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Message ID: 2597     Entry time: Tue Jun 29 17:29:16 2021
Author: Stephen 
Type: Things to Buy 
Category: 2um Photodiodes 
Subject: Integrating 2um PD measurements into Cryo Vacuum Chamber 

Radhika and I started discussing in detail the items needed to transfer the 2um PD setup into the Cryo Vacuum Chamber.

1) Electrical

To interface with the PD setup, it seems that we will need want to use the feedthrough already in use on the IRLabs cryostat. This square-flanged feedthrough appears to host the in-vacuum cabling. The in-air cabling would ideally also be reused.

To implement this, we will need to modify a blank 2.75" conflat flange (in hand in QIL boxes on wire shelf) with a the following features:

  • through bore, 1.18 diameter on center.
  • a 4x #4-40 tapped hole square bolt pattern, 1.062" spacing on center.
  • preferably, a hand-polished o-ring sealing area.

I will take care of this part through the PMA shop.

2) Optical

The Cryo Vacuum Chamber windows are Thorlabs VPCHW42‐C (ref. D2000310-v1). The broadband AR coating is rated for 1050-1700 nm (here's the data sheet), with a steep climb in AR coating reflectance. There is also fused silica substrate transmission to worry about. Perhaps the easiest way to proceed would be to repeat Koji's Transmission test (ref. QIL/2458) for the windows already in use on the Cryo Vacuum Chamber, and see if we can accept ~10% loss (or more).

Else, perhaps we scavange the IRLabs cryostat and create another custom blank CF modification?

Or buy a new, suitable window with CF interface? (<---- preferred option)

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