I assume that we are prepared to live with the pitch bias situation of ETMY (i.e. we can achieve a configuration in which there is some pitch bias to the coils, and the OSEMs are inserted such that the PD outputs are half their maximum value). Or at least that we don't want to go through the whole standoff-regluing procedure for ETMY as well.

So today I took the optic out, and began to make some preparations for the air bake.

• Both optics are now sitting in their respective metal donuts. 
• How do we want to bake the optics? Bob has said he has prepared the oven for this bake, and that he has configured the temperature controller to a setpoint of 34C, and a ramp time of 2 hours to reach that temperature from lab temperature (we should check this before putting the optics in there with our independent temperature sensor - also, he is away for the week now so we can't get his input on any of these). But what about the actual logistics of how the optics are going to be housed? Specifically:
  • Do we want the donut to sit on some sort of tray? Presumably it is not ideal to have the HR surface in close proximity to the oven floor? 
  • Does the oven need any special cleaning?
  • Do we cover the donut+optic setup with a glass jar? If we do, any particles we eject off the optic can't escape the confines of the bowl, and if we don't, detritus from elsewhere may settle on the optic?
  • How long do we want this bake to last? 24hours? 48 hours? Bob didn't have an answer when I asked him earlier in the afternoon...
• I also removed the suspension block from the top of the towers of both ETMX and ETMY, so that Steve could work on sanding them before we acetone-wipe and bake the towers themselves.
  • It was very apparent that the weights of the two pieces were largely different (ETMY suspension block ~350g, ETMX suspension block ~960g), even though they have the same physical dimensions.
  • Investigation into why this was yielded nothing conclusive. But Steve and I think that the ETMY suspension block is made out of Aluminum rather than SS, which would explain why the wire grooves seem deeper in the ETMY piece than the ETMX piece. It is worth noting that the specification calls for SS and not aluminum. But the top piece of the ETMY suspension (and indeed the old ETMX suspension) looks different from the specification, in that they don't have tapped holes for the secondary wire clamps (see Attachment #1).
  • I'm not sure if this is important, but it is worth noting. Steve and I also checked the remaining suspension towers. We think that ITMY, BS, SRM and PRM have the correct (to specification) suspension block. We couldn't get a look at ITMX and didn't want to take the door off. So ETMY (and possibly ITMX) will be the only suspension(s?) with a different suspension block.
• Steve's sanding efforts did not go ideally.
  • He was successful in removing the wire grooves.
  • But the sharp edge which is supposed to clamp the wire seems to have been rounded a little bit (see Attachment #1). 
  • Overall, the section that we was sanded looks lower (i.e. its like we've dug a small channel into the plane of the suspension block)
  • Given that we suspect the ETMY suspension block is Aluminum, it is likely that attempting to sand it will yield an even deeper channel.
• Do we want to bake the suspension towers in the large baking oven? Presumably we don't want to bake the optics with anything else. But does the large oven need any special cleaning before we stick the towers in there?
• ETMY has some acetone marks on it. I will try and have this removed by drag wiping with more acetone and isopropanol prior to the bake tomorrow. Anyways we will first-contact clean the HR (and AR) sides after the bake before installing the optic.

In summary, the questions that remain (to me) are:

1. Are we okay using an Al suspension block?
2. How perfectly do we want wire grooves from prior suspensions removed? It looks like sanding doesn't work well, do we want to consider sending this into the shop?
3. Baking logistics, as described above.

I think we can start the baking of the optics tomorrow. The timeline for the suspension towers is unclear, depends on how we want to deal with the sanding dilemma.