反散射穆斯堡尔谱仪

为了用穆斯堡尔效应更方便地真实地研究金属材料的相变、断裂、表面腐蚀等,我们研制了一台反射式穆斯堡尔谱仪,对谱仪上用的反射式正比计数器的窗口材料、计数器结构、封接方式等作了一些工作,摸索出一批经验数据,我们的反射式正比计数器可以改变入射γ射线与样品表面的角度,使用流动的氩 5％甲烷混合气或使用氦 5％甲烷混合气,能量分辨率优于25％,可以长期连续工作,对于不同形状的样品适应性强,更换样品方便。     

微计算机穆斯堡尔谱仪

本谱仪为一台带微型计算机的匀加速穆斯堡尔谱仪。它利用了FH-1913型穆斯堡尔谱仪的基本部件,但其数据收集和控制部件改为由TRS-801微型计算机及相应的接口和软件来实现。组成中不再需要由硬件构成的多道分析器。 谱仪中的接口与改进后的函数产生器之间有同步信号和步进信号传送。接口与主机之间的数据传送采用程序中断方式。软件由BASIC语言和汇编语言编写。谱仪内存共有48K,其中程序只占13K,数据和缓冲只占4.6K。     

高计数率穆斯堡尔谱仪

本文论述了我们研制的高计数率穆斯堡尔谱仪,将它与常用穆斯堡尔谱仪作了比较,并利用512道,在道计数率超过20万次/h条件下,测量了磁带样品和考古样品的穆斯堡尔谱。     

多路背散射穆斯堡尔谱仪

多路背散射穆斯堡尔谱仪包括多丝正比室、多路数据获取和处理系统(包含有多路前放和数字单道、多路数据获取单元、控制微机和图像显示器)。该谱仪具有高的几何效率,可实时数据采集和处理,可以同时获取几个来自不同深度和方向的信息。     

穆斯堡尔谱仪中的时钟产生器

本文阐述了用于穆斯堡尔谱仪中的时钟产生器的特点和工作原理。对新研制生产的FH1085A型时钟产生器的主要技术性能作了介绍。     

穆斯堡尔谱仪的激光测速装置

本文叙述了穆斯堡尔谱仪激光干涉绝对测速的方法,介绍了一台配用高精度穆斯堡尔谱仪的激光测速装置,其测速范围为±5mm/s～±300mm/s,并具有穆斯堡尔谱与速度谱同时测量的性能。本文列举了部分测试结果,     

基于LabVIEW的虚拟穆斯堡尔谱仪

在LabVIEW平台上利用数据采集卡实现穆斯堡尔谱仪的速度驱动和脉冲计数功能,构成一台虚拟穆斯堡尔谱仪。谱仪操作界面友好,功能丰富,参数满足实验要求,已用于实际测量。     

小型化穆斯堡尔谱仪换能器的研制

换能器磁钢采用新型的稀土磁性材料SmCo5替代传统的AlNiCo5.换能器直径67.5 mm,长113.5 mm,总重1.36kg.室温下,差误信号与参考信号的峰-峰值之比小于0.4%;测量所得的25 μm α-Fe薄膜的穆斯堡尔谱的内双线线宽优于0.23 mm/s.换能器能够长时间稳定地测量穆斯堡尔谱,达到了设计精度的要求.     

一种微机化穆斯堡尔谱仪波形发生器

基于８７５１单片机的穆斯堡尔谱仪波形发生器用１２位Ｄ／Ａ转换器产生高线性度的三角波电压基准信号，并用８位Ｄ／Ａ转换器精确地控制三角波电压基准信号的幅度，同步信号和步进信号可任意延迟，以获取高质量的折叠谱。该波形姨生器可通过面板上的ＤＩＰ开关或ＩＢＭ－ＰＣ等微机的串行口实现控制。     

穆斯堡尔谱仪速度非线性测定的探讨

在穆斯堡尔谱仪中,驱动速度的质量指标主要在于它的稳定性和非线性。稳定性将在谱线宽度中反映出来,它主要取决于零电平漂移、参考信号幅度的微小不稳定以及驱动电路中放大单元的不对称漂移。而后二者通常在整个速度扫描中可以好于10~(-4)。速度的非线性是一个更重要的指标,它取决于速度参考信号的线性、反馈回路的增益以及拾波线圈响应的线性度(图1)。如果采用多道分析器,道址——道位置间的非线性关系也是一个重要的影响因素。而速度的非线性直接影响谱峰的位置,从而影响所得穆斯堡尔参数的精度。     

多道脉冲幅度分析中的数字基线估计方法

介绍了用于多道脉冲幅度分析的数字基线估计方法的基本特点,利用泛函变分方法推导了最小噪声基线滤波器的计权函数．利用Fourier变换导出了数字基线估计的频率响应,探讨了参数取值对其幅频特性的影响。还利用MATLAB模拟了电荷灵敏前置放大器输出的噪声电压信号,验证了最小噪声数字基线估计的处理效果。研究结果表明,数字基线估计方法能实现最佳基线估计,特别适于在数字化多道脉冲幅度分析中使用。     

Medium power pulse sources for deflection chamber modulation

Based on solid state elements and a power pulse transformer, two pulse sources have been constructed for the switching of the ETH AMS facility ion source for the isotopes ¹⁴C/¹²C, ¹⁴C/¹³C, ¹⁰BeO/⁹BeO and ³⁵Cl/³⁶Cl/³⁷Cl. The first one is a pulse generator in which the output amplitude is controlled by switching a dc-voltage on and off by thyristors and power transistors. The maximum output amplitude amounts to 10 kV with an upper limit for the pulse length of 300 μs. The second unit is a pulse amplifier with a bipolar output amplitude of ± 3 kV which uses power MOS-FETs to drive the pulse transformer.     

谱仪放大器中滤波成形电路的一种改进设计

对改进的5阶Butterworth滤波器网络进行了更深入的分析和仿真,并设计出了Sallen-key型有源滤波网络作为谱仪放大器中的滤波成形电路,在Protel DXP中进行了电路仿真,输出的结果满足设计要求.     

On theoretical research for nonlinear tearing mode

The analytical approaches for nonlinear tearing mode have been reviewed.It is shown that Rutherford's model has triggered numerous studies on the nonlinear tearing mode.Its physical picture is clear meanwhile its mathematical method is ingenious but still puzzling to understand.It is trying to find how the ‘nonlinear behavior' resulted from the linear equation by a nonlinear transform.It is indicated that Li's model for the tearing mode includes the linear growth,Rutherford's behavior and the new behavior.It was found that the quasilinear modification of magnetic field provided a new damping mechanism for nonlinear growth.The new behavior w~ t1/2 becomes dominant if the mode is weakly unstable.It is shown that many analytical methods have been developed to calculate the criterion parameter D' of the tearing mode.Li's instability criterion can cover the previous results in the limit cases.     

BaF2正电子寿命谱仪时间分辨率的改进

介绍了不同材料,不同形状的封装对BaF2晶体光收集的影响。使用聚四氟乙烯薄膜对BaF2晶体作伞状封装,光收集效果较好,在此条件下,常规正电子湮灭寿命谱仪的时间分辨率在^22Na能窗下达到180ps。     

A digital long pulse integrator for EAST Tokamak

A digital integrator has been developed to be compatible with the long pulse plasma discharges on the Experimental Advanced Superconductor Tokamak (EAST), in which the induced signal is modulated by a chopper, and a field programmable gate array (FPGA) in the 16-bit digitizer is used to realize the digital integration in real time. After rectification and integration, the drift is almost linear and stable in controlled temperature, so a period of 50 s is used to determine the linear drift rate for drift compensation. The integration data can be directly transferred to the reflective memory (RFM) card, which is installed in the same PCI eXtensions for Instrumentation (PXI) chassis, so the data transmission can be also done in real time. The test results show that the real time data transmission rate is up to 10 kHz, the integration drift is typically less than 0.4 uVs/s and drift performance is a little worse in real long pulse discharge, which can be reduced further by using more precise data acquisition.     

Readout electronics for a high-resolution soft X-ray spectrometer based on silicon drift detector

The readout electronics for a prototype soft X-ray spectrometer based on silicon drift detector (SDD),for precisely measuring the energy and arrival time of X-ray photons is presented in this paper.The system mainly consists of two parts,i.e.,an analog electronics section (including a pre-amplifier,a signal shaper and filter,a constant fraction timing circuit,and a peak hold circuit) and a digital electronics section (including an ADC and a TDC).Test results with X-ray sources show that an energy dynamic range of 1-10 keV with an integral nonlinearity of less than 0.1％ can be achieved,and the energy resolution is better than 160 eV@5.9 keV FWHM.Using a waveform generator,test results also indicate that time resolution of the electronics system is about 3.7 ns,which is much less than the transit time spread of SDD (＜100 ns) and satisfies the requirements of future applications.     

聚变脉冲中子源特性的近距离测量方法

介绍在近距离条件下,测量聚变脉冲中子源的时间谱、能谱和产额的一种方法-两测点解谱法,对该方法的局限性作了简要地讨论。