High Rate Photon Irradiation Test with an 8-Plane TRT Sector Prototype

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High Rate Photon Irradiation Test with an 8-Plane
TRT Sector Prototype

• J. Valls
• For the ATLAS-TRT Collaboration

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Outline

• Goals
• FE Electronics
• Experimental Setup
• CERN X5-GIF
• Weizmann Institute Irradiation Facility
• Results
• Occupancies and Rates
• Occupancy Cross-talk
• Hit Detection Efficiencies
• Summary

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Transition Radiation Tracker
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Goals

• Characterize and study the performance of near to
  final TRT FE electronics
• Demonstrate basic operation of the detector at
  high counting rates

• Two high rate irradiation tests planned
• CERN X5 GIF
• 137Cs (662 keV photons), 0.5 MHz
• Weizmann Istitute Irradiation Facility
• 60Co (1.1 and 1.3 MeV photons), 0.5-20 MHz

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ASDBLR and DTMROC
ASDBLR Amplifier Shaper Discriminator with
Baseline Restoration
DTMROC Digital Time Measurement and ReadOut
Controller
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Web Boards
Arc-shaped PC boards

• Interface between signal from straws and FE
  electronics
• Hold the HV decoupling capacitors, HV isolation
  resistors, and input protection circuit of FE
  chips

Signal circuit
HV traces and petals
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TRT Endcap Sector Prototype
12 DTMROC (24 ASDBLR) 192 channels
8 planes x 24 straws 192 straws
Web boards
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FE Characterization

• Calibration of individual DTMROC threshold DACs
• relationship between DAC counts and
  voltages
• Calibration of individual ASDBLR channels
• relationship between input signal amplitude
  
• and discriminator thresholds

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DTMROC Calibrations
V/DAC (low1)
V/DAC (low0)
V f(DAC)
V/DAC (high0)
V/DAC (high1)
5.3 mV/DAC
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ASDBLR Calibrations

• Measure S-curves for different input signals to
  extract gain and discriminator offsets
• Threshold scans for a given input signal are
  characterized by S-curves

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ASDBLR Calibrations
Low Threshold
High Threshold
Gain
Gain
Offset
Offset
0.86 0.09 mV/eV (gain) 122 30 mV (offset)
0.07 0.01 mV/eV (gain) 99 27 mV (offset)
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ASDBLR Calibrations
Vinp 0.5 mV ( 230 eV)
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ASDBLR Threshold Spread
Offset Threshold Spread w.r.t. Nominal Threshold
(chip average)
Nominal Threshold 200 eV
12 ASDs shown
All 192 channels
? 50 eV
? 50 eV
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X5- GIF Facility
Irradiator Radioactive 137Cs photon source (662
keV)
X5 GIF Facility Test area with an adjustable
high background flux of photons, simulating high
rate background conditions
Maximum Photon Flux 107 ?/s/cm2
Hit Probability per Photon (0.2 mm Al
converter) 0.5 - 1
Charged Particle Rate 5x104 electrons/s/cm2 (LHC
106 particles/s/cm2)
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Weizmann Irradiation Area
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Weizmann Irradiation Facility
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Flex board
WEB 1
WEB 2
Special web flap configuration with analog
control
Photon Source
Straws sharing different web flaps (3 flaps per
web)
DTMROC (2 ASDBLRs) 16 straws
ASDBLR (HV Group)
Flex PCB
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Occupancy Definitions

• Straw Occupancy
• Ratio of events with at least one hit over total
  number of events
• Rates calculated from occupancies
• Hits
• LT hits at least one low threshold bit set
• LE hits at least one leading edge
• HT hits at least one high threshold bit set

(for either 1 or 3 beam crosses)
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Noise Occupancies and Rates
X5 GIF
1.0 ? 1.1 (3 BC) 130 ? 143 kHz (3 BC) (200 eV)
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Rates
Analog Monitoring Straw (MHz) Leading Edge (250 eV) (MHz) High Threshold (3 keV) (MHz)
0.5 1.4 0.8 1.0 0.2
1.0 2.4 1.2 1.6 0.2
2.7 3.6 1.2 3.0 0.5
4.7 5.2 1.4 4.4 1.0
9.4 9.6 2.8 10.3 1.8
15.0 10.5 2.8 13.7 1.9
19.0 12.0 3.4 19.5 3.1
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Energy Spectrum Shapes
Low Threshold Occupancies
High Threshold Occupancies

• Harder energy spectrum at low rates
• Softer at high rates

1.0 MHz

• Low threshold occupancies higher at low
  thresholds for low rates
• Flat at high rates

15.0 MHz
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Irradiation Area
60Co
9.4 MHz
4.7 MHz
2.7 MHz
Gamma Source Shielded (5 cm Lead)
High Rates (softer energy spectrum)
1.0 MHz
Low Rates (harder energy spectrum)
0.5 MHz
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Test-Beam Energy Spectrums
20 GeV electrons
20 GeV pions
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Energy Spectrum Shapes
0.5 MHz
1.0 MHz
Low Threshold 250 eV
2.7 MHz
4.7 MHz
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Energy Spectrum Shapes
0.5 MHz
1.0 MHz
Low Threshold 300 eV
2.7 MHz
4.7 MHz
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Cross-Talk
Ccoupl

• Conductive coupling in the straws which share the
  same decoupling capacitor
• Parasitic capacitive coupling at the end of the
  straws

Cblock
Riso
Signal return
HV filter

• Internal channel-to-channel cross-talk of the
  analog ASDBLR chip
• Cross-talk through connecting traces on the
  flex-rigid boards and web board

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Occupancy Cross-Talk
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Occupancy Cross-Talk
5 keV
7 keV
3.12.9 increase
2.72.1 increase
11 keV
Background Rate 0.5 MHz
4.02.9 increase
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Occupancy Cross-Talk
5 keV
3 keV
2.01.8 increase
Background Rate 1.0 MHz
2.01.4 increase
9 keV
2.41.3 increase
11 keV
2.61.3 increase
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Occupancy Cross-Talk
3 keV
5 keV
1.31.2 increase
Background Rate 2.7 MHz
1.4 increase
9 keV
11 keV
1.61.1 increase
1.61.1 increase
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Occupancy Cross-Talk
400 eV
250 eV
0.5 MHz
170-200 (250 eV)
140-190 (400 eV)
250 eV
400 eV
2.7 MHz
30-60 (250 eV)
20-50 (400 eV)
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HT Occupancy Cross-Talk
No Cross-Talk in High Threshold Occupancies
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Hit Detection Efficiencies

• Use calibrated internal test pulse signals
• 15 DAC ? 600 eV (50 Occ)
• 21 DAC ? 1 keV (50 Occ)
• Test pulse signals adjusted in time to arrive
  always at the same position (middle BC)
• Hit efficiency (per channel)
• fraction of events with a LE hit in a selected
  time window over total number of events

No Irradiation
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Time Over Threshold
Low Threshold 250 eV
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Time Over Threshold
Low Threshold 600 eV
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Time Distribution of LEs
15.0 MHz
1.0 MHz
4.7 MHz
19.0 MHz
2.7 MHz
9.4 MHz
Low Threshold 250 eV
Loss of width from undershoot and pile-up
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Time Occupancies

• Time occupancies are defined as the ratio between
  time occupied by LEs in 3 BCs over total time

Low Threshold
15.0 MHz
1.0 MHz
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Hit Detection Efficiencies
Low Threshold
Test Pulse 600 eV
Test Pulse 1000 eV
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Hit Detection Efficiencies
Lab Measurements 18.6 ns, 2.8 keV 37.2 ns, 3.9
keV 55.8 ns, 3.9 keV
Input Test Pulse 600 eV
Test Beam
These Measurements
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Hit Detection Efficiencies
Test-Beam Drift-Time 2.5 ? Efficiency
Input Test Pulse 1000 eV
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Hit Efficiencies (Summary)
Counting Rate (MHz) Hit Efficiency () Test-Beam Drift-Time (2.5 ?) Efficiency ()
0.0 100.0 ? 0.3 86
0.5 96.8 ? 2.6
1.0 96.4 ? 2.2
2.7 92.6 ? 2.5
4.7 89.8 ? 2.6
6.5 75
9.4 69.7 ? 3.0 66
12.5 61
15.0 59.1 ? 2.9
17.4 52
19.0 37.9 ? 2.6
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Summary (part 1/3)

• Noise ocupancies (250 eV, middle BC)
• 0.5 ? 170 kHz
• Occupancies under irradiation (250 eV, middle BC)
• 3.6 ? 1.4 MHz (data) ? 0.5 MHz
  (monitor straw)
• 13.0 ? 5.2 MHz (data) ? 4.7 MHz
  (monitor straw)
• 26.3 ? 10.5 MHz (data) ? 15.0 MHz (monitor
  straw)

• Background energy shapes similar to those from
  past electron test-beams for most of the data.
  Harder energy spectrums for data taken at low
  rates (0.5-1.0 MHz)

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Summary (2/3)

• Occupancy cross-talk
• Confirm results from previous X5 GIF test
• Low threshold occupancies (250 eV)
• 0.5 MHz ? 170 - 200 for 5 - 11 keV signals
• 1.0 MHz ? 100 - 160 for 5 - 11 keV signals
• 2.7 MHz ? 30 - 60 for 5 - 11 keV
  signals
• High threshold occupancies slightly affected
  (lt10)

• Hit detection efficiencies
• Up to 5 MHz ? gt 90
• Rapid decrease for gt 5 MHz

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Thanks..
Weizmann Institute Of Science

• George Mikenberg
• Meir Shoa
• Staff irradiation unit
• Gideon Ben Moshe
• Shaul Ovadya