KAGRA Logbook

IOO (General)

yutaro.enomoto - 22:57 Wednesday 20 January 2016 (633)

RFPD for PMC REFL broken

I am so sorry that I have to report this accident.

Today I accidentally broke RFPD (JGW-D1201280) for PMC REFL. The reason why it was broken is presumably that -18 V voltage supply was turned off (my foot touched the switch lever of the supply but I didn't notice that at that time) and was left off for a few minutes, even though +18 V was on. Then Nakano-san and I found that both DC and RF output signal from the RFPD behaved strangely.

Awai-san and I surveyed the circuit of RFPD and finally found that at least two Op. Amps. in the DC output line were broken.

For the time being, an RFPD from CLIO will be used for acquisition of the error signal of PMC.

Supplying only +18V (or -18V) would damage RFPDs seriously, so please be careful of DC voltage supplies.

I hope no one will cause the same kind of accident.

Comments to this report:

tomotada.akutsu - 23:18 Wednesday 20 January 2016 (634)

Well, but from the viewpoint of foolproofing, such a habit like "dead by half suppling" would not be nice. Did LIGO engineers who designed this (I believe/assume they are just copies of LIGO and we just change the resonant frequencies) design like this? It would be nice to ask them... (or someone has already asked??)

yutaro.enomoto - 22:29 Thursday 21 January 2016 (641)

Today I sent an email to the engineer who designed it and asked him if such a problem is known or reported in LIGO. So let us wait for a reply from him.

tomotada.akutsu - 7:55 Friday 22 January 2016 (645)

Ok, and it would be worth mentioning the higher temperature in the room where the RFPD for the PMC used.