Ryan C, M Robinson, R Kumar

Given below is the summary of work done in the triples lab in the last two months regarding assembly of A+ HRTS suspension for O5 (refer to alog 76635 which gives the details about the first assembly in March 2024- assembly s/n 02). We have assembled four new suspensions (assembly s/n 03, 08, 01, 11), which brings the total number of assembled (with BOSEMs) and characterized suspension in the lab to five. All five assembly till now has been for the FREESTANDING version (only the base differs- which is as per D1900287).

In this round of assembly and testing procedure of HRTS we have made two new improvements as listed below,

1. Class B PEEK wire install tool (top mass to PUM - as shown in the picture attached) - This new PEEK part has been designed by the RAL team after we had wire breaking issues in the first round of assembly. Using this new tool we can safely and quickly install the wires between top mass and PUM outside the cage on the optical bench.

2. Vibration Isolation set up as shown in view01 and view02 - While running transfer function measurements, the HRTS suspension was strongly coupling-in with the lab/building environment (ground vibrations, doors, HVAC etc). To partially isolate the SUS, we now have an optical bench (12in by 18in, Thorlabs Nexus Breadboard) sitting on a 1inch thick viton pads (placed at the four corners of the bench). Also, Chris fabricated a hard top transparent cover for us to protect against the turbulent air flow in the lab.

Cage S/N 03 (April 2024)

Suspended masses (as per specifications):-

Top Mass = 749gm, Penultimate mass = 803gm, Dummy optic = 300gm

Transfer function measurements for HRTS assembly S/N 03 is attached here.

Cage S/N 08 (April 2024)

Suspended masses (as per specifications):-

Top Mass = 755gm, Penultimate mass = 803gm, Dummy optic = 301gm

Transfer function measurements for HRTS assembly S/N 08 is attached here.

Cage S/N 01 (May 2024)

Suspended masses (as per specifications):-

Top Mass = 752gm, Penultimate mass = 804gm, Dummy optic = 300gm

Transfer function measurements for HRTS assembly S/N 01 is attached here.

Cage S/N 11 (May 2024)

Suspended masses (as per specifications):-

Top Mass = 750gm, Penultimate mass = 803gm, Dummy optic = 301gm

Transfer function measurements for HRTS assembly S/N 11 is currently under processing and the latest plots will be attached soon.

Conclusions: - The transfer function measurements ties-up nicely to the model, however we do see some low frequency coupling and unwanted peaks. The cross coupling and unwanted peaks are due to environmental noise which is difficult to fully isolate in the lab.

I will also post a plot comparing the transfer function measurement results for all five suspension that we have tested.