quad module testing 18 th january 2013 kate doonan university of glasgow

QUAD MODULE TESTING18th January 2013Kate Doonan

University of Glasgow

Quad Module: 200μm ROC• Chip ID 1 – no longer working

due to accidental damage. Bonds will be checked

• Chip ID 3 – not working: no RX signal. Bonds will be checked.

• Chip ID 4 – not wire-bonded yet

• Chip ID 2 – Working: Tuned to 3200e and 1600e thresholds Working Chip

2

Chip ID 2 Characterisation• Biased to -100V at room temperature

• Module kept from heating by constant airflow from fan from the side

• Kept from light exposure using dark box

• Leakage current 50nA in complete darkness

3

Chip ID 2: Tune to 3200e threshold• Threshold tuned to 3200e

• Best result obtained through standard TDAC-FDAC-TDAC cycle during tuning

4

• Initial TDAC tune gave better result but ToT had to be tuned

• Taken sample of pixels here to make scan shorter

Chip ID 2: Tune to 3200e threshold

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• Low Noise: 116.4e.

• Sigma of 200e is considered acceptable


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• Log Y used to look in detail at noise


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• See chip is tuned to ToT ~8 @ ref. charge of 20ke

• Again, best result obtained through TDAC-FDAC-TDAC cycle

Chip ID 2: Tune to 8ToT @ 3200e

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• Initial FDAC tune gave good ToT but altered threshold value considerably


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Noise Occupancy @ 3200e: 10 mill events

• Bias OFF

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• Mask produced for pixels with occupancy over 1,000

• Bias -100V

Noise Occupancy @ 3200e: 10 mill events

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• Bias OFF

• Some pixels exhibit crosstalk when sensor is unbiased

Crosstalk @ 3200e Threshold

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• Bias -100V

• Fewer pixels exhibiting crosstalk at -100V

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• A number of pixels are shown to be disconnected around the edges

• Will use ROOT macro to ascertain exact number of pixels that are disconnected

3200e Threshold Scan 0V – bump yield

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• Zoom into 120e region• Judging by eye, ~6,500 pixels exhibit noise around 120e giving a

yield of ~25% disconnected pixels


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Behaviour of Single Chip• Noise plots of single chip (VTT Assembly 15) at threshold of 3200e:

0V 100V

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• Threshold tuned to 1600e• Some pixels remain tuned to

threshold of 3200e • Tuning down was very quickly

done


17

• Again, low noise: 133e

• Sigma <200e


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• ToT not perfect but in correct region.• Could be improved with more

fine-tuning.


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• Bias OFF

Noise Occupancy @ 1600e

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• Bias -100V

Noise Occupancy @ 1600e

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• Chip exhibits more crosstalk at this lower threshold


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• No discernible peak around 120e

• Compare to biased assembly in next slide


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• Pixels with highest noise values are on top in occupancy plot


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• Zoom into top rows of occupancy plot

• Noise in these pixels is >500e


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• Looking at SCURVES for a sample of pixels

• HOT PIXEL

1600e Threshold Scan 0V SCURVES

Row 4, Column 14:

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• WELL-BEHAVED PIXEL


Row 261, Column 31:

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• SWITCHED-OFF/BROKEN PIXEL


Row 144, Column 13:

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Summary• Chip 2 can be tuned to threshold of 3200e and 1600e and a ToT

of 8

• ~25% disconnected pixels

• In general, this assembly behaves as a single chip assembly• Nothing to indicate otherwise

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Work yet to do …• Fine-tuning of Chip 2 to threshold of 1600e/ToT=8

• Use ROOT macro to find number of disconnected bumps on Chip 2

• Set-up Sr90 scans – beta particles should penetrate to other side to be detected in PMT for triggering

• Try Am241 scans – HITOR not bonded and it is thought that this is needed for Am241 scans

• Wire-bonding of Chip 4

• Tuning and characterisation of Chip 4

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quad module testing 18 th january 2013 kate doonan university of glasgow

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