Development of Large-Area LGADsFor Space Application
A. Bisht 1,2 † G. Borghi2 M. Boscardin2 M. Centis Vignali2 F. Ficorella2
O. Hammad Ali2 G. Paternoster2
1Universita degli Studi di Trento, Italy
2Fondazione Bruno Kessler, Italy
38th RD50 Workshop, 2021
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Introduction: Requirements of Time Resolving Tracking in space Experiments
Velocity resolution crucial forisotopic measurements:
δM
M=δp
p+ γ2
(δβ
β
)
• d and anti-d
• 3He/4He
• 6Li/7Li
Advantages of 4D tracking• Identification of back-scattered
hits from calorimeters.
• Ghost hits in “Si-MicroStrip”detectors.
• Time-of-flight (ToF) measurement
• Improved e/p identification
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Space LGADs: Need for large channel?
• Rate is not as high as in HEP
• Power Issue→ Reduce the number of channels
• “Typical” Silicon sensor: strip, ∼ 100µm pitch, 50-60 cm long (∼ 1 cm2)
• Timing (∼ 50-60 ps) is desired.
• Low Earth Orbit Experiments→Radiation is not an Issue
Solution?
LGADsExcellent Timing resolution!!
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Specification of the DUT
LGAD Pads
• Pads with different area: 1 ×1 mm2, 2.5 × 2.5 mm2, and 5× 2.5 mm2
• Metal frame
1 × 1 mm2 2.5 × 2.5 mm2 5 × 5 mm2
4 cm3.5 cm
LGAD Strips
• 3.5 cm long, 192 µm pitch(Total 16 strips)
• Strip 15 is with single longopening
• Strip 13 is with multi openings
• The metal openings are 8.5mm apart
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MoVeIT Production
Standard LGAD Technology Active Thickness: 45 µm
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Experimental Setup: TCT
• Particulars TCT setup
• Particulars broadband amplifier (53 dB)
• IR and Red Laser
• Beam Monitor
• 3 channel passive readout board
• V(t).
• Baseline Correction.
• Non measuring strips are terminatedusing 50Ω termination.
• Collected charge is given as:
Q =
∫ tf
t0
I(t)dt,
• Normalization of charge/amplitude.
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Gain Comparison
Gain Definition:
Gain =QLGAD
QPIN
0 50 100 150 200
(V)biasV
0
5
10Gai
n
MoveIT Wafer-13 Pads, IR
2 1 mm×1
2 2.5 mm×2.5
2 5 mm×5
MoveIT Wafer-13 Pads, IR
2 1 mm×1
2 2.5 mm×2.5
2 5 mm×5
0 50 100 150 200
(V)biasV
0
5
10Gai
n
MoveIT Wafer-14 Pads, IR
2 1 mm×1
2 2.5 mm×2.5
2 5 mm×5
MoveIT Wafer-14 Pads, IR
2 1 mm×1
2 2.5 mm×2.5
2 5 mm×5
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1 × 1 mm2 2.5 × 2.5 mm2 5 × 5 mm2
Charge at Vbias = -200 V
Amplitude at Vbias = -200 V
Significant non-uniformity of amplitude in pad with large area.
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Big Pad Anomaly
Amplitude Map
0 1000 2000 3000 4000 5000 6000
m)µX-Axis (
0
1000
2000
3000
4000
5000
6000
m)
µY
-Axi
s (
2
4
6
8
10
12
Am
plitu
de (
mV
)
Rise-Time Map
0 1000 2000 3000 4000 5000 6000
m)µX-Axis (
0
1000
2000
3000
4000
5000
6000
m)
µY
-Axi
s (
0
0.2
0.4
0.6
0.8
1
1.2
1.4
(ns
)ris
eτ
• Significant decrease in amplitude towards center in non metallized big pads.
• Increase in rise-time towards center for the same data.
• This might be a resistive effect of the implant.
• It needs to be studied in a systematic way with some modelling and simulations.
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Resistance Modelling
• Resistance of implant with metal frame.
• Maximum resistance at the center of the pad as seen by the signal.
• Similar shape observed in the experimental data.
Need more in depth study to fit experimental data.
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Hit Map of Strip (single opening)
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Charge and Amplitude v/s Strip Length
0 10 20 30Strip Length (mm)
50
55
Nor
m. C
harg
e (a
rb.)
MoveIT Wafer 13 LGAD IR
Strip 15
Strip 13
0 10 20 30Strip Length (mm)
14
16
18
20
22
Nor
m. A
mpl
itude
(ar
b.)
MoveIT Wafer 13 LGAD IR
Strip 15
Strip 13
• Non uniformity in charge collection.
• Both strips shows similar trend
• Non-uniformity in the gain layer (sensors in the outer edge of wafer)
• Amplitude increases with increase in distance from readout
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Strip 15: Ratio & Rise Time
• Ratio of amplitude and charge shows a linear rise along the strip length.
• Read-out is from the left pad for both strips.
• Decrease in rise time along the strip length for both strips.
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Ratio (Amplitude/Charge)
0 10 20 30Strip Length (mm)
0.25
0.3
0.35
Am
plitd
ue/C
harg
e (a
rb.)
MoveIT Wafer 13 LGAD IR
Strip 15
Strip 13
Reflection
• The ratio increases as we move away from the readout pad.
• The ratio of amplitude and charge shows consistent behaviour for both strips.
• Change in signal shape.
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Summary and OutlookThe single channel big pads and long strips from the standard LGAD technology werestudied using the IR-TCT.
• Change in signal shape has been observed in the big pads.→ Resistive effect of implant
• Significant change in the amplitude along the strip.
• The rise time changes in both big pads and long strips.→ Signal reflection might be a cause for different signal shape. We need to study theeffect of reflection in more detail and find an optimal solution to corrected it (ifnecessary).
• New production batch devoted to space application.→ Will be used to study these effects and other parameters.
• Upcoming Timing setup (90Sr).
Acknowledgment: We would like to thank MoVeIT group.
Thank you for your attention
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