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Entry  Fri Sep 22 18:38:15 2017, awade, DailyProgress, Vacuum, Baking bake chamber 2017-09-22_18.16.42.jpg
    Reply  Thu Sep 28 21:15:12 2017, awade, DailyProgress, Vacuum, Cleaning refcav Au coated heat shields 13x
       Reply  Fri Sep 29 20:06:21 2017, awade, DailyProgress, Vacuum, Cleaning refcav Au coated heat shields 2017-09-29_19.36.57.jpg2017-09-29_19.33.34.jpg
          Reply  Sat Sep 30 17:09:03 2017, awade, DailyProgress, Vacuum, Cleaning refcav Au coated heat shields 
Message ID: 1934     Entry time: Thu Sep 28 21:15:12 2017     In reply to: 1933     Reply to this: 1935
Author: awade 
Type: DailyProgress 
Category: Vacuum 
Subject: Cleaning refcav Au coated heat shields 

Its time to clean parts to go into vacuum. I tested the Branson EC ultrasonic cleaning solution on a couple of gold coated DC connector pins.  Close visual inspection shows that doesn't seem to be any damage, pitting or dulling of the surface quality from 90 minutes at 60 C with the alkaline (12.5 pH) 2-3 % solution (by volume).  Pictures are attached below of the pins, left is pre clean examples and right is post clean examples.

I've unwrapped the gold coated shields and caps and inspected them.  Photos of one of the shields (loaded in front of bath). There were some minor scratch imperfections from the original manufacture and it isn't blindingly shiny (i.e. polished) but is otherwise in a good state.  Similar to aluminum foil we probably don't want a super shiny surface for room temperature emissivity at ~10 µm. According to RaNA the dull side of Aluminum foil has a lower emissivity at 10 µm than the shiny side. He may have a reference to add.


The sonic bath has been cleaned. I've made a tray holder to suspend beakers in the main bath (pictures attached). These beakers have clean DI water and Branson EC detergent to loosen any dirt and oil.  The main sonic bath is filled with regular tap water and some general use surfactant to improve the transfer of mechanical energy.  Usually surfactant is recommended to lower surface tension. This improves cavitation in and around the parts to be cleaned. Although it may not be necessary the main bath.  I found that the standing wave pattern on the surface was much stronger once I added a bit of general purpose non-foaming surfactant. It seems to be doing a better job so this is probably the way to go.

The shields were suspend from thin wire, small pins for crimping and connecting are just directly in the small beakers.  I was unable to fit the end caps into this cycle so they will have to be done tomorrow.

The shields were put in for 90 minutes at 60 C with ~ 3% solution of Branson EC surfactant.  Once the time is up I will pull them out, wash them down thoroughly with deionized water and then with isopropanol/methanol.  They'll be left in the flow bench overnight to air dry and I'll put them in for a bake cycle tomorrow.

Quote:

I'm now preparing the bake rig for baking the ref cavity shields.  

I've cleaned out the inside of the bake rig vacuum chamber with some clean fabric wipes and methanol.  The setup is out in the hall to avoid stinking out the lab.  The vacuum pump has been hooked up and is pumping.  I've used a AC heating strap wrapped around the chamber and used cooking grade aluminum foil as crude insulation to help with heat build up. To control temperature I have a variac salvaged from the EE workshop broken pile (only thing wrong was a loose knob). To monitor temperature a thermocouple is taped on with Kapton tape to sense temperature.

The rig has reached 120 C in 15 minutes and I'm now adjusting the variac percentage of total power to give something stable around 100 C.   

Will bake for a few hours and then let cool overnight.

 

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