aLIGO LHO Logbook

H1 CDS

david.barker@LIGO.ORG - posted 09:57, Wednesday 03 December 2025 - last comment - 11:30, Wednesday 03 December 2025(88336)

Upgrade h1susex to all LIGO-DACs

WP12901 Daniel, Marc, Fil, Jonathan, Richard, Jeff, Oli, EJ, Dave:

Following from Monday's success in upgrading h1susey to the new LIGO-DACs on Tuesday 02dec2025 we upgraded h1susex to use LIGO-DACs.

This was a slightly different upgrade compared to h1susey because for the past 18 months h1susex ESDs have been driven using an early version of the LIGO-DAC. The h1susetmx model was using the GenStd 18/20-bit DACs for the upper stages and the LIGO-DAC for the L3 and ESD. The other models (h1sustmsx and h1susetmxpi) continued to use the Gen Std DACs.

The ESD and PI drives were being driven by a single 20bit-DAC using the special PI-AI chassis (first 6 chans through standard filters and output via DB15, last 2 chans through PI filters and output via DB9). When we upgraded the ESD drives to the LIGO-DAC we retained the original PI-AI chassis for these signals and temporarily installed the spare PI-AI chassis for h1susetmxpi 20bit-DAC's exclusive use.

The original LIGO-DAC used the 8-channel interface card. This card took the 32 channels from the LIGO-DAC and outputed the first 8 using its onboard DB25 connector. The remaining 24 channels were distributed using 3 Header Slot Plates (each with a DB25) ribbon cabled to the interface card. To fit these into the chassis, we displaced the two BIO cards to A4-3 and A4-4.

The IO Chassis changes were then:

Remove first-gen LIGO-DAC card, its 8chan interface card and the 3 header slot plates.

Remove the 3 18bit-DACs and their interface cards

Remove the 2 20-bit DACs and their interface cards

Install 2 LIGO-DACs in A1-4 and A2-2 with their new LIGO-DAC interface cards

Move the 2 BIO cards back to A4-1 and A4-2.

Fil upgraded all the AI chassis for LIGO-DAC SCSI Connection, duplicating what was done at EY. The second LIGO-DAC drives the PI-AI chassis, the first LIGO-DAC drives the 2 standard AI chassis, now daisy chained together.

Temporary cabling from the original LIGO-DAC chans 16-31 looped over to h1iscex were removed.

LIGO-DACs ADDED

DAC0 S2500451	Interface card SN007
DAC1 S2500456	Interface card SN005

Cards Removed

First Gen LIGO-DAC	S2400042
LIGO-DAC Interface Card	"2" in marker pen
18bit-DAC	110425-32
18bit-DAC	110425-22
18bit-DAC	101208-74
20bit-DAC	190219-10*
20bit-DAC	150311-01 (S1700286)
18/20-DAC Interface card	S1200225
18/20-DAC Interface card	S1104340
18/20-DAC Interface card	S1201759
18/20-DAC Interface card	S1102690
18/20-DAC Interface card	S1102687

* 20bit-DAC installed into h1iscex, now suspect.

Comments related to this report

jeffrey.kissel@LIGO.ORG - 09:58, Wednesday 03 December 2025 (88337)CAL, SUS

Link

Tagging SUS and CAL, as these are the DAC cards for SUS ETMX. 

We have done the logical thing of applying a gain factor of 1024x in the COIL and ESDOUTF banks to again mimic the calibration function of a 18- bit, like the factor of 4x that's been in play for a while after we upgraded to a 20-bit DAC. But, of course at the calibration group's level of precision / accuracy the DAC cards / and channels within will NOT have the same calibration as 2^18 / 20 [ct/Vpp_differential] * 2^10 = 2^28/20 [ct/Vpp]. 

This will change the open loop gain magnitude of the top mass damping loops, but to a much less important degree.
I expect a similar level of impact on ISC loops wrapped around ETMX too.

Also now that these LIGO 32CH DAC have had their maximum output voltage tuned to spit out 10.0 Vpp differential at the output of the AI chassis. 
This is unlike the 18-bit DAC who's output saturated at ~9.7 Vpp, or the 20-bit DACs who's output saturated at ~9.3Vpp.

david.barker@LIGO.ORG - 10:00, Wednesday 03 December 2025 (88338)

Link

Model Changes:

h1iopsusex (Dave) modified to new DAC configuration. SWWD section updated to new DAC cards

h1susetmx, h1sustmsx, h1susetmxpi (Jeff, Oli) updated to new DAC configuraiton.

All models built and installed with RCG5.5.2

filiberto.clara@LIGO.ORG - 11:30, Wednesday 03 December 2025 (88343)

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The following AI Chassis were modified for installation of the LIGO 32 CH DAC:

AI Chassis D1000305 S1104367 (SUSEY-C1, slot U32, new assembly drawing D2500353)
AI Chassis D1000305 S1001202 (SUSEY-C1, slot U31, new assembly drawing D2500353)
AI Chassis D1500177 S1500299 (SUSEY-C1, slot U26, new assembly drawing D2500400)

The rear panel and DAC AI Interface Board D1000551 were removed. A new D2400308 LIGO DAC Anti Image Chassis Rear Panel and LIGO DAC AI Interface D2500097 were installed.