[Jeff Kissel, Rick Savage, Eddie Sanchez, Patrick Thomas, Timesh Mistry]

Update for 07th October 2019

EX NCAL Mount Fit Check

We went to the X end with the NCAL, NCAL mount and NCAL drill fixture to assess the fitment and the clearances of the hardware. The full assembly was test fitted at EX and there is sufficient clearance.

In order to set the NCAL mount upon the BSC pier, we had to remove the L brackets that would hold the Gibon clamps. The NCAL mount fits as the drawings indicate. The only discrepancy is that the NCAL mounts sits a bit lower than expected because the part of the NCAL mount that would bolt to the HEPI pier sits about 5mm low. Otherwise, the NCAL mount clears all vacuum tank flanges and ribbing as well as the resting on the BSC pier. Bolting to the NCAL mount to the HEPI pier is optional therefore, we will look to not bolting the NCAL mount to the HEPI pier.

We held the NCAL mount in place using the Gibson clamps whilst we mounted the NCAL on-top. The full assembly seems very stable however, we have concerns over the 1/4-20 bolts called out to hold the NCAL mount to the BSC pier. We will look to the Hazard Analysis form to see of we should use 3/4 bolts instead.

Using a permanent marker, we marked where the NCAL holes locate on the BSC pier. Once marked, we removed the NCAL mount from the BSC pier. We fitted the NCAL drill fixture to the BSC pier and adjusted the set screws until the drill fixure was level (using the bubble on a spirit level). We left the NCAL drill fixture in place before leaving the X end in preparation for drilling in the near future.

We have yet to survey the NCAL in order to get a relative location to the ETMX optic. The exact point reference point on the NCAL to survey has yet to be determined.

First Spin with Tungsten Masses

For the first time at LHO, we spun the Newtonian Calibrator with the tungsten masses installed in the rotor. This was done in the optics lab with the NCAL dog clamped to the optics bench. We tested spinning the NCAL at 1Hz, 5Hz, 10Hz, 20Hz and 30Hz. The motor ran smoothly however, the Beckoff filter drive parameters need to be double checked against the values given in LHO alog 50512. We ran the NCAL thought the Beckhoff/TwinCAT3 interface as there is no network ability in the optics lab to run using the EPICS interface (and the MEDM screen). We know this works from other tests so we are not that concerned.

At 10Hz, the apparent vibration noted in LHO alog 50961 is no longer present. At higher frequencies, the NCAL motor is more audible than when running without the masses in the rotor however this is expected. We attempted to measure the vibrations by using the accelerometer supplied by Krishna. Using a SRS755 spectrum analyser, we looked at the PSD of the accelerometer whilst the NCAL was spinning at 10Hz. We saw a peak at 10Hz in the spectrum as well as a comb of lines spaced at 10Hz. The magnitude of the combs increased with each order. It is unclear what could be causing this. We did have the accelerometer located in a different position to previous measurments. We think that the coupling from the motor to the NCAL shaft can be improved by using a flex servo coupler. This would relieve stresses associated with the motor and the NCAL shaft being slightly misaligned (either at an angular offset or horizontally offset).