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Update on MPTS

This update provides details on the tasks performed recently, including the installation of new hardware, calibration of existing and new hardware, and software updates. It also discusses the new radial channel allocation and ne profile calibration using Rayleigh and Raman scattering. Additionally, it mentions the analysis of raw data, data correction factors, and other tasks to be done.

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Update on MPTS

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  1. Update on MPTS B.P. LeBlanc Princeton Plasma Physics Laboratory NSTX Results Review July 26-27, 2006 Princeton, NJ APS-DPP-2005-LeBlanc-1

  2. Tasks Performed Recently • Install new hardware • 10 polychromators, 40 preamplifiers and ancillary electronics • Comprehensive calibration of existing hardware and new hardware • Spectral calibration of each polychromator • New optical configuration • APD gain vs. high voltage • Typical gains 35-75 • Fast- and slow-electronics’ transfer function • Relates fast data (TS/Rayleigh/Raman) to slow data (calibration) • Rayleigh and Raman calibration • Software update APS-DPP-2005-LeBlanc-2

  3. Ten new channels instrumented with 4-wavelength GA polychromators and EG&G APD’s with PPPL preamplifiers GA polychromator PPPL preamplifier Fiber bundle Fast signal output Control signals Slow signal output APS-DPP-2005-LeBlanc-3

  4. New Radial Channel Allocation • Enhance outer edge resolution 8 channels • Better inner resolution 2 channels • Split – for the first time – the output end of a fiber bundle to improve spatial resolution Outer split bundle R =144.5 cm±0.5cm Inner split bundle R =143.6cm±0.5cm APS-DPP-2005-LeBlanc-4

  5. ne Profile Calibration • Phases I and II polychromators have 6 spectral channels, including one at Rayleigh wavelength • So far ne calibration done with Rayleigh scattering • But could also be done with Raman scattering • Phase III polychromators have 4 spectral channels, but none at Rayleigh wavelength • ne profile calibration with Raman scattering • Since Rayleigh signal is much larger than Raman, need to ascertain extinction ratio of Rayleigh light at Raman spectral location. APS-DPP-2005-LeBlanc-5

  6. Extinction for Ratio Phase III Significant amount of Rayleigh light enters the 1053-nm filter Extinction ratio for 1064-nm light through 1053-nm filter Existing channels APS-DPP-2005-LeBlanc-6

  7. Raw Data Acquired • Phase III hardware has acquired data for during the last two NSTX experimental runs • Raw data signals • Top: fast signal (Thomson scattering) • Bottom: slow signal (plasma light) APS-DPP-2005-LeBlanc-7

  8. Data Analysis30-channel vs. existing 20 channels • New calibration of existing 20 channels • Good match to previous calibration • Slightly higher temperature for Te > 2 keV • New channels’ analysis unsatisfactory • Systematic error corroborated by large c2 Black: old 20-ch calibration Red: new 20-ch calibration Arrows: new channels APS-DPP-2005-LeBlanc-8

  9. Correction Factors • Computed from exiting adjacent channels • Appear independent of Te • Appear independent of APD high voltage • Suggest problem might be optical APS-DPP-2005-LeBlanc-9

  10. Other Tasks to be Done • Fix the new channels • Investigate optical issue with new polychromators • Pursue density calculation and scaling, which might reveal relevant issues • Compute 30-point profiles and load tree • Improve laser delivery optics • Eliminate nel time modulation associated with lasers • Procure and install polarizer on viewing optics • Eliminate needs to close one view-optics shutter at high density APS-DPP-2005-LeBlanc-10

  11. MPTS Implementation • MPTS is a multi-time multi-spatial point Thomson scattering diagnostic, which routinely provides Te(R,t) and ne(R,t). • So far two 30-Hz Nd:YAG lasers • 36 fiber bundles already viewing plasma • Output end can be split for improved resolution • Phased implementation • Phase I 60 Hz 10 channels • Phase II 60 Hz 20 channels • Phase III 60 Hz 30 channels APS-DPP-2005-LeBlanc-11

  12. Polychromator 206Focal decentration APS-DPP-2005-LeBlanc-12

  13. Collecting Optics29 out of 36 fiber bundles instrumented Fiber bundle holder 36 bundles in place Vacuum Window Laser beam (LB), laser tube (LT), TF coil (TF), focal point (FP), primary mirror (PM), aperture stop (AS), image of laser path (IM), fiber bundle (FB), plasma edge (PE), major radius (R), center stack (CS), vacuum window (VW) APS-DPP-2005-LeBlanc-13

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