rich.abbott@LIGO.ORG - posted 15:28, Tuesday 05 March 2019 - last comment - 14:17, Tuesday 23 August 2022(47308)
ESD Grounding at End-X
Filiberto, Ed, Richard, Rich A ETM-X ESD drive system has been floated from any connection to ground. After establishing that the whole system is floating WRT rack or building ground, we made a single connection to the beam tube as a reference point (see attached PDF diagram) Summary of Actions: I. For cable HI-SUS-ETMX-90 cut pin 8 (and unused pin is by accident) to remove a ground in the D1100809 AA Chassis Interface Board (CH I to 6) input connection. The actual cut was made in the gender changer on the front panel D 15 monitor output of the HV AMP. This cable is the HV monitor read back for the HV Amplifier Box. 2. Removed all rack ground connections in remote DC power supplies. The returns of all the DC outputs were previously connected to the rack/building ground 3. Connected the HV Amp & LV AMP to beam tube ground next to ESD rack. This is the single ground point for the ESD system 4. Installed dielectric breaks between rack and HV ESD amps 5. Verified entire ESD system is floating, then deliberately grounded to beam tube 6. Lifted cable shield connection on cable H1-SUS-ESD-5 at the LV Driver PI input connector (D-I 5) 7. Lifted cable shield connection on cable H1-SUS-ESD-6 at AA input (LV Driver monitors D-9) 8. Restored ground voltage mon (PEM) between beam tube & top of LV ESD Amp 9. Transitioned back to permanent ESD DC supplies in remote DC racks 10. Swapped HV preamp back to the one that was originally installed in EX so the 3RD IFO unit can be returned to the H2 building
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Work done under WP 8112.
The ESD ground to the Beam Tube was chosen to get us as close to the OPTIC potential ground as possible. We know have equipment like the ring heater grounded in the chamber that is could create ground path concerns for us. This may not be ideal but after testing Robert has been doing seems like a good step.
A *very* late entry, but the electrical shielding of the ESD driver chassis has come up recently again as we've found some evidence for excess electrical noise in August 2022 a la LHO aLOGs 64526 or 64478. As such I dug back through my pictures from Dec 2019, when I first discovered that this work had happened and/or that the electrical grounding of the ESD low-voltage driver chassis had been... "reconfigured" ... in this way. In 2019-12-10_H1SUSETMX_L3_ESD_Driver_Shielding_AtChassis, I show the connection to the low-voltage chassis. Note -- this cable from the low-voltage chassis goes up an electrically connects to the chassis of the UK high-voltage chassis as well before heading to electrically connect to the beam tube. This is not explicitly drawn in Rich's diagram above. While I haven't seen it with my own eyes, I've confirmed this with Fil, verbally, today (2022-08-23). In 2019-12-10_H1SUSETMX_L3_ESD_Driver_Shielding_FromRACtoChamber.jpg I show the connection to the chamber.
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