KAGRA Logbook

DGS (General)

takahiro.yamamoto - 21:41 Wednesday 25 March 2026 (36654)

Deployment of V2 IO-chassis and the front-end computer for EX0

[Nakagaki, Ikeda, YamaT]

This is similar work of ITMX (klog#36572) and ITMY (klog#36625).
A preliminary research about a situation of both end stations was reported in klog#36635.

I/O chassis of K1EX0 was replaced from V1 (S1604791) to V2 (S2416131).
The front-end computer was also replaced from V3 to V4, but it hasn't been moved from EX0 rack to EXV1 rack due to a miscommunication about laying MTP cables.
We cannot complete this work until purchasing some cables in April.
ADC/DAC noise measurement is planned to be done tomorrow.

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I/O chassis replacement
We replaced the V1 I/O chassis (S1604791) at U18-21 of EX0 rack as V2 I/O chassis (S2416131). In this time, all PCIe cards were moved from V1 I/O chassis to V2 I/O chassis in stead of preparing V2 I/O chassis in which attached spare PCIe cards. Though this procedure involves a risk of taking long time if we need to restore all due to some trouble with V2 I/O chassis, we determined that’s highly unlikely based on the past experiences. (Besides, there’s also the fact that it’s not realistic to prepare same number of spare cards as one of installed cards.) On the other hand, an advantage of this procedure is S-number of used ADC/DAC boards isn't changed.

Front-end replacement
In the original plan, the front-end computer was planned to be moved from the the EX0 rack (1F) to the EX1 rack (2F) as part of the upgrade from the V3 server to the V4 one. An combination of V2 I/O chassis and V3 server has a limitation about a number of attached PCIe cards and EX0 has many ADC/DAC boards. So replacing V2 I/O chassis at EX0 requires to upgrade also the front-end server. Moving front-end server from the EX0 rack to EX1 rack is the most important advantage of using V2 I/O chassis. Because of specification of the cables for V1 I/O chassis, we couldn't separate the servers from analog electronics in the 1st floor of the end stations. Another concern was the increasing number of daisy-chain segments and growing latency across various networks, including RFM.

For this reason, we tried to install a new V4 server in the EX1 rack at first. But a gender of MTP at the splice box was different from one in the discussion in advance. Because MTP pins are very thin and are easily broken, we designed the entire assembly so that the connector of cables which is wired by ourselves would be female. So MTP of breakout cable we have has female connector. The splice box at EX1 rack has unfortunately also female receptor and we couldn't connect them.

Finally, we gave up to install V4 server in the EX1 rack today and installed it at U13-14 in the EX0 rack after removing the V3 server. So the replacement of I/O chassis and front-end computer were finished but the upgrade task hasn't been completed yet. To proceed it, MTP breakout cables with male connector must be purchased. We can resume this task after April.

Side Note
Some SDF differences on the EX0 models remained.

k1tmsx

All differences are accepted in safe.snap (see also Fig.1)

k1calex

It comes from CAL_EX guardian was in FAULT and was paused. It's related to a shutdonw of laser itself (see also klog#36639). For such case, SAFE state should be defined as allowing to stop a laser output without stopping/pausing. Otherwise, any other maintenance cannot be down while the laser output is stopped. In this time, I manually removed all DAC output, then all values accommodated with the set point in safe.snap.

Images attached to this report

36654_1774442161_ScreenShot_2026-03-25_10.17.16.png

Comments to this report:

satoru.ikeda - 16:48 Thursday 26 March 2026 (36663)

[YamaT, Nakagaki, Ikeda]

This work is related to K-Log#36654.

We used the new V2 IO chassis to measure the noise levels of the ADC and DAC.
For the DAC measurement, the Whitening Chassis used the S1402923 port (on the Board2 side).
Since the input side of this Whitening Chassis is a D-Sub 15-pin female connector, an adapter was required for connection.

During DAC measurements, the Whitening Chassis provided a 42 dB gain.

[Data]
/users/DGS/measurements/{ADC,DAC}/K1EX0/2026/0326_V2_IO_CHASSESS/

Images attached to this comment

Non-image files attached to this comment

japanese.txt

takahiro.yamamoto - 19:24 Thursday 26 March 2026 (36665)

At the end of today's work, we transported the V3 server and the V1 I/O chassis (S1604791) which were used as K1EX0 to the corner station.

The V1 I/O chassis on which HIB adapter card is still attached is stored at U8-11 of C2 rack. It will be kept as a spare chassis or be used on the test stand at the SK building. The V3 server on which IRIG-B and HIB host card are still attached is stored at U10-11 of the P7 rack. It may be used to upgrade V0 and V2 front-end servers (PX1, MCF, and IY0) if a number of the V4 servers becomes insufficient.

takahiro.yamamoto - 20:42 Monday 11 May 2026 (36872)

[Ikeda, Nakagaki, YamaT]

Abstract

All the necessary items had been gathered just before holidays, so K1EX0 front-end computer was moved to EX1 rack at the 2nd floor.
Though some equipment which is no longer necessary such as Timing Fanout are still in the EX0 rack, replacement of EX0 IO chassis itself was completed.
Clean-up of unnecessary equipment will be able to be done not on the maintenance day because we don't need to stop anything for this work.

Because an IRIG-B issue (klog#36705, klog#36819) was reproduced on K1EX0, IRIG-B card was also replaced as one which has no problem on the test stand.
After then, the issue was removed, so we kept to use the new IRIG-B card for K1EX0.
Problematic one will be checked again on the test stand.

Details

Although the IO chassis had been replaced in klog#36654, the move of the front-end computer to the second floor had been postponed due to a shortage of necessary cables. Because the necessary cables were obtained just before holidays, we moved the front-end computer from U13-14 of EX0 rack around the EXC chamber to the U22-23 of EX1 rack at the 2nd floor. There were no major issues with this work, and we didn't encounter any problems around PCIe cards such as ADC and DAC. With this work completed, the replacement of the EX0 I/O chassis is now completed, and the equipment in the EX0 rack such as the timing fanout, IRIG-B chassis, KVM, and 12V DC power supply unit is no longer needed. However, this unnecessary equipment is still left at EX0. Since it can be removed without disrupting the digital system, we plan to remove it at an convenient time.

After moving the computer to the second floor, the IRIG-B issue reproduced during the first startup, and neither a reboot nor a cold boot resolved the problem. Though we have not identified a clear cause or solution for this issue yet, we replaced the IRIG-B card with one that has no problem on the test bench, and the issue was removed. So we kept to use the new IRIG-B card for K1EX0. We cannot conclude this issue is caused by an individual difference of IRIG-B card from today's result yet. If so, a problematic cards on another front-end computers also must be replaced (at least 3 cards). We faced this issue in 3 of 4 front-ends that we worked on recently. Though I'm not sure it comes from a problem rate or just bad luck, it’s possible that a certain percentage of the cards currently in use at the coner station have the same problem, which may require replacements for more units.