This morning we moved the electronics rack to within ~2.5m of the target chamber, leaving room for the ribbons cables of ~5m length which connect the preamps to the amplifiers in the rack.

Then I continued in attempts to solve the iris arm problem, see eLog entry #3.

When comparing to the CAD drawing (entry #4) David pointed out the iris was mounted the wrong way around, and that it should be rotated 180 degrees. I attempted this yesterday but decided to investigate more thoroughly.

I made three changes in total:

1. I replaced the lemo cable on the Si diode with a shorter one (~7.5mm) from Edinburgh, reducing the chance to catch the lemo between the lid and chamber wall

2. I moved the diode mount away from the upstream chamber wall to be certain there was no collision here

3. I removed the nylon screws intended to connect the S2 to the nylon standoffs on the iris

After each change I reattempted mounting the central lid with the iris attached, after the third correction it fit! This suggested the nylon screws were slightly too long.

I measured the thickness of the S2 detector serial no 2323-18:

PCB board thickness = 2mm

Yamatchi connector thickness = 8mm

Bond wire solder thickness on back of S2 ~1mm

The thread of one nylon screw was cut from 6mm to 4.5mm, after screwing this back onto the iris standoff I found the lid still fit onto the chamber. There will be enough thread to still mount the S2's.

At ~13:20 we then went to lunch