Pulse Shape Simulation for Germanium Detectors · hitZ h1 Entries 21285 Mean 2.258 RMS 1.048 Radius...

Nov. 10, 2008

Jing Liu @ GERDA Collab. Meeting, Gran Sasso

Pulse Shape Simulation for Germanium DetectorsAn Overview

MaGe Pulse Shape Simulation Force

Nov. 10, 2008 Jing Liu @ GERDA Collab. Meeting, Gran Sasso 2/19

Why we need it

γ

γ

Multi-site event in one piece of cake

Multi-site event in unsegmented detector

We need pulse shape analysisAND

Good signal & background samplesto train PSA method

Andverify discrimination efficiency


Why we need it

DEP of 2.6 MeV

DEP

Single Compton Scattering events

h1Entries 847515Mean 2.6RMS 0.9211

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trie

s

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hitR h1Entries 847515Mean -0.0004349RMS 0.838

Z (cm)-1 -0.5 0 0.5 1

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trie

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h1Entries 847515Mean -0.0004349RMS 0.838

hitZ


Radius (cm)0 0.5 1 1.5 2 2.5 3 3.5

En

trie

s

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hitR {abs(segEnergy[1][0]-1592)<1.} h1Entries 21285Mean 0.5124RMS 0.8097

Z (cm)-1 -0.5 0 0.5 1

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trie

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hitZ {abs(segEnergy[1][0]-1592)<1.}

DEP

DEP

0νββ

0νββ


How to do it

Ge Detectore h

γ1. Simulate Edep using MaGe

2. Group hits according to limits on bandwidth and sampling rate, determine the amount of e-h pairs and their original position

3. Calculate electric field

4. Calculate the drift of charge carriers

5. Calculate induced signals in the electrodes based on the drift trajectory and the weighing potential

6. Fold in effects of electronics, eg. noise, bandwidth, decay time, etc.


Group hits Stolen from Reyco Henning

1.02 MeV electron


Electric field – please refer to Daniel’s talk for greater detail

Ge Detectore h

γ

E

ερ

=⋅∇ E

Poisson’s Equation:


Calculate the drift :: Mobility


Calculate the drift :: Crystal structure


Calculate the drift :: Mobility parameterization


Calculate the drift :: Determine anisotropy in any direction

Simulation


Calculate the drift :: Drift trajectories


Numbers of signals recorded by different segments

1

2

3

4

5

6

65

432

1Nev

t

Phi (degree)


Determine the crystal axis orientation using the occupancy plot

Nev

t

Phi (degree) Angle between axis and boundaryDiff

eren

ce b

etw

een

MC

& d

ata


Signals induced in the electrodes – please refer to Daniel’s talk for detail

Cha

rge

[a.u

.]

Time [ns]

trajectory1

2

1

2

( )

cityDrift velo :)(ectoryDrift traj :)(

field potential, Weighting:,

depositionenergy by

createde/h ofNumber :)(

)())(()(

))(()()(

/

/

/

tvtr

E

E

EN

tvtrEENtI

trENtQ

ww

dep

dephe

wdephe

wdephe

−−−

−

=

−=

r

r

ϕ

Ramo’s Theorem:

ϕ


Ideal pulse shape

1

2

3

4

56


Simulation of decay time


Fold in bandwidth


Let’s add some noise


Summary, Acknowledgement & Outlook

• Now we can simulate the whole signal formation process in germanium detector system!

• Many thanks to Majorana MC group!

• Validation of the simulation on the way

• Pulse shape analysis follows


Find back 0νββ events occur between two segments


Calculate the drift :: Parameters fitted with experimental data


Calculate the drift :: Electron drift velocity

Effective electron mass tensor:

Fraction of electrons in certain directions


Calculate the drift :: Hole drift velocity


Pulse rise time

Pulse Shape Simulation for Germanium Detectors · hitZ h1 Entries 21285 Mean 2.258 RMS 1.048 Radius...

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