X-ray Streak Camera Research Articles

X-ray streak camera cathode development and timing accuracy of the 4ω ultraviolet fiducial system at the National Ignition Facility

The convergent ablator experiments at the National Ignition Facility (NIF) are designed to measure the peak velocity and remaining ablator mass of an indirectly driven imploding capsule. Such a measurement can be performed using an x-ray source to backlight the capsule and an x-ray streak camera to record the capsule as it implodes. The ultimate goal of this experiment is to achieve an accuracy of 2% in the velocity measurement, which translates to a ±2 ps temporal accuracy over any 300 ps interval for the streak camera. In order to achieve this, a 4ω (263 nm) temporal fiducial system has been implemented for the x-ray streak camera at NIF. Aluminum, titanium, gold, and silver photocathode materials have been tested. Aluminum showed the highest relative quantum efficiency, with five times more peak signal counts per fiducial pulse when compared to Gold. The fiducial pulse data were analyzed to determine the centroiding statistical accuracy for incident laser pulse energies of 1 and 10 nJ, showing an accuracy of ±1.6 ps and ±0.7 ps, respectively.

Ultra fast x-ray streak camera for ten inch manipulator based platforms

Ultra fast x-ray streak cameras are a staple for time resolved x-ray measurements. There is a need for a ten inch manipulator (TIM) based streak camera that can be fielded in a newer large scale laser facility. The Lawrence Livermore National Laboratory ultra fast streak camera's drive electronics have been upgraded and redesigned to fit inside a TIM tube. The camera also has a new user interface that allows for remote control and data acquisition. The system has been outfitted with a new sensor package that gives the user more operational awareness and control.

Simultaneous high-resolution two-dimensional spatial and one-dimensional picosecond streaked x-ray pinhole imaging

A Kentech x-ray streak camera was run at the LLNL compact multipulse terawatt (COMET) laser to record simultaneous space- and time-resolved measurements of picosecond laser-produced plasmas. Four different x-ray energy channels were monitored using broadband filters to record the time history of Cu targets heated at irradiances of 10(16)-10(19) W∕cm(2). Through the Cu filter channel, a time-resolution below 3 ps was obtained. Additionally, an array of 10 μm diameter pinholes was placed in front of the camera to produce multiple time-resolved x-ray images on the photocathode and time-integrated images on the phosphor with 10 and 15 times magnification, respectively, with spatial resolution of < 13 μm.

Diagnosing laser-driven, shock-heated foam target with Al absorption spectroscopy on OMEGA EP

Results on diagnoses of laser-driven, shock-heated foam plasma with time-resolved Al 1s-2p absorption spectroscopy are reported. Experiments were carried out to produce a platform for the study of relativistic electron transport. In cone-guided Fast Ignition (FI), relativistic electrons generated by a high-intensity, short-pulse igniter beam must be transported through a cone tip to an imploded core. Transport of the energetic electrons could be significantly affected by the temperature-dependent resistivity of background plasmas. The experiment was conducted using four UV beams of the OMEGA EP laser at the Laboratory For Laser Energetics. One UV beam (1.2kJ, 3.5ns square) was used to launch a shock wave into a foam package target, consisting of 200mg/cm3 CH foam with aluminum dopant and a solid plastic container surrounding the foam layer. The other three UV beams with the total energy of 3.2kJ in 2.5ns pulse duration were tightly focused onto a Sm dot target to produce a point X-ray source in the energy range of 1.4–1.6keV. The quasi-continuous X ray signal was transmitted through the shock-heated Al-doped, foam layer and recorded with an X-ray streak camera. The measured 1s-2p Al absorption features were analyzed using an atomic physics code FLYCHK. Electron temperature of 40eV inferred from the spectral analysis is consistent with 2-D DRACO Radiation-hydrodynamic simulations.

Studies of intense-laser plasma instabilities

The PALS high power iodine laser system in Prague (λ=1.315μm) was used to study non-linear processes in a laser-produced plasma at intense laser beam interactions with planar targets. The focus setting allows to alter the non-linear interaction of the main laser pulse with the ablated plasma produced by the front edge of a nanosecond laser pulse (300ps FWHM). The arisen non-linear effects significantly influence the behavior of electrons, which accelerate fully striped or highly charged fast ions. Variations in time of the expanding plasma, recorded at the target surface by the use of Kentech low-magnification soft X-ray streak camera on ∼2ns time scale, are presented and discussed. Narrowing, arching and even splitting of expansion paths in the target-normal space-time diagram are shown. These phenomena are ascribed to the magnetic field, self-generated at high laser intensities, which may become strong enough to cause pinching of the expanding plasma.

Measurement of implosion trajectory for hohlraum-radiative-driven

The measurement of implosion velocity is the core problem of inertial confinement fusion and it is also a key quantity of estimation of fusion ignition. A clear implosion trajectory X-ray image of hohlraum-radiative-driven CH-capsule is obtained in Sheng-GuangII laser facility with 1600 J laser energy, triple frequency and 1 ns pulse width. KB-microscope coupled with X-ray streak camera whose temporal resolution is about 10 ps is used for diagnosis. The maximal velocity of implosion is about 160 km/s which can be extracted from the experimental trajectory data. The experimental data are compared with Multi1D simulation results of velocity and both are in good agreement with each other.

Spectral response calibration of Au and CsI transmission photocathodes of X-ray streak camera in a 605500 eV photon energy region

A method is described of measuring absolute spectral response for Au and CsI transmission photocathodes in soft X-ray streak camera, which is of great importance for the inertial confinement fusion (ICF) diagnostics. Transmission photocathode is conventionally employed as photo-to-electron conversion accessories. To derive quantity information of X-ray spectra, the absolute response of photocathode must be calibrated in a range of interest. Here Au and CsI transmission photocathodes with slits are calibrated respectively on Beijing Synchrotron Radiation Facility (BSRF), in a photon energy range of 60 eV5500 eV. This method has an uncertainty less than 10% and good feasibility. Calibration results are in good agreement with the calculation results obtained from the Henke's photon emission model, with CH substrate effect revised.

基于成像板-X射线条纹相机的精密耦合技术

基于成像板-X射线条纹相机的精密耦合技术

2-ps Hard X-Ray Streak Camera Measurements at Sector 7 Beamline of the Advanced Photon Source

A hard X-ray streak camera capable of 2-ps time resolution is in operation at the Sector 7 beamline of the Advanced Photon Source. It is used for laser-pump, X-ray probe experiments using the Ti:Sapphire femtosecond laser system installed on the beamline. This streak camera, combined with standardized and prealigned experimental setups, can perform time-resolved liquid-phase absorption spectroscopy, reflectivity, and diffraction experiments.

Visualization of the Nonlinear Laser-Plasma Expansion

The high-power iodine laser PALS is used to study nonlinear processes in a laser-produced plasma. Longitudinal structures of the expanding plasma, recorded by using an X-ray streak camera on a time scale <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim$</tex></formula> 2 ns, are presented. Various bright spots, expansion-path curvature, and even their splitting are shown. These phenomena are ascribed to the effect of magnetic field, self-generated at high laser intensities.

Measurements of Electron Transport in Foils Irradiated with a Picosecond Time Scale Laser Pulse

The heating of solid foils by a picosecond time scale laser pulse has been studied by using x-ray emission spectroscopy. The target material was plastic foil with a buried layer of a spectroscopic tracer material. The laser pulse length was either 0.5 or 2 ps, which resulted in a laser irradiance that varied over the range 10(16)-10(19) W/cm(2). Time-resolved measurements of the buried layer emission spectra using an ultrafast x-ray streak camera were used to infer the density and temperature conditions as a function of laser parameters and depth of the buried layer. Comparison of the data to different models of electron transport showed that they are consistent with a model of electron transport that predicts the bulk of the target heating is due to return currents.

Uncertainty propagation through polynomial fitting and integration procedures with GUM and Monte Carlo applied to x-ray streak camera yield measurements

On the Laser Integration Line (LIL) facility at Commissariat à l'Energie Atomique (CEA) near Bordeaux (France), streak cameras (SCs) are extensively used as x-ray detectors by plasma physicists for the recording of transient phenomena as short as 100 ps. For proper interpretation of the experimental results measurements of the SC yield are carried out before each experimental campaign. The yield is actually an indirect measurement that depends on several other measured quantities. The uncertainty associated with the yield is evaluated using the analytical GUM approach and the Monte Carlo (MC) approach using GUM Supplement 1. It is shown in particular that in the assessment process the standard uncertainty and the probability density function of some input quantities propagate through polynomial fitting functions and integrals. A sensitivity analysis is also performed to identify the critical input quantities. The study shows that after correction of the manufacturer's fact sheet the GUM evaluation converges to MC evaluation when the uncertainties associated with non-linear input quantities become small. When propagating uncertainties through integrals it is observed that the uncertainty of the output quantity is mainly dominated by strong correlation effects with the covariance components adding up to produce large uncertainties. Finally, by comparing the experimental yield with a theoretical model good agreement is found.

Hard X-ray streak camera at the Advanced Photon Source

Abstract An X-ray streak camera capable of 1 to 2 ps time resolution has been in operation for the past two years at Sector 7 of the Advanced Photon Source (APS). It is typically used for laser-pump and X-ray probe experiments by using the Ti:Sapphire laser system installed in Sector 7. Techniques currently supported through standardized and pre-aligned experimental setups are liquid-phase absorption spectroscopy, reflectivity, and diffraction. With the laser running at 1 or 5 kHz, about 30% of the laser power is split off to trigger a photoconductive switch generating the deflection voltage ramp in the streak camera. Alternatively, the laser oscillator can be used to excite the sample at a rate of 88 MHz corresponding to the 324-bunch fill pattern of the APS. The deflection voltage is then a 1.05 GHz signal amplified to 10 W, which is obtained by tripling the APS RF.

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.

Analysis of processes participating during intense iodine-laser-beam interactions with laser-produced plasmas

The high-power iodine laser PALS was used to generate highly charged Ta ions and to study non-linear processes in laser-produced plasma. Longitudinal structures of the expanding plasma, obtained by using an X-ray streak camera on a time scale ∼ 2 ns, are presented. Various bright spots (moon-like, half-moon-like), expansion-path curvature and even their splitting were recorded. These phenomena are ascribed to the effect of the magnetic field that is self-generated at high laser intensities.

Recent Advances in the Development of X-Ray Cameras Inserted Inside a Pressurized Box for LMJ Plasma Diagnostics

For the first plasma diagnostics to be deployed at the Laser Megajoule (LMJ), the Commissariat à l'Energie Atomique (CEA) is developing ultrafast x-ray imaging cameras to analyze spatial and temporal evolution of laser-plasma interaction parameters. These cameras, which operate in the target chamber vacuum, are composed of a one-dimensional (1-D) streak or a two-dimensional (2-D) gated detector, power supply units, control electronic modules, and a charge-coupled device (CCD) readout system. In order to optimize their definition and to ensure easy maintenance, these cameras are packaged inside a hermetically sealed chamber comprised of a pressurized box (air box), which also enable the electronics to operate at atmospheric pressure and provide protection of the camera against the harsh operating environment induced by fluxes of neutrons, x-rays and gamma rays, and electromagnetic radiations. This paper introduces the work led by CEA concerning the development of the air box which integrates the x-ray streak and framing cameras for the first LMJ plasma diagnostics experiments, with regard to the integration and operational constraints of the facility.

Development of a time-resolved soft x-ray spectrometer for laser produced plasma experiments

A 2400 lines/mm variable-spaced grating spectrometer has been used to measure soft x-ray emission (8-22 Å) from laser-produced plasma experiments at Lawrence Livermore National Laboratory's Compact Multipulse Terrawatt (COMET) Laser Facility. The spectrometer was coupled to a Kentech x-ray streak camera to study the temporal evolution of soft x rays emitted from the back of the Mylar and the copper foils irradiated at 10(15) W/cm(2). The instrument demonstrated a resolving power of ∼120 at 19 Å with a time resolution of 31 ps. The time-resolved copper emission spectrum was consistent with a photodiode monitoring the laser temporal pulse shape and indicated that the soft x-ray emission follows the laser heating of the target. The time and spectral resolutions of this diagnostic make it useful for studies of high temperature plasmas.

Subpicosecond hard x-ray streak camera using single-photon counting

We have developed and characterized a hard x-ray accumulating streak camera that achieves subpicosecond time resolution by using single-photon counting. A high repetition rate of 2 kHz was achieved by use of a readout camera with built-in image processing capabilities. The effects of sweep jitter were removed by using a UV timing reference. The use of single-photon counting allows the camera to reach a high quantum efficiency by not limiting the divergence of the photoelectrons.

Interaction of two plasma jets produced successively from Cu target

AbstractOur earlier papers demonstrate a very simple method of plasma jet formation, consisting in irradiating a massive planar target of a relatively high atomic number by a partly defocused laser beam. Our present interest is concentrated on interaction of the plasma jet with other media. This paper is aimed at investigations of interaction of two jets launched successively on Cu target. Our attention was paid to the role of radiative cooling in the plasma jet formation. The experiment was carried out at the PALS iodine laser facility. The laser provided a 250-ps (full width at half maximum) pulse with energy of 130 J at the third harmonic frequency (λ3 = 0.438 µm). Two successive jets were produced on a massive flat Cu target provided with a cylindrical channel 5 mm long and 400 µm in diameter. Since the focal spot diameter of the laser beam on the target surface was larger than that of the channel (800 µm), the annular irradiation of the target face resulted in creation of the first plasma jet, whereas the second jet was produced by action of the central part of laser beam on the channel wall. Three-frame interferometric system, X-ray streak camera, and a set of ion collectors were used as diagnostic tools.

X-ray monochromatic high-speed imager for FIREX fast ignition research

A novel x-ray imager, consisting of two toroidally bent Bragg crystals and a 2D image sampler using a conventional x-ray streak camera, has been demonstrated for use in fast ignition resaerch. Sequential and 2D monochromatic x-ray images of laser-imploded core plasma were successfully obtained with a temporal resolution of 20 ps, a spatial resolution of 31 μm, and a spectral resolution of over 200, simultaneously.