KAGRA Logbook

MIF (General)

kazuya.yokogawa - 18:47 Thursday 13 December 2018 (7375)

Frequency measurement of the new PROMETHEUS laser

[Izumi, Eleonora, Yokogawa]

Related klog: #6239

Today, the new PROMETHEUS laser for ALS (Y arm) system was delivered, so we measured frequency of this laser by tuning the crystal temperature.

The attached figure shows the result. Green dots show the measurement result of the new PROMETHEUS laser. Also, the measurement result of the main laser and the PROMETHEUS laser for X arm measured on Sep. 21st are shown in red and blue dots respectively. The frequency differences between the main laser and two PROMETHEUS lasers need to be around 40 MHz since the beat-note signal is locked to 40 MHz by PLL. However, the overlap range (gray region) is very narrow and the frequency of the main laser can be set only every 1.5 GHz in order to lock the main laser to the reference cavity. (FSR of the reference cavity is 1.5 GHz.)

I believe that the beat-note signal for ALS Y arm system can be seen...

Images attached to this report

Comments to this report:

kazuya.yokogawa - 22:58 Thursday 13 December 2018 (7384)

Before saying about the frequency measurement, I should have mentioned about a important thing. The new PROMETHEUS laser was delivered to Mozumi in this morning, so we took it to the PSL room and swapped the problematic PROMETHEUS laser for the new one. The problematic one will be sent for repair to the manufacturer.

NOTE

Since we put the new laser loughly, we have to start the alignment from scratch.

Images attached to this comment

kiwamu.izumi - 11:11 Friday 14 December 2018 (7391)

For the book keeping purpose, here is a list of the log entries that describe the history the old Prometheus (2143A).

Feb. 6th 2018 (4124); 2143A was installed on the POP table in order to test out TMSY. At this point no issue was found with 2143A
Aug. 6th 2018 (5724); the installation of the ALS optics in the PSL enclosure began.
Aug. 8th 2018 (5758); 2143A was moved from the POP table to the PSL table.
Aug.9th 2018 (5772); the issue was spotted for the first time.
Aug.11th 2018 (5786); the issue developed.
Aug.13th 2018 (5798); the situation momentarily improved.
Aug - Dec. 2018 (no logs); the laser was left off. Sometimes we switched it on, but it did't run for hours.