单质硫:合成含硫杂环的优质硫源

含硫杂环化合物在药物、分子器件和材料等诸多领域应用广泛,因而其合成方法备受关注.合成含硫杂环的关键在于分子中C—S键的构建,一般通过含硫有机物或无机物参与的C—H键功能化或C—X键偶联反应来实现.单质硫价廉易得,性质稳定,是合成含硫杂环的优质硫原子供体,因而以单质硫为原料合成含硫杂环成为人们研究的热点.综述了近年来以单质硫为硫源合成各种含硫杂环的研究进展情况.     

Application of the DRS4 chip for GHz waveform digitizing circuits

A new fast waveform sampling digitizing circuit based on the domino ring sampler (DRS), a switched capacitor array (SCA) chip, is presented in this paper, which is different from the traditional waveform digitizing circuit constructed with an analog to digital converter (ADC) or time to digital converter. A DRS4 chip is used as a core device in our circuit, which has a fast sampling rate up to five gigabit samples per second (GSPS). Quite satisfactory results are acquired by the preliminary performance test for this circuit board. Eight channels can be provided by one board, which has a 1 V input dynamic range for each channel. The circuit linearity is better than 0.1%, the noise is less than 0.5 mV (root mean square, RMS), and its time resolution is about 50 ps. Several boards can be cascaded to construct a multi-board system. The advantages of high resolution, low cost, low power dissipation, high channel density and small size make the circuit board useful not only for physics experiments, but also for other applications.     

基于PXI总线的阵列探测器数据获取系统

描述了一种适用于阵列探测器的数据获取系统。系统基于PXI总线, 采用标准NIM插件作为前端电子学。系统软件采用C/C++语言编写, 在线分析通过调用ROOT类库实现, 系统运行在Linux操作系统下。多次测试结果表明, 系统稳定可靠, 单个ADC通道可以处理的最大事例率为40 kHz。A data acquisition system for array detectors is described. The system is based on PXI bus with standard NIM modules used as front\|end electronics. The system software is written in C/C++ language with its online analysis modules realized by ROOT class library. Several runs of the system under Linux show that it is reliable and is capable of handling event rates up to 40 k events/s for 1 ADC channel.     

Development of front-end readout electronics for silicon strip detectors

Front-end readout electronics have been developed for silicon strip detectors at our institute. In this system an Application Specific Integrated Circuit (ASIC) ATHED is used to realize multi-channel energy and time measurements. The slow control of ASIC chips is achieved by parallel port and the timing control signals of ASIC chips are implemented with the CPLD. The data acquisition is carried out with a PXI-DAQ card. The software has a user-friendly GUI developed with LabWindows/CVI in the Windows XP operating system. The test results show that the energy resolution is about 1.14% for alpha at 5.48 MeV and the maximum channel crosstalk of the system is 4.60%. The performance of the system is very reliable and is suitable for nuclear physics experiments.     

应用于在束PET的光纤链路设计

医用重离子加速器(Heavy-Ion Medical Machine,HIMM)中安装在束正电子发射断层扫描装置(In-beam Positron Emission Tomography,In-beam PET)可实现治疗时对肿瘤靶区的照射剂量和位置分布的实时监测功能.在束PET工作时,事件经探测器阵列采集,由前端数据...     

[Au25(SR)18]-团簇的相干振动动力学研究

利用飞秒时间分辨光谱,可观测叠加在电子态动力学上的相干振动动力学. 从金团簇的相干振动中,不仅能提取电子与振动的耦合信息,也能得到力学性质和电子结构,进而有望实现微小质量探测等应用. 本文利用飞秒时间分辨的瞬态吸收探测了[Au₂₅(SR)₁₈]^-团簇的相干振动动力学,通过对相干振动的频率、相位、波长分布的详细分析进一步揭示了其来源. 在[Au₂₅(SR)₁₈]^-团簇的飞秒瞬态吸收动力学中可以观测到频率为40 cm^-1和80 cm^-1的两种振动,均来源于团簇中心Au₁₃核的振动. 通过对相干振动的相位分析发现频率为80 cm^-1的振动来自于对电子态之间吸收频率的调制,而频率为40 cm^-1的振动来源于对电子态之间吸收强度的调制. 同时,研究发现[Au₂₅(SR)₁₈]^-团簇相干振动的频率对其表面配体不敏感,该振动是来源于Au₁₃核的本征性质.     

Study of time resolution by digital methods with a DRS4 module

A new Digital Pulse Processing(DPP) module has been developed, based on a domino ring sampler version 4 chip(DRS4), with good time resolution for La Br3 detectors, and different digital timing analysis methods for processing the raw detector signals are reported. The module, composed of an eight channel DRS4 chip, was used as the readout electronics and acquisition system to process the output signals from XP20D0 photomultiplier tubes(PMTs). Two PMTs were coupled with La Br3 scintillators and placed on opposite sides of a radioactive positron22 Na source for 511 ke V γ-ray tests. By analyzing the raw data acquired by the module, the best coincidence timing resolution is about 194.7 ps(FWHM), obtained by the digital constant fraction discrimination(d CFD) method,which is better than other digital methods and analysis methods based on conventional analog systems which have been tested. The results indicate that it is a promising approach to better localize the positron annihilation in positron emission tomography(PET) with time of flight(TOF), as well as for scintillation timing measurement,such as in TOF-?E and TOF-E systems for particle identification, with picosecond accuracy timing measurement.Furthermore, this module is more simple and convenient than other systems.     

2-取代苯并噁唑类化合物合成研究进展

2-取代苯并噁唑类化合物在医药、农药以及配位催化等领域有广阔的应用前景,因而其合成方法备受关注.近年来,微波促进、水为介质、无溶剂合成、组合化学以及过渡金属催化等一系列高效、绿色的合成方法在2-取代苯并噁唑类化合物的合成中得到广泛的应用.按照不同的合成原料和合成方法进行分类,综述了近年来2-取代苯并噁唑类化合物合成研究的新进展.     

塑料闪烁体阵列探测器读出ASIC中峰值保持电路的设计

塑料闪烁体阵列探测器(PSD,简称塑闪阵列探测器)的输出信号经过前置放大器和滤波成形电路后输出准高斯波形,利用峰值保持电路可对准高斯波形信号的峰值进行采样和保持,以便后续的电子学系统对其进行进一步的分析。本工作采用180 nm CMOS工艺设计并实现了一款峰值保持电路ASIC芯片,每通道主要由跨导放大器(OTA)、电流镜和充电电容三部分电路组成。实验室电子学功能和性能测试结果表明:峰值保持电路功能良好;输入动态范围为33~940 mV,非线性误差优于0.8%,下垂速率好于8.6 μV/μs,峰值探测延迟时间小于35 ns,芯片单通道静态功耗为825 μW,达到设计要求。     

使用超快拉曼光谱技术研究四极矩给体-受体-给体分子的激发态动力学

具有对称结构和四极矩性质的给体-受体-给体分子在激发态通常展现出从离域的电荷转移态向局域的电荷转移态转化的电荷重分布过程，该现象已被多种超快时间分辨光谱技术进行了大量研究. 飞秒受激拉曼光谱是一种常用的超快时间分辨光谱，该光谱可以通过检测分子内特定的振动模来研究分子激发态动力学. 本研究采用的4，4''-(1，3-丁二炔-1，4-二基)双(N，N-二(4-甲氧苯基)苯胺)含有位于中间位置的两个相邻炔基(电子受体)和对称分布在分子两侧的N，N-二(4-甲氧苯基)苯胺(电子给体). 研究发现，飞秒受激拉曼光谱能够实时观测该分子在溶剂中发生的激发态电荷重分布过程. 该结果将有助于深入研究具有相邻特征官能团的对称四极矩分子光致电荷局域/离域动力学.