Study about behavior of a prototype ASIC for the upgraded ATLAS - - PowerPoint PPT Presentation

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Study about behavior of a prototype ASIC for the upgraded ATLAS - - PowerPoint PPT Presentation

Apr 03, 2024 114 likes •285 views

Yamagaya Shohei Study about behavior of a prototype ASIC for the upgraded ATLAS pixel detectors with low thresholds Year-End-Meeting 2019/12/23 Shohei Yamagaya (Osaka univ.) Introduction 2 ATLAS pixel detector will be upgraded for HL-LHC.

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SLIDE 1

Year-End-Meeting 2019/12/23 Shohei Yamagaya (Osaka univ.)

Yamagaya Shohei

Study about behavior of a prototype ASIC for the upgraded ATLAS pixel detectors with low thresholds

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SLIDE 2

Yamagaya Shohei 2019/12/23 Year-End-Meeting

Introduction

2

  • Prototype ASIC for the new pixel detector
  • Name : RD53A
  • Can judge if there is a hit or not
  • Can estimate amount of input charge
  • It has registers to configure its circuits.

New Pixel Detector

  • Total Size : 4cm × 4cm
  • Pixel Size : 50um × 50um
  • 4 ASICs with 1.28 Gbps readout

ATLAS pixel detector will be upgraded for HL-LHC.

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SLIDE 3

Yamagaya Shohei 2019/12/23 Year-End-Meeting

ASIC

3

A threshold voltage is set by ASIC’s register values.

  • We have to tune them to set the threshold as we aim for.
  • All pixels should have similar thresholds after tuning.

1 pixel of the sensor

Register Global Pixel

Threshold voltage

Front-End Circuit

  • Comparator with threshold
  • ADC (Time over Threshold)

HitMap, ADC value

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Yamagaya Shohei 2019/12/23 Year-End-Meeting

500 1000 1500 2000 2500 3000 Threshold 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 # pixels

ThresholdDist target:1720

Threshold_1d

Entries 26112 Mean 0.3786 ± 1767 Std Dev 61.17 Underflow Overflow 6 Integral 2.611e+04

Threshold_1d_copy

Entries 26112 Mean 0.3786 ± 1767 Std Dev 61.17 Underflow Overflow 6 Integral 2.611e+04

ThresholdDist target:1720

Threshold tuning

4

Flow chart of tuning

Change Global Reg measure threshold Similar to target? No YES Change Pixel Reg measure threshold Similar to target? No YES

Finish

500 1000 1500 2000 2500 3000

Threshold[e]

200 400 600 800 1000

# pixel Threshold_Distribution

hist

Entries 380 Mean 32.97 ± 1822 Std Dev 359.2 Underflow Overflow 333 Integral 2.277e+04

Threshold_Distribution

Pixel individuality

Measured threshold [e] # pixels # pixels Measured threshold [e]

After global tuning After pixel by pixel tuning

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Yamagaya Shohei 2019/12/23 Year-End-Meeting

Requirement for ASIC

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  • One of the requirements for the new ATLAS detector
  • Untuned pixels < 0.3% of all && threshold dispersion < 40[e]

tmp_thre

Entries 26112 Mean 0.203 ± 966.3 Std Dev 32.8 Underflow Overflow Integral 2.611e+04

500 1000 1500 2000 2500 3000 threshold[e] 1 10

2

10

3

10

4

10 # pixels

target_threshold : 900

tmp_thre

Entries 26112 Mean 0.2076 ± 947.1 Std Dev 33.54 Underflow Overflow Integral 2.611e+04

target_threshold : 900

Untuned pixels Measured Threshold # pixels Measured threshold =0

  • Measured threshold =0
  • |Measured threshold - target one| > 3σ

Definition of untuned pixels

No one studied tuning and threshold behavior 
 even though it has the requirement to fulfill

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Yamagaya Shohei 2019/12/23 Year-End-Meeting

Setup

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  • YARR : a project for rapid readout from ASIC (developed by LBNL)
  • It has an algorithms to tune each pixel’s threshold.
  • It will be also used for QA/QC test in mass-production.
  • Untuned pixels were counted for each target threshold.
  • Target threshold’s range : 0 ~ 2000 [e]


because pixel detector’s threshold will be 600 ~ 800[e].

FPGA board (FW : YARR-fw)

PCIe YARR-SW

Adapter card

Display
 Port Setup

ASIC

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SLIDE 7

Yamagaya Shohei 2019/12/23 Year-End-Meeting

Untuned pixels

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  • Case : a threshold is different from target
  • That pixel’s individuality is too large for pixel register to tune it.
  • Too low -> pixel register (5bit) = maximum(15)
  • Too high -> pixel register = minimum(-15)
  • other

15 − 10 − 5 − 5 10 15 20 TDAC 1 10

2

10

3

10

4

10 # pixels

TDACDist target:1700

scan failed no response

  • ut_saturated
  • ut_notsaturated

TDACDist target:1700

Pixel Register’s value #pixels

Pixel Register’s value Dist.

  • Blue : Too high or Too low
  • Other
  • Measured threshold = 0
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SLIDE 8

Yamagaya Shohei 2019/12/23 Year-End-Meeting

Untuned pixels

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  • Measured Threshold = 0 ：divided into 2 types
  • The threshold measurement was failed.
  • Non responsive pixels

Threshold

Initial state

Noise floor

After global tuning

Pixels below noise floor output nothing. Algorithm can’t tune such pixels to target threshold

Non responsive pixels are predicted to increase with low target threshold.

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Yamagaya Shohei 2019/12/23 Year-End-Meeting

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Threshold_vs_target

200 400 600 800 1000 1200 1400 1600 1800 2000 target_threshold[e] 500 1000 1500 2000 2500 3000 Threshold[e]

Threshold_vs_target

200 400 600 800 1000 1200 1400 1600 1800 2000 target_threshold 20 − 10 − 10 20 mean-target threshold

Threshold behavior

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Measured Threshold [e] Threshold mean Measured - target [e] Target Threshold [e]

  • Target threshold > 200 [e]
  • | measured - target | < 10[e]
  • Threshold tuning is succeed
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SLIDE 10

Yamagaya Shohei 2019/12/23 Year-End-Meeting

Ratio of untuned

10

200 400 600 800 1000 1200 1400 1600 1800 2000 target_threshold

4 −

10

3 −

10

2 −

10

1 −

10 1 # pixels

LowerLimit0

scan failed no response

  • ut_TDAC=15
  • ut_TDAC=-15
  • ut_notsaturated

LowerLimit0

Ratio of the untuned pixels

Target threshold [e] Ratio of untuned pixels

Color rule ▶︎ • Threshold 3σ away from mean

  • Too high
  • Too low
  • Pixel Reg is not saturated
  • Non-responsive pixels
  • configuration’s problem

Requirement for pixel detector

untuned pixels < 0.3%

The requirement is satisfied! (400 < target threshold < 800[e]).

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SLIDE 11

Yamagaya Shohei 2019/12/23 Year-End-Meeting

Conclusion

11

  • The ASIC for the new ATLAS pixel detector was tested about a

threshold tuning of each pixel.

  • We found the ASIC satisfy the requirement for it.
  • The increase of non responsive pixels with low threshold was

revealed for the first time.
 And, they are dominant with a target threshold below 400 [e].

  • This result will be a good benchmark for QA/QC tests in mass-

production of the prototype ASIC and revised one.

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SLIDE 12

Back Up

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Yamagaya Shohei 2019/12/23 Year-End-Meeting

Threshold scan

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  • YARR’s scan consists of the 4 functions.

10 20 30 40 50 20 40 60 80 100 Occupancy Vcal Scurve-320-96-403.169325

Number of hits Injection charge 50% Threshold How to measure thresholds

  • Tuning : a scan + change global/pixel register’s value
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Yamagaya Shohei 2019/12/23 Year-End-Meeting

Avoid “non responsive"

14

  • Before the tuning to target, the one to 800[e] was done.

  • > This process can reduce non-responsive pixels

Threshold Noise floor Threshold Pixels with a threshold below noise floor are decreased!

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SLIDE 15

Yamagaya Shohei 2019/12/23 Year-End-Meeting

Avoid “non responsive”

15

200 400 600 800 1000 1200 1400 1600 1800 2000 target threshold

4 −

10

3 −

10

2 −

10

1 −

10 1 # pixels

no response no response

200 400 600 800 1000 1200 1400 1600 1800 2000 target threshold

4 −

10

3 −

10

2 −

10

1 −

10 1 # pixels

no response no response

Target threshold [e]

Ratio of untuned pixels

Ratio of “non responsive pixels”

normal tuning Tuned initial state