Mathieu Benoit

Occupancy studies for CLIC_ILD inner layer and Update on Digitization: Tuning with data, Lorentz

angle effects

Mathieu Benoit

Outline

• First results on Occupancy for the inner layer of CLIC_ILD Following design from workshop

• Inclusion of Magnetic Field effects in Digitization

• DESY 2-4 GeV electrons data using Timepix single chip card

(sub) Barrel 0 orLeft Outer barrel

(sub) Barrel 1 orLeft inner barrel

(sub) Barrel 2 orCentral barrel

(sub) Barrel 3 orRight inner barrel

(sub) Barrel 4 orRight Outer barrel

Simulation• For Now simulation of layer 0+1, results here for layer 0 , the most critical at r=29

mm• Simulation with Livermore Low EM Physics list

– Max Step-size in Silicon =1 um– Include detla rays , fluorescence

• Geometry : – Magnetic Field = 4 T– Berylium beam pipe (600um)– Inside beampipe : air at 1 e-2 bar

• Timepix-Like digitization– 20x20um pixels– 50 um thickness– Resistivity = 10 kOhm cm– Threshold = 500e

– Lorentx angle not taken into account here

• Plots are preliminary, need to include actual gap in phi – Module 90 (top right) missing, being processed

mini workshop on engineering aspects of the CLIC vertex detectors

5

Barrel layout (layer 0+1)

• To ensure hermeticity, layer 0+1 need to be placed closer to IP than MC model– Option 1:

• Radius(layer 1) = 29 mm (31mm before)• Radius(layer 2) =30.87mm (32.87mm before) • To avoid volume overlap, slightly tilt the ladders (here 1.5°)

– Option 2: • Tilt sensors by lorentz angle (ex: 15 deg)• Add 1-2 ladders (here , 2-> Icosagon !)• Move back to larger radius (here 31.221 mm)

15/03/12


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Barrel layout (layer 0+1, option 1)

An option to option 1: Shifting layer 2 vs layer 1 (here 1mm), ladder per ladder to avoid overlapping gaps

Single hitsDouble layer, holding on the same mechanical structure not shown here

15/03/12

Event Display (1k primary tracks)

HitMap in Layer 0

Hitmap Layer 0 (per Train per Chip)

Occupancy per module in layer 0%

Occupancy per module in layer 0 (polar view)

%

Cluster size subbarrel 0 layer 0

HitMap in Layer 1

HitMap (per Train per mm2)

Occupancy per module in layer 1%

Occupancy per module in layer 0 (polar view)

%

Occupancy Simulation

• 2 Scenario : – 20 um pixels, same geometry + B-Field effect, layer

0-5

– 25 um pixels, layer back by 4mm in r + B-field effects layer 0-5

• In both scenario we need to add hadronic components, disks


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Lorentz angle• Lorentz angle depends on mobility which depends on Electric

field and eventually on dopant concentration

• In a 50um 10kOhmcm p-type wafer, 10V bias, E≈[1600,2700]V/cm– Vary with resistivity, bias voltage

• In a planar sensor, E is proportional to V applied– V applied is proportional to thickness2 (Full depletion voltage)– For thin sensor, at full depletion voltage, Electric field is very low– To be investigated : How much over Full depletion can we apply voltage

15/03/12

Lorentz angle effects in Digitization

• I have added as an option in the digitizer to tak into account the Magnetic field in the motion equation of the charge in the sensor.

– The Lorentz angle is calculated at each integration step taking into account :• Local mobility and electric field • Hall Scattering factor

Lorentz angle effects (0 degrees incidence, B=4T)

Lorentz angle effects (75 degrees incidence, B=4T)

Lorentz angle effects (0 degrees incidence, B=4T), tilted by Lorentz angle

Lorentz angle effects (Cluster Size)

!!

Lorentz angle increases cluster size (in average) -> Increase occupancy

DESY data with low energy (2-4 GeV) electrons

• We were allowed to join ATLAS DBM testbeam at DESY to acquire some data with Timepix using low energy electrons (2-4 GeV) (No Tracking)– 6M Frames at 100V 0 deg– 5K Frames at 0,25,50,75 deg– 5k Frames at 0deg, 5V, 10V, 50V– 5k Frames at Ikrum 25,50,100

• In average 500 clusters per frame• ToT mode

Some DESY plots (cluster size)

Conclusion

• Detailed simulation of inner layer for CLIC_ILD new design show higher occupancies than CDR numbers : – Layer is 4 mm closer than before -> Higher occupancy– Phi dependence observed in the end-of-stave chips– Next simulation to be perfomed with B-Field effects included,

larger pixels

• Lorentz angle effects have been encoded in the digitizer– Debugged using the new event display feature of the digitizer– Ready for use in occupancies studies

Mathieu Benoit

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