Timing shifts due to NIF beam repointing

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Repointing a NIF beam to hit a target position off target chamber center (TCC) will introduce a timing shift due to changes in the light pathlength. This shift could be important for target experiment requirements even for targets placed at TCC, since beam timing test shots will place beams up to 15 mm off TCC in order to spatially separate them on foil targets. In particular, timing errors due to beam repointing need to be considered against the 30 ps RMS timing requirement. Since the repointing process will keep the beam passing through a fixed point in the final optics ... continued below

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12 p. (0.2 MB)

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Koch, J August 15, 2007.

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Repointing a NIF beam to hit a target position off target chamber center (TCC) will introduce a timing shift due to changes in the light pathlength. This shift could be important for target experiment requirements even for targets placed at TCC, since beam timing test shots will place beams up to 15 mm off TCC in order to spatially separate them on foil targets. In particular, timing errors due to beam repointing need to be considered against the 30 ps RMS timing requirement. Since the repointing process will keep the beam passing through a fixed point in the final optics assembly (the conversion crystal) by tip/tilt adjustments of two turning mirrors (LM5 and LM7), the problem naturally divides into two parts: Timing offsets past the conversion crystal due to target positioning changes, and timing offsets behind the fixed point on the conversion crystal due to turning mirror adjustments. Timing offsets past the conversion crystal can be significant, but are trivial to calculate exactly; however, an exact calculation of timing offsets behind the fixed point on the conversion crystal would require a three-dimensional optomechanical raytrace model to be developed for every beamline, and this would be difficult and expensive. In this memo, I estimate the magnitude of timing offsets due to pathlength changes behind the conversion crystal by analysis of a worst-case model. I conclude that these timing offsets are insignificant compared with the current allocation in the 30 ps RMS timing requirement, and that more detailed raytrace modeling of individual beams is not necessary.

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12 p. (0.2 MB)

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PDF-file: 12 pages; size: 0.2 Mbytes

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  • Report No.: UCRL-TR-233810
  • Grant Number: W-7405-ENG-48
  • DOI: 10.2172/924960 | External Link
  • Office of Scientific & Technical Information Report Number: 924960
  • Archival Resource Key: ark:/67531/metadc902293

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Creation Date

  • August 15, 2007

Added to The UNT Digital Library

  • Sept. 27, 2016, 1:39 a.m.

Description Last Updated

  • April 13, 2017, 4:12 p.m.

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Koch, J. Timing shifts due to NIF beam repointing, report, August 15, 2007; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc902293/: accessed September 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.