A Linear Amplifier Suitable for High Counting Rates

A linear amplifier suitable for high counting rates is described. The amplifier uses double-delay-line shaping to minimize base line shifts and to enable timing signals to be obtained from the zero crossover. Miniature delay lines are used and the amplifier is designed to work with lines as short as 100 nanoseconds. It has a maximum gain of 500 and a rise time of 18 nanoseconds. To minimize delay line reflections, the lines are terminated at both ends. A novel circuit is used to obtain the delay line shaping. The amplifier has good overload characteristics and is constructed very compactly. It plugs into a frame designed to accomodate a series of compatible circuits of modular design. The front panel space required is 3.6 by 7 inches. Circuitry and performance are described.     

Analysis of hot leg natural circulation under station blackout severe accident

Under severe accidents, natural circulation flows are important to influence the accident progression and result in a pressurized water reactor （PWR）. In a station blackout accident with no recovery of steam generator （SG） auxiliary feedwater （TMLB＇ severe accident scenario）, the hot leg countercurrent natural circulation flow is analyzed by using a severe-accident code, to better understand its potential impacts on the creep-rupture timing among the surge line, the hot leg, and SG tubes. The results show that the natural circulation may delay the failure time of the hot leg. The recirculation ratio and the hot mixing factor are also calculated and discussed.     

Recent Developments in Delay Line Readout of Multiwire Proportional Chambers

The application of electromagnetic delay line readout methods for determining the track positions of ionizing particles in multiwire proportional chambers is described. Construction techniques for large area chambers, which allow the use of all three planes for track position measurements are given. The construction and characteristics of electromagnetic delay lines optimized for wire chamber readout are discussed.     

A high precision time-to-digital converter based on multi-phase clock implemented within Field-Programmable-Gate-Array

In this paper, the design of a coarse-fine interpolation Time-to-Digital Converter (TDC) is implemented in an ALTERA’s Cyclone FPGA. The carry-select chain performs as the tapped delay line. The Logic Array Block (LAB) having a propagation delay of 165 ps in the chain is synthesized as delay cell. Coarse counters triggered by the global clock count the more significant bits of the time data. This clock is also fed through the delay line, and LABs create the copies. The replicas are latched by the tested event signal, and the less significant bits are encoded from the latched binary bits. Single-shot resolution of the TDC can be 60 ps. The worst Differential Nonlinearity (DNL) is about 0.2 Least Significant Bit (LSB, 165 ps in this TDC module), and the Integral Nonlinearity (INL) is 0.6 LSB. In comparison with other architectures using the synchronous global clock to sample the taps, this architecture consumed less electric power and logic cells, and is more stable.     

Measurement of response time and detection of degradation in pressure sensor/sensing-line systems

A team evaluated several methods for remote measurement of the response time and detection of degradation (blockage or air in lines) of pressure sensor/sensing line systems typical of nuclear power plants. A method was developed for obtaining the response time of force-balance pressure transmitters by briefly interrupting the power supply to the transmitter. The data thus generated are then analyzed in conjunction with a model to predict transmitter response to an actual pressure perturbation. The research team also evaluated a pressure perturbation method for determining the asymptotic delay time of a pressure-sensing line and found that this method yields accurate results for essentially unblocked sensing lines. However, these pressure perturbation tests are not recommended for use in nuclear power plants because they are difficult to implement on-line. A third method for remote measurement applied noise analysis methods that yielded accurate estimates of asymptotic delay times for blockage or air in sensing lines. Even though noise analysis methods worked well in the laboratory, it is recommended that further evaluation be performed in operating nuclear plants.     

基于延迟线的二维读出多丝正比室电路

针对在多丝正比室中粒子入射到阳极丝产生信号的延迟时间与原初电离的位置有关这一特点,设计了一种基于延迟线方法多丝正比室的电子学读出系统,重点介绍了该电子学系统中的延迟线设计,包括延迟线的结构和延迟单元参数的理论计算。并给出了该延迟电路的模拟仿真和实际测量的结果,验证了这种方法的可行性及优越性。     

Carry-chain propagation delay impacts on resolution of FPGA-based TDC

The architecture of carry chains in Field-Programmable Gate Array （FPGA） is introduced in this paper. The propagation delay time of the rising and falling edges in the carry chains are calculated according to the archi- tecture and they are predicted not equal in most cases. Tests show that the measuring results of the propagation delay time in EP3C 120F484C8N series FPGA of Altera are in line with the inference. The difference of propa- gation delay time results in different accuracies of Time-to-Digital Converter （TDC）. This phenomenon shall be considered in the design of TDC implemented in FPGA. It can ensure better accuracy.     

Evaluation of the RCS depressurization strategy for the high pressure sequences by using SCDAP/RELAP5

As part of the evaluation for a severe accident management strategy, a reactor coolant system (RCS) depressurization in optimized power reactor (OPR)1000 has been evaluated by using the SCDAP/RELAP5 computer code. An indirect RCS depressurization by a secondary depressurization by using a feed and bleed operation has been estimated for a small break loss of coolant accident (LOCA) without a safety injection (SI). Also, a direct RCS depressurization by using the safety depressurization system (SDS) has been estimated for the total loss of feed water (LOFW). The SCDAP/RELAP5 results have shown that the secondary feed and bleed operation can depressurize the RCS, but it cannot depressurize the RCS sufficiently enough. For this reason, a greater direct RCS depressurization by using the SDS is necessary for the 1.35 in. break LOCA without SI. A proper RCS depressurization time and capacity leads to a delay in the reactor vessel failure time from 7.5 to 10.7 h. An opening of two SDS valves can depressurize the RCS sufficiently enough and the proper RCS depressurization time and capacity leads to a delay in the reactor vessel failure time of approximately 5 h for the total LOFW. An opening of one SDS valve cannot depressurize the RCS sufficiently enough.     

Signal, Noise and Resolution in Position-Sensitive Detectors

An analysis is presented of signal, noise and position resolution relations for some of the most interesting position-sensing methods. "Electronic cooling" of delay line terminations is introduced in order to reduce noise in the position-sensing with delay lines. A new method for terminating transmission lines and for "noiseless" damping which employs a capacitance in feedback is presented. It is shown that the position resolution for the charge division method with resistive electrodes is determined only by the electrode capacitance and not by the electrode resistance, if optimum filtering is used.     

A calculation model for breakdown time delay and jitter of gas switches under hundred-nanosecond pulses and its application in a self-triggered pre-ionized switch

In this paper,a calculation model for the breakdown time delay and jitter of gas switches under hundred-nanosecond pulses is proposed and applied in a self-triggered pre-ionized switch.The effects of injection time of pre-ionization,pulse rise time,and the pre-ionization jitter are discussed and verified through experiments.It indicates that the pre-ionization should be injected when the electric field is high enough in the gap,injection after 80％peak-time can ensure its effectiveness.Then the statistical time delay jitter will be determined by the pre-ionization jitter,which is an intrinsic restriction of the self-triggered switch.However,when the changing rate of the pulsed electric field exceeds a certain value,the breakdown time delay jitter can be partly offset in the formative stage because the formative time delay has an exponential relationship with the electric field.Therefore,lower time jitter can be obtained under pulses with a shorter pulse rise time.In general,the results of the calculation model agree with the experimental results,and the experimental parameters which lead to a low jitter can also be used as a reference.     

Pseudo Two-Dimensional Analysis of Fluid-Structure Interaction due to Pressure Wave Propagation in Straight Pipe

A new computer program SPICA developed for evaluating fluid-structure interaction (FSI) due to pressure wave propagation in straight pipe is presented. In SPICA, equations of one, instead of two, dimensional fluid dynamics are coupled with those of two-dimensional structural dynamics. This simplification is expected to improve computing time significantly without reducing the accuracy of calculation.

The validity and the effectiveness of SPICA is shown by good agreement of the pressure time histories and deformations predicted by SPICA with the experimental results of FSI in straight pipe, and by the fact that the results are obtained with the computing time a factor of 100 smaller than that for conventional fully two-dimensional program. Finally, the limitation of the simplification used in SPICA is discussed briefly.     

A PVT Insensitive Vernier-Based Time-to-Digital Converter With Extended Input Range and High Accuracy

A monolithic Vernier-based time-to-digital converter (TDC) with 37.5 ps time resolution and theoretically unlimited input range has been integrated in TSMC 0.35-mum standard 2P4M CMOS technology. Since the proposed circuit utilizes a single-stage Vernier delay line (VDL) for both coarse and fine measurements, no other interpolation circuit is required. The operation frequencies of the single-stage Vernier delay line are stabilized against process, voltage and temperature (PVT) variations by dual phase-locked loops. The proposed TDC successfully eliminates the element mismatch, input range limitation, external bias adjustment and complicated calibration problems. The measured differential nonlinearity is plusmn0.2 LSB, and the measured integral nonlinearity is plusmn0.35 LSB. The power consumption is 150 mW at 100 k samples/s full conversion speed, and the chip size is as small as 0.222 mm². All the packaged chips were tested to be fully functional over -40degC to 100degC ambient temperature range and 3.0 V to 3.9 V supply voltage range with extremely low resolution variations     

亚纳秒触发脉冲延时分配器设计

介绍了上海光源储存环注入系统冲击磁铁定时触发脉冲延时分配器的设计和研制。采用可控专用延时芯片设计了该触发脉冲延时分配器,实现1路光脉冲输入,4路延时独立可调的快前沿低抖动电脉冲输出,输出脉冲延时调整步长0.25 ns、可调延时范围64 ns。除具有延时功能外,还具有联锁保护、输出脉冲状态、联锁输入状态显示等功能,不仅可以通过仪器面板操作,还可以通过RS232接口遥控。     

A TDC-Based System for X-Ray Imaging Detectors

An image acquisition system is presented for use with position sensitive detectors (PSD). The system is based on a high-resolution time-to-digital converter (TDC) and a field programmable gate array (FPGA). The detectors use gas as absorbing medium and two delay lines to identify the coordinates of each detected particle. The TDC translates the time information coming from the delay lines into digital words, from which the particle position coordinates are encoded. The FPGA is responsible for processing each event, controlling the data acquisition and communicating with a personal computer. 256 pixels$times$256 pixels images are stored into an on-board memory. This resolution is increased to 512 pixels$times$512 pixels by using a time multiplexing technique. The maximum data acquisition rate is 1.2 million events per second. X-ray images obtained with the system are shown, which illustrate the overall performance.     

一种高精度、大量程时间间隔计数器的设计

时间间隔测量方法有多种,如计数法、游标法、模拟内插法、延迟线内插法、时间电压变换法等.通过对这几种测量方法的分析比较,提出了一种大量程、高精度的时间间隔测量方法,并从实现原理和设计方法进行了阐述.该方法已成功应用于GPS铷钟中,对于同类时间间隔计数器设计具有借鉴意义.     

Enhancement of energy dispersive residual stress analysis by consideration of detector electronic effects

The effects of the germanium detector electronics on diffraction line patterns is investigated. It is shown that not only the detector resolution and the throughput but also the energy stability depend on both the specific detector settings and the dead time. For a moderate resolution versus throughput setting a correction function is proposed and applied to the near-surface residual stress analysis of three samples with considerably different stress states. It is demonstrated that without the correction function ghost stresses up to hundreds of MPa in the near-surface region are obtained. The correction procedure is verified by conventional X-ray measurements. In conclusion, the authors strongly suggest quantifying the electronic shifts of any individual detector systems prior to the analysis of residual stresses.     

Nanosecond laser preheating effect on ablation morphology and plasma emission in collinear dual-pulse laser-induced breakdown spectroscopy

Focus-offset collinear dual-pulse laser-induced breakdown spectroscopy is designed and used to investigate the laser ablation and spectral intensity with an aluminum alloy sample. The laser crater morphologies and ablation volumes were measured. An inter-pulse time delay dependent ablation efficiency on a nanosecond laser-heated sample was observed, which was similar to the trend of spectral intensity versus inter-pulse time delay in the delay time less than 3 μs. Based on the observation, the nanosecond pulse laser preheating effect on subsequent second laser ablation and signal enhancement is discussed, which will be helpful for understanding the ablation and signal enhancement mechanism in the standard collinear DP-LIBS technique.     

延迟线定时的触发判选电路

本文介绍一种可用于正负电子对撞机谱仪的延迟线定时的触发判选电路。它是一种简单、快速的判选逻辑,主要用以排除宇宙线,其定时时间分辨小于20ns。     

An explicit solution for a renewal process with waiting time and its variational principle

The forward and backward equations for the conditional probability density are derived for a reliability system consisting of a single component whose repair is subject to a delay time in providing a spare part but whose mean rate of repair is otherwise constant and whose time to failure is exponentially distributed. Exact solutions are quoted. These equations are then shown to be an adjoint pair that provide stationary conditions for a variational principle, in elementary form, from which all properties of the systems can be predicted with an accuracy greater than that implied by the trial functions or approximations used. A second or specific form of variational principle provides specific estimates to questions at hand. The second or adjoint field in the first elementary principle is the backward Kolmogorov solution and the in the specific form is the importance function, as used in nuclear reactor theory. The solutions are given for long-time and in a recurrence relation form valid for all times so that approximate solutions can be checked. Approximations suitable for variational trial functions are given. Two examples give the effect of a change of delay time for a steady state and an initial transient, respectively.