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