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MDC-II LVL-1 Trigger Khaled Teilab for the MDC Trigger Team Why do we need MDC Trigger? Current Trigger is based on multiplicity in META detector Problem: Tracks have META hit but no MDC Information –> Events are useless : include MDC information in the trigger decision -> Gives about a factor of 2 more statistics MDC Trigger Implementation Particles crossing any drift cell produce a signal on field/cathode planes Signal is collected at the HV input to the chamber (HV filter box) Problem: Large capacitance –> low signal/noise ratio MDC II stable chambers short drift times (40 – 160 ns) Status Cyprus Meeting Used field plane readout Used analog summing of amplified signals 55-75% efficiency at the working point 65-85% efficiency at 1790V (40V above working point) New Scheme Rossendorf: New HV filter boxes for cathode readout Wolfgang: New discriminator board Amplified cathode signals are first discriminated then summed to define multiplicity Sergey: Improved amplifier No improvement in S/N due to correlated noise Minimized time delay Wolfgang: Alternative amplifier high amplification short rise time short life time Properties of Amplifiers Sergey Amplification ~ 120 Delay ~ 55ns Rise time ~ 65ns Input impedance 50Ω Robust Wolfgang Amplification ~ 20000 Delay ~ 45 ns Rise time ~ 40ns Input impedance 1kΩ Not reliable: trips can kill channels Typical Signals Positive signals come from Sergey's amplifier Negative signal comes from Wolfgang's amplifier Each signal is for a different cathode plane Main Problem: Noise Noise 3 times higher than electronic noise is observed Repetition rate: 5 MHz Noise increases if HV connectors are plugged in Pulser connection to the field planes was introducing noise Pulser connection is removed Due to noise: reduced efficiency (trigger threshold) Cosmics Results using Sergey's Amplifier based on Offline Analysis Efficiency at the HV working point about 60% at the same voltage Wolfgang's amplifier showed roughly about 25% more efficiency (needs verification) Efficiency at 1790V about 80% MDC-Trigger Signal is 50-150ns earlier than TOF coincidence signal Different Multiplicities Summary Digital summing is implemented Cathode readout doesn't provide advantages in S/N due to correlated noise and larger capacitance Timing is no longer crucial We have a perfect amplifier from Sergey We still have too high noise Current efficiency is not yet satisfactory Outlook Currently looking for grounding/shielding problems A new dedicated filter designed by Wolfgang will be tested soon If succeeded in reducing noise we can reach more than 90% efficiency for multiplicity I at 1790 V During the test run this month we will check trigger efficiency in beam and hadron/lepton ratio.