A framed, 16-image Kirkpatrick–Baez x-ray microscope

Abstract

A 16-image Kirkpatrick-Baez (KB)-type x-ray microscope consisting of compact KB mirrors [F. J. Marshall, Rev. Sci. Instrum. 83, 10E518 (2012)] has been assembled for the first time with mirrors aligned to allow it to be coupled to a high-speed framing camera. The high-speed framing camera has four independently gated strips whose emission sampling interval is ∼30 ps. Images are arranged four to a strip with ∼60-ps temporal spacing between frames on a strip. By spacing the timing of the strips, a frame spacing of ∼15 ps is achieved. A framed resolution of ∼6-μm is achieved with this combination in a 400-μm region of laser-plasma x-ray emission in the 2- to 8-keV energy range. A principal use of the microscope is to measure the evolution of the implosion stagnation region of cryogenic DT target implosions on the University of Rochester's OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The unprecedented time and spatial resolutions achieved with this framed, multi-image KB microscope have made it possible to accurately determine the cryogenic implosion core emission size and shape at the peak of stagnation. These core size measurements, taken in combination with those of ion temperature, neutron-production temporal width, and neutron yield allow for inference of core pressures, currently exceeding 50 Gbar in OMEGA cryogenic target implosions [Regan et al., Phys. Rev. Lett. 117, 025001 (2016)].

Properties of hot-spot emission in a warm plastic-shell implosion on the OMEGA laser system

“…Spect3D was used to simulate the target emission from the implosion. Since the KBFRAMED [42] is always used to investigate the hot-spot evolution in experiments, the effect of the KBFRAMED response should be considered within the Spect3D simulation. The spectral response of the KBFRAMED x-ray camera is shown in Fig.…”

“…(6)] can be reasonably used to investigate the x-ray emission properties in our warm-plasma implosion. In the experiment, the 16-channel KBFRAMED in the 4 to 8 keV photon energy range [42] was used to measure the hot spot x-ray emission evolution. The 17% intensity contour radius R 17 of the gated x-ray image is related to the hot-spot radius [5,42].…”

“…In the experiment, the 16-channel KBFRAMED in the 4 to 8 keV photon energy range [42] was used to measure the hot spot x-ray emission evolution. The 17% intensity contour radius R 17 of the gated x-ray image is related to the hot-spot radius [5,42]. For the shot 84605, the gate time is ∼ 30 ps, and the spatial resolution is ∼ 6 µm.…”

“…For the shot 84605, the gate time is ∼ 30 ps, and the spatial resolution is ∼ 6 µm. A resolution grid was used to obtain the spatial resolu- tion, a lineout through a single intensity-corrected image taken through the central 200-µm-wide region, and the measured pattern was compared to the Gaussian-blurred step pattern whose FWHM is 6 µm [42]. Spatially and temporally blurs have been performed over the detector resolution and gate width, and the KB spectral response [shown in Fig.…”

“…11(b), and the measured and fitted intensity profiles taken along the dashed lines through the center of the images are shown in Fig. 11(c) [5,42].…”