1. Photosensor Work at UCSC Concentrate on technologies that are: –Newer than conventional PMT –Now or soon in commercial production Multianode & high QE PMT –Develop test infrastructure (also for G-APDs) –Some initial tests Geiger-APD –Otte brings expertise & ideas from his PhD work No financial support –Borrowed & scavenged equipment –Free undergraduate labor

2. MAPMT Tests Hamamatsu R8900-M16-203 Base from Argonne 1 pe ADC spectrum Using amplifiers from STACEE

3. Photon Detection Efficiency Courtesy of MPI Munich Reference signal Test signal Diffusing Teflon Hamamatsu R7600U-200 Photonis XP2970/02 Wash U QE measurement

4. Tests have shown that the G-APD can in principle be used: N. Otte and coworkers at MPI/PSI/ETH: Vienna Conference on Instrumentation 2007 ICRC 2007 NDIP 2008 4 MPPC-33-050C from Hamamatsu: sensor size: 3x3mm² single cell size: 50x50µm² nominal bias: 70.4V dark rate at nominal bias: ~2MHz gain at nominal bias: 7.5*10 5 MAGIC Pixel Size the devil is in the detail: can costs be sufficiently reduced that the G-APD becomes competitive to the PMT? optical crosstalk could limit low energy performance on trigger level is temperature dependence an issue? how severe are parameter fluctuations from device to device … Extensive R&D program ahead that has to figure out if the G- APD can be used to meet our physics goals

5. Status and Plans at UCSC setting up infrastructure to evaluate G-APDs -photon detection efficiency measurements -temperature chamber -… MPPCs ordered from Hamamatsu in contact with several other producers Status: Plans: test available devices R&D on G-APD pixel for a small ACT – towards a first comprehensive field test in 2009? we are just beginning, especially for G-APDs AGIS R & D Proposal: design of prototype camera(s), including choice of sensor(s) how sensor features impact trigger performance procure and test sensors for prototype camera(s)