HEPI transfer functions
The first set of transfer functions was measured on BSC8 from 2mHz to 500Hz. The 700mHz-10Hz frequency band was measured in 2 configurations:
- ISI undamped (2012_02_15)
- ISI damped (2012_02_16)
The HEPI transfer functions can be seen at:
- LHO_HEPI_BSC8_TF_L2L_Raw_from_ACT_to_IPS_2012_02_16.fig
- LHO_HEPI_BSC8_TF_L2L_Raw_from_ACT_to_IPS_2012_02_16.pdf
- LHO_HEPI_BSC8_TF_L2L_Raw_from_ACT_to_L4C_2012_02_16.fig
- LHO_HEPI_BSC8_TF_L2L_Raw_from_ACT_to_L4C_2012_02_16.pdf
The ISI damping loops are effective between 1Hz and 8Hz. The effect on HEPI transfer functions is limited but visible on the 1.25Hz and 5 Hz resonances. A comparison between the two configuration can be found at:
- LHO_ISI_BSC8_Comparison_TF_L2L_ACT_H_to_L4C_H_20120215_vs_20120216.fig
- LHO_ISI_BSC8_Comparison_TF_L2L_ACT_H_to_L4C_H_20120215_vs_20120216.pdf
- LHO_ISI_BSC8_Comparison_TF_L2L_ACT_V_to_L4C_V_20120215_vs_20120216.fig
- LHO_ISI_BSC8_Comparison_TF_L2L_ACT_V_to_L4C_V_20120215_vs_20120216.pdf
If you look carefully, you can see light bumps at the junctions between the different sections (10mHz for instance) of the transfer functions. To evaluate the non linearity, I drove a sine wave at 200mHz and 4Hz using different amplitudes (100cts, 300cts, 1000cts, 3000cts, 5000cts) (attachment).
