Alignment to IOT2L through JAC

Jennie W, Jenne D, Masayuki N

 

Today Jenne and I went into HAM1 and onto IOT2L.

Our first priority was to check the input alignment to the JAC after alignment efforts yesterday to check we were not locking to a HOM mode. We locked the JAC with a power of 0.1 on the TRANS_A_LF_OUT channel.

I checked after lens JAC_L3 which is right before the steering mirror into the HAM1 output periscope. Here the beam looked like a 10 mode (two lobes in the horizontal axis). Further upstream (just after JAC cavity this was not obvious due to the beam size.

We used the steering mirror between the input periscope and JAC + the PSL periscope PZT mirror to improve the alignment. To do this we changed yaw in the closer mirror and pitch in the PSL PZT mirror as the input periscope switches the P and Y around.

We recovered a value of 0.22 on TRANS_A_LF_OUT which matches with the values we got on friday the last time we had a good TM00 lock on the JAC cavity.

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After this Jenne went to the table to look at the beam we found yesterday which is at the edge of the MC REFL periscope mirrors in yaw and clips on the BS1 optic.

I started changing the tilt of the beam through HAM2 by changing the pitch of the mirror right before the HAM1 output periscope. This did not really change the beam position so we moved to a further away mirror (JM2) to translate the beam.

During this process we also became unable to lock the JAC using the guardian. More details at the end.

After some iteration we were able to see a beam on the MC REFL PD but have not been able to walk the beam to see any signals on the MC REFL WFS orflashing from the IMC on the MC TRANS PD.

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After a break we went to the control room and did some checking of the MC sus alignments. We found problems with the alignment of MC3 - Dave and Ollie debugged this.

Jenne then did some walking of the MC mirrors and by moving MC1 she could get a larger signal on MC REFL. We might be able to use this tomorrow by moving MC1 to this 'wrong' ( ie. not consistent with the nominal IMC alignment before JAC was installed) place and walking MC1 back while changing the in-vac fixed mirrors in HAM1 to reover the beam on MC REFL PD.

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During the day an electronics chassis was swapped that does the whitening for the TRANS PD A. The signal stopped getting to the diode so Daniel gave us the go-ahead to bypass this - this might need to be fixed properly at some point, it is level 10 on the rack closest to HAM1, next to the PSL enclosure. I took put IN3 and OUT 3 cables and connected them with a TNC connector.

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This afternoon and evening we tried to trouble-shoot the JAC locking.

There was also an incorrect gain that got reset by the model restart for h1lsc earlier today but fixing this (JAC_DITHER_PD_IN gain was set to 200 and should be 4) did not allow us to lock.

After changing the servo gain in the dither lock Jenne noticed that this had no effect on the lock level/noise on the TRANS PD.

After checking with Masayuki the problem seems to be that the fast channel to drive the PZT is not connected somehow at the racks but the Beckhoff controller can be used to drive the PZT - will consult with Daniel/Marc tomorrow.