the first results on cryogenic semiconductor detectors for advancing the lhc beam loss monitors...
TRANSCRIPT
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