A technique for measuring the difference of times of arrival of laser beams at a target based on analysis of the X-ray emission from a target on the Iskra-5 facility

A technique for measuring the difference of times of arrival of laser beams at a spherically irradiated target in experiments on the 12-channel Iskra-5 facility is described. This technique is based on detection in test experiments of X rays from a specially designed target with a slit X-ray streak camera. The obtained information is used to perform time locking of laser pulses recorded at the output of the facility’s amplifying stages with a multichannel photochronographic system. The results of recording laser pulses at the output of the amplifying stages obtained in working experiments allow determination of the difference of times of arrival of laser beams at a target with an accuracy no worse than 50 ps.     

Time-resolved spectra of dense plasma focus using spectrometer, streak camera, and CCD combination

A time-resolving spectrographic instrument has been assembled with the primary components of a spectrometer, image-converting streak camera, and CCD recording camera, for the primary purpose of diagnosing highly dynamic plasmas. A collection lens defines the sampled region and couples light from the plasma into a step index, multimode fiber which leads to the spectrometer. The output spectrum is focused onto the photocathode of the streak camera, the output of which is proximity-coupled to the CCD. The spectrometer configuration is essentially Czerny-Turner, but off-the-shelf Nikon refraction lenses, rather than mirrors, are used for practicality and flexibility. Only recently assembled, the instrument requires significant refinement, but has now taken data on both bridge wire and dense plasma focus experiments.     

Recording the time dependence of the electron temperature and absolute yield of continuous and line X-rays from flat Au targets irradiated on the Iskra-5 facility

Two techniques for recording the absolute yield of continuous X rays in the spectral range > 1 keV and M-series line X rays from flat Au targets irradiated with one channel of the Iskra-5 facility are described. In the first and second methods, radiation is detected with a KAP-crystal-based spectrograph and an X-ray streak camera with a 50-ps time resolution, respectively. Both techniques allow obtainment of absolute values of the yields of continuous and line X-ray radiations from laser plasma that coincide within the measurement accuracy. The time-dependent plasma electron temperature is measured with an X-ray streak camera.     

A technique for studying the spectral composition and duration of radiation accompanying a shock wave at the rear surface of materials under direct laser irradiation

A photochronographic technique for studying the spectral composition and duration of radiation that accompanies the appearance of a shock wave on the rear surface of a loaded target has been developed. The spectral resolution of this technique was evaluated. A method of the through calibration of the recording channel using radiation of a source with the known spectrum was proposed. The results of the performed calibration are used to restore the spectral distribution on the basis of the obtained spectrochronograms.     

Streak cameras for laser fusion experiments

Results of the streak camera development for the new laser facility UFL-2M are presented. This streak camera can be used for diagnosing laser beams and plasma parameters. Its main characteristics are as follows: the maximum temporal resolution is ≤5 ps, the spatial resolution is ≥20 line pairs/mm, and the dynamic range is ≥1000.     

Effect of riblets on the streaky structures excited by free stream tip vortices in boundary layer

In this study, experimental investigations were made regarding the effect of riblets on the streak instability in boundary layer. The streak instability is now regarded as a major source of the self-regeneration mechanism for the hairpin type coherent structures in turbulent boundary layer flow. Thus, it is important to control the instability to suppress the drag-inducing vortical structure in terms of drag reduction. Toward enhancing the measurement accuracy and spatial resolution, an enlarged version of riblets was applied to a streak which was artificially induced by a microwing in a laminar boundary layer. It is found that the riblets have attenuation effect on the streak instability, i.e., to reduce the spanwise velocity gradient of the quasi-streamwise streak in boundary layer.     

Segmentation and classification of streaks in a large-scale particle streak tracking system

In this paper we propose improvements to particle streak tracking. The main focus is an improved segmentation method considering local image statistics combined with classic edge detection and removal of the scene background, which at the same time suppresses the noise. Furthermore, we will describe the streak features used and suggest a greedy algorithm to solve the classification problem of binarized streak segments. Finally, results using the presented algorithm are compared to those using the original particle streak system.     

Development of the accelerated testing procedure of streak tubes: Basic provisions

Results of the studies of the sensitivity change in the course of the mean-time-between-failures tests of streak tubes produced by the Dukhov All-Russia Research Institute of Automatics, are presented. It is shown that for the correct determination of the lifetime of these streak tubes during accelerated tests, one should take into account the correction function attributable to processes of reversible changes in the sensitivity of the streak tube photocathode. The designed procedure for accelerated tests of streak tubes is described the basic distinction of which from the existing procedures consists in using this correction function.     

Measurement of the Dead Time of an Optoelectronic Streak Camera with Different Linear Sweep Ranges

A method for measuring the dead time of an optoelectronic streak camera with different linear sweep ranges is described. The proposed method was used for the PN-1 streak camera. Photographs of the time-resolved emission of a DRSh350-2 mercury arc flash lamp for linear sweep ranges of 50 and 100 ns are presented. The dead times of the PN-1 streak camera for linear sweep ranges of 25, 50, and 100 ns were 5, 75, and 105 ns, respectively. The photographs of time-resolved second-harmonic spectra emitted by plasmas of copper and aluminum targets that were obtained in experiments on the interaction of nanosecond laser radiation with the matter using a streak camera are presented.     

A spectroscopic complex for time-resolved registration of plasma-jet parameters at the PF-3 facility

A spectroscopic complex for measuring the parameters of plasma jets that are generated in a facility of the plasma-focus type and the parameters of a stationary gas in which these jets propagate is described. The complex consists of an STE-1 crossed-dispersion spectrograph and a K008 streak camera, which is placed together with a notebook computer and a no-break power unit inside a shielding box for protection against electromagnetic noise. The K008 camera is equipped with an additional image intensifier on the basis of an EP-10 image-converter tube. The spectrum image is recorded with a standard SU-05M video camera and processed with the Klen-5m dedicated program, which automatically corrects the distortion and scan nonuniformities and subtracts regular noise. The complex makes it possible to obtain the time dependences of the intensities and shapes of several spectral lines in a range of scans from a few nanoseconds to milliseconds and to promptly tune the system to the required spectral ranges. Within one discharge of the facility, a digital image of the time-integral spectrum is simultaneously recorded in the entire visible region.     

X-ray diffraction from shock-loaded polycrystals

X-ray diffraction was demonstrated from shock-compressed polycrystalline metals on nanosecond time scales. Laser ablation was used to induce shock waves in polycrystalline foils of Be, 25-125 microm thick. A second laser pulse was used to generate a plasma x-ray source by irradiation of a Ti foil. The x-ray source was collimated to produce a beam of controllable diameter, which was directed at the Be sample. X-rays were diffracted from the sample, and detected using films and x-ray streak cameras. The diffraction angle was observed to change with shock pressure. The diffraction angles were consistent with the uniaxial (elastic) and isotropic (plastic) compressions expected for the loading conditions used. Polycrystalline diffraction will be used to measure the response of the crystal lattice to high shock pressures and through phase changes.     

Streak camera measurement of subnanosecond plastic scintillator properties

A streak camera technique with temporal resolution of 20 ps has been used to measure the fluorescence properties of several subnanosecond plastic scintillators. The method employs a vacuum light pipe coupled to an optical streak camera. The scintillators are excited by a 200-ps x-ray pulse generated by a 1.06-microm Nd:YAG laser focused onto an iron target. The time history of the low-energy x-ray pulse is measured with an x-ray streak camera. Results are given for NElll plastic scintillators doped with benzophenone or acetophenone, for PVT doped with butyl-PBD, and for a ZnO phosphor doped with Ga.     

等离子体诊断用成像型软X射线三色谱仪设计

围绕激光惯性约束聚变研究中内爆靶丸的辐射流诊断需求,设计了一种兼顾空间成像功能的三色软X射线谱仪。该谱仪的设计中心能点为210eV、680eV和800eV,能谱分辨率E/ΔE为5~10。采用X射线掠入射光学结构,实现了三个能点的一维聚焦成像,在1mm视场内空间分辨率优于10μm。采用X射线周期多层膜,获得了三个能区的能谱响应,多层膜测试结果满足设计要求。以光学设计和多层膜为基础,建立了系统的光线追迹模型,分析了可控的空间位置误差和瞄准误差对系统光谱分辨和空间分辨的影响,为装调方案及瞄准方法设计提供了精度依据。该谱仪与条纹相机结合,可用于我国强激光装置上的等离子体诊断实验。     

Calibration Procedures for X-ray Streak Cameras and Elements of X-ray Measuring Circuits

Setups developed for the calibration of X-ray streak cameras and of elements of X-ray measuring circuits are described. Calibration procedures are described and calibration results related to the absolute spectral sensitivity, spatial resolution, distortion, sensitivity nonuniformity over the screen, sweep speed and nonlinearity of an X-ray streak camera, as well as the results of the calibration of filters and mirrors used in recording laser-plasma X-rays are presented. The absolute-calibration error for the streak camera is within ±10%, and the calibration error for the filter and mirrors is within ±2%. Methods for processing photochronograms are described that, using the calibration data, allow the correction of distortions introduced by the streak camera.     

Novel streak-resolving algorithm for particle streak velocimetry

In this paper, a novel streak-resolving algorithm is proposed for particle streak velocimetry (PSV) to resolve velocity fields for a single image frame with multiple particle streaks. A model streak function, which was based on the temporal integral of the particle image intensity moving along its trajectory during the exposure period, was approximated using a multivariable least-square fit procedure to reconstruct the streak information and the corresponding particle trajectory. Lagrangian tracking was achieved, and the velocities were evaluated by differentiating the resolved particle trajectory with respect to time. Two types of flows, accelerating parallel flow and the rotational flow of Hill’s vortex, were used to generate synthetic streaks for the performance tests. Three types of relative error were defined and used to evaluate the performance of the algorithm in terms of statistical mean and standard deviation (SD) errors. The accuracy of the fitted streak parameters, such as particle image intensity and diameter, were also evaluated and compared. The results reveal that the error and SD were low if the image noise is below 1.0%; for noise levels of 5.0%, the error was up to 10% with an SD of up to 12%. The error and SD of the particle image intensity and particle image diameter for both flow types were also 0%–7% for clean and up to 12% for noisy images. The processing results for experimental streak images of flow past a cylinder reveal that these images can be resolved using the proposed algorithm with a residual mean error of 4.38 and an SD of 9.48. These results suggest that the proposed novel approach can be used to resolve velocity fields with only a single image frame and without expensive hardware for high-speed imaging and thus is suitable for diverse applications.     

超快电子脉冲的时域压缩

实现电子脉冲在时域上的压缩是提高条纹相机以及超快电子衍射仪等超快诊断仪器时间分辨能力的关键,本文提出用时间聚焦的方法来改善超快诊断技术的时间分辨能力.通过在时间聚焦电极上加随时间线性增加的电场来补偿光电子在光电阴极和阳极之间的时间弥散,从而使快电子相对变慢,慢电子相对变快,达到在时域压缩电子脉冲的目的.用Monte C...     

转镜式高速摄影机角跟踪精度的检测

为了提高转镜式高速摄影机测量弹丸运动轨迹的精度,本文通过合理假设和理论推导,依据弹丸外弹道飞行运动模型得到了弹丸飞行过程的数学模型。结合室内检测条件,设计了用于转镜式高速摄影机角跟踪精度的检测装置并分析了测试原理。用该设备实测了转镜式高速摄影机的角跟踪精度,并对检测装置的测量不确定度来源进行了分析。结果显示:被测转镜式高速摄影机的角跟踪精度为(0.34±0.06)°,检测装置的相对不确定度为3.0″;不确定度来源主要为角度测量不确定度和焦距测量不确定度。实验结果表明,设计的检测装置具有较高的准确度和可靠性。     

Time resolved cathodoluminescence in the scanning electron microscope by use of the streak technique

Minority carrier lifetime is one of the basic material properties in optoelectronic devices and material. Both the micrometer range dimensions of the devices and lifetime variations around defects in materials require a lifetime measurement technique with both high spatial and high temporal resolution. In order to meet these requirements a highly efficient cathodoluminescence (CL) measurement system has been developed consisting of a commercial scanning electron microscope extended for integral and spectral CL-measurements and a streak camera with subnanosecond time resolution as time resolving detector. The lifetime is determined by evaluation of CL-decay time after excitation of the specimen by an electron beam pulse, which is blanked in less than 50 ps by an adjustable plate capacitor. The CL-light is collected by an adjustable, ellipsoidal mirror and can be dispersed in a vacuum monochromator. The monochromator exit slit is imaged on to the photocathode of the streak camera, which transforms the temporal distribution of the photon intensity into a lateral distribution on the camera phosphor screen after amplification by an integrated microchannel plate. By this technique it is possible to record the complete CL-decay simultaneously, thus avoiding all measurement falsifications by system instabilities. The resulting intensity distribution is read out by a SIT vidicon camera with subsequent multichannel analyser, providing an intensity plot versus streak time in less then 1 min for each beam spot location. The technique is therefore well suited for lifetime mapping experiments. The best time resolution of the complete system achieved today is about 100 ps. Its performance is here demonstrated by measurements of the temperature dependence of the CL-decay in a highly Se-doped GaAs specimen in the temperature range from 90 K to 300 K.     

Standard design for National Ignition Facility x-ray streak and framing cameras

The x-ray streak camera and x-ray framing camera for the National Ignition Facility were redesigned to improve electromagnetic pulse hardening, protect high voltage circuits from pressure transients, and maximize the use of common parts and operational software. Both instruments use the same PC104 based controller, interface, power supply, charge coupled device camera, protective hermetically sealed housing, and mechanical interfaces. Communication is over fiber optics with identical facility hardware for both instruments. Each has three triggers that can be either fiber optic or coax. High voltage protection consists of a vacuum sensor to enable the high voltage and pulsed microchannel plate phosphor voltage. In the streak camera, the high voltage is removed after the sweep. Both rely on the hardened aluminum box and a custom power supply to reduce electromagnetic pulse/electromagnetic interference (EMP/EMI) getting into the electronics. In addition, the streak camera has an EMP/EMI shield enclosing the front of the streak tube.     

Visualization of underwater sympathetic detonation of high explosives

The experiment for the sympathetic detonation ( Sudo et al., 1951) (Fukuyama et al., 1958) in water was conducted. Composition B (RDX: 64%, TNT: 36%, Detonation velocity: 7900m/s) was used for both donor (the thickness was 50mm, and the diameter was 31mm) and receptor charges. The distance between the donor and the receptor, and the thickness (5, 7.5, 10mm) of the receptor were varied in the experiments. In order to investigate the basic characteristics of the underwater sympathetic detonation of high explosive, the sympathetic detonation phenomena were visualized by a high-speed camera (HADLAND PHOTONICS, IMACON790) in forms of streak and framing photographs. The 200 ns/mm streak velocity was used when the streak photographs were taken. In the framing photographs, the interval time was 2μs. Manganin gauges (KYOWA Electronic INSTRUMENTS CO. SKF-21725) were used for the pressure measurements. The gauges were set under the receptor. The pressures during the complete and incomplete explosions were measured.