We performed some tests with the Vibration absorbers of stage 1 with different Vitton pads (identical contact surface and different thicknesses). Measurements done without the vibration absorbers lids.

Parameters Surface: 0.25"x0.25"

Thickness:

- 0.0625"

- 0.125"

- 0.25"

Results:

- Reduction by a factor of 6 of the 217 Hz resonance on X, Y, RX, RY using pads with a thickness of 0.125".

2 measurements (2012 01 06 no vibration absorber - 2012 01 11 6 vibration absorbers)

https://svn.ligo.caltech.edu/svn/seismic/BSC-ISI/H2/ITMY/Data/Figures/Transfer_Functions/Comparisons/

LHO_ISI_BSC8_Comparison_TF_C2C_ST1_ACT_H_to_ST1_L4C_H_20120106_vs_20120111.fig

LHO_ISI_BSC8_Comparison_TF_C2C_ST1_ACT_V_to_ST1_L4C_V_20120106_vs_20120111.fig

- With the thickest pads (0.25") the vibration absorber are less effective

- With the thinnest pads (0.0625"), performances are similar (slightly better)

Next step:

- Tests with the lids on