Status of the Prototype of the CBM Micro Vertex Detector

M. Deveaux, Goethe University Frankfurt for the CBM-MVD collaboration

2

Physics goals of CBM

CB

M

M. DeveauxImportant probe: Open charm

Open charm reconstruction: The challenge

M. Deveaux 3

[W. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745]

SIS18

SIS100SIS300

A collision rate of ~105/s Au+Au is required

4M. Deveaux,

Open charm reconstruction: Concept

Primary Beam: 25 AGeV Au Ions (up to 109/s)

Primaryvertex Secondary

vertex

Short lived particle D0 (ct = ~ 120 µm)

Detector 1Detector2Target

(Gold)

z

Reconstruction concept for open charm

Reconstructing open charm requires: • Excellent secondary vertex resolution (~ 50 µm)=> Excellent spatial resolution (~5 µm)=> Very low material budget (few 0.1 % X0)=> Detectors in vacuum

• A good time resolution to distinguish the individual collisions (few 10 µs)

• Very good radiation tolerance (>1013 neq/cm²)

Central Au + Au collision (25 AGeV)

5M. Deveaux

Sensors for the MVD

CBMSIS300

MAPS*(2003)

MAPS* (2012)

MIMOSA-26

Binary, 0

Single point res. ~ 5 µm 1.5 µm 1 µm 4 µm

Material budget < 0.3% X0 ~ 0.1% X0 ~ 0.05% X0 ~ 0.05% X0

Rad. hard. non-io. >1013 neq 1012 neq/cm² >3x1014 neq >1013 neq

Rad. hard. io > 3 Mrad 200 krad > 1 Mrad > 500 krad

Time resolution < 30 µs ~ 1 ms ~ 25 µs 110 µs

Optimized for one parameter Current compromise

Monolithic Active Pixel Sensors(MAPS, also CMOS-Sensors)

• Invented by industry (digital camera)• Modified for charged particle detection

since 1999 by IPHC Strasbourg • Also foreseen for ILC, STAR, ALICE…

=> Sharing of R&D costs.

The MVD for SIS100

M. Deveaux 6

Status of FAIR:

SIS100 available 2018SIS300 available later

Need SIS300 for opencharm production in A-A

Physics cases at SIS100 (MVD)

• Measure open charm in p-A (p-p?) collisions Needs ~106 p-Au collisions/s

• Measure light vector mesons in A-A collisions Use MVD as low momentum tracker Tag and reject conversion pairs => reduces Background Needs ~104 Au-Au collisions/s

M. Deveaux 7

Running conditions (SIS-100):S

. Sed

diki

, C. D

rits

a

• Radiation doses per year, incl. factor 3 security margin• Occupancy incl. factor 10 security margin

Mi-26 p-A (@5cm)

Au-Au (@5cm)

Au-Au (@10cm)

Max. coll. rate [Hz] “1x104” 2x106 2x104 2x104

Peak occupancy [%] 0.7 3.5 6 3.5

Ionizing rad. dose [MRad] 0.5 0.5 2 0.5

Non Io. rad. dose [neq/cm²] > 1x1013 1.5x1013 1x1013 0.5x1013

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Status of the sensor R&D

9M. Deveaux

Sensor R&D: The operation principle

Reset+3.3V+3.3V

Output

SiO2 SiO2 SiO2

N++ N++N+ P+

P-

P+

15µm50µm

10

Sensor R&D: Tolerance to non-ionising radiation

+3.3VOutput

SiO2 SiO2

N++

N+SiO2 SiO2

P++ P++ P++

GND GND

+3.3V

11

Sensor R&D: Tolerance to non-ionising radiation

+3.3VOutput

SiO2 SiO2

N++

N+SiO2 SiO2

P++ P++ P++

GND GND

+3.3V

Key observation: Signal amplitude is reduced by bulk damage

12

Sensor R&D: Tolerance to non-ionising radiation

+3.3VOutput

SiO2 SiO2

N++

N+SiO2 SiO2

P++ P++ P++

GND GND

+3.3V

Electric field increases the radiation hardness of the sensorDraw back: Need CMOS-processes with low doping epitaxial layer

E

S/N of MIMOSA-18 AHR (high resistivity epi-layer)

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Plausible conclusion: Radiation tolerance ~1014 neq/cm² reached• Cooling required to operate heavily irradiated sensors

Preliminary

Safe operation

0 5 10 15 20 25 300

10

20

30

40

50

60

70

80

10µm 12.5µm 25µm

T=-34°C/-70°CS

ign

al t

o N

ois

e (

Ru

-10

6 )

Radiation dose [1013neq

/cm2]

Mimosa-9 (2005)20 µm standard epi

0.2 x 1013 neq/cm²

D. D

oerin

g, P

. Sch

arre

r, M

. Dom

acho

wsk

i

D.Doering, HK 12.8P. Scharrer,HK 53.13

Sensor R&D: Tolerance to ionising radiation

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Pixel with pedestal correction

~1000 discriminators

On - chip cluster-finding processor

Output: Cluster information(zero surpressed)

Imagers:

Tolerate 1-2 MRad if cooled.

Fast pixels are so far vulnerable:

• More transistors• No space for radiation tolerant

layout in 0.35µm CMOS.

Þ Current tolerance: 0.5 MRad

Next steps: Migrate design to 0.18 µm CMOS processÞ Higher intrinsic radiation toleranceÞ Less space constraintsStatus: First sensor (MIMOSA-32) under test.

M. K

oziel, PhD

15

Tolerance to non-ionising radiation - Annealing

0 40 80 120 160 200 240 280 320 3600

50

100

150

200

250

300

350

400

450

irradiated with 200 krad X-ray

1013 neq

/cm²

xRay + neutrons no radiationLe

akag

e cu

rren

t [f

A]

Net anneal time [h]

T=20°C T=80°C

-70%

Annealing alleviates ionizing radiation damage substantiallyNo indication for reverse annealing => Recover detector on the fly(?)

D. D

oering

MIMOSA-19imager

M. Deveaux 16

MVD-Simulation

Global design: How many MVD stations?

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5 cm

Targ

et

MV

D 1

MV

D 2

ST

S 1

ST

S 2

ST

S 3

Vacuumwindow

Global design: How many MVD stations?

M. Deveaux 18

5 cm

Targ

et

MV

D 1

MV

D 2

ST

S 1

ST

S 2

ST

S 3

Vacuumwindow

Global design: How many MVD stations?

M. Deveaux 19

5 cm

Targ

et

MV

D 1

MV

D 2

ST

S 1

ST

S 2

ST

S 3

Vacuumwindow

Global design: How many MVD stations?

M. Deveaux 20

5 cm

Targ

et

MV

D 1

MV

D 2

ST

S 1

ST

S 2

ST

S 3

Vacuumwindow

Global design: How many MVD stations?

M. Deveaux 21

5 cm

Targ

et

MV

D 1

MV

D 2

ST

S 1

ST

S 2

ST

S 3

Vacuumwindow

Global design: How many MVD stations?

M. Deveaux 22

5 cm

Targ

et

MV

D 1

MV

D 2

ST

S 1

ST

S 2

ST

S 3

Vacuumwindow

Global design: How many MVD stations?

M. Deveaux 23

Open charm in Au-Au 25 AGeV, accepted background tracks per collision.Bad reconstruction

Some bad hits

Good hits

Accepted after cut on:p > 1 GeVpt > 0.3 GeVImpact parameter

Not applied:Secondary vertex cutImpact parameter of mother particle

Adding a third station might improve system performance substantially! Needs full physics simulation before concluding

C. T

rage

ser,

HK

53.

19

Global design: How many MVD stations?

M. Deveaux 24

5 cm

Targ

et

MV

D 1

MV

D 2

ST

S 1

ST

S 2

ST

S 3

Vacuumwindow e+

e-

Sensor response simulation:J. Enders - HK 53.18M. Domachowski - HK 57.5

System integration – An MVD for CBM

M. Deveaux 25

CBM-MAPS consume ~1W/cm²

How to bias?How to evacuate heat? …

…without material

Aim for thickness of 0.3% X0

(=0.3 mm Si equivalent)

How to fix the sensors?

… in vacuum?

Integration concept of the MVD

Vacuum operation requires light and actively cooled device. • Use cooling support from diamond to move heat out of

acceptance• Put heat sink and FEE outside acceptance

CBM acceptance

Outside acceptance

Beam hole

z[cm] rout rin

5 2.5 0.55

10 5.0 0.55

15 7.5 0.75

rout

Geometry of MVD-stations

Discri

Sensor D

iscr

i

Sen

sor

Discri

Sensor

Discri

Sensor D

iscr

i

Sen

sor

Discri

Sensor

Discri

Sensor

M. Deveaux 27

T. Tischler

MIMOSIS1B

MIMOSIS1A

Discri

Sensor

Discri

Sensor

Discri

Sensor

Integration concept of the MVD

MVD Prototype (mock up)

Simulation: Material budget of a first MVD station

Conservative estimate close to 0.3% X0

Improve using FPC with aluminum

T. Tischler

300 µm Si equivalent

Sensor

Cable

Support

Hea

t sin

k

Validation of the cooling concept

29

25 W / 16 cm²

DT = ~10K

Vacuum compatible cooling concept for 1W/cm² seems robust.

Aim: Validate the cooling concept with TPG

Observation:• Temperature gradient on the station appears acceptable• A 150 µm CVD diamond support might be sufficient for station 1• Diamond => liquid heat transport needs optimization

T. Tischler

Prototype: Beam test setup

M. Deveaux 30

Ambitioned performances:• Up to 10 MIMOSA-26 running @10k frames/s, 3.5µm resolution.• Local DAQ based on HADES TRB - 1.6 Gbps data, scalable.• Actively cooled prototype (<0.3% X0)• Passively cooled telescope arms (0.05% X0)

T. Tischler

MVD Prototype

Reference telescope

Prototype: Beam test setup

M. Deveaux 31

2 MIMOSA-26 operated with …. the prototype readout electronics

See C.Schrader, HK 41.5See B. Milanovic, HK 41.6

Summary

M. Deveaux 32

• CMOS MAPS provide an unprecedented compromise between precision measurements and rate capability.

• Their performances were massively improved within 10 years.

• MAPS are considered for STAR, CBM, ILC, ALICE, eRHIC …

=> Industrial trends help: Expect further improvements

Integration concept for the CBM-Micro Vertex Detector:• Host MAPS on a vacuum compatible diamond cooling support• Readout with ultra thin flex print cables• Build local DAQ based on HADES TRB

Status: • Prototype under construction, beam test middle 2012

Outlook: The story has just startedIdea from R. De Oliveira, W.Dulinski

SERNWIETE (mechanical demonstrator)A bended MIMOSA-26 in a foil

Thanks to the CBM-MVD collaboration:

PICSEL group, sensor production

AG Prof. Stroth, MVD integration radiation tolerance studies

M. Deveaux