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AdV-INJ (Input Beam Monitoring system)
melo, spinicelli - 18:52 Tuesday 06 April 2021 (51333) Print this report
BPC slow drift

After verifying the BPC signals calibration (entry #51205), we have analyzed them from January 2021 to the end of March 2021 in order to see if the signals present any drift trends. For that purpose, we have applied an unwrap technique to all signals (X, Y, TX and TY), i.e., we have considered all the moments in which we have brought the BPC to the center of the corrections, and summed the signals in order to see the long term effect.

The results have been the following:

For TX and TY there has been a positive and negative drift respectively of the order to two hundred micro-radians.

For X and Y, instead, there has been a negative and positive drift, respectively, of the order of a few mm (3 mm for X and 5 mm for Y).

We are still investigating to understand better what could be the cause of this effect.

Comments to this report:
chiummo, Melo, Spinicelli - 10:11 Wednesday 07 April 2021 (51339) Print this report

The drift of the previous entry is referred to the corrections applied to the piezo (first row of the attached plot) in order to keep the beam pointing steady along the time. Without the corrections, the beam would have drifted by the amount quoted above (, but in fact the pointing stayed where we set it on the sensors (second row of the the attached plot).

It is intersting also to note that we have a kind of monitor of the outgoing beam not attached to the EIB, namely the IBJM quadrant (third row of the attached plot), an out-of-loop sensor - pick off of the far field BPC quadrant - sitting on a small breadboard on the north side of EIB. We will try to calibrate it to see if we see any relevant slow drift.

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