1. MPI Seminar, October 7, 2008Thomas Schweizer, Development of a new low-threshold Trigger M. Shayduk, M. Rissi, T. Schweizer, N. Otte, M. Lopez for the MAGIC collaboration Padova, October 8-10, 2008

2. MPI Seminar, October 7, 2008Thomas Schweizer, Analogue sum trigger concept o Summation of patch of 18 pixels in 24 patches in a ring-shape o Idea: a) Summing up all single photons increases signal to noise ratio b) Fluctuations of shower larger than Poissonian fluctuations of NSB background o Afterpulse problem: high noise rate o Solution: clipping of signal Discriminator threshold in PhE Single pixel spectrum with afterpulses NSB Afterpulses Signal Clipper Σ Analog sum of 18 pixels Signal Clipper... Discriminator... Clipped at 6-8 PhE Threshold at 24-27 PhE

3. Effect of clipping the signal/ Comparison of prototype test and MC NSB Afterpulses Showers Sum of 18 pixels Trigger rate distribution vs threshold

4. Analogue sum trigger concept o Optimization of the trigger pattern 30 GeV gamma light pool Maximal probability to trigger at ~100m Trigger region should be a ring around 0.6deg Average Phot.Angle vs Impact

5. MPI Seminar, October 7, 2008Thomas Schweizer, Optimization of trigger for lowest threshold - Pulse width of sum signal: 2.5-3.0 ns (Signal/NSB ratio) - Number of pixels in analogue sum: 12-18 pixels - Clipping level (6-8 PhE) - Shape of patches (oriented toward center) - Topology of trigger region (optimal for 10-20 GeV showers) Effective area [m 2 ] Effective area Standard Trigger 10 100 GeV Sum Trigger At 20 GeV: Factor 6 improvement

6. Installation in La Palma (October 2007) Thomas Schweizer Nepomuk Otte & Maxim shayduk Michael Rissi

7. MPI Seminar, October 7, 2008Thomas Schweizer, Performance: Comparison standard trigger and sum trigger 25 GeV threshold sum trigger 55 GeV threshold standard trigger Event distribution

8. MPI Seminar, October 7, 2008 Sum Trigger: Advantages 1. Low cost + simplicity (20kEuro, 2/3 of price: SMA connectors and cables !) conventional OpAmps: OPA699, OPA695. 2.Lowest possible trigger threshold (prove of principle: Crab Pulsar Detection, 16 th October, Science ). 3.Handles PMTs with rather high afterpulse rate (choose cheaper PMs). 4.Very low power consumption (no fast ECL comparators). 200 channels ~100 Watt !!! (5Vx20A)