[Tamaki, Yokozawa, Ushiba]

Abstract:

We performed tapping test around MCF (outside of the clean booth) without PRFPMI lock.
We cannot see any large broadband excess of IMMT1 TRANS QPD1 and MCE TRANS QPDs.
It is better to have a more systematic tapping test (or injection test) around MCF.

Detail:

We performed tapping test at beam duct between MCF and MCE (-X side, close to MCF but outside of the clean booth), which is the same place tapped in klog24298.

First, we engaged whitening filter of MCE trans QPDs for improving the sensitivity of these QPDs.
Figure 1 shows the comparison of the spectra without whitening (brown), with 1st whitening (blue), and with 1st and 2nd whitening (red).
To engage 1st and 2nd whitening filters, sensitivity of these QPDs are improved and some structure above 100 Hz can be seen.

After that, we started to tap the beam duct by hand and see the trans QPD signals.
Figure 2 shows the spectra of IMC trans QPDs (sorry but I forgot to take reference of MCE trans QPDs...).
Red line shows the spectra when tapping and black line shows the spectra when being calm.
Peaks below 100 Hz were increased but no significantly large excess in IMMT1 trans QPD signals above 100 Hz, whcih was observed previous measurement (klog24298).

Then, we performed the same measurement when XARM was locked with IR.
Figure 3 shows the result.
Black and red lines show the spectra with and without XARM lock when tapping.
We saw large excess at high frequency only in IMMT1 trans QPD2 in this time but found it was a fake later.
Tapping at that time seems too strong and IMMT1 trans QPDs were saturating during the measurement (fig4).
This means we need to check how strong we can tap the chamber during the tapping test.
I'm not so sure how strongly tapping the chamber during the last measurement (klog24298) but it seems better to do it again while checking the time series of each signal.

Additinaly, I checked the feedback signals of IMC LSC and ASC during tapping (fig5).
It seems no significant change appears in pitch feedback, feedback signals of L for MCE and Y for all were increased during the tapping.
Since we have no time to do the tapping test enough systematically, it is better to continue the test around IMC systematicaly.