South Pole Report for B2 and SPICE (that's the name now, right?)
by Obrient, Roger (Guest)
Hi all,
Here's what's going on at Pole:
Immanuel & Kirit are looking at side-lobe data. They can see the source in all detectors, although not at every dec angles. We've measured both pols with attenuator settings "rocky"®=50 & "severe_backlash"(sb)=50 where the power=4,000 ADU at co-polor pixel peaked up. We have started to repeat the maps with "r=40, sb=0, which will unlock a co-polar pixel on boresight. We hope this is strong enough to see the side-lobes. The schedule will run flux_loop_init at each elevation step to help deal with this. Speaking of the amplified noise source, the ESD-safety situation down here seems pretty lousy. Could someone (Martin, Abby, or Clem) pack lots of ESD-wrist band and long cables?
Immanuel & Kirit shoveled snow for 30 min; Kirit want's credits towards his graduation for this. Roger & Immanuel examined the mount for a couple hours to look for problems causing the halts in side-lobe scans. We spent a while watching the az-drive slew back and forth, but were never present when it halted. Thanks to Clem and Robert for suggestions, although none of the tests or examinations showed anything definitive. We are continuing with a side-lobe map schedule since the halts to the az drive do not seem violent. The earliest we would pull rx1 from the mount is tomorrow evening.
Grant & Roger hope they have completed FTS data collection. We taped a mirror to the output grid & ran the FTS at dec=0, we collected data at dec=315 to compare against 135 deg, only 4 pointing, one on each tile. Finally, we took a scan with the FTS fixed mirror displaced one bolt hole towards the beam-splitter. We could not find the thick-grill filter. All of this data is now reduced. John Kaufman is incrementally building a lengthy BICEP-2 post that summarizes the systematic cuts. He and Grant have conspired to express these figures in terms of Rel-Gain. Initial figures suggest that the rel gain repeatability for dec rotations is 1% (Bicep-1 level), but perhaps not the 0.2% we would want for r=0.01. This figure is better for other systematic checks, although we have not finished the different pointing test yet. First tests of different pointings look like they vary 0.8%. There really is a lot to this, so interested parties should read John Kaufman's very thorough post. He still won't have it all up by tomorrow's meeting.
We are not fully illuminating the beam with this FTS, which might explains some of the challenges with the pointing/dec rotation checks. Should we consider bringing an integrating sphere down next year (or late this season) for SPICE FTS measurements?
Sarah and Howard collected efficiency data, noise data, SQUID sweeps, and conducted knock tests on B2 & SPICE. She has put posts up on SQUIDS, OE, and fast Noise. Howard has done some for forebaffle on/off and knock tests, will be up tomorrow (after meeting). All seem consistent with previous measurements.
Best,
Roger
