[Nakano, Takano, Aso, Tomura, Ushiba]

We tested many things to investigate the strange behaviour of the ALS signals.
Detail of this investigation has been already posted by Nakano-kun..

At the final stage of this work, we removed the RF PD interface from the digital rack and  what happened.
Then, I accidentially saw the spark between RF PD interface and digital rack and it caused the ALS0 computer down.

After this spark happened we discussed and suspected that the PD ground is connected to the optical table and it has an electric charge.
We are not sure this kind of electric charge is there and also related to the ALS strange behaviour.

So, we will check the voltage between optical table and digital rack.
We also plan to measure the PD ground is floated from the optical table or not.