R. Lane, J. Kissel, M. Barton

In order to continue investigation on the  16Hz phenomena  in the X1 SUS Test Stand we made a comparison between the BSFM model and the QUAD model. Running both models simultaneously we took power spectra of several OSEMs using DTT to measure the same physical OSEMs four different ways (both BSFM/QUAD channels, both Test Points (OSEMINF_IN1) and Frame Builder (OSEMINF_IN1_DAQ) channels). These OSEMs are mounted on BSFM01, and readout by the electronics associated with bsctestand2. The electronics (cables, satellite amps, I/O chassis) are identical, however new OSEMs are in place (the QUAD OSEMs went with the QUAD).

As expected in the F1 and RT channels, all four measurements agree. However the QUAD SD Test Point Channel (X1:SUS-QUAD_R0_OSEMINF_SD_IN1) has a loud 16Hz harmonics.

Of interesting note, and confirming the intermittancy of the problem, while setting up the test, the 16Hz harmonics switched to the RT OSEM for one on/off iteration of the test (sadly we didn't capture this, you'll just have to believe us). This confirms the existence of some stochastic digital problem (in addition to the fact that there are brand new OSEMs being readout).

The source models for the front end code that we're running can be found here: 
~/sus/trunk/Common/FrontEnd/models/x1susbsfm.mdl (BSFM)
~/sus/trunk/Common/FrontEnd/models/x1susquad.mdl (QUAD)

The DTT template for the measurement can be found here:
~/sus/trunk/QUAD/X1/Common/dtt_templates/BSFM_QUAD_16Hz_channelcomparison_110615.xml