====== Telecon 20180206 ======

Attending: Brian, Roger, Jacques, Julian, Tom, Toki, Kris, Hannes, Shaul, Karl, Qi

Notes by : Karl/Qi \\

=== Agenda===

  * Focal Plane Configuration (Kris, Karl, others)  {{::focalplane_update_20180206.pdf|focal plane slides}}
    * including ADR and Readout boards
      * {{::180118_pico_mechtherm_sidecut_w_angles.jpg?50|}} 
      * ADR drawing:{{::piper_cadr_basics.pdf|PIPER ADR CAD}}
  * Cosmic Rays (Jeff f.; Roger)
  
  
=== Notes ===

Focal Plane Configuration

  * Orientation of scan VS orientation of detector rows
     * Kris repeated the concern again from last week; with the hexagone wafers and current scan strategy, is it important to align rows of detectors with direction of scan?
     * multiple detectors on a row can scan over the same track if they are aligned with direction of scan
     * Shaul pointed out that even now there are detectors are one row, every other column though
     * It's not very clear if this matters
     * Spin rate is dominant over precession, so scan direction is about straight from left to right as shown
     * Shaul: each pixel has both polarizations; we want Q and U pairs, thus the word "detector" may be misleading here
     * Jacques: arrangement of focal plane, cross scan sampling; shaul: we will take look into Jaques's paper about cross scan sampling in terms of spin, precession etc.
     * Kris: faster precession, if compare 10 days to 10 hrs, gives better sky map coverage; however, if compare 10 hrs to 2 hrs, not sure if it makes a big difference
     * Jacques: holes on sky map will affect systematics over the focal plane
     * Shaul: fundamental questions have not be addressed, Q and U layout has not been done
     * Q and U alignment is flexible within wafer


  * ADR
    *shaul: current model has a tank next to focal plane for ADR, but it does not need to be there there
    *Tom: PIPER ADR
      *continuous ADR, 4 stages
      *stage 1, attached to brown color plate, which attach the focal plane 
      *about 9'' by 8'' by 3''
      *For PICO, one more intermediate stage, stable temperature; every 6 days, one extra ADR stage; so 5 stages in arrangement, slight larger than PIPER's
      *0.1 K fluctuates between magging and demagging; Tom will look into it how large the fluctuation is for next week


  * Focal Plane
    * change: 1)central wafer, split into three: F and GHI;2) 4mm space between edges of wafers based on different experiments (4.2mm for EBEX, 4-5mm for POLARBEAR, 5.5mm for BICEP)
    * Shaul: let's make space to 5mm
    * less F detectors, more GHI, same numbers for others
    * wire bonding
      * traditional: edge of wafer, constrains # you can bond; for F G H I, not enough space
      * "bump-bonding", instead of the edge, you can wire bond the entire wafer, needed for GHI
    * readout
      * for TDM, 4 mm^2; for FDM, mainly due to large capacitors, 50-80 mm^2
      * FGHI need some special packing, working on

  * sizes of mirrors
    * we need to increase mirror sizes if we want to use more diffraction limited field of view
    * dimensions are shown in the slides

Cosmic Rays
  *Roger: signals long-time constant spikes
  *TES for X-rays, they do not see it as a driven issue; worth looking into it