SLD Polarimeter
Testbeam 2007
The up to now best polarisation measurement performed on an electron beam was done within the SLD experiment at SLAC (ΔP/P ≈ 0.5%).
When asking our SLAC colleagues for some details on how they contructed the gas tubes in their Cherenkov detector they offered us to send the whole thing to DESY. We took this opportunity without hesitation and some months later, in May 2007, the SLD Cherenkov detector arrived at DESY in Hamburg. After opening the detector and studying its interior we recommissioned it in our lab and found that eight of the nine PMTs still worked.
Apart from learning about the construction of gas tubes, this gave us the opportunity to do first measurements before constructing our own prototype. We gathered very helpful experience in DESY II testbeam measurements and were also able to test and optimize our DAQ system, which was originally designed for our photodetector teststand in the lab.
By the end of October 2007 we started our very first testbeam period with the unmodified SLD Cherenkov detector in the DESY testbeam 21. After some days (and nights) of hard work everything was running smoothly and we collected a big amount of data. The setup and also some first results are summarized in a diploma thesis.
In a second step we exchanged six of the nine original PMTs with different types of photodetectors, amongst others a SiliconPM. The altered detector was again put into the testbeam in December 2007, which gave us the honour to be the very last DESY testbeam users before the eight month shutdown from January to September 2008 ;-)
Some impressions...
