2008-01-02 Fiske results

Finally some visual results from the Fiske step routine.

fiske results1.png

This image shows the FFO as it's always drawn: bias current on the Y axis and resulting measured voltage on the X axis. The color displayed is the voltage on the SIS junction.

The blue lines are the scans as executed by the Fiske macro. As a reminder, such a macro is a list of commands for the FPGA on the electronics boards. The Fiske macro keeps the FFO bias on a single value, while the FFO control line is stepped up. As can be seen, the control isn't very regulated; the blue lines shift a little at the left and right edge. Well, actually it shifts more than a 'little'. The left is completely off :-)

To fix this, the starting point (the most left point) of each scan should be in line with the previous scan. The first point that's just over Vstart (see previous entries) is probably very nice.

What's happening now is that the procedure tries to find a good point in the scan part of the macro -- when actually a good point could reside in the find up part of the macro. So this problem is fixed by searching in that first find up part as well.

Note that currently, an analysis is run on each line. Normally, the scan would be stopped since the analysis was positive. This is the case when the blue line sees that it's right inside a cloud of points, where reading out the PLL IF voltage reports 0.4 V and higher). However, my Russian colleague gave the advice to let it run somewhat and see whether the analysis can be better.