Feb 2006 Jean-Sébastien Graulich Slide 1

TOF Front End electronics

o Reminder: TOF requirement

o Time Walk correction

o Open options• Constant Fraction Discriminator• Charge Measurement• Time over Threshold Measurement

Feb 2006 Jean-Sébastien Graulich Slide 2

TOF RequirementsTOF Requirements

Time resolution:Time resolution:50-70 ps resolution

-> Choice of TDC: CAEN V1290 (25 ps LSB, >1000 Evt buffer)

Particle rateParticle rate~ 2 MHz in TOF0

Charge measurement is not requiredCharge measurement is not required

Feb 2006 Jean-Sébastien Graulich Slide 3

Timing is affected by the signal amplitudeTiming is affected by the signal amplitude

2 Usual Solutions: 2 Usual Solutions: Use Constant Fraction Discriminator (CFD) Measure amplitude and correct

Time Walk Time Walk CorrectionCorrection

TimeWalk

Time over threshold

Thresh.

Tim

e W

alk

Co

rre

ctio

nExample from Harp

Feb 2006 Jean-Sébastien Graulich Slide 4

Possible OptionsPossible Options

Option 1. Constant Fraction Discriminator (CFD)Option 1. Constant Fraction Discriminator (CFD)The time walk is corrected automatically in the discriminator

Threshold value depends on the amplitude

Advantage: Advantage: Easy CablingEasy Cabling and and No ADCNo ADC

DrawbackDrawback No information at all on the charge (Energy

Deposit) Cost: TDC +Cost: TDC + ~ 125 EUR/ch (CFD)~ 125 EUR/ch (CFD)

PMT CFDBNC Cable

TDC

Trigger Logic

Feb 2006 Jean-Sébastien Graulich Slide 5

Possible OptionsPossible Options

Option 2. Measure the Charge with a QDCOption 2. Measure the Charge with a QDC Advantage: Advantage: More PreciseMore Precise and and

Good Charge MeasurementGood Charge Measurement DrawbackDrawback

General MICE ADC problem (No suitable QDC exists yet!) Requires Splitters More cabling

Cost: TDC +Cost: TDC + ~ 125 EUR/ch (DISC)~ 125 EUR/ch (DISC) ~ 200 EUR/ch (QDC)~ 200 EUR/ch (QDC)

~ Delay Cables (~20 m/ch)~ Delay Cables (~20 m/ch)(Assuming free splitters)(Assuming free splitters)

Gate Signal

PMT

DISCRI

CableDelay

TDC

Trigger LogicSplitter

QDC

BNC Cable

Feb 2006 Jean-Sébastien Graulich Slide 6

Possible OptionsPossible Options

Option 3. Measure the Charge with any available Option 3. Measure the Charge with any available SolutionSolution

Same Advantages and Drawbacks as 2.Same Advantages and Drawbacks as 2. Cost: TDC +Cost: TDC + ~ 125 EUR/ch (DISC)~ 125 EUR/ch (DISC)

~ ~ ?????? EUR/ch (ADC) EUR/ch (ADC)~ Delay Cables (~20 m/ch)~ Delay Cables (~20 m/ch)

(Assuming free splitters)(Assuming free splitters)

Feb 2006 Jean-Sébastien Graulich Slide 7

Possible OptionsPossible Options

Option 4. Measure the Charge with Time Over Threshold Option 4. Measure the Charge with Time Over Threshold PrinciplePrinciple

Advantage: Advantage: Easy CablingEasy Cabling and and Charge Measurement Charge Measurement (not linear though)(not linear though)

Good PrecisionGood Precision for Time Walk Correction for Time Walk Correction

NINO = ASIC developed by CERN/MIC for Alice TOFNINO = ASIC developed by CERN/MIC for Alice TOF Discriminator with ToT “proportional” to the Charge (at low Discriminator with ToT “proportional” to the Charge (at low amplitude)amplitude) Proven technique, providing 50 ps resolution Proven technique, providing 50 ps resolution (IEE TNS Vol 51-5 (2004) 1974-(IEE TNS Vol 51-5 (2004) 1974-1978)1978)

Very Cheap: 2 EUR/chVery Cheap: 2 EUR/ch

Drawback Drawback Requires Board development !

Cost: TDC +Cost: TDC + Discri. board production (~50 EUR/ch) Discri. board production (~50 EUR/ch)

PMT NINO TDC

Trigger LogicWidth ~Charge

Rising edge + Trailing edge Time Measurement

Feb 2006 Jean-Sébastien Graulich Slide 8

PlanPlan

Options 1. and 2. Will be tested in Options 1. and 2. Will be tested in June/July at BTFJune/July at BTF

Additional Test with TDC CAEN V775 Additional Test with TDC CAEN V775 to allow comparing with previous to allow comparing with previous results (HARP)results (HARP)

Options 3. and 4. are under Options 3. and 4. are under investigationinvestigation