FranciscoL, [Remote: RickS]

After one week of moving the inner beam to the center of the Rx (alog 77967), on May 28, we moved the beam down. This completes a cycle in which we characterize the XY comparison value to both directions of the pcal beam movement - one side right, one side down.

Attachment 'BothBeamsBefore' shows the beams before making any changes. Attachment 'AlignedTarget' shows the alignment with the beam height gauge. The pdf 'EndStationLog.pdf' lists the voltage values after each significant step of procedure T2400163. The steps represent writing down a voltage value after a particular change of the system. Some steps were recorded multiple times after minor changes.

• 'Initial' - Nothing has changed, reading voltmeter after plugging it to "Rx PD Mon".
• (1) Alignment of the target.
• (2) Only inner beam at Rx detector. (see image 'InnerBeamBefore')
  • The beam voltage was maximized by moving both axis. The first value is before attempting to move anything. The second value comes from attempting to maximize by making a horizontal move The third value resulted from moving the beam counter-clock wise from the vertical axis, an equivalent to moving the beam up.
• (3) Finalized beam movement. (see image'InnerBeamAfter')
  • The first value was from an accidental move up. The second value was after moving the beam down. The third value is from attempting to maximize the signal by moving the horizontal axis.
• (4) Both beams at Rx detector, target still on (see image 'BothBeamsAfter')
• (8) Target off. The measurement was recorded after placing the pcal enclosures.

The voltage ranged by ± 0.01 V during the measurement, mostly noticed when the target is placed on the integrating shpere. We might need to look closer at the seismic isolation configuration to reduce the noise during this - and potentially also end station - measurement procedure.

The 'Initial' measurement is *equal* to the last voltage measurement from the previous movement, done on May 21 (alog 77967). The initial and final voltage measuremed during todays procedure did not change.

With the movement made today, we expect that the X/Y comparison will change by +21.15 HOPs.