Oscillations from dewar monitoring.



     Beam 2a,2b of alfa has looked noisier that the other beams for about a year. These two beams had been switched to an open loop bias card back some time in dec09. On 15feb11 it was found that the total power variation of these beams had a periodicity of about 5.22 seconds. This was later traced to the monitoring of the bias voltages and currents that occurs approximately every 5 seconds.

    To get a better idea of the problem and when it occurred, data was taken:

Mock data at  10hz.

    The data was taken with the telescope sitting still. 10 hz sampling was used with a 172 MHz bandwidth. Only the upper band (that did not include the radars) was used.

A2010 data with 1 second sampling.

      A2010 data (alfalfa) was looked at to see when the problem occurred.


processing: x101/110208/alfamon.pro,allfamonwapp.pr, 110215/alfamon.pro,110216/alfamon.pro