[Murtaza, Koji]

ITMX / BS / PRM sat amps were removed from the rack and checked on the workbench. They all work fine with the OSEM simulation box.

With the correct circuit, the LED mon should be 5V, and the PD readout should be 2.6~3.0V (i.e. the differential output has twice the voltage difference of this number).

ITMX Sat Amp fixed:

• The internal wiring for CH1-4 was not connected (or disconnected by mechanical impact) (Attachment 1)
• PD1 channel for CH1 had a metal debris on the transimpedance opamp (Attachment 2)
• The internal board for CH5-6 was connected in the opposite direction. This was because both connectors on the board had the wrong genders.
  This was replaced with a spare. (There was two spares and I consumed one now) (Attachment 3)
   
• Put a ventilated lid instead of the solid lid.

BS Sat Amp:

• All the CHs just worked fine.

PRM Sat Amp:

• Found the bias selector jumpers had not been installed. Fixed. (Attachment 4/5)

Plan for Sept 20, 2023

For morning people:

• We don't need to replace the long cables. They seem all fine.
• Close the lid of the repaired sat amps. Use a lid with ventilation slits (there is an extra with the empty unit on the same desk).
• Install the sat amps back to the racks. Connect all the cables us. Check if this makes the OSEM values to positive 10~20k counts.
  • If not, check LED mons and PD mons. If they are OK the sat amp is working fine. Track the signal down to the AI chassis to see if the units after the sat amp are working well.
• The SRM2 and ITM2 cables ( connected to the sat amps at the back of the units) cross (i.e. have twisted) at the rack. Please reroute and nicely coil them up.
• Fix the custom cable issues: "The custom cable fastening screw on PRM(1st) was stripped at the flange side. It needs a thread dyeing. The SRM(2st) has the hex nut broken on the sat amp. Need to be fixed."
• Put the proper labels on the long cables at the flanges and the sat amps. The labels should indicate where the connectors are supposed to be connected.
• Clean up the mess and the tools from the lab.

The

After the weekly meeting, we'll continue to work on the suspension control. The lab will be turned to be LASER HAZARD in the afternoon.

I asked CDS mattermost for help. Chris (Wipf) checked it and reported it is working fine as usual (without fixing anything).

I've reverted the copied C1MCS.txt back in the chans dir (/opt/rtcds/caltech/c1/chans). The filter coefficients were loaded from the GDS screen. The filters were properly updated.

Here is the info from Chris:

Some transient NFS problem, maybe?

One possible clue is that the filter file that the FE actually loads is not chans/<model>.txt,
but chans/tmp/<model>.txt. Before loading, the filter file is copied into the tmp directory,
and a diff of the two files is written to chans/tmp/<model>.diff.
This diff file should normally be an empty file, indicating that the two files match.
But it was not empty at first, so there must have been some issue with the previous load.
After I reloaded, the diff then became empty.

I found the actuator calibration is more complicated. The numbers I reported in the previous elog was not correct.

Here I summarize the numbers of the voltage-to-current conversion.

=== Previous===

=== New ===

e.g. ITMX face coil electronics are x4.6 stronger than the previous coil electronics.

MC1/MC2/MC3 damping restored

I tweaked the coil actuation gains for MC1/MC2/MC3 according to Koji's updated calculations:

With foton and load coefficients working as expected, these coil output filters were successfully added to MC2 and MC3.

Damping tests

Note: While burt restoring C1MCS to a pre-upgrade state, a "NOT OK" flag popped up and the coil balancing gains for MC1/MC2/MC3 were reset to +-1. Koji showed me how to access the original values in c1mcs.snap (using grep) and I restored the coil gains to their values from 9/12/2023.

Next steps

[Paco, Radhika]

IMC LOCKED

We used the pre-upgrade C1:SUS-MC1/2/3_SUSPIT/YAW/POS_INMON values as a baseline to restore IMC alignment.

Procedure we followed:

I noticed the same issue today with C1RMS.txt, when trying to update the coil actuation gains for SRM. The filter changes were saved to chans/C1RMS.txt, so next I checked chans/tmp/. There is no chans/tmp/C1RMS.txt, or chans/tmp/C1RMS.diff. The updated filters do not load.

Update from Chris:

C1RMS.txt is a remnant from some model that doesn't exist anymore. It can be removed.

I went ahead and deleted chans/C1RMS.txt and chans/tmp/C1RMS.txt.

[Koji, Murtaza, JC]

Regarding PRM/BS:

• PRM2 cable and BS2 cable were wrongly connected. This was corrected.
   
• This makes the BS face OSEM values reasonable.
  However, the side signal is still close to zero. We confirmed that the sat amp outputs (LED mon/PD mon/PD diff out) looked reasonable for all five BS OSEMs.
  The side signal issue stays downstream of the Vertex ADC adapter.
   
• PRM2 has no issue with the sat amp.
• PRM1: We found that all the LED mon goes down to 0.17V when the vacuum flange is connected.
  It was found that the reference voltage for the LED (TP11 of D080276) went down to low number (like 0.15V) when the in-vac OSEMs were connected.
  I found that this output was not stable. So, I replaced the U4 chip (AD8672), but this didn't help the voltage sagging issue.
• Murtaza and I started checking the short circuits on the flange. We found that Pin 5 (OSEM PD1 Kathode) and Pin 1 (invac cable shield?) only have 5.1 Ohm. Pin 1 is connected to the vacuum chamber.
  • What does it mean? The PD has the reverse bias voltage of 10V applied on the PD Kathode. This bias voltage is shorted to ground via 5 Ohm. To keep the bias line at 10V, we need 2 A.
  • We don't have many options:
    - We can disconnect the internal wire for pin5 from the cable. (Prepare a ribbon cable). This should make the other OSEM PDs properly biased.
    We may be able to use an independent power supply to provide some amount of reverse bias (10V 2A is too much. Probably 1V 0.2A or 2.5V 0.5A?) so that the UL PD somewhat work.

This morning I recalculated the scale factors between OSEM sensor readings after/before the upgrade. BS values seemed reasonable:

[UL: 7.5199148, UR: 9.7845377, LR: 10.8113698, LL: 8.58337867, SD: 4.9020585]

The SD reading is positive and nonzero, even though its still smaller than the face sensor readings.
 

C1:PEM-BS_ACC_EAST_Z

• The slotted disks that capture the wires do not have the alignment bore used to center the wire in the hole
  
• We didn't correctly route the far field QPD cable so it runs funny
  
• We didn't have a tool which could be used to get two of the DCPD preamp box mounting screws (which are M3's chub!)
  
• We don't have the cable clamps to tie off the electrical cables to the intermediate mass
  
• We don't have any of the cabling from the OMC-SUS top to the rack so we can't test anything
  
• We haven't uploaded pretty pictures for all to see
  

• The bottom plate of the EQ stops is too thick so that it bumps into the tombstones
  
• The vertical member on the "waist" EQ stops is too close to the breadboard, possibly interfering with the REFL beam
  
• The "waist" EQ stops are made from a thin plate that doesn't have enough thickness to mount helicoils in
  
• Helicoil weren't loaded in the correct bottom EQ stops
  
• The DCPD cable loops over the end EQ stop looking nasty but not actually making contact
  

- Turn off the MC autolocker. Relock the MC with only the acquisition settings; no boosts
  and no RGs. This makes it re-acquire fast. Turn the MC-WFS gain down to 0.001 so that
  it keeps it slowly aligned but does not drift off when you lose lock.

- Use low-ish gain on the FSS. 10 dB lower than nominal is fine.

- Setup the o'scope (100 MHz BW or greater) to do single shot trigger on the MC2 trans.

- Flip FSS sign.

- Quickly flip sign back and waggle common gain to get FSS to stop oscillating. MC
  should relock in seconds.