11th RD50 Workshop, CERN 12-14 Nov. 20071
Results with thin and standard p-type detectors
after heavy neutron irradiation
G. Casse
11th RD50 Workshop, CERN 12-14 Nov. 20072
OUTLINE:
• Introduction
• Motivations for using p-type substrates in high radiation environments
• Motivations for investigating thin (140µm) vs standard (300µm) detectors
• Charge Collection Efficiency results up to 1x1016 n cm-2
• Summary and future work
11th RD50 Workshop, CERN 12-14 Nov. 20073
N-side read-out for tracking in high radiation environments?
Schematic changes of Electric field after irradiation
Effect of trapping on the Charge Collection
Efficiency (CCE)
Collecting electrons provide a sensitive advantage with respect to holes due to a much shorter tc. P-type detectors are the most natural solution for e collection on the segmented side.
Qtc Q0exp(-tc/tr), 1/tr = .
N-side read out to keep lower tc
11th RD50 Workshop, CERN 12-14 Nov. 20074
Effect of trapping on the Charge Collection
Distance
Qtc Q0exp(-tc/tr), 1/tr = .
After heavy irradiation thin detectors should have a similar CCE as thicker ones.
vsat,e x tr = av
av (=1e14) 2400µm
av (=1e16) 24µm
From G. Kramberger et al., NIMA 476(2002), 645-651.
e = cm-2/ns
h = cm-2/ns
11th RD50 Workshop, CERN 12-14 Nov. 20075
Silicon miniature microstrip detectors and irradiation
Mini microstrip, ~1x1 cm2, 128 strips, 80 µm pitch, designed by Liverpool and produced by Micron on 300µm and 140µm thick wafers.
RD50 mask (see: http://rd50.web.cern.ch/rd50/)
Irradiation and dosimetry:TRIGA Mark II research reactor Reactor Centre of the Jozef Stefan Institute, Ljubljana, Slovenia
11th RD50 Workshop, CERN 12-14 Nov. 20076
Method: measure the charge collection of the segmented devices using an analogue electronics chip (SCT128) clocked at LHC speed (40MHz clk, 25ns shaping time). The system is calibrated to the most probable value of the m.i.p. energy loss in a non-irradiated 300µm thick detector (~23000 e-).
Fast electron source: 90Sr, triggered with scintillators in coincidence.
11th RD50 Workshop, CERN 12-14 Nov. 20077
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
0 200 400 600 800 1000 1200
Bias (V)
Co
llec
ted
ch
erg
e (k
e)
After 3 10 1̂5 n/cm 2̂
After 1.6 10 1̂5 n/cm 2̂
After 1 10 1̂6 n/cm 2̂
After 0.5 10 1̂5 n/cm 2̂
Now µ-strip detector CCE measurements up to 1x1016 n cm-2!!
Results with neutron irradiated Micron detectors
11th RD50 Workshop, CERN 12-14 Nov. 20078
A correction of the result at 5x1014 n cm-2
Comparison of the measurements on 30k Micron detectors irradiated to the nominal of 5x1014 cm-2 in March 2006 and October 2007
0.0
5.0
10.0
15.0
20.0
25.0
0 200 400 600 800 1000 1200
Bias (V)
Co
llect
ed C
har
ge
(ke)
11th RD50 Workshop, CERN 12-14 Nov. 20079
Now µ-strip detector CCE measurements up to 1x1016 n cm-2!!
Results with neutron irradiated Micron detectors
0.0
5.0
10.0
15.0
20.0
25.0
0 200 400 600 800 1000 1200
Bias (V)
Co
llec
ted
ch
erg
e (k
e)
3 10^15 n/cm^2
1.6 10^15 n/cm^2
1 10^16 n/cm^2
0.5 10^15 n/cm^2
11th RD50 Workshop, CERN 12-14 Nov. 200710
Charge collection efficiency vs fluence for micro-strip detectors
irradiated with n and p read-out at LHC speed (40MHz, SCT128 chip).
0
5
10
15
20
25
30
0 20 40 60 80 100 120
Fluence (1014 neq cm-2)
Co
llec
ted
ch
arg
e (
ke
) Neutron irradiation 900V
Neutron irradiation 600V
Proton irradiation 800V
11th RD50 Workshop, CERN 12-14 Nov. 200711
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
150 200 250 300 350 400 450 500
Bias (V)
Co
llec
ted
Ch
arg
e (
ke
-)
300 microns
140 microns
6.0
8.0
10.0
12.0
14.0
16.0
18.0
0 200 400 600 800 1000 1200
Bias (V)
Co
llec
ted
Ch
arg
e (
ke
-)
300 µm thick
140 µm thick
5x1014 (?) neq cm-2 1.6x1015 neq cm-2
Comparison of CCE with 140µm and 300µm thick detectors from Micron
irradiated to various n fluences, up to 1x1016 cm-2!
11th RD50 Workshop, CERN 12-14 Nov. 200712
0.0
1.0
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10.0
0 200 400 600 800 1000
Bias (V)
Co
llec
ted
ch
erg
e (k
e)
300µm thick
140µm thick
3x1015 neq cm-2 1x1016 neq cm-2
Comparison of CCE with 140µm and 300µm thick detectors from Micron
irradiated to various n fluences, up to 1x1016 cm-2!
0
5
10
15
20
150 350 550 750 950 1150
Bias (V)
Co
llec
ted
Ch
arg
e (k
e)
300 microns
140 microns
300 micron (new irr)
11th RD50 Workshop, CERN 12-14 Nov. 200713
Ratio of the charge collected by thick to thin detectors as a function of fluence
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0.2
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0.6
0.8
1
1.2
1.4
1.6
0 200 400 600 800 1000 1200
Bias (V)
Rat
io o
f th
ick/
thin
sig
nal
5x10^14 cm -̂2
1.6x10^15 cm -̂2
3x10^15 cm -̂2
1x10^16 cm -̂2
3x10^15 cm -̂2 2nd meas.
11th RD50 Workshop, CERN 12-14 Nov. 200714
0
2
4
6
8
10
12
1 10 100 1000 10000
Eq. days @ 20 oC
Co
llect
ed C
har
ge
(ke)
500 V
700 V
900 V0
2
4
6
8
10
1 10 100 1000 10000
Eq. days @ 20 oC C
olle
cted
Ch
arg
e (k
e)
500 V
700 V
900 V
140 µm thick 300 µm thick
Annealing of irradiated dettectors after 1x1016 n cm-2
11th RD50 Workshop, CERN 12-14 Nov. 200715
0
0.2
0.4
0.6
0.8
1
1.2
1 10 100 1000 10000
Eq. days @ 20 oC
Rat
io o
f th
ick/
thin
sig
nal
500V
700V
900V
Ratio of the charge collected by thick to thin detectors as a function of the annealing
time for detectors irradiated to 1x1016 n cm-2
11th RD50 Workshop, CERN 12-14 Nov. 200716
CONCLUSIONS:P-type detectors tested up to 1x1016 n cm-2 show a extremely good signal and adequate radiation tolerance for the LHC upgrade to 10 times higher luminosity.
These measurements are the first reference measurements for highly segmented silicon detector made in planar technology (microstrip and pixel detectors) at these doses!
After heavy irradiations the CCE of thin and thick detectors becomes similar. The choice of optimal thickness can be dictated by the need of reducing the detector mass rather than increase of the signal after irradiation (at least up the remarkable dose of 1x1016 n cm-2!!).
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