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)
M. Deveaux 13
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
M. Deveaux 14
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?
M. Deveaux 17
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