Position resolution for the CMS Barrel Pixel Detector after irradiation Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy Enver Alagöz on behalf of CMS Pixel Testbeam collaboration 11th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD08) 1 - 4 October 2008 Siena, Italy
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Position resolution for the CMS Barrel Pixel Detector after irradiation
Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy
Enver Alagöz
on behalf of CMS Pixel Testbeam collaboration
11th Topical Seminar on Innovative Particle and Radiation Detectors(IPRD08) 1 - 4 October 2008 Siena, Italy
Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy 2
• 3-D Tracking with 66 M pixels
• Barrel layers at radii: 4.4 cm, 7.3 cm and 10.2 cm
• Pixel cell size: 100x150 μm2
• Pixel sensor thickness: 285 μm
• ~ 1 m2 Silicon in 3.8T fieldpixel module
The CMS Pixel Detector
Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy
Motivations
•At the innermost CMS pixel barrel layer, radiation exposure expected to be 3x1014 neq/cm2/year at the full LHC luminosity (1034 cm-2 s-1)
•For the first time the CMS pixel barrel sensors with the final dimensions (100x150x285 µm3) and the final readout chip were tested in magnetic field.
•Charge collection
•Leakage current and damage rate
•Hit reconstruction algorithm and eta correction
•Analysis procedure
•Position resolution3
Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy
Experimental Setup
• Telescope fully equipped with unirradiated pixel sensors• new PCB for the irradiated samples• Two peltier cooling elements and chiller• Nitrogen gas flushed into the cooling box• 2x6 mm PIN diode trigger
Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy
Leakage Current vs Fluence
]-2 cmeq
Fluence [n0 0.2 0.4 0.6 0.8
1510!
Leakag
e C
urr
en
t [A
]
0
5
10
15
20
25
30
-610!
Leakage currents (Ileakage) - at 200V - at 263 K
8
Ileakage ! !
Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy
Leakage Current Damage Rate
]-2 cmeq
Fluence [n0 0.2 0.4 0.6 0.8
1510!
]-1
[A
cm
"
0
10
20
30
40
50-18
10!
9
RD48 (ROSE)
![Acm!1] =Ileakage[A]
Volume[cm3] · ![neqcm!2]
! = (3.99± 0.03)! 10!17Acm!1
independent of fluence as expected
Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy
Vertical Coordinate
Hit Reconstruction
10
xcenter
xhit
Winner
Wx
T1/2
qfirst
qlast
L
xhit = xcenter +qlast ! qfirst
qlast + qfirst|LorentzShift|! 1
2LorentzShift
• Pitch is 100 µm• No rotation α = 0• T is thickness
• Lorentz Shift = T x tan(θL)• Wx = T x tan(α) + Lorentz Shift
•This algorithm is used only for the unirradiated sensor
Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy
Analysis procedure
Cuts:1) Cluster charge < 50000 electrons2) Fiducial cut3) One hit per ROC per event4) Cluster of size 2 pixel for the telescope ROCs5) Cut on the correlation offset
Alignment:7) Least-square fit to 4 points in telescope and extrapolate the prediction from the fit8) Get residuals for the test sensors
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!total =!
!2telescope + !2
DUT
Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy
Position resolution
χ2
Prob(χ2, 2)
- new sensor - 200V bias- 3T- two pixels- pitch 100 µm
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Residual [mm]-0.1 -0.05 0 0.05 0.1
0
50
100
150
200 !total ! 9µm
Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy 13
Eta correction
Xhit = XL + F(!) · pitch
F(!) =
! eta!1 "(!)d!
! 1!1 "(!)d!
Enver Alagoz, IPRD08, 1-4 October 2008, Siena, Italy 14