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A prototype of a picosecond x-ray streak camera has been developed and tested by Commissariat a l’Energie Atomique et aux Energies Alternatives to provide plasma-diagnostic support for the Laser Megajoule. We report on the measured performance of this streak camera, which almost fulfills the requirements: 50-μm spatial resolution over a 15-mm field in the photocathode plane, 17-ps temporal resolution in a 2-ns timebase, a detection threshold lower than 625 nJ/cm2 in the 0.05–15 keV spectral range, and a dynamic range greater than 100.

Streak cameras are widely used to record the spatio-temporal evolution of laser-induced plasma. A prototype of picosecond X-ray streak camera has been developed and tested by Commissariat a l’Energie Atomique et aux Energies Alternatives to answer the Laser MegaJoule specific needs. The dynamic range of this instrument is measured with picosecond X-ray pulses generated by the interaction of a laser beam and a copper target. The required value of 100 is reached only in the configurations combining the slowest sweeping speed and optimization of the streak tube electron throughput by an appropriate choice of high voltages applied to its electrodes.

We present the characterization of an ultrafast x-ray streak camera based on a new bilamellar x-ray tube. This camera, named FX1, has been tested in static (imaging) and dynamic (sweep) mode with several continuous and pulsed sub-picosecond UV and X-ray sources. The FX1 camera was designed to overcome some limitations observed with the PX1 camera which has been used previously at INRS to achieve high resolution sub-picosecond time resolved spectroscopy of ultrafast laser produced plasmas. Line Spread Function measurements indicated a strong improvement of the static image contribution to the temporal resolution compared to the PX1 camera performances [Rev. Sci. Instr. 71, 3627, 2000]. Furthermore a much higher dc extraction field can now be sustained at the photocathode-acceleration slit region. The FX1 camera has been successfully operated in various experimental conditions. An upper limit of the temporal response of the FX1 has been measured in the keV x-ray range in single shot mode with a laser-based x-ray source (2keV) having a duration (FWHM) of 1.4 ps. The FX1 camera has also been coupled to photoconductive switches and testesd in accumulation mode [Rev. Sci. Instr. 73, 1617, 2002] with VUV light produced with the 1 kHz Ti:sapphire laser of the CELIA. A newly assembled test-bench is now currently used at INRS for the characterisation of streak cameras in both single-shot and accumulation mode with the 10Hz Ti:sapphire laser of INRS.

In an effort to improve the performances of streak cameras, experimental and theoretical studies were conducted, aimed at measuring the noise in a camera. This would be achieved through the evaluation of the camera's noise factor and by additionally pointing out the possible sources of noise. It was shown for our camera, a TSN 506 Thomson camera, that the noise factor is due partly to signal loss (factor 1,8) and partly to noise addition (factor 2,6). Moreover, noise was shown to be additive and Poissonian, mostly due to shot noise and photoelectric conversions.

A novel subpicosecond x-ray streak camera (called PX1) was developed by the INRS group for subpicosecond time resolved spectroscopy in x rays and X-UV range. Using the PX1 camera, we have measured keV x-ray pulses with a 950 fs FWHM and a 850 fs rise time. The camera has also been coupled to ultrafast photoconductive switches and tested in jitter-free mode as a signal averaging detector. This instrument allows to analyze ultrafast changes in short wavelength signals with an unlimited dynamic range.

High precision and high dynamic range measurements are required to properly characterize the pulseshape in ICF laser systems. The dynamic range and precision of the measurements that can be made with streak tubes is determined by the number of photoelectrons that can be transported to the recording screen per channel and per temporal sample of the signal. They are limited by the overall current that the tube can deliver without distorting the signal. In order to build tubes with the large dynamic ranges required by this application, we need to understand at what current density level the tube response becomes nonlinear. We present results of experiments made by using a laser illuminating several streak tubes at various intensities. We show that charge depletion in the photocathode can occur in pulsed mode and limit the signal to levels well below that where space charge induced nonlinearities appear. The use of scientific grade CCD's for recording the streak traces has allowed the introduction of a new method to measure the absolute current in the tube. A 2D PIC electron optics code has been used to simulate the propagation of the beam in the input diode (photocathode/accelerating electrode) and in the drift region (accelerating electrode/screen) of a bilamellar streak tube. We compare the numerical results with the experiments. We conclude by comparing the bilamellar and classical electron optics tubes and show the advantages of the former tube design for this application.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We present results of the characterization of an ultrafast x-ray streak camera, based on Photonis (formerly Philips Photonics) P860 tube, developed for use in ultrashort laser-produced plasma research. The streak camera presented here (called PX1) has been extensively characterized with continuous and pulsed x-ray sources. Time resolution of 350 fs in the keV x-ray range has been achieved, while maintaining a high spatial resolution of 40 μm along a direction perpendicular to the time dispersion axis. It is shown that the streak camera response is lower when the photocathode is illuminated by a pulsed source than when used with a continuous one. This effect seems to be related to a change in the phosphor response. The camera has been used to achieve high-resolution subpicosecond time-resolved spectroscopy of ultrashort laser plasmas allowing the measurements of K-shell line emission durations of 700 fs.