1. TOF Front End electronics
Reminder: TOF requirement
Time Walk correction
Open options
Constant Fraction Discriminator
Charge Measurement
Time over Threshold Measurement
Feb 2006
Jean-Sébastien Graulich

2. Jean-Sébastien Graulich
TOF Requirements
Time resolution:
50-70 ps resolution
-> Choice of TDC: CAEN V (25 ps LSB, >1000 Evt buffer)
Particle rate
~ 2 MHz in TOF0
Charge measurement is not required
Feb 2006
Jean-Sébastien Graulich

3. Jean-Sébastien Graulich
Time Walk Correction
Timing is affected by the signal amplitude
2 Usual Solutions:
Use Constant Fraction Discriminator (CFD)
Measure amplitude and correct
Time
Walk
Time Walk Correction
Thresh.
Time over threshold
Example from Harp
Feb 2006
Jean-Sébastien Graulich

4. Jean-Sébastien Graulich
Possible Options
Option 1. Constant Fraction Discriminator (CFD)
The time walk is corrected automatically in the discriminator
Threshold value depends on the amplitude
Advantage: Easy Cabling and No ADC
Drawback
No information at all on the charge (Energy Deposit)
Cost: TDC + ~ 125 EUR/ch (CFD)
BNC Cable
PMT
CFD
TDC
Trigger Logic
Feb 2006
Jean-Sébastien Graulich

5. Jean-Sébastien Graulich
Possible Options
Option 2. Measure the Charge with a QDC
Advantage: More Precise and Good Charge Measurement
Drawback
General MICE ADC problem (No suitable QDC exists yet!)
Requires Splitters
More cabling
Cost: TDC + ~ 125 EUR/ch (DISC) ~ 200 EUR/ch (QDC) ~ Delay Cables (~20 m/ch) (Assuming free splitters)
Gate Signal
PMT
DISCRI
Cable
Delay
TDC
Trigger Logic
Splitter
QDC
BNC Cable
Feb 2006
Jean-Sébastien Graulich

6. Jean-Sébastien Graulich
Possible Options
Option 3. Measure the Charge with any available Solution
Same Advantages and Drawbacks as 2.
Cost: TDC + ~ 125 EUR/ch (DISC) ~ ??? EUR/ch (ADC) ~ Delay Cables (~20 m/ch) (Assuming free splitters)
Feb 2006
Jean-Sébastien Graulich

7. Rising edge + Trailing edge Time Measurement
Possible Options
Option 4. Measure the Charge with Time Over Threshold Principle
Advantage: Easy Cabling and Charge Measurement (not linear though) Good Precision for Time Walk Correction
NINO = ASIC developed by CERN/MIC for Alice TOF Discriminator with ToT “proportional” to the Charge (at low amplitude) Proven technique, providing 50 ps resolution (IEE TNS Vol 51-5 (2004) ) Very Cheap: 2 EUR/ch
Drawback
Requires Board development !
Cost: TDC + Discri. board production (~50 EUR/ch)
PMT
NINO
TDC
Rising edge + Trailing edge Time Measurement
Trigger Logic
Width ~Charge
Feb 2006
Jean-Sébastien Graulich

8. Jean-Sébastien Graulich
Plan
Options 1. and 2. Will be tested in June/July at BTF
Additional Test with TDC CAEN V775 to allow comparing with previous results (HARP)
Options 3. and 4. are under investigation
Feb 2006
Jean-Sébastien Graulich