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MiniBoone Detector: Digitization at Feed Through

Student: John Odeghe ;SC State , Fermi Lab Intern

Supervisor: JinYuan Wu;Fermi Lab

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Outline

•Mini Boone Detector•The need for changing digitization design•Digitization at Feed through•The TDC FPGA Design•Performance Tests and Results•Conclusions

General Description

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Demonstrate photon – electron identification Develop cold electronics

Implementation of cold electronics in Gaseous Argon (GAr)

Purity: Test of GAr purge in large, fully instrumented vessel

Refine sensitivity estimates for next generation detectors

Test ability to run on surface Develop tools for analysis Develop cost scaling model for larger

detectors

MicroBooNE LAr TPC Development Goals

MicroBooNE detector: 150 tons total Liquid Argon 89 tons active volume TPC: ~2.5 x 2.3 x 10.4m long Ionization electrons drift to beam right 30 PMTs peek through the wire chambers on beam right Will use BNB and NuMI beams at FNAL for physics program

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LArTPC around US

General Description: LArTPCs

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Passing charged particles ionize Argon Electric fields drift electrons meter to wire chamber planes Induction/Collection planes image charge, record dE/dx

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Readout channel information flow

Short Falls of current Design• Poor Noise Handing• Limited cable Run

Source: MicroBooNE ConceptualDesign Report , Feb 2010

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Digitization at Feed Through

• The goal is to digitize the analog signals before they are contaminated by noise.

• However, digitization processes create noise that may contaminate signals.

• Therefore, it is a natural to minimize digital activities in the digitization processes.

• Q: How many bit transitions are considered to be minimal?A: 1 bit transition/data sample.

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Single Slope TDC

AMP &Shaper

AMP &Shaper

AMP &Shaper

AMP &Shaper

ADC

ADC

ADC

ADC

FPGA AMP &Shaper

AMP &Shaper

AMP &Shaper

AMP &Shaper

FPGATDC

TDC

TDC

TDC

R1 R1C

R2

VREF

T1

V1

T2

V2

T3

V3

T4

V4

The current design consist of ADC feeding digitized data to the FPGA for analysis. But we can Implement a TDC on an FPGA. This allows us to directly feed analog signals to the FPGA, eliminating extra ADC hardware. This scheme proves even more efficient in digitization.

Quick Facts on our TDC FPGA• Implemented on Altera Cyclone FPGA• Primary firmware employs delay chains to determine transition time•Wave Union launcher is implemented to ameliorate ultra wide bins effect• TDC can run to a precision of 70 ps (LSB)

RC circuit creates Ramping reference voltage, which is compared with analog signals in FPGA. Hit time is measured to a high precision. Signals can be reconstructed using the hit times.

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Fast TDC Card

TDC FPGA

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Performance Tests

•Oscilloscope pictures•Optimized range common mode signals•Calibration •Test Signals •Histograms

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Oscilloscope Pictures

Pic. 1 Ramping signals (1MHz)

Pic. 2 Ramping signals generated from clock.

Pic. 3 Sampling using the ramping Signals

• Tests Start with analyzing critical signals

• Using a scope we can check the differential ramping signals.

• The ramping RC signals are derived from clocking signals in the board

• The ramping signal serves as a sampling signal (in pic. 3 a slower ramp is sampled)

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Common mode Signals

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5115

120

125

130

135

140

145

150

155

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5340

350

360

370

380

390

400

410

Voltage Offset (V) Voltage Offset (V)

Tim

e (

ns)

Tim

e (

ns)

• Device is designed for differential Input Signals• Performance can be compromised owing to offset of input signal.• We can investigate this behavior by feeding common mode signals• Observe that optimization is attained within the described range

optimized

optimized

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Calibration

0 250 500 750 1000-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

CalculatedMeasured Ramping UpMeasured Ramping Dwn

Time (ns)

Volt

ag

e (

v)

• Check for accuracy of device by matching measured samples with calculated curve

• Generate a lookup table for time conversions

• Understand slight aberrations

• Moving forward in data interpretation

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Test Signal

40000 80000-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

Ramping up signal

Ramping dwn signal

Time (ns)

• With the calibration formula obtained we can regenerate input signals

• Ramping up and ramping down samples are converted and plotted in the same graph

• Notice that both signal samples match

• A pulse signal is fed to an input channel

• Controlling the TDC through a serial port, the signal is sampled

• Raw data from the sampling is saved to a remote computer

• The goal is to recreate the signal using the array of hit time sampled

Am

pli

tud

e (

v)

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Histograms

0 5 10 15 20 25 30 350

4000000

8000000

12000000

Histograms of Hits on channel 7 (Ramping Down)

Bins

Hit

s

0 5 10 15 20 25 30 350

2500000

5000000

7500000

Histogram of hits on channel 7 (Ramp-ing up)

Bins

Hit

s

• Histograms plot bins on the LSB of Hit Time• It’s a pictorial evaluation of precision of the TDC.• With a constant amplitude signal, we expect a sharp pic and

little variance• Channel 7 is supplied with a constant amplitude signal.• Histograms of both ramping up and ramping down samples

confirms our prediction

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Histograms

0 5 10 15 20 25 30 350

4000000

8000000

12000000

Histogram of Hits from Ramping Down Signal

Bins

Hit

s

0 5 10 15 20 25 30 350

2000000

4000000

6000000

histogram of hits from Ramping up Signal

bin

hit

s

• A varying amplitude like the pulse signal will be interesting to analyze on a histogram.

• Observe the noticeable peak and the smaller bumps. 40000 80000

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

Ramping up signal

Ramping dwn sig-nal

Time (ns)

Am

pli

tud

e (

v)

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Acknowledgment

•Fellow SIST Interns•SIST Committee•14th floor WH PPD crew

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Questions