KAGRA Logbook

MIF (ITF Control)

kiwamu.izumi - 17:44 Friday 01 March 2019 (8268)

The old Prometheus back in the PSL

Ryosuke, Kiwamu,

Related logs: 7384, 7391

We brought the old Prometheus (2143A) back into the PSL room.

We left it running at a pump-diode current of 2.2 A, the nominal value, with the mechanical shutters closed. We will see if 2143A survives through the weekend.

[Why are we doing this?]

Sumida-san (8267) kindly offered to test 2143A with us today after the inspection with the new Prometheus.
- The key point he has been raising via emails was that we had to run Prometheus lasers at sufficiently high AC voltage preferably above 100 V.
We later figured out that the AC power used by 2143A was not as high as 100 V in the PSL room. It was measured to be about 94 V.
Sumida-san thinks that such a low AC power may explain the strange behaviors of the laser that we had seen.
We tested this theory by actually powering up the 2143A laser with a healthy AC power slightly greater than 100V in the electronic room at Mozumi.
- It turned out that the laser was able to run without a strange shutdown!
- Although, we tested this for 10 min. at most.
We decided to leave the laser running during the weekend to check out the long-term stability.

That's why we brought this laser unit back into the PSL.

Comments to this report:

kiwamu.izumi - 10:52 Monday 04 March 2019 (8291)

GGG, Kiwamu,

Guiguo kindly had a look at our 2143A laser in the PSL room for us in this morning to see if the laser had survived during the weekend.

The answer is: It survived at a nominal current of 2.2 A without a spontaneous shutdown.

Here are pictures that Guiguo took for us in this morning -- we can see that the indicator lights are still on

Images attached to this comment

kiwamu.izumi - 11:00 Monday 04 March 2019 (8292)

Addendum:

Sugimoto-kun and I checked the output optical power of 2143A on the 1st of March, Friday. They were:

2-ish W for 1064 nm
100 mW for 532 nm

The measurements were done by a Thorlabs hand-held power meter.

The AC power of the 2143A laser is now connected to the UPS that we installed the other day (7887) which supplies an AC volt of more than 100 V. So far, our observations support the thoeory that the spontaneous shutdown of 2143A (a summary of which can be found in 7391) were caused by too-low AC voltage.

kiwamu.izumi - 4:26 Thursday 14 March 2019 (8395)

An update on this topic.

We are concluding that the insufficiently low AC voltage was the cause for the spontaneous shutdowns of 2143A.

Since the 1st of this month, the old Prometheus or 2143A has been up and running without a spontaneous shutdown. We have dismantled the temporary setup and put 2143A back on the table to let it serve for the Y arm ALS system today on the 13th (8394).