VLVnT09, Athens, Greece, 13-15 October 2009 Time over Threshold Electronics for Neutrino Telescopes George Bourlis In the framework of the KM3NeT Design

VLVnT09, Athens, Greece, 13-15 October 2009

Time over Threshold Electronics Time over Threshold Electronics for Neutrino Telescopesfor Neutrino Telescopes

Time over Threshold Electronics Time over Threshold Electronics for Neutrino Telescopesfor Neutrino Telescopes

George Bourlis

In the framework of the KM3NeT Design Study


Time over ThresholdTime over ThresholdTime over ThresholdTime over Threshold

Analogue signal

Comparators’ output

t1t2t3 t4 t5 t6 HPTDC output


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GPS Input

USB PortTrigger Output5 PMT Signal Inputs

25ps accuracy TDC

HPTDC

• 32 channels (LR) – 8 Channels (HR)

•25ps (HR) to 100 ps (LR) accuracy

•Self Calibrating


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EZ-USB FX2 HPTDC CONTROLEZ-USB FX2 HPTDC CONTROLEZ-USB FX2 HPTDC CONTROLEZ-USB FX2 HPTDC CONTROL


ToT In Action ToT In Action ToT In Action ToT In Action


Board Debugging ConfigurationBoard Debugging ConfigurationBoard Debugging ConfigurationBoard Debugging Configuration

Trigger

Input

splitter

splitter

discriminator

- Offset of each input

- Scale of each input

- Timing among input channels

- Minimum threshold that can be applied to the channels of each input


Multiplication factor vs ThresholdsMultiplication factor vs ThresholdsMultiplication factor vs ThresholdsMultiplication factor vs Thresholds

- Pulses exceeding 2V are not distorted but truncated and can still be reconstructed

Multiplication factor 1x 1x 1.5x 2.5x 5x

Measured factor 0.991 1.0035 1.503 2.7735 4.995

Minimum Threshold (mV) 9.78 5.25 1.69 1.57 1.42

Maximum Threshold (mV) 2000 2000 1333 800 400

- 1.57mV corresponds to around 1/3 of a MIP for the HELYCON detectors

- 800mV corresponds to 150-200 MIPs for the HELYCON detectors


Charge (pCb)

Single pe

HELYCON PMT & DetectorHELYCON PMT & DetectorHELYCON PMT & DetectorHELYCON PMT & Detector

Photomultiplier Tube

PH: XP1912

At “nominal” High Voltage

Gain: ~ 4 105

<charge>/p.e. ~ 0.07pCb

<pulse height>/p.e. ~ 1.05mV

Rise Time: 1.2 ns

Charge (in units of mean p.e. charge)

At the Detector Center

Data

- Monte Carlo Prediction


Sample PulsesSample PulsesSample PulsesSample PulsesInput 1


Charge vs Time over ThresholdCharge vs Time over ThresholdCharge vs Time over ThresholdCharge vs Time over ThresholdC

ha

rge

(p

C)

Time Over Threshold (s)

1st Threshold only 1st & 2nd Threshold 1st, 2nd & 3rd Threshold

4mV

50mV

15mV

3 thresholds


Charge versus Time over ThresholdCharge versus Time over ThresholdCharge versus Time over ThresholdCharge versus Time over Threshold

3mV

70mV

10mV20mV

40mV

100mV

6 thresholds

The chosen thresholds allow the reconstruction of higher pulses with good accuracy, while smaller pulses (fewer thresholds crossed) can still be reconstructed with acceptable accuracy


Charge ParameterizationCharge ParameterizationCharge ParameterizationCharge Parameterization

kkCharge= a (tot)

Parameterization of the charge vs the sum of the times over threshold for each of the areas were 1, 2, 3, 4, 5 or 6 thresholds were crossed


Charge EstimationCharge EstimationCharge EstimationCharge Estimation

- Estimated Resolution 4.3%

- Pull distribution sigma of 1.04 ± 0.07

Measured Charge – Estimated Charge

Measured Charge

4 thresholds

Measured Charge – Estimated Charge

Estimated Error


Charge Estimation ResolutionCharge Estimation ResolutionCharge Estimation ResolutionCharge Estimation ResolutionCharge estimation resolution vs number of thresholds crossed

Thresholds crossed 1 2 3 4 5 6

Charge estimation resolution (%) 13.6 6.9 5.6 4.3 3.4 2.9


ConclusionsConclusionsConclusionsConclusions

- The time over threshold technique allows for charge estimation with very good resolution for higher pulses (even if the thresholds do not go very far up the pulse height). This resolution goes down to ~3% with 6 thresholds which is sufficient both for the HELYCON and the KM3NeT telescopes.

- Lower pulses can still be reconstructed with acceptable accuracy if the lower thresholds are more closely spaced near the baseline.

- Charge estimation resolution depends on the number of thresholds crossed and on their specific values. The choice of the applied thresholds depends on the pulses recorded.





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VLVnT09, Athens, Greece, 13-15 October 2009 Time over Threshold Electronics for Neutrino Telescopes George Bourlis In the framework of the KM3NeT Design