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ICN-UNAM
M.Sc. Javier Ruiseco
Dr. Guy Paic
M.Sc. Enrique Patiño
FCE-BUAP
Dra. Aurora Vargas
Dr. Sergio Vergara
Ing. Ricardo De Gante
INTRODUCTION

Read Out Chambers are going to be
replaced by new technology due to read
out rates.

Gas Electron Multipliers “GEMs” were
chosen to facilitate the read out rate at
50KHz.
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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GEM
1) GEM arquitecture
example
3) GEM’s foil.
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
3) A closer look into a
GEM’s foil.
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Why an Ammeter is needed?

Due to electron multiplication, sometimes, due to high
ionization, sparks occur, and they tend to damage
GEM’s foils.

Therefore, a current monitoring system is needed to
watch out for sparks without introducing noise to the
GEM amplification!.
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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The Ammeter
First Prototype: Microcontroller
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Disadvantages
 Microcontroller’s ADC
resolution (0 - 0.6V)
 Greater noise induction
 Programming In Situ
 Fixed sampling rate
 The 8 or 12 channels are on
the same PCB
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Ammeter: Second Prototype
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3
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Advantajes of the
second prototype:
-Introduces an FPGA
as central
processing, which
controls all channels.
-Sampling rate can
be easily
reconfigured.
-Each channel on a
single daugther
board.
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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GBTx
 Bidirectional
radiation
tolerant chip.
 Provides:
• Timming &
Trigger Control
• DAQ
• Slow Control
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Our DAQ System
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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1.
FPGA
2.
WiFi module
3.
Lemo connector board
1
2
3
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Tests and Results

Connected the ammeter in series on Gem’s
Top Layer 1.
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Thick GEM with Saturated
Voltages

On our TGEM, this values are the
maximum to prevent damaging the
GEM.
 Drift: -1630V
 Top1: -1600V
 Bottom1: -900
 Top2: -880V
 Bottom2: 0V
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Monitoring
Note: 23k samples ~= 1 hour
Duration of test: aprox. 2 hours
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Osciloscope Detection with this
Configuration
• The noise produced by the ammeter connection is so low that it cant be
measured.
With ammeter; 100mV/div
No ammeter; 500mV/div
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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
Spark Detection
Sparks detected
by ammeter and
we could hear
the sound they
produced
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Calibrating the Ammeter to Improve its Offset
Vo1=𝑉𝑖𝑛 ∗ 0.151487
𝑉𝑜1
𝑉𝑜2 =
2
𝑉𝑜3 = 𝑉𝑜2 ∗ 5
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Test

Vin tested: 2mV, 5mV, 10mV, 50mV, 500mV, 1V,
5V
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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
Magnifying first three
cases(2mV,5mV,10mV):
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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ADC Characterization
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Average ADC noise: 17.5nA
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Conclusions

The noise produced by the ammeter
connection is so low that it cant be
measured (TGEM), this is important.
 ADC (16bits)
The ADC has an internal noise of
11.46 counts.
 Ammeter resolution 3nA
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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Future Work

Test the ammeter with the GEMs at
Frankfurt.

Gain the project approval.
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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THANKS
M.Sc. Javier Ruiseco Lopez, Taxco, Gro. Octubre
2015
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