Rl

A

R fb

Cfb

Cac

+Bias

A

R fb

Cfb

A

R bf

Cfb

v0

v1v2

V0,out

V1,outV2,out

A simple detector model to describecrosstalk in segmented detectors

Bart Bruyneel, IKP Köln 2006

AGATA:

Cac = 1000pF

Cfb = 1.2pF

A (Core) = 80000

A (Seg) = 10000

(Rl = Rfb = 1G)

Small signal equivalent scheme

Z00 i0

Z22

i2

Z 11

i 1

Z02 Z 0

1

Z12

v1v2

v0 Seg–to –ground impedances Zii

Seg–to –Seg capacities: Zi,j = (sCij)-1 ; i≠j

Currents to electrodes:

Potentials at electrodes:

Small crosstalk if:

are small compared to

Segment-to-ground impedance Zii

and Core-to-gound impedance Z00

Z00 i0

Z22

i2

Z 11

i 1

Z02 Z 0

1

Z12

A

R fb

Cfb

vi

Vi,out

ACfb

V0,out

Rfb

A

AVi

ii

Miller EquivalentMiller Equivalent

Zii ~ (sACfb)-1

ACfb

V0,out

Rfb

A

AV0

i0

Cac

Cac~ 1nF

ACfb ~ 10nF

Z00 ~ (sCac)-1

ImpedanceImpedanceIn realityIn reality

A

R fb

Cfb

V0,outCac

v0

Seg

men

tsS

egm

ents

Co

reC

ore

SummaryRl

+Bias

v0

v1v2

ACfb

V0,out

Rfb

A

AVi

ii

ACfb

V0,out

Rfb

A

V0

i0

CacA

i

ACCCC

ACCCC

ACCACC

sCfbac

fbac

fbfb

fbout

1

1

1

1

v

1202

1201

0201

Core-to-Seg Segment-to-Segment

Segment-to-Core

Since Cac << ACfb, Core-to-Segment

crosstalk dominates

C0-X4 = 1.19 pF

C0-X5 = 1.16 pF

C0-X6 = 0.98 pF

C0-X1 = 0.943 pF

C0-X2 = 0.666 pFC0-X3 = 0.980 pF

Agata Agata measured capacities:measured capacities:

Core and Segment crosstalk

T020102012,

T2

T0201011,

T1

1202

1201

0201

1)1(1 v

11 :doubles

11 v

011 :singles

1

1

1

1

v

acacfbout

acacfbout

fbac

fbac

fbfb

fbout

CCxCCxACCxxC

xxi

CCCCACC

i

i

ACCCC

ACCCC

ACCACC

sC

Core normalization

Seg. normaliz.

Observed shift in segments

acac CCCC 0201 1sumSegment

-0.002

-0.0015

-0.001

-0.0005

0

0 10 20 30

CrosstalkMatrixSegments

0 10 20 300

10

20

30

Experiment

Segment sum shifts in 2-folds vs. hit pattern

Theory

Segment 1

Seg

men

t 2

Experiment

Segment 1

Seg

men

t 2

Column averages

Seg 1

Re

lativ

e s

hift

s theoryExp.

D3: problem“R

ing

2”

Ring toneighbor

Cac

1000pF800pF600pF

Core shifts in singles (experimental)R

ela

tive

sh

ifts

-5.00E-04

-4.00E-04

-3.00E-04

-2.00E-04

-1.00E-04

0.00E+00

1.00E-04

2.00E-04

0 5 10 15 20 25 30 35

Segment Number

• Most important crosstalk:

from core to segment

on the 0.16% level in reality,

0.10% explained by the model

• Segment to core crosstalk:

~ 0.03% level observed

10 times bigger than predicted

Conclusion