[lydia, gautam]

Summary: Third unsuccessful attempt at getting ETMX suspended. I think we should dial the torque wrench back down to 1.0 N m from 1.5 N m for tightening the primary clamp at the top of the SOS tower. No damage to magnets, standoff successfully retrieved (it is sitting in the steel bowl)

Details:

• We burned through two sets of wires today.
• First, the assembly Eric and I had put together last night failed when Eric tightened the wire clamp (no torque wrench was used I think?)
• This afternoon, Lydia and I re-assembled the suspension once again. Standoff was successfully inserted, coarse pitch balancing was achieved relatively easily - we think that the coarse pitch balance can be achieved if the end of the wire standoff closer to the groove is ~0.5mm ahead (i.e. towards HR side) of the guide rod.
• Checked leveling of scribe lines, gave an extra 0.25 turns on the winches in anticipation of the wire sagging
• Inserted OSEMs just short of magnets, verified that they were approximately centered, if anything, slightly above center, again in anticipation of the wire sagging. 
• After taking pictures, we went ahead and attempted to clamp the wire (ALL EARTHQUAKE STOPS WERE ENGAGED)
• Eric commented that the clamp piece did not slide in smoothly on the dowels (indeed it does not come off very easily either, I have just left it on for now). I don't remeber it being so difficult prior to us sending it into the maching shop to get rid of the grooves made by the suspension wire the first time around. But with the torque wrench, the piece moved in relatively easily (we had sanded down rough edges prior to putting this piece onto the suspension earlier in the afternoon.
• I could feel that the torque wrench coming up on its limit. But the wire snapped before the torque wrench clicked. As far as I am aware, there were no rough edges on the piece, but perhaps we missed a spot?
• I took the opportunity to discharge the optic using ionized nitrogen at 40psi. After about 2-3 minutes of a steady stream, I verified that a piece of the suspension wire no longer gets attracted to the barrel, as was the case earlier today.

Unfortunately I don't know of a more deterministic way of deciding on a "safe" torque with which to tighten the bolts except by trial and error. It is also possible that the clamping piece is damaged in some way and is responsible for these breakages, but short of getting the edges chamfered, I am not sure what will help in this regard.

Unrelated to this work: earlier today before the first wire failure, while I was optimistic about doing fine pitch balancing and gluing the standoff, I set up an optical lever arm ~3m in length, with the beam from the HeNe on the clean bench at 5.5 in above the table, and parallel to it (verified using Iris close to the HeNe and at the end of the lever arm). I also set up the PZT buzzer - it needs a function generator as well for our application, so I brought one into the cleanroom from the lab, isopropanol wiped it. The procedure says apply 5Vrms triangular wave at 1000Hz, but our SR function generators can't put out such a large signal, the most they could manage was ~2Vrms (we have to be careful about applying an offset as well so as to not send any negative voltages to the PZT voltage unit's "External input". All the pieces we need for the fine pitch balancing should be in the cleanroom now.