BRS Drift Trends - Monthly FAMIS

Closes FAMIS#38813, last checked 88386

BRS Driftmon
Auxiliary BRS Channels

Everything is looking normal

Ops Day Shift Start

TITLE: 01/27 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: MAINTENANCE
    Wind: 4mph Gusts, 3mph 3min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.33 μm/s 
QUICK SUMMARY:

LVEA is still LASER HAZARD

JAC EOM update Tue/Jan/27 (Elenna, Keita, phone consultation with Valera)

Summary:

A day of success.

• We installed the RTP crystal with "in-between" mounting method (alog 88900) with an indium foil between the crystal and the front plate but not between the crystal and the electrode.
• Crystal is captured in EOM (no slipping out).
• Frequencies before tuning were in general smaller than we got previously with alumina. Not sure if that is due to indium or something else.
• Tuning was successfully performed.
• The tuning was done with the front plate facing down on an isulator plate because it's easier that way. As soon as the EOM was oriented correctly, there's a small but non-negligible frequency shift. Tapping made a small change, too.
• We will retune tomorrow with the correct orientation, tap repeatedly (in a hope that eventually we'll get to the bottom of whatever potential) and retune if necessary.

HAM1 alignment work

[Jennie, Jason, Masayuki]

Summary:

We aligned the HAM1 output beam to the IMC and verified the power transmission through HAM2. The beam path through JAC_L2/L3 was centered, and alignment to the IMC was improved. Preparation for EOM installation is nearly complete, with final measurements planned for tomorrow.

---

Details:

• IMC Alignment and Transmission Recovery:

  We initially aligned the HAM1 output beam to the IMC. The IMC transmission signal (TRANS_NSUM) peaked at ~8 counts (with 30 dB whitening) under optimal alignment. However, after Jennie and Jason reverted the MC suspensions, the transmission dropped to <4 counts. We re-aligned JM2 and JAC_M3, successfully recovering the signal to ~6 counts. The second-largest peak was the TEM01 mode, approximately 1/6 the height of TEM00, which we considered acceptable for now.

• Power Check on IOT2 Table:

  With the recovered alignment, we measured 51 mW of power between the periscope mirrors on the IOT2 table. The HAM1 output was measured at 52 mW, confirming that no significant power loss occurred through HAM2. We then centered the output irises accordingly.

• Beam Centering at JAC_L2/L3 and Final IMC Alignment:

  The beam at JAC_L2/L3 was offset by about a quarter inch. We transversely shifted the lenses to center the beam, followed by re-alignment of JM2 and JAC_M3 to re-optimize the IMC transmission. Although JM2 adjustments typically disturb beam alignment through the lenses, only a single iteration was needed to restore IMC alignment. The peak height was slightly better than before this work.

• Irises for EOM Installation:

  Irises were installed between JM2 and JM3 in preparation for the EOM. With this, we believe most of the pre-installation alignment work has been completed.

• Next Steps (Planned for Tomorrow):

  • Measure polarization purity via IMC transmission.

  • Measure the beam size on the IOT2 table.

  • Perform finer alignment of the JAC input.

  • Measure JAC throughput prior to EOM installation.

   

 

PCAL EX End Station Measurement.

Dripta & I went to the EX to do a PCAL End station measurement followed by a TX module maintenance.

Obligitory Beam spot pic.
We followed T1500062-V21, with out much deviation until the measurements were finished. We did continue on with a TX module maintenance that we have not yet finished yet. Our plan is to go back tomorrow to finish the OLTF Optical Follower Servo measurement. We did leave the LASER HAZARD STATUS at EX in SAFE. 

The ES measurement went smoothly.
Beam spot after ES measurement & TXmodule maintence!

python generate_measurement_data.py --WS PS4 --date 2025-11-03
Reading in config file from python file in scripts
../../../Common/O4PSparams.yaml
PS4 rho, kappa, u_rel on 2025-11-03 corrected to ES temperature 299.5 K :
-4.7017855975867215 -0.0002694340454223 2.686163396659873e-05
Copying the scripts into tD directory...
Connected to h1daqnds1
martel run
reading data at start_time:  1453573090
reading data at start_time:  1453573550
reading data at start_time:  1453573950
reading data at start_time:  1453574260
reading data at start_time:  1453574700
reading data at start_time:  1453575050
reading data at start_time:  1453575167
reading data at start_time:  1453575840
reading data at start_time:  1453576170
Ratios: -0.4588903912882054 -0.46880057152484483
writing nds2 data to files
finishing writing
Background Values:
bg1 =        9.720121; Background of TX when WS is at TX
bg2 =        4.686352; Background of WS when WS is at TX
bg3 =        9.770692; Background of TX when WS is at RX
bg4 =        4.628189; Background of WS when WS is at RX
bg5 =        9.797052; Background of TX
bg6 =        0.801247; Background of RX

The uncertainty reported below are Relative Standard Deviation in percent 

Intermediate Ratios
RatioWS_TX_it      = -0.458890;
RatioWS_TX_ot      = -0.468801;
RatioWS_TX_ir      = -0.453881;
RatioWS_TX_or      = -0.463503;
RatioWS_TX_it_unc  = 0.073150;
RatioWS_TX_ot_unc  = 0.076593;
RatioWS_TX_ir_unc  = 0.078168;
RatioWS_TX_or_unc  = 0.089042;
Optical Efficiency
OE_Inner_beam                      = 0.989262;
OE_Outer_beam                      = 0.989063;
Weighted_Optical_Efficiency        = 0.989162;

OE_Inner_beam_unc                  = 0.049361;
OE_Outer_beam_unc                  = 0.054133;
Weighted_Optical_Efficiency_unc    = 0.073259;

Martel Voltage fit:
Gradient      = 1636.767509;
Intercept     = 0.537748;

 Power Imbalance = 0.978861;

Endstation Power sensors to WS ratios::
Ratio_WS_TX                        = -1.077945;
Ratio_WS_RX                        = -1.393587;

Ratio_WS_TX_unc                    = 0.045600;
Ratio_WS_RX_unc                    = 0.039824;

=============================================================
============= Values for Force Coefficients =================
=============================================================

Key Pcal Values :
GS           =      -5.135100; Gold Standard Value in (V/W)             
WS           =      -4.701786; Working Standard Value             

costheta     =      0.988362; Angle of incidence
c            =      299792458.000000; Speed of Light
             
End Station Values : 
TXWS         =        -1.077945; Tx to WS Rel responsivity (V/V)
sigma_TXWS   =        0.000492; Uncertainity of Tx to WS Rel responsivity (V/V)
RXWS         =        -1.393587; Rx to WS Rel responsivity (V/V)
sigma_RXWS   =        0.000555; Uncertainity of Rx to WS Rel responsivity (V/V)

e            =        0.989162; Optical Efficiency
sigma_e      =        0.000725; Uncertainity in Optical Efficiency

Martel Voltage fit : 
Martel_gradient         =        1636.767509; Martel to output channel (C/V)
Martel_intercept   =        0.537748; Intercept of fit of     Martel to output (C/V)

Power Loss Apportion : 
beta          =        0.998895; Ratio between input and output (Beta)  
E_T          =        0.994017; TX Optical efficiency 
sigma_E_T          =        0.000364; Uncertainity in TX Optical efficiency 
E_R          =        0.995117; RX Optical Efficiency 
sigma_E_R          =        0.000365; Uncertainity in RX Optical efficiency 

Force Coefficients : 
FC_TxPD          =        7.900822e-13; TxPD Force Coefficient 
FC_RxPD          =        6.178276e-13; RxPD Force Coefficient 
sigma_FC_TxPD          =        4.646331e-16; TxPD Force Coefficient 
sigma_FC_RxPD          =        3.364222e-16; RxPD Force Coefficient 
data written to ../../measurements/LHO_EndX/tD20260127/

 

OPS Day Shift Summary

TITLE: 01/28 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:

IFO is in IDLE for PLANNED MAINTENANCE

Good progress on activities today.

• HAM7 - Cables were nudged in suspicion of rubbing due to OPO transfer functions that were "off" (alog 88917, alog 88913). The result were much better OPO Transfer Functions - alog 88921 Work will continue tomorrow.
• HAM1 - Work has continued on the EOM which was successfully tuned, but there are still frequency changes that are unstable. Frequencies are 10, 20 kHz off. Work is continuing.
• BSC2 - Inspection and walkabout.
• EX - PCAL Measurements successful. They will transition to Laser Safe shortly.

Other:

• Fire Pump Test at 10AM - successful
• Beckhoff Restart
• DAQ Restart
• HVAC Work on airhandlers done across the site

LOG:

Start Time	System	Name	Location	Lazer_Haz	Task	Time End
22:49	SAF	LVEA IS LASER HAZARD	LVEA	YES	LVEA IS LASER HAZARD \u0d26\u0d4d\u0d26\u0d3f(\u239a_\u239a)	16:49
15:44	FAC	Nellie	LVEA	Y	Technical Cleaning	17:06
15:51	SUS	Betsy	LVEA	Y	BSC2 Inspection	17:51
15:51	FAC	Randy	LVEA	Y	BSC2 Inspection	16:22
16:01	FAC	Kim	LVEA	Y	Technical Cleaning	17:06
16:33	FAC	Richard	LVEA	Y	BSC2 Inspection	17:07
16:33	FAC	Randy	LVEA	Y	BSC2 Inspection	23:04
16:42	PCAL	Tony, Dripta	PCAL Lab	N	PCAL Meas.	17:13
17:10	FAC	Eric, Chris	EX, EY, MX, MY	N (YES EX)	Air Handler and HVAC Maintenance	18:28
17:14	PCAL	Tony, Dripta	EX	Y	PCAL Measurement	19:17
17:16	EE	Fil	LVEA	Y	Moving electronics by HAM6	20:21
17:33	ISC	Jennie	LVEA	Y	Turning on light pipe	17:35
18:06	FAC	Kim, Nellie	LVEA	Y	Technical Cleaning	18:44
18:08	SUS	Rahul	LVEA	Y	HAM7 OPO	18:31
18:14	TCS	Matt, Sophie	JOAT/Vac-Prep Lab	N	CHETA	15:14
19:05	EE	Marc	HAM1	Y	EOM Electronics	20:11
19:06	EE	Daniel	LVEA	Y	HAM6 Electronics	20:11
19:07	OPS	Oli	LVEA	Y	Reminding Daniel about a meeting	20:21
19:07	COC	Masayuki, Jennie	LVEA	Y	HAM1 EOM	20:45
19:08	SUS	JAson	LVEA	Y	HAM1 EOM	20:46
21:08	EE	Fil	LVEA	Y	HAM6 Electronics	23:06
21:11	PCAL	Tony, Dripta	EX	Y	PCAL Meas.	01:11
21:37	SUS	Sheila, Rahul	LVEA	Y	HAM7	22:48
21:45	COC	Elenna, Keita	Optics Lab	N	EOM	00:34
22:05	SUS-FAC	Travis, Jim, Betsy, Gerardo, Tyler, Randy	LVEA	Y	BSC2 Inspection	23:04
22:10	COC	Masayuki, Jason	LVEA	Y	HAM1 JAC	00:07
22:13	TCS	Marc, Jennie	Vac-Prep/JOAT Lab	N	CHETA Lable Table Cable	23:59
00:41	EE	Marc	LVEA	Y	EOM Reconnection	01:41

 

Dramatic Improvement in H1SUSOPO TFs after Adjusting Cable Dressing; Still Some Work Tho

J. Kissel

Took a set of TFs after Rahul and Sheila re-dressed the cables surrounding the H1SUSOPO (LHO:88920). The TFs -- especially Y to Y look a *lot* better with the higher frequency modes re-aligning with historical measurements and the model. There's still some mode splitting in the lowest mode, that I suspect is the transverse/vertical/yaw system not quite yet as soft as it used to was. Rahul mentions they did *not* address the cables that were zip-tied to the H3/V3 spring post so that could be it.

We'll discuss and game plan more with the crew tomorrow.

Data templates saved here:
    /ligo/svncommon/SusSVN/sus/trunk/OPOS/H1/OPO/SAGM1/Data
        2026-01-27_2316UTC_H1SUSOPO_M1_WhiteNoise_L_0p02to50Hz.xml
        2026-01-27_2316UTC_H1SUSOPO_M1_WhiteNoise_P_0p02to50Hz.xml
        2026-01-27_2316UTC_H1SUSOPO_M1_WhiteNoise_R_0p02to50Hz.xml
        2026-01-27_2316UTC_H1SUSOPO_M1_WhiteNoise_T_0p02to50Hz.xml
        2026-01-27_2316UTC_H1SUSOPO_M1_WhiteNoise_V_0p02to50Hz.xml
        2026-01-27_2316UTC_H1SUSOPO_M1_WhiteNoise_Y_0p02to50Hz.xml
Again ran in the configuration where only the DOF being driven was undamped.

Field Racks ISC-R5 and ISC-R6

WP 12991
WP 12994
D1200196 ISC-R5 Layout
D2400300 - ISC-R6 Layout
D1900511 - ISC/SQZ Wiring Diagram

In preparation for the installation of BHD, the following work was done to the HAM6 field racks:

1. ISC-R3 is now on its own set of power supplies for ±18V
2. ISC-R5 and ISC-R6 share a set of power supplies for ±18V
3. ISC-R3, ISC-R5, and ISC-R6 share a set of power supplies for ±24V
4. ISC-R5 was updated to D1200196-v15
5. ISC-R6 was updated to D2400300-v1

Racks are not complete. Missing electronics will be installed when available.

F. Clara, D. Sigg

WP 12998 cont Installing the new VM cluster

Test stand log book entries that document the setup and testing prior to production

• Setting up Proxmox 9 servers for testing
• Reworking the Proxmox Setup
• Failure testing the new proxmox
• Testing migrating a VM between proxmox clusters

Physical layout

The following components are racked together in rack 12.

1. sw-msr-pve0 - switch that connects the nodes to each other and to the core.  It runs the internal cluster traffic, and contains the links to the outside world.
   1. Connected to the core via a lag.  I have spare ports in both the core and the switch so that I can increase the bandwidth if needed
2. pve-node[0,1,2] - the nodes

Basic setup

When I updated the ipmi address in the bios I also did the install of the proxmox nodes.  I follow the basic routine in reworking the proxmox setup for pve-node0.

• Created a zfs raid z1 using /dev/sda & /dev/sdb
• Gave the nics descriptive names:
  • onboard 10g copper port 0 - nic1 - 10.20.0.50 (the web interface)
  • onboard 10g copper port 1 - nic2 - not used
  • solar flare 10g nic port 0 - nicdata0 - will be used as a bonded interface for VM traffic
  • solar flare 10g nic port 1 - nicdata1 - will be used as a bonded interface for VM traffic
  • intel e810 port 0 - niccluster0 - for the cluster corosync network
  • intel e810 port 1 - nicceph0 - for the ceph networks

Repeat this for pve-node1 & 2, incrementing the ip addresses.

Cluster network configuration creation

Configured the niccluster0 interface on each node

• Set to 10.200.0.50
• Set mtu to 900
• Set to autostart
• Added comment "PVE Corosync Network"

Did the same on each node, and a ping test.

Cluster creation

On pve-node0 go to the datacenter / cluster and click on create cluster

• Pick a name, "CDS-VM"
• Select the 10.200.0.50 interface

Then on the other nodes to to datacenter / cluster and click join cluster

• Get the join information from pve-node0 datacenter / cluster / join information, copy it to the clipboard
• Paste the join information into the join window
• Put in pve-node0's root password in the password box
• Select the 10.200.0.5? link

Support subscription activation and updates

Now that the basic pieces are in place and will not need a reinstall, it is time to enable the subscription on each node.

Go to each node to the subscription section and upload the subscription key.

Now run updates against the enterprise repo and reboot each machine.

Configure the ceph network

• Assign 10.201.0.5?/24 to the nicceph0 interface
• Enable autostart
• Set comment "Ceph Network"
• Set mtu 900
• Apply the configuration

Repeat for all nodes

Install Ceph

Go to datacenter / ceph page.  When prompted, select install ceph

• Install squid (Ceph 19.2)
• Use the enterprise repositories
• Do the install
• Set the configuration
  • Select the 10.201... interface
  • Use the public network for the cluster network
  • Set the initial monitor node as pve-node0
  • Leave the replicas and minimum replicas values at default.
• Go to the other nodes
  • Only the install process is needed, not the config

Clean up disks

We had used these machines for other testing in the test stand, we will go through and clean up the disks prior to use.

• remove partitions from the disks w/ fdisk (as needed)
• then clean up the disk with "ceph-volume lvm zap /dev/sd[X] --destroy"

This was done on /dev/sdc and /dev/sdd on the systems

Create the Ceph OSD (Object Storage Deamon)

On each machine go to ceph/OSD

• Create OSD
• Disk /dev/sdc
• DB Disk use OSD Disk
• Encrypt OSD
• WAL Disk use OSD/DB disk

Repeat for /dev/sdd.

After a minute they should show up on the ui.

Add more Ceph monitors

Add pve-node1 and pve-node2 as ceph monitors and managers.

Add a Ceph pool

pve-node0 /ceph / pool

• Create Pool
• name StoragePool

Setting up the VM data links, a bonded bridged network

Go to network / Create / Linux Bond

• Name bond0
• autostart
• slaves nicdata0 nicdata1
• mode LACP (802.3ad)
• Comment VM Data Bond
• mtu 9000
• Apply Configuration

Create a data bridge, network / Create / Linux Bridge

• Name vmbr1
• autostart
• vlan aware
• Bridge ports bond0
• Comment VM Data Bridge
• mtu 9000
• VLAN IDs 2 3 20 21 22 98 99 101 105 106

Do this on each of the nodes.

Notes

When creating VMs we want to connect the network to vmbr1 and specify the vlan tag that should be used as this setup gives us access to more than one vlan.

HAM7 OPO health check investigation - took fresh pictures (in chamber) for comparison, looking for cable inteferances.

Jeff, Sheila, Rahul

Details about OPO health check issues (Yaw dof. - frequencies are off and unnecessary peak observed) is currently being analyzed - see Jeff's alog 88913.

This morning we discussed about possible cable interferences in OPO.

I went into the chamber and took fresh pictures of the OPO from several angles, focusing on cable routing, cable resting on the OPO etc - please find them attached below. I will compare them with the pictures posted in LHO alog 61643 (by Sheila in 2022) and look for possible culprits (a few of them already).

Moving cables could cause some misalignment, hence we will start doing so once Sheila gives us a green light.  

H1SUSOPOS TFs post-OPO Crystal Swap / Translation Stage Improve -- Something Quite Off

J. Kissel, R. Kumar, B. Weaver, S. Dywer

Context
After the SQZ team felt done with OPOS suspension the re-install of the OPO (with an upgraded translation stage) we're following up on
    - Ryan's first look of the suspension's health (LHO:88851) 
    - After restoring the OPOS to normal control system configuration (LHO:88872) 
    - After recentering the AOSEMs (LHO:88910)

Measurement
I gathered more standard health check TFs. In doing so, I spruced up the excitation frequency response and data gathering templates to ensure good coherence. I also ran the TFs with all the damping loops besides the excitation degree of freedom ON to reduce incoherent motion from cross-coupling. The refreshed templates are 
    /ligo/svncommon/SusSVN/sus/trunk/OPOS/H1/OPO/SAGM1/Data
        2026-01-26_2054UTC_H1SUSOPO_M1_WhiteNoise_L_0p02to50Hz.xml
        2026-01-26_2054UTC_H1SUSOPO_M1_WhiteNoise_P_0p02to50Hz.xml
        2026-01-26_2054UTC_H1SUSOPO_M1_WhiteNoise_R_0p02to50Hz.xml
        2026-01-26_2054UTC_H1SUSOPO_M1_WhiteNoise_T_0p02to50Hz.xml
        2026-01-26_2054UTC_H1SUSOPO_M1_WhiteNoise_V_0p02to50Hz.xml
        2026-01-26_2054UTC_H1SUSOPO_M1_WhiteNoise_Y_0p02to50Hz.xml


Results
Attached is comparison of 
    - the opos dynamical model (Equations of Motion matrices: ssmake_voposus.m rev 12322; parameter set: oposopt_h1susopo_fit rev 12322)
    - the most recent, best at-vacuum, measurement of L1's OPOS
    - the last, best, at-vacuum measurement of H1's OPO prior to moving from HAM6 to HAM7
    - the last, bext, at-vacuum measurement of H1's OPO after moving to HAM7 (with a payload almost identical to what's installed now)
    - yesterday's measurement described above.

Focusing on page 6 first, one can clearly see that YAW to YAW transfer function is wildly different, implying a significant change to the dynamics of the suspension.
There's more supporting (but less signficant) evidence in 
    - pages 1 and 2 which shows and increase in the primary L / T resonance from 1.25 Hz to a split 1.32 Hz / 1.39 Hz
    - pages 1 thru 6 (all diagonal elements of the TF matrix) and pages 7 thru 20 (most off-diagonal elements) all showing a huge (tho incoherent) resonance in yaw at 4.98 Hz that was not there before
    - Nominally an oversight in the design, the expected large V to Y coupling looks quite impeded.

Discussion
After conversing with Sheila about what might have changed, or what might be impacting the dynamics, she reviews the changes:
    - The OPO cavity assembly (D1500296) has only a few changes -- the translation stage within is new, and there are now thin remote-control cables coming out of the assembly that weren't present before.
    - Those new remote control cables have been bundled into a pre-existing bundle, potentially making the system stiffer. We guess that this is the likely culprit of our problems.
    - Further the re-placement of the OPO assembly on the OPOS was not precise. It's plausible that the physical location of the cavity is now *slightly* different position, *potentially* changing the balance and mass ratio of how much moving mass is in which translational DOF. Maybe the source of L / T resonance shifts, but I doubt it. 

Also, conversing with Betsy and Rahul about the state of cables they found while centering the OSEMs:
    - They see a collection of cables (OSEM and SQZ) on the "far" (+Y) H3/V3 side of the OPOS that are resting on the platform without a good, dressed, soft connection between the platform and where the cable stress is relieved on the base.

Conclusion

We need to address / free-up the dynamics of this suspension before closing up the chamber.

Restored sliders on IMC SUS to December 3rd state

Jennie W, Jason O, Sheila D, Masayuki N,

 

Following Jim bringing HAM3 HEPI online (alog #88909) and isolating HAM3 ISI.

Jason and I restored the MC1, 2 and 3 sliders to their position on December 3rd during a lock when the mode-cleaner was locked with 2W input, HAM2 and 3 ISO Gain was , HAM2 and 3 ISI Guardian was set to 'isolated' and 2 and 3 HEPI guardian was set to 'RoBUST ISOLATED'.

This lock state for the IMC Guardian is 100. 

 

JAC EOM Monday (Elenna, Keita, with remote help from Stephen, Michael, Matt and Gabriele)

Nothing wrong with our previous reflection dip measurements with alumina.

We (MichaelL, StephenA, MattH, Gabriele, Elenna and myself) had a meeting in the morning. 

Looking at the "with the alumina" reflection screen shots, Michael didn't see any serious problem so we decided that the electrode-crystal-face plate capacitance is OK. We won't worry about that, we'll just make sure that there's no visible gap.

Third mounting method ("in-between") was proposed and tested.

Stephen proposed an in-between method where we use washers between the input side plate and the front plate (bottom of three_methods.png cartoon). After the washer contacts the face plate AND the input side plate, screws are gently tightened in a balanced manner like in Appert method.  (In a retrospect this is not that different from Laxen method except the way screws are tightened and that the input side plate contacts with the face plate at two points.) 

We first tried to use a presicion thickness shim washer for 1/4-20 screws but I didn't like that they're too big. We ended up using smaller stamped washers that is 0.039" or 0.99mm thick (according to the caliper). That's not flat but seems OK to me.

This in-between method worked in that it was doable and gave us a reasonable reflection dips.

Mechanical stability test of Appert method and in-between method. The latter is better, we'll use that for the real RTP.

My original concern for the original Appert method (middle of three_methods.png cartoon) was that somehow the screw gets loose during transport or after a large change in the in-chamber temperature and the tuning will be off. Upon hearing this, Stephen proposed a test to loosen one screw and see if the tuning changes. We performed this test for both Stephen method and the in-between method. (Spoiler: yes.) We measured all four dip frequencies right after the alumina piece was mounted but only tracked the frequency change of 118MHz peak.

Loosening one screw changes the frequency, but the frequency change for the in-between method is an order of magnitude smaller (10 to 30kHz) than the original Appert method (300kHz) when the FWHM (or rather the width between the points where reflection is 6dB larger than the bottom of the dip) is about 70kHz or so. This is just one trial but I'm convinced that in-between method (or maybe Laxen method too though we haven't tried) is better, so that's what we'll do for the real crystal.

We only loosened the screws on the output side for both mounting methods. 

	Initial four frequencies	Shaking?	Loosen 1st screw	Loosen 2nd screw
In-between method	9.142, 24.110, 45.972, somewhat smaller than 118.214kHz	changed to 118.214kHz, unclear why. (Something like 10k or 20kHz change, couldn't cause another change by gentle tapping.)	118.214 -> 118.240 (+26kHz)	118.240 -> 118.251 (+11kHz)
Original Appert method	9.14685, 24.107, 46.066, 118.322	118.322 -> 118.592, caused by gentle tapping. (+270kHz)	118.592 -> 118.876 (+284kHz)	118.876 -> noman's land (>1MHz)

Shake and it will shift, we need to measure it again in chamber?

It's good to know that the in-between method can somewhat withstand the loosening of the second screw (because the tighter screws still support the face plate). However, it's disappointing to find that the assembly is susceptible to shaking.

In the in-between method, we couldn't record the initial 118MHz dip because it jumped up by 10kHz or so in front of our eyes when we were moving around the table. Not sure what happened but I assumed that it was some kind of shaking. However, I gently tapped the front and side plates and couldn't cause another shift.

In the original Appert method, since we knew something could happen, I tapped the front and side plates and there was a huge jump. See the difference between initial_118.jpg and taptap_118.jpg.

Even though we'll use in-between mounting method, it's plausible that the frequency shifts during transport or when the EOM lands on the ISI surface. I'm thinking we'll have to measure it in situ after everything is tuned in the lab.

What's to come tomorrow.

We'll install RTP and tune. Before doing that, though, I'll discuss inserting indium foil between the crystal and the front plate with Masayuki. Michael suggested that (and even between the crystal and the electrode, though that would be tricky) today, Masayuki and I talked about the possibility briefly last week, it just sounds like a good thing as a buffer to absorb gaps here and there.

Other things.

In the previous alog (88886) in one of the pictures (gap.jpg), there was a time when it looked as if the circuit board was slightly bowed. We took a picture of the electrode today (electrode_contactpoint.jpg) and it looks as if the electrode is more abraded close to the outside edge of the crystal, so maybe the board bowing is real.

 

 

CHETA Progress - second table

S Muusse, M. Todd

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New QCL unit (0920) has been put in place of original unit (0923) which is malfunctioning (cause unknown). Initial profiling has taken place and L1 focal length is 10% larger than spec.

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QCL unit failure summary:

All day on 2026-01-21 we were running the laser at 900mA doing beam profiles and alignment work. No malfunctioning was witnessed and the laser unit was operating as expected, similar to the laser unit we had run in December for a week. Before lasing we set the following limits on the LD and TEC, per the datasheet.

1. LD current limit was set to 1.05A
2. LD voltage limit was set to 12.9V
3. TEC operating temperature was set to 20C

On 2026-01-22 we turned the laser on to do some more beam profiling with the same limit settings as yesterday, but setting the LD current to 1A (forward voltage was around 12.2V) as was done when we originally profiled this laser in September. We were in the middle of setting up for a new beam profiling measurement (alignment showed the beam was fine, as usual) and we blocked the beam with a high power beam dump at the laser head while installing the profiler. Upon removing the beam dump, we noticed no power was coming out of the laser, and then noticed the forward voltage had dropped to around 800mV. We noticed no sounds or smells or any other signs that something had stopped, only sudden lack of light coming from the unit. All other settings were fine, meaning the controller had not faulted and was still outputing 1A LD current and the TEC was maintaining 20C.

We ran the following checks to see if we could remedy the problem, without success.

1. Checked the cable connection to the laser unit (pins on the laser unit looked fine)
2. Checked the Laser Controller cable connections (pins in the DSUB connectors looked fine)
3. We tried a completely new laser controller box and new cable. The settings were similarly set and the same behavior was seen with the forward voltage response to the LD current setpoint.
4. We tried changing the TEC setpoint to be 25C, and the same behavior was seen with the forward voltage response to the LD current setpoint, and failing to lase as usual.
5. We used the same cable and laser controller on the previous QCL unit, and it operated as expected --- lasing fine as usua

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QCL 0920 profiling summary:

Replaced broken unit with 0920 and confirms it lases as spec'd. We built telescope as modelled but beam profile was 75% of expected beam width at L2. We subsequently profiled the laser output and confirmed QCL output q measured previously by Matt was still correct. We became suspicious of the true focal length of L1. Then we profiled multiple places after L1 and fit a q parameter using a non-linear fit. A plot of this fit is attached. Using these 2 q parameters the focal length of L1 was estimated to be 220mm instead of 200mm as spec. We think this is mostly because L1 focal length stated by manufactorer is for 588nm where the refractive index is almost 3% larger than at 4.6um. Focal length in the model was modified to reflect our estimated f1 which predicted a beam size closer that measured earlier. 
Side note: the scanning slit beam profiler reflects significant amount of 4.6um light which is observable on a thermal beam card. 

HAM1 update - JAC damper

Jason. JennieW, Rahul

This morning we added the damper parts to the JAC in HAM1 chamber - see picture attached. The cables were re-routed slightly so that they don't interfere with the damper.

I have finger tightened the screws of the damper for now - since no torque spec was provided and we were worried that tightening them too much might affect its position/angle.

2nd HXDS received from LLO

Yesterday I picked up the shipment from LLO contain the 2nd HXDS (first HXDS shipment alog87998) and related ASSEYs and brought it to the Triples lab. 

Uwrapping and inspecting was uneventful, the zip ties were intact, the shock pads untripped and the humidity indicator was unchanged in color. The outer (front, back) and inner (front, back) bags were in good condition, unwrapping the suspension I found no play with the blades.  All the nuts and dowel pins were tight and well seated, the ICS looks good except for it seems to be missing the HDS Intermediate Mass Fixture (D2000230-V1, s/n 08). The part is scribed as V1, on the dcc there's a V2 with two added 8-32 helicoils taps that, based on D1900352 which uses V2, I should be able to see from the front and I don't, so this is a V1 plate and not an incorrectly scribed V2. I believe these two missing 8-32 holes are where we will attach the BOSEM Mounting plate (D2000257). The first HXDS we received in November had the V2 plate. We may have to do a small rework to update it to V2, or have LLO send the V2 part if possible.