aaron.sevigny@LIGO.ORG - posted 09:06, Wednesday 27 November 2013 - last comment - 12:42, Wednesday 27 November 2013(8758)
Replaced Sus Ham-A Coil Drivers
Replaced the Ham-A Coil Drivers in SUS C4 (U7, U8, U13, U14) with ones modified as requested in E1201027.
These are the HAM-A Drivers for the HAUX; Optic Name Name on Drawing* Rack Location Chassis Serial Number IM1 SM1 C4 - U14 S1201156 IM2 PMMT1 C4 - U8 S1201162 IM3 PMMT2 C4 - U7 S1201155 IM4 SM2 C4 - U13 S1201165 * aLIGO SUS HAM2 System Wiring Diagrams, Current Version, D0902810-v7 This means that the output impedance for these drivers is significantly less that before, which means both the noise and the drive strength have decreased by a factor of a factor of 10 (calculation below). This explains why we need much more drive from the IM's DAC in order to retain the same alignment offsets (see LHO aLOG 8759), and as Cheryl mentions, in some cases (IM3), the DAC saturates before we can get to the desired alignment offset. So, we either need to physically offload the alignment on the SUS themselves or reduce the output resistors enough to be able to both obtain the desired alignment while still meeting the noise reduction goal. (Icoil / Vin)_after (Vin/Vout)_after / (Rcoil + 2*Rout_after ) ------------- = ----------------------------------------- (Icoil / Vin)_before (Vin/Vout)_before / (Rcoil + 2*Rout_before ) (Rcoil + 2*Rout_before) = ------------------------ (Rcoil + 2*Rout_after) (Rcoil.aosem = 19.8 [Ohm] [see LLO aLOG 3340]) (Rout_before = 100 [Ohm]) (Rout_after = 1200 [Ohm] (Icoil / Vin)_after ------------- = 0.098 (Icoil / Vin)_before