Reports until 10:44, Wednesday 15 December 2010
X1 SUS
mark.barton@LIGO.ORG - posted 10:44, Wednesday 15 December 2010 - last comment - 13:27, Friday 15 April 2011(414)
Quad test stand pitch/yaw range
Betsy, Jeff and I did a measurement of the maximum obtainable pitch and yaw range on the rebuilt Quad #2 using an optical lever. According to Norna's write up, T1000268-v1 ( https://dcc.ligo.org/cgi-bin/private/DocDB/ShowDocument?docid=11868 ) we should be able to get 1.4 mrad in each direction at the optic. At the DOF Test screen we applied successively offsets of +2556 and -2556 in pitch and +7863 and -7863 in yaw, which with the usual output matrix maxes out (32K) at least one of the OSEMs. The resulting deflections of the optical lever spot were +9.5 and -11.5 cm in vertical (+=down) and +5.5 and -6.5 cm in yaw (+=left). The optical lever baseline was 4.98 m. 

This implies a total range of 1 mrad in pitch and 0.5 mrad in yaw, which is rather less than expected. A big chunk of this is that the actual UK driver boxes for the test stand were not built to the 200 mA max output assumed in T1000268. To check this, the voltage across the face1 coil was measured at the simulated vacuum flange, with 32K-1 of offset applied at the Output Filters screen. The resistance (including that of the cables) was 39.9 ohms and the voltage was 3.69 V implying a maximum current of 92.5 mA.

The fact that the pitch range is larger than the yaw is probably connected with the fact that the fundamental pitch mode frequency is rather lower than in the model, i.e., there is more pitch compliance than expected.
Comments related to this report
mark.barton@LIGO.ORG - 13:24, Friday 15 April 2011 (721)
Further investigation revealed that the driver boxers are not the problem. The LHO ones have all been tested to 200 mA for 20 V input - see S0900011, S0900012, S0900013. The early low-capacity drivers that Norna recalled were apparently sent to LASTI - according to Brett Shapiro those were 75 mA units.
mark.barton@LIGO.ORG - 13:27, Friday 15 April 2011 (722)
Correction: test reports S0900011, S0900012, S0900013 were for LLO. Test reports S0900050, S0900051 and S1000001 are for LHO. In any case all top drivers for both sites have been tested to 200 mA.