TMS Meeting Minutes, October 1, 2020

Attendees: Andrew, Breann, Heejoo, John, Matthieu, Trenton, Yang (Zoom Meeting)


Meeting discussion summary:

  • Heejoo took SuperFoc data with Olga
  • Had issues with software crash of the system
  • Waited 20 minutes for the laser to stabilize, and thought there might be some comm problem between software and laser
  • Was unable to restart software after this
  • Note: Never try to turn off software while the laser is stabilizing
  • Andrew notes that the eTalon software works very well when you stay within the standard operating parameters
  • Heejoo noted substantial change in mirror diameter
  • Andrew believes there may be a problem with instability because fibers brush on mirror flange (physically coupling)
  • Believes it's much more likely that fibers are brushing on flange
  • Heejoo and Trenton to do more data analysis to get to the bottom of this
  • Going to look at other fiber channels as well, to see if this is a problem on other channels
  • When looking across the mirror for diameter or LBTI bearing, fibers run into flange
  • GMTO planning to combat this problem with a flat mirror on the end of the fiber
  • Able to run the fiber tangential to the mirror edge, so no brushing on the flange

  • Heejoo preparing data for upload to Google Drive
  • Has started analysis of pose of primary + LBCr system vs. the LBC images
  • Heejoo plans to have this data by the end of this week or early next week

  • Andrew on Field Aberrations Software Tool
  • The tool in use in Japan is comparable with the performance of the Hartmann test
  • On VST, only two small det's intra and extra focal at edges of field
  • With LBC, we can analyze the ENTIRE FOV
  • We can analyze all sorts of modes across the field
  • Able to fit a shape to the detector surface (shape term) as well as all of the
  • Modal, low order shape, fitting first 20 Zernike modes to the detector surface shape distribution
  • There will be residual changes in the pupil that aren't analyzed by standard wavefront analysis
  • Andrew suggests first 20 some Zernikes to a detector surface and pick up the residual wavefront aberration
  • Andrew to connect Trenton with Subasa next week to kick this off at LBT

  • New MPO Casette/Collimator
  • Heejoo has not yet had a reply from Christian about this purchase order
  • Going to call a meeting with Christian or contact Laura
  • Yang believes the current software approach is not very good for what we are trying to do
  • The program is stateless, meaning you have no previous information accessible
  • In the future, the software will be able to keep track of internal state changes over the course of the night
  • For now, we may need to do this in an ad hoc way
  • By John's suggestions, you don't have to skip the last measurement to get your correction vector for dropped channels

    Interesting Result (Andrew)
  • Air sensor prototype measurement
  • What is the sign of the correction for air temperature change?
  • As the air cools, the refractive index of air drops, and the measured length increases
  • However, when the steel cools, the mechanical distances shorten
  • The air and steel partially compensate one another as temperature drops

  • Next week, there are LBC runs planned
  • Potentially opportunities to run TMS, though John cautions us against using up all of our TMS time w/o having something we need to fix

-- TrentonBrendel - 02 Oct 2020
Topic revision: r2 - 02 Oct 2020, TrentonBrendel
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