The first results on cryogenic semiconductor detectors for advancing the LHC beam loss
monitors
Presented by
Vladimir Eremin
on behalf of Ioffe PTI (St.Petersburg)
RIMST (Zelenograd) BE-BI-BL, Cryo lab., and RD39 (CERN) teams
V. Eremin, Bari, 29.05 – 1.06.12
The new BLM arrangement
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TCT cryogenic module
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Arrangement with 5 cryogenic modules
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Inside the cryostate
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Cryostat
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The beam test area
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Charge collection
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Electron collection
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Hole drift velocity
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Collected charge in Silicon and Diamond detectors
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Sc diamond detector polarization
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Polarization time in diamond
• The polarization criteria
E(x)
x
t = 0Neff = 0 t=tpol
Neff = Ncr
Detector at:Vb = 1000VW = 500umNcr = 1e12 cm-3
ncr = Ncr x W = 1e11cm-2
Polarization time (estimation)R = 1e6 MIP cm-2 c-11MIP – 1e4 pairsCCE = 0.9
ntr = 1e4x(1-CCE)xR = 1e9 cm-2 c-1
tpol = ncr / ntr = 100 c
More details on polarization:B.Dezillie, et al. NIM A 452, 2000,p.440
Polarization by trapping:MGA (2.7eV)
σtr =1e-15cm2, Ntr=1e15 cm-3)RTTrapping time = 1e-7cDetrapping time = 1e35 cCollection time = 1e-8 s
V. Eremin, Bari, 29.05 – 1.06.12
P+ N+
Neff(t)
+_
Electric field evolution in detectors under bulk polarization
Critical time tcrE(x)
x
t = 0
tpol = C*V / {I*(1-CCE)}
At Jbulk = 1e-9 A/cm2
tpol = < 1000c !!!!Critical for deep level rich semiconductors
V. Eremin, Bari, 29.05 – 1.06.12
E(x)
x
Me Me
Neff(t)
+_
Electric field evolution in detectors under charge accumulation at the
contacts
Critical time tcr
tpol = C*V / {I*(1-CCE)}
At Jbulk = 1e-9 A/cm2
tpol = < 1000c !!!!Critical for the wide band semiconductor detectors with M-S-M structure
t = 0
V. Eremin, Bari, 29.05 – 1.06.12
P+ N+
Neff(t)+
Double side injection structures as a possible solution
E(n+) = E(p+) = 0
E(x)
x
t = 0
Critical condition: Injection at cryogenic temperatures.The best candidate – silicon P-I-N structure withhigly doped contacts.
V. Eremin, Bari, 29.05 – 1.06.12
Comparison of Surface-barrier and
P-I-N detectors
Me
Surface
Bulk
S/B detectoror M-S-M
Me
P+(boron)
Bulk
N+(phosphorus)
Me
P-I-N
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Electric field and potential at the detector entrance window
0.0E+00
5.0E+18
1.0E+19
1.5E+19
2.0E+19
2.5E+19
3.0E+19
3.5E+19
4.0E+19
4.5E+19
5.0E+19
0 50 100 150 200Depth, nm
Co
nce
ntr
atio
n, c
m-3
-4.E+04
-2.E+04
0.E+00
2.E+04
4.E+04
6.E+04
8.E+04
1.E+05
1.E+05
0 50 100 150 200
Depth, nm
Bu
ild in
fie
ld, V
/cm
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
0 50 100 150 200Depth, nm
Po
ten
tial
, V
Degenerate SiliconSi=Me
V. Eremin, Bari, 29.05 – 1.06.12
Conclusions
• Polarization could be a major drawback for Diamond and Silicon detectors operated at high counting rate at very low temperatures.
• The possible solution for Silicon detectors is a P-I-N structures with thin and abrupt highly doped contacts.
• For Diamond detectors the solution is not evident. • The modules with optimized P-I-N structures must be
studied with MIP’s laser simulator and in test beams of 2012.
Thank you for your attention
V. Eremin, Bari, 29.05 – 1.06.12
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