MDC-II LVL-1 TriggerMDC-II LVL-1 Trigger

Khaled TeilabKhaled Teilab

for thefor the

MDC Trigger TeamMDC Trigger Team

Why do we need MDC Why do we need MDC Trigger?Trigger?

Current TCurrent Trigger is based on multiplicity in rigger is based on multiplicity in META detectorMETA detector

Problem: Tracks have META hit but no Problem: Tracks have META hit but no MDC Information –MDC Information –> Events > Events are uselessare useless

: include MDC information in the : include MDC information in the trigger decision -> Gives about a factor of trigger decision -> Gives about a factor of 2 more statistics2 more statistics

MDC Trigger MDC Trigger Implementation Implementation

Particles crossing any drift cell Particles crossing any drift cell produce a signal on field/cathode produce a signal on field/cathode planesplanes

Signal is collected at the HV input Signal is collected at the HV input to the chamber (to the chamber (HV filter boxHV filter box))

Problem: Large capacitance –> Problem: Large capacitance –> low signal/noise ratiolow signal/noise ratio

MDC IIMDC II stable chambersstable chambers short drift times (40 – 160 ns)short drift times (40 – 160 ns)

Status Cyprus MeetingStatus Cyprus Meeting

Used field plane readoutUsed field plane readout

Used analog summing of amplified Used analog summing of amplified signalssignals

55-75% efficiency at the working 55-75% efficiency at the working pointpoint

65-85% efficiency at 1790V (40V 65-85% efficiency at 1790V (40V above working point)above working point)

New SchemeNew Scheme Rossendorf: New HV filter boxes for cathode Rossendorf: New HV filter boxes for cathode

readoutreadout No improvement in S/N due to correlated noiseNo improvement in S/N due to correlated noise

WolfgangWolfgang: : New discriminator boardNew discriminator board Amplified cathode signals are first Amplified cathode signals are first

discriminated then summed to define discriminated then summed to define multiplicitymultiplicity

Sergey: Improved amplifierSergey: Improved amplifier Minimized time delayMinimized time delay

WolfgangWolfgang: : Alternative amplifierAlternative amplifier high amplification high amplification short rise timeshort rise time short life timeshort life time

Properties of AmplifiersProperties of Amplifiers

SergeySergey Amplification ~ 120Amplification ~ 120 Delay ~ 55nsDelay ~ 55ns Rise time ~ 65nsRise time ~ 65ns Input impedance 50Input impedance 50ΩΩ RobustRobust

WolfgangWolfgang Amplification ~ 20000Amplification ~ 20000 Delay ~ 45 nsDelay ~ 45 ns Rise time ~ 40nsRise time ~ 40ns Input impedance 1kInput impedance 1kΩΩ Not reliable: trips can kill Not reliable: trips can kill

channelschannels

Typical SignalsTypical Signals

Positive signals come from Positive signals come from Sergey's amplifierSergey's amplifier

Negative signal comes from Negative signal comes from Wolfgang's amplifierWolfgang's amplifier

Each signal is for a different Each signal is for a different cathode planecathode plane

Main Problem: NoiseMain Problem: Noise

Noise 3 times higher than Noise 3 times higher than electronic noise is observedelectronic noise is observed

Repetition rate: 5 MHzRepetition rate: 5 MHz

Noise increases if HV Noise increases if HV connectors are plugged inconnectors are plugged in

Pulser connection to the field Pulser connection to the field planes was planes was introducing noiseintroducing noise Pulser connection is Pulser connection is

removedremoved

Due to noise: reduced Due to noise: reduced efficiency (trigger threshold)efficiency (trigger threshold)

Cosmics Results using Sergey's Cosmics Results using Sergey's AmplifierAmplifier

based on Offline Analysisbased 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 at the same voltage Wolfgang's amplifier showed

roughly about 25% more efficiency (needs verification)roughly about 25% more efficiency (needs verification)

Efficiency at 1790V about 80%Efficiency at 1790V about 80%

MDC-Trigger Signal is 50-150ns earlier than TOF MDC-Trigger Signal is 50-150ns earlier than TOF coincidence signalcoincidence signal

Different MultiplicitiesDifferent Multiplicities

SummarySummary

Digital summing is implementedDigital summing is implemented Cathode readout doesn't provide advantages in S/N due to Cathode readout doesn't provide advantages in S/N due to

correlated noise and larger capacitancecorrelated noise and larger capacitance

Timing is no longer crucialTiming is no longer crucial We have a perfect amplifier from SergeyWe have a perfect amplifier from Sergey

We still have too high noiseWe still have too high noise Current efficiency is not yet satisfactoryCurrent efficiency is not yet satisfactory

OutlookOutlook

Currently looking for grounding/shielding problems Currently looking for grounding/shielding problems A new dedicated filter designed by Wolfgang will be tested A new dedicated filter designed by Wolfgang will be tested

soonsoon

If succeeded in reducing noise we can reach more than If succeeded in reducing noise we can reach more than 90% efficiency for multiplicity I at 1790 V90% efficiency for multiplicity I at 1790 V

During the test run this month we will check trigger During the test run this month we will check trigger efficiency in beam and hadron/lepton ratio.efficiency in beam and hadron/lepton ratio.