Calibration of the sub-aperture backscatter system on OMEGA EP
The sub-aperture backscatter (SABS) diagnostic on the OMEGA EP Laser System is a diagnostic that is used to measure the backscattered and sidescattered light during laser–plasma interaction experiments that are relevant to high-energy-density physics and inertial confinement fusion. The diagnostic collects stimulated Brillouin scattering (SBS) UV light at around 351 nm and stimulated Raman scattering (SRS) in the visible-light regime in the 420–720-nm-wavelength range and provides spectrally and temporally resolved information. Five 1-in. light collectors, composed of a lens, ground glass diffuser, and coupling into a 300-μm fiber, are positioned behind the last steering mirror on one of the four beamlines to catch a portion of the beam cross section (~1.5%) of the emission that is scattered into the beamline. The SRS light is collected in two light collectors, combined, and transported via graded index fibers to a streaked spectrometer. The SABS-SRS streak spectrometer has a temporal and spectral resolution of 100 ps and 1 nm, respectively. Three other light collectors collect, combine, and transport the SBS signal to a Hamamatsu high-voltage photodiode, where an oscilloscope digitizes the data, providing a time resolution of better than 1 ns. To obtain an absolute energy calibration of SRS measurements, light signals of known energy and wavelength were injected into the light collectors one at a time. The resulting counts on the streak camera charge-coupled device for SRS are then correlated with the incident fluence of scattered light at the light collector in order to allow a quantitative assessment of streak camera sensitivity to determine the energy of the scattered light during experiments. The measurements were performed in situ from the light collectors to the detectors. Other offline measurements provided the transmission of the optics between the target chamber center and the light collectors.
- Research Organization:
- Univ. of Rochester, NY (United States). Lab. for Laser Energetics
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA); New York State Energy Research and Development Authority; University of Rochester
- Grant/Contract Number:
- NA0003856
- OSTI ID:
- 1988225
- Journal Information:
- Review of Scientific Instruments, Vol. 94, Issue 5; Conference: 24. Topical Conference on High-Temperature Plasma Diagnostics, Rochester, NY (United States), 15-19 May 2022; ISSN 0034-6748
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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