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

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

V. Eremin, Bari, 29.05 – 1.06.12

TCT cryogenic module

V. Eremin, Bari, 29.05 – 1.06.12

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

V. Eremin, Bari, 29.05 – 1.06.12

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