the cbm sensor digitizer

C.Dritsa, St.Odile, 08 September 2011C.Dritsa, St.Odile, 08 September 2011 11

The CBM sensor digitizerThe CBM sensor digitizer

C.DritsaC.DritsaIKF-Frankfurt, IPHC-StrasbourgIKF-Frankfurt, IPHC-Strasbourg

(now at JLU Giessen)(now at JLU Giessen)


OutlineOutlineMotivationMotivationModel requirementsModel requirementsDescription of the modelDescription of the model

Important definitions (1)Important definitions (1)charge generationcharge generationcharge sharingcharge sharing

EvaluationEvaluationImportant definitions (2)Important definitions (2)Comparison with experimental dataComparison with experimental data

OutlookOutlook


MotivationMotivationDigitizer model developed in order to allow Digitizer model developed in order to allow simulating the CBM-MVD.simulating the CBM-MVD.

In collaboration with the In collaboration with the IPHC-PICSELIPHC-PICSEL group in Strasbourg and the group in Strasbourg and the IKF-MVDIKF-MVD group in Frankfurt.group in Frankfurt.

It was inspired by a detector response It was inspired by a detector response model developed for the ILC vertex tracker model developed for the ILC vertex tracker – M. Battaglia, “Response simulation of CMOS pixel sensors for M. Battaglia, “Response simulation of CMOS pixel sensors for

the ILC vertex tracker” , Nuclear Instruments and Methods in the ILC vertex tracker” , Nuclear Instruments and Methods in Physics Research A 572 (2007) 274–276Physics Research A 572 (2007) 274–276


CBM-MVD response model requirementsCBM-MVD response model requirements

Realistic simulations allowing to simulate:Realistic simulations allowing to simulate:– Cluster properties: size, shape Cluster properties: size, shape – pixel sizepixel size– vary number of ADC channels of the readoutvary number of ADC channels of the readout– particles impinging with high incident anglesparticles impinging with high incident angles– noise, fake hitsnoise, fake hits

Rapid simulation featuresRapid simulation features– simulate collision pile upsimulate collision pile up– delta electrons (of concern in CBM) delta electrons (of concern in CBM) – fast, allowing high statistics simulationsfast, allowing high statistics simulations


Spirit of the modelSpirit of the model

Challenge:Challenge:– Charge carrier transport process too complex Charge carrier transport process too complex

and slow for simulation and slow for simulation

Solution:Solution:– Parameterization of the sensor responseParameterization of the sensor response– Use experimental dataUse experimental data– GEANT provides only entry and exit GEANT provides only entry and exit

coordinates of the particle in the volumecoordinates of the particle in the volume– no dE/dx from GEANTno dE/dx from GEANT


Reference dataReference dataData acquired at CERN/SPS with pions 120 GeV/cData acquired at CERN/SPS with pions 120 GeV/c

Sensor under test: MIMOSA17Sensor under test: MIMOSA17– AMS 0.35AMS 0.35– standard low resistivity epitaxial layerstandard low resistivity epitaxial layer– analogue output (12 bit charge resolution)analogue output (12 bit charge resolution)– 30 30 µµm pixel pitchm pixel pitch

Particle incident angles 0-75 degreesParticle incident angles 0-75 degrees(90 degrees is parallel to the sensor plane)(90 degrees is parallel to the sensor plane)


The digitizerThe digitizer


24

025

iiQQ

MP

V

Important definitions (1)Important definitions (1)

Landau

Lorentz


Other featuresOther features

Simulated by random sampling of a Simulated by random sampling of a distribution following a Gauss law with distribution following a Gauss law with adjustable µ, adjustable µ, σσ

mean=0mean=0

σσ =15 electrons =15 electrons

Number of ADC bits adjustableNumber of ADC bits adjustable 12 bits12 bits

Pixel pitch adjustablePixel pitch adjustable 30 µm30 µm


The model: InputThe model: InputThe charge of the cluster The charge of the cluster is taken by random is taken by random sampling of the sampling of the experimental distribution experimental distribution for 25 pixelsfor 25 pixels

0 degrees incident angle

The charge distribution The charge distribution among the pixels in the among the pixels in the cluster is based on a 2D cluster is based on a 2D Lorentz distribution Lorentz distribution (derived from the 1D)(derived from the 1D)

0 degrees incident angle

Landau:Accumulated charge on 25 pixels

The simulation of inclined particles is derived by this initial parameterization.


The model: charge generationThe model: charge generation

QQ00, l, l00 : known : known

lincl: provided by : provided by GEANTGEANT0

0 l

lQQ incl

incl

inclincl lQ ,00 , lQ


The model: charge distributionThe model: charge distribution

Charge provided by Landau (25 pixels)Charge provided by Landau (25 pixels)The trajectory is divided in segmentsThe trajectory is divided in segmentsA Lorentz function corresponds to each segmentA Lorentz function corresponds to each segment

Illustration for inclined track


The modelThe model

L(xk,i,yk,i)

Charge on pixel i

Sum over segments (k)

x,y-coordinatesof pixel i Pixel pitch

LorentzAmplitude

Lorentzwidth

x,y-coordinatesof segment k


EvaluationEvaluation


Important definitions (2)Important definitions (2)

Number of PixelsAc

cum

ulat

ed c

harg

e (M

PV)

Q1 Q2

Q3

Q1>Q2>Q3…

Qi

Q1 Q2

Q3

Q1

Q1+Q2

Q1+Q2+Q3

Q1+Q2+…+Qi

Qi<0(i~N)

1 2 3 N…

The accumulated charge plot describes the charge sharing among the pixels of the cluster:

e.g. the seed pixel collects ~30% of the total cluster charge.

Accumulated charge plotAccumulated charge plot


Evaluation: MPV of LandauEvaluation: MPV of Landau


Evaluation: sigma of LandauEvaluation: sigma of Landau


EvaluationEvaluation

Average number of pixels/clusterAverage number of pixels/cluster


Evaluation: shapeEvaluation: shapeSimulation Experimental data


Summary and outlookSummary and outlook

Digitizer model developed for the CBM-Digitizer model developed for the CBM-MVD and successfully tested with MVD and successfully tested with experimental data.experimental data.

Model was successfully tested on High-Model was successfully tested on High-Resistivity sensors (M.Domachowski)Resistivity sensors (M.Domachowski)

Successfully tested on neutron irradiated Successfully tested on neutron irradiated sensors (M.Domachowski)sensors (M.Domachowski)

Simulation of MIMOSA-26 data Simulation of MIMOSA-26 data sparcification in process (Q.Li)sparcification in process (Q.Li)


AcknowledgmentsAcknowledgments

Thanks to:Thanks to:

the IPHC-PICSEL group and the IKF-MVD group.the IPHC-PICSEL group and the IKF-MVD group.

In particular:In particular:

IPHC:IPHC: J.Baudot, M.Goffe, R.DeMasi, M.Winter J.Baudot, M.Goffe, R.DeMasi, M.Winter

IKF:IKF: M.Deveaux, M.Domachowski, Q.Li, J.Stroth M.Deveaux, M.Domachowski, Q.Li, J.Stroth


BackupBackup


High-Res MAPS: Measurement vs. simulation

0 5 10 15 20 250

100

200

300

400

500

600

700

800

900A

ccum

ulat

ed c

harg

e [e

- ]

Number of pixels

Measurement Simulation

Simulation of irradiated MAPS in CBM-Root Melissa Domachowski - CBM Collaboration Meeting, Dresden 2011

Simulation of HR-MAPS with the MVD-digitiser: OKSimulation of irradiated MAPS: OK

Melissa Domachowski


Particle yieldsParticle yields

the cbm sensor digitizer

Documents

charge resolution30

charge distributioncharge

charge generationq0

inputthe charge distribution

experimental distribution

motivationdigitizer

detector response model

cbm sensor digitizerc