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Entry  Thu Feb 23 01:38:21 2012, Zach, Laser, GYRO, input-side viewports installed vp_installed1.pngvp_installed2.pngvp_installed3.png
    Reply  Wed Mar 7 09:05:22 2012, steve, Laser, GYRO, input-side viewports installed & design flaw 
Message ID: 1636     Entry time: Wed Mar 7 09:05:22 2012     In reply to: 1622
Author: steve 
Type: Laser 
Category: GYRO 
Subject: input-side viewports installed & design flaw 

Quote:

I cleaned the viewport components and began installing them this afternoon. All the parts were cleaned and the chambers were prepped, but I was only able to install the two input-side viewports tonight. The cleaning procedure was as follows:

  • All o-rings:
    • DI water/isopropyl solution ultrasonic bath for 20 minutes
    • Isopropyl wipe
  • Steel CF338 flanges:
    • Acetone wipe
    • Methanol wipe
    • Optics paper wipe on knife edges just before mating with the copper gasket
  • Delrin brace ring:
    • Methanol wipe
  • Windows
    • Isopropyl drag wipe

The mounting went largely without incident except for the placing of the thin Teflon gaskets. These are meant to go around the circumference of the inner (vacuum-seal) Viton o-rings to keep the window glass from compressing against the steel around the o-ring at vacuum. The problem is that without o-ring compression, the gasket is free to slide down into a position where it would obstruct the glass/Viton seal, which is obviously no good. It could be that the glass will never actually touch the metal anyway, but if it does we might want to consider some other option. 

I also re-cleaned the inside of the 4 corner chambers with acetone and then methanol, having removed all optics from them first. 

Photos:

vp_installed1.png vp_installed2.png

vp_installed3.png

As you can tell from the second picture above, there is no longer enough space at the edge of the table for a steering mirror into the vacuum from the N side. It looks like I can make room by sliding the entire vacuum system to the S by an inch or so. The way the flexi-hoses are designed, they compress quite noticeably upon pump-down. So, unless the corner chambers are bolted to the table, the system does not have the correct form factor at atmosphere (if the chambers are bolted, then the flexi-hoses are just put under stress). For this reason, it is best to move the tanks around after the system has been evacuated, so this is what I plan to do.

Another benefit of moving it while evacuated is that I can do a test run of the system without any optics inside. I also plan to use the resistive heating tape we have to "bake" the chamber in-situ before re-venting and installing the optics.

I am waiting to find out if I can borrow the cryo turbopump, but if not I will have to share with the coating Q setup (which will suck). The other two viewports will be installed tomorrow and I can go from there.

 The viewport should be assembled in horizontal position first and installed on CF later. Drill holes into the delrin piece so you can reach the CF bolts.

 The delrin part should be bigger to protect the optic, o-ring from dust.

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