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 Current Trigger is based on multiplicity in META detector Problem: Tracks have META hit but no MDC Information –> Events are useless 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 : 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 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) Signal is collected at the HV input to the chamber (HV filter box) Problem: Large capacitance –> low signal/noise ratio Problem: Large capacitance –> low signal/noise ratio MDC II MDC II stable chambers stable chambers short drift times (40 – 160 ns) short drift times (40 – 160 ns)

Status Cyprus Meeting Used field plane readout Used field plane readout Used analog summing of amplified signals Used analog summing of amplified signals 55-75% efficiency at the working point 55-75% efficiency at the working point 65-85% efficiency at 1790V (40V above working point) 65-85% efficiency at 1790V (40V above working point)

New Scheme Rossendorf: New HV filter boxes for cathode readout Rossendorf: New HV filter boxes for cathode readout No improvement in S/N due to correlated noise No improvement in S/N due to correlated noise Wolfgang: New discriminator board Wolfgang: New discriminator board Amplified cathode signals are first discriminated then summed to define multiplicity Amplified cathode signals are first discriminated then summed to define multiplicity Sergey: Improved amplifier Sergey: Improved amplifier Minimized time delay Minimized time delay Wolfgang: Alternative amplifier Wolfgang: Alternative amplifier high amplification high amplification short rise time short rise time short life time short life time

Properties of Amplifiers Sergey Sergey Amplification ~ 120 Amplification ~ 120 Delay ~ 55ns Delay ~ 55ns Rise time ~ 65ns Rise time ~ 65ns Input impedance 50Ω Input impedance 50Ω Robust Robust Wolfgang Wolfgang Amplification ~ Delay ~ 45 ns Rise time ~ 40ns Input impedance 1kΩ Not reliable: trips can kill channels

Typical Signals Positive signals come from Sergey's amplifier Positive signals come from Sergey's amplifier Negative signal comes from Wolfgang's amplifier Negative signal comes from Wolfgang's amplifier Each signal is for a different cathode plane Each signal is for a different cathode plane

Main Problem: Noise Noise 3 times higher than electronic noise is observed Noise 3 times higher than electronic noise is observed Repetition rate: 5 MHz Repetition rate: 5 MHz Noise increases if HV connectors are plugged in Noise increases if HV connectors are plugged in Pulser connection to the field planes was introducing noise Pulser connection to the field planes was introducing noise Pulser connection is removed Pulser connection is removed Due to noise: reduced efficiency (trigger threshold) 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% Efficiency at the HV working point about 60% at the same voltage Wolfgang's amplifier showed roughly about 25% more efficiency (needs verification) at the same voltage Wolfgang's amplifier showed roughly about 25% more efficiency (needs verification) Efficiency at 1790V about 80% Efficiency at 1790V about 80% MDC-Trigger Signal is ns earlier than TOF coincidence signal MDC-Trigger Signal is ns earlier than TOF coincidence signal

Different Multiplicities

Summary Digital summing is implemented Digital summing is implemented Cathode readout doesn't provide advantages in S/N due to correlated noise and larger capacitance Cathode readout doesn't provide advantages in S/N due to correlated noise and larger capacitance Timing is no longer crucial Timing is no longer crucial We have a perfect amplifier from Sergey We have a perfect amplifier from Sergey We still have too high noise We still have too high noise Current efficiency is not yet satisfactory Current efficiency is not yet satisfactory

Outlook Currently looking for grounding/shielding problems Currently looking for grounding/shielding problems A new dedicated filter designed by Wolfgang will be tested soon 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 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. During the test run this month we will check trigger efficiency in beam and hadron/lepton ratio.