Soft X-ray Streak Camera Research Articles

X-ray transmission photocathode sensitivities at λ = 0266 μm

The absolute sensitivity of two soft x-ray stream camera transmission photocathodes was measured at λ = 0.266 μm. The photocathodes were mounted in a Lawrence Livermore National Laboratory soft x-ray streak camera and were compared in sensitivity to a more conventional UV photocathode. Measurements were performed with a 30-psec 0.266-μm pulse from a frequency-quadrupled glass laser. The study revealed photocathode substrate transmission at 0.266 μm, minimum UV energy density requirements, temporal response, and an estimate of streak camera dynamic range for UV exposure.

Quantitative intensity measurements using a soft X-ray streak camera

A soft X-ray streak camera (SXRSC) has been calibrated in order to make absolute flux measurements of X-rays emitted from laser-produced plasmas. The SXRSC developed at the Lawrence Livermore National Laboratory and described in a companion paper in this issue is used to time-resolve X-ray pulses to better than 20 ps. The SXRSC uses an Au photocathode on a thin carbon substrate which is sensitive to X-rays from 100 eV to greater than 10 keV. Calibrations are done in the dynamic mode using a small laser-produced X-ray source. The SXRSC is calibrated by comparing its integrated signal to the output of calibrated X-ray diodes monitoring the source strength. Details of the experiment along with data from a typical calibration are presented. The measured SXRSC intensity response is linear over greater than two orders of magnitude. Using these calibrations, absolute intensities can be measured to an accuracy of ± 30 percent. An example of its use as a flux monitoring device is presented.

A soft X-ray streak camera

A soft X-ray streak camera is presented which offers wide application for picosecond recording of transient signals in the spectral range from the VUV to the very hard X-ray region. Specific demonstration results are presented from laser-fusion diagnostic studies. Dynamic characterization of the streak camera, new photocathode studies, and the application of intermediate and broad spectral selectivity techniques are discussed.

Space And Time Resolved Soft X-Ray Spectra Using X-Ray Transmission Gratings

Gold transmission gratings with 0.3 Am spatial period, 0.6 Am thick have been fabricated and are being used for the spectroscopy of high temperature, laser-produced plasmas. A transmission grating has been coupled with a soft x-ray streak camera, producing the first time resolved (20 psec resolution) continuous x-ray spectrum over the range 0.1 to 1.5 keV from a laser-produced plasma. In addition, a transmission grating has been coupled with a high resolution, Wolter-design x-ray microscope to produce an imaging spectrometer of unprecedented spatial and spectral resolution. In laboratory experiments the imaging spectrometer demonstrated a spectral resolving power, (A/AA) of 200 and a spatial resolution of 1 µm.

Time-resolved x-ray transmission grating spectrometer for studying laser-produced plasmas

The development of a new time-resolved x-ray spectrometer is reported in which a free-standing x-ray transmission grating is coupled to a soft x-ray streak camera. The instrument measures continuous x-ray spectra with 20-psec temporal resolution and moderate spectral resolution (deltalambda >/= 1 A) over a broad spectral range (0.1-5 keV) with high sensitivity and large information recording capacity. Its capabilities are well suited to investigation of laser-generated plasmas, and they nicely complement the characteristics of other time-resolved spectroscopic techniques presently in use. The transmission grating spectrometer has been used on a variety of laser-plasma experiments. We report the first measurements of the temporal variation of continuous low-energy x-ray spectra from laser-irradiated disk targets.