Transcript PSI_seu

Preliminary PSI SEU Studies
• Study SEU effects by measuring the BER of the
link in p/p beams at PSI.
• Measure the SEU rate as a function of current in
PIN diode <I(PIN)>
• SEU rate decreases with increasing <I(PIN)> 
SEU occurs in PIN diode.
• SEU occurs when energy above DORIC threshold
is deposited in active region of PIN diode.
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PSI Beams Used
p (p) contamination in p(p) beam <~10%
Particle
Momentum (MeV/c)
Flux (cm-2s-1)
p
300
2.9 106
p
350
5.7 107
p
405
1.2 108
p
465
1.2 108
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Flux Measurements
• Flux measured with rate in counter with 2mm diameter
scintillator attached directly with optical grease to small
Hamamtsu PM. Flux corrected for deadtime due to
discriminator pulse width (100ns).
• Flux checked for one run by Al foil activation analysis.
Measure 24Na activity with Ge(Li) counter. Agreed to
within 10 %.
• At low beam intensity we checked rate in small counter
with rate in large counter, Consistent with measured beam
profile.
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BER Scans
1.0E+00
1.0E-01
1.0E-02
1.0E-03
1.0E-04
BER
1.0E-05
No Beam BER
No Beam 90% c.l.
405 MeV pi/p F=5 10**6
405 MeV/c pi/p F=1.210**8
300 MeV/c pi/p F=2.9 10**6
1.0E-06
1.0E-07
1.0E-08
1.0E-09
1.0E-10
1800
90% c.l. no errors in 7200s
1.0E-11
1.0E-12
10.0
100.0
1000.0
<I(PIN)> mA
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SEU Analysis(1)
• For <I(PIN)> above 30 mA there is no measurable BER
with beam off.
•  BER above this value is due to SEU effects.
• BER decreases with <I(PIN)>  SEU occur in analogue
part of system. Sensitive volume of PIN (350 mm diameter,
15 mm thick) >> sensitive volume of transistors.
dominant SEU is due to energy above threshold being
deposited in sensitive volume of PIN.
• For the same beam type/momentum the SEU rate scales
with luminosity.
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SEU Analysis(2)
• There is no value of <I(PIN)> in the range explored for
which the SEU rate is zero.  must accept a finite SEU
rate in our TTC system.
• To compare different beam particle/momentum/flux(F)
define a SEU cross section as sSEU=BER/F
• sSEU correlates with sTOTAL
• Shape of sSEU versus <I(PIN)> similar for different beam
momenta/particle type.
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SEU Cross Sections
1.00E-14
405 MeV/c pi+
2
s (cm )
1.00E-15
300 MeV/c pi+
1.00E-16
465 MeV/c p
350 MeV/c pi+
1.00E-17
1.00E-18
0
50
100
150
200
250
300
350
400
<I(PIN) mA>
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SEU Analysis(3)
•
Large sSEU at 300 MeV/c correlates with total cross
sections. Other ratios do not scale with sTOTAL
• Need detailed SEU calculations (Huitenen) to understand
results..
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Particle
Momentum
(MeV/c)
sTOTAL
p
300
196.4
p
350
127.5
p
405
71.3
p
465
26.3
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ATLAS Implications(1)
• Can use this data to predict BER for ATLAS
operation at any flux. Convolute sSEU with
spectrum
dN

BER  s SEU ( p)
dp
dp
– Model #1: pessimistic. Take sSEU from momentum
with largest value of sSEU (300 MeV/c).
– Model #2: guess. Take average from p at 3 different
momenta.
– Model# 3: Realistic. Requires detailed simulation
(Huitenen) to give prediction of sSEU with momentum.
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SCT Implications.
• Minimum value of <I(PIN)>=75 mA
• Pessimistic model gives
– sSEU =3 10-16 cm-2
• SCT maximum flux (barrel layer 3)
– F= 2 106 cm-2 s-1
• Predict (worst case + pessimistic model)
– SEU = 6 10-10 s-1
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SEU and Energy Deposition
• Use simple model for DORIC to relate <I(PIN)> to
minimum energy deposition in PIN to trigger DORIC
Emin
•
•
•
•
•
•
E
 1012  I PIN  I h  eh
ew0
Emin minimum energy to tirgger DORIC (MeV)
IPIN mean PIN current
Ih hysterisis current in DORIC
Eeh energy required to create eh pair in Si (3.6 eV)
e electron charge
w0 1/RC time constant of DORIC i/p (109 s-1)
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SEU vs Emin
1.0E-14
s SEU cm
2
1.0E-15
405 MeV/c pi+
300 MeV/c pi+
1.0E-16
465 MeV/c p
350 MeV/c
1.0E-17
1.0E-18
0.0
2.0
4.0
6.0
8.0
10.0
Emin (MeV)
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Conclusions
• SEU rates measured at high fluxes.
• Significant SEU rates expected in ATLAS
• BER < 10-9 can be maintained for SCT. BER expected ~
few 10-10 . Acceptable provided frequent soft resets are
issued (~ 1 Hz).
• BER > 10-9 expected for Pixel detector. Needs study to
assess significance of this result (Pixel detector has more
robust data format for L1 triggers).
• Requires calculations from Huitenen to make accurate
predictions for ATLAS environment.
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