为105.9μm,探测效率为99.3%,该指标可以满足现阶段CSR外靶终端大部分核物理实验对反应靶点的定位要求。

列车人工气候室飘雪实验参数设计研究

列车驾驶员视野能见度直接关乎行驶安全,国际标准规范CEN-TR 16251中要求列车需进行覆雪实验,但目前规范中并未明确飘雪实验参数设置。为明确列车人工气候室飘雪实验参数,并满足均匀覆雪要求,以某列车人工气候室为研究对象,综合考虑冰雪粒径、初始风速和人工气候室风速等参数,依据列车人工气候室飘雪过程冰雪粒子运动特性预测模型,设计9个实验工况,并进行数值模拟及优化。研究结果表明:当列车头模型加入后,会引起气候室内气流组织产生变化,影响冰雪粒子的运动特性,降低预测模型的准确性,进而导致依据预测模型设计的9个实验工况中,仅有5个工况的列车头冰雪粒子捕捉率达到了85%~96.7%,列车头冰雪粒子覆盖率达到80%~85.7%,能满足列车头玻璃均匀覆雪要求,另外4个设计工况未能满足列车头玻璃均匀覆雪要求。进一步地,采用正交实验法优化不满足要求工况中的设计参数,结果显示,优化后列车头冰雪粒子捕捉率最大可达64%~98.1%,列车头冰雪粒子覆盖率可达80.1%~92.2%。本文以“均匀覆雪,兼顾节能”为原则,设计、优化并最终确定了能满足列车头玻璃均匀覆雪要求的9个实验室测试工况,结果可为列车人工气候室飘雪实验提供指导。

北京谱仪Ⅲ主漂移室快速径迹重建系统

阐述了北京谱仪Ⅲ(BESⅢ)主漂移室快速径迹重建系统的基本原理和程序结构。通过对蒙特卡罗(MC)产生的一些典型的单事例、bhabha事例和双muon事例数据的运行结果的分析,初步证明了程序的可靠性。

使用氦基工作气体的小单元漂移室性能的研究

报道了用于低动量带电粒子高精度测量的小单元漂移室的初步研究结果。在 1m长的小单元漂移室内 ,首先以氦基混合气体得到室体正常工作状态 ,然后充以氦基混合气体对室性能作了测试。结果表明 ,55Fe5 .9ke V X射线在氦气中显示出较好的光电峰 ;沿丝方向输出和对不同漂移距离输出信号均匀 ;用三室法通过宇宙线测得平均空间分辨率为 15 5 μm。

BESⅢ漂移室的高压供电系统

介绍了BESⅢ漂移室的高压供电系统,分别阐述了漂移室信号丝高压的确定方法,高压供给电源,高压分配方案,高压板的设计,高压控制程序等。

北京谱仪-Ⅱ主漂移室干扰噪声的研究

研究了北京谱仪－Ⅱ主漂移室干扰噪声（ｐｉｃｋ－ｕｐ噪声）的主要表现形式，分析了噪声的来源，提出了解决办法。

北京谱仪漂移室读出电子学2×576个通道的研制

本文概述了北京谱仪漂移室读出电子学的任务,特点,比较详细地介绍了电路框图,工作原理及设计考虑,给出了作为大系统的一部分——已研制成功的576个时间通道和576个电荷通道的测试结果,收到了预期的效果。

BESⅢ中的卡尔曼径迹拟合(英文)

基于卡尔曼滤波方法,开发了漂移室径迹拟合算法。在软件中仔细处理多次散射、能量损失等物质效应,处理磁场不均匀性的影响,考虑重力下垂、单丝空间分辨和其他刻度因素。描述了漂移室径迹拟合软件包的设计实现、主要算法,并用模拟样本对算法及其相关参数进行了优化。对其性能进行的研究表明,拟合结果的各种分布是合理的,本软件对径迹参数、误差矩阵以及动量分辨率都有所改善,对低动量的强子径迹更为明显,从而对BESⅢ物理结果有较为显著的影响。