Development of a Silicon Tracking and Vertex Detection System for the CBM Experiment at FAIR

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Development of a Silicon Tracking and Vertex
Detection System for the CBM Experiment at FAIR
Johann M. Heuser, GSI Darmstadt, Germany for the
CBM Collaboration VERTEX 2006,
Perugia, Italy, September 2006

• The international Facility for Antiproton and Ion
  Research
• The Compressed Baryonic Matter experiment
• The Silicon Tracking and Vertex Detection System
  
• Performance requirements, Detector concept, RD
  activities

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Facility for Antiproton and Ion Research
_at_ GSI Darmstadt
FAIR 2015
existing GSI
Start of construction 2007/2008 staged
commissioning 2011-2014 Full operation, CBM
2015
International project
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Five Research Communities at FAIR
Heavy-ionsynchrotrons
Ion source
SIS-100, SIS-300
SIS-18
U 35 GeV/n p 90 GeV
Unilac
CBM
Nuclear Matter Physics with HI beams, 35-45
GeV/n, x1000
HESR
Rare Isotope Prod. Target
Super FRS
Antiproton Prod. Target
Hadron Physics with antiprotons 0 - 15 GeV
Nuclear Structure Astrophysics with radioactive
beams, x10 000 and excellent cooling
FLAIR
CR- RESR
Plasma Physics x600 higher target energy
density 600kJ/g
NESR
High EM Field (HI) _ Fundamental
Studies (HI p) Applications (HI)
100 m
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Compressed Baryonic Matter-Experiment
SIS-300 up to U92,15-35 GeV/nucleon, beam
intensities up to 109/s, Z/A 0.5 nuclei
up to 45 GeV/nucleon
? exploration of the QCD phase diagram with
heavy-ion collisions! ? investigation of nuclear
matter at highest baryon densities but still
moderate temperatures in AA collisions
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CBM Physics Case

• Milestone in mapping the QCD phase diagram would
  be the (unambiguous) discovery of either the
  critical point or the 1st order phase transition
• Top-energy SPS, RHIC, LHC
• high T, low mB region
• most probably phase crossover
• High mB region !
• - onset of deconfinement?
• - 1st order phase transition?
• - critical point?
• Earlier experiments at AGS, low-energy
  SPS
• limited in observables, statistics
• New RHIC plans low energy runs

SIS 300 _at_ FAIR ideal for 2nd generation
experiment!
CBM rare probes, high interaction ratescharm,
dileptons, fluctuations, correlations
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CBM collaboration
Korea Korea Univ. Seoul Pusan National
Univ. Norway Univ. Bergen Germany Univ.
Heidelberg, Phys. Inst. Univ. HD, Kirchhoff Inst.
Univ. Frankfurt Univ. Kaiserslautern Univ.
Mannheim Univ. Münster FZ Rossendorf GSI
Darmstadt Poland Krakow Univ. Warsaw
Univ. Silesia Univ. Katowice Nucl. Phys. Inst.
Krakow   Portugal LIP Coimbra
gt 40 institutions gt 350 Members
Croatia RBI, Zagreb China Wuhan Univ. Hefei
Univ. Cyprus Nikosia Univ.   Czech
Republic CAS, Rez Techn. Univ. Prague France
IReS Strasbourg Hungaria KFKI Budapest Eötvös
Univ. Budapest India VECC Kolkata IOP
Bhubaneswar Univ. Chandighar Univ. Varanasi
Romania NIPNE Bucharest Russia IHEP
Protvino INR Troitzk ITEP Moscow KRI, St.
Petersburg Kurchatov Inst., Moscow LHE, JINR
Dubna LPP, JINR Dubna LIT, JINR Dubna MEPHI
Moscow Obninsk State Univ. PNPI Gatchina SINP,
Moscow State Univ. St. Petersburg Polytec.
U. Ukraine Shevshenko Univ. , Kiev to be
approved by CB
open for new partners!
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The CBM Experiment

• tracking, momentum, vertex reconstruction
  silicon pixel/strip detectors (STS) in
  magnetic dipole field
• electron ID RICH TRD ( ECAL)
• ? p suppression ? 104
• hadron ID TOF ( RICH)
• photons, p0, m ID ECAL
• event characterization (PSD)
• high speed DAQ, only high-level triggers
• not necessarily fixed layout!
• more like facility

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Alternative CBM setup Dimuons

• Dimuon setup studied with active muon
  absorbers (Fe C detector layers) after the
  Silicon Tracker

• ... move absorbers out for hadron runs.

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Silicon Tracking and Vertexing

• Challenge AuAu collisions, 25 GeV/n
• high track densities
• ? 600 charged particles in ? 25o
• high r/o speed, radiation hardness 10 MHz
  interaction rate (109 ions/s on 1 ?int
  target), only high-level triggers.

• Tasks
• track reconstruction for particles with 0.1 GeV/c
  lt p ? 10-12 GeV/c , momentum resolution 1 at
  1 GeV/c,large lateral coverage
• primary and secondary vertex reconstruction
  (resolution ? 50 mm)
• V0 track pattern recognition (low-mass vector
  mesons ?lepton pairs, open charm decays,
  hyperons, ee- pairs from g-conversion)

D ? ppK- (ct 317 mm) D0 ? K-p (ct 124 mm)
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Conceptional Detector Geometry
Vertexing "VTS" 2 (3) MAPS stations. ? z
(5), 10, 20 cm? 150 µm Si? In vacuum. No
layout yet. Tracking "STS" 2 HYBRID Pixel
stations? z 30, 40 cm ? 750 µm Si? No
layout yet. 4 Micro-STRIPS stations? z 50,
60, 75, 100 cm? 400 µm Si? Detailed station
layout.
very thin
low-mass
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• GEANT implementation
• dipole magnet,
• 1Tm bending power
• VTS in vacuum section
• beam pipe
• STS stations

1 m
Activities started on optimization of layout,
robust tracking, vertexing, detector/system RD
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Microstrip Tracking Stations
Sensor arrangement and hit digitization scheme.
Old concept "radial" arrangement of sectors
New concept
? double-sided sensors? 50 µm strip pitch,
15 deg stereo angle? strip lengths 4-12 cm? r/o
through thin, long analog cables !
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Microstrip Stations conceptional structure
Station 6z 60 cm
Station 5z 50 cm
Station 8z 100 cm
Station 7z 75 cm
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Momentum Resolution
Thickness effective,sensor support/cables. How
much passive material (support, cables etc) will
finally add up? Readout What sensor thickness
for what S/N? Detailed simulations being
prepared. Study impact on physics.
thin standard thick thick-2
thick-3 MAPS 2150 µm 2150 µm
2150 µm 2 150 µm 2 150 µm Hybrid
2200 µm 2750 µm 2800 µm 21000 µm
21600 µm Strips 4200 µm 4400 µm
4800 µm 41000 µm 41600 µm
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Track Reconstruction Efficiency
Track finder Cellular Automaton and Kalman
Filter - with 2 Hybrid Pixel 4 Strip
Stations, - standard settings ? include
vertex, ? hits in gt3 consecutive stations.

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Microstrip-Only Track Reconstruction
What's the design goal? Important Include
robustness!
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Tracking with four strip projections per station
Microstrip-only tracker
Tracking double stations strips Vertexing with 2
MAPS stations either at 5 cm 10 cm, or
at 10 cm 15 cm.
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Microstrip Double-Stations
-3.75o
xy uv
3.75o
0o
3.75o
-3.75o
-11.25o
11.25o
?z ? 1 cm
4 hit projections on the strip planes
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Tracking Stations Layout Studies
Occupancies
Up to 5 in hottest sectors of station 5
(central collisions). Go down with radial
distance from the beam axis, and with distance
from the target ...... as expected. The CA
track finder yields tracking efficiencies
97. Together with tracking study powerful
design tool. Design criteria - Save r/o
channels in outer regions Longer strips
there! - Short strips close to beam line.
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Microstrip Sensor Development
r/o direction
Two streams of activities double-sided,
different technologies 1) In CBM Collaboration
(RD at MSU SiLab, Moscow) 300 µm,
polysilicon biassing, p-stop connectivity
top/bottom sides 2) RD at GSI, together with
CIS, Germany 300 µm, punch-through
biassing, p-spray, double-metal
connectivity r/o at top/bottom edge
n side "vertical" strips
p side "stereo" strips
r/o direction
n side "vertical" strips
p side with "double metal"
blue double metal connections of strips in
regions I to III
III
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RD with CIS Erfurt, Germany (http//www.cismst
.de/english/frameset.html)
CBM Opportunity to participate in reseach
project of CIS (focus on rad hard detectors).
CBM sensor prototypes as "test objects".
Sensor design finished 10/2006.End 2006 batch
of 20 wafers. Plenty of sensors for a variety
of tests of r/o electronics and detector
concept. Set up Silicon labs at GSI other
institutes. Test beam telescope at GSI.
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Microstrip Detector Readout
Two streams of activities 1) In the CBM
Collaboration (MEPhi/MSU, Moscow) RD on
fast self-triggered low-power electronics
blocks 2) Exploration of the NXYTER chip in
collaboration with the Consortium
DETectors for Neutron Imaging
http//jra1.neutron-eu.net/jra1

• dual polarity
• input pitch 50.7 µm
• 128 channels per chip
• amplitude measurement
• data driven token-ring r/o architecture
• count rates 160 kHz/strip
• charge collection 30 ns peaking time
• small (2 ns) timing jitter
• thresholds gt 2700 e
• dynamic range different for /-
• power 13 mW/channel (high!!!)
• produced in 0.35 ?m CMOS

Specs very similar to the CBM needs! 1st chip
submission in March 2006.

• Close ties to the project through Head of
  GSI Detector Lab
• GSI significant participation in
  funding of chip submission (Summer 2006).

Aim Test and modify this chip. Construction of
a demonstrator microstrip detector module for
CBM.
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N-XYTER Submitted via CMP Dies Expected Sept.
25th 2006
8 LVDS output lines at 4 x 32MHz time stamp,
channel no. 1 differential, analog output
128 analog inputs poisson distributed at 32
MHz total average input rate
AMS CMOS 0.35µ with thick metal four
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Study on Mechanical Structure Elements
(microstrip module)
2-module structure, building block of detector
stations
Study together with ITEP Moscow Based on ALICE
ITS studies, and CBM STS layout concept.Carbon
fibre.
module
"very preliminary,
brain-storming designs"
flat cable routing
sensor holders
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Vertex Tracking System

• Sensor Requirements
• pitch 20 µm ?
• thickness below 100 µm ?
• single hit resolution ? 3 µm ?
• radiation tolerant, design goal 1013 neq/cm2
• ultimate read-out time 5-10 µs

Hybrid pixels at least for now - too thick-
too large pixels - power dissipation requires
cooling.

• Monolithic Active Pixel Sensors (MAPS)
• RD together with IPHC (IReS) Strasbourg
• development of fast column//architecture
• development of radiation tolerant sensors
  (from some 1012 to 1013 neq /cm2)

SOI pixels in a small process interesting!
MAPS with depletion layer sounds interesting!
longer lifetime of first MAPS station
enlarge distance from target 5 cm ? 10 cm
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RD goals with MAPS Radiation tolerance
readout speed

• RD goals with MAPS
• radiation tolerance 1012 ? 1013 1 MeV nequiv.
  
• readout time 10 ?sec, column parallel
  r/o
• Expected situation in CBM
• Fluence at 1st MAPS station
• 10 1-MeV nequiv. per event
• ? detector partly destroyed after 1012
  reactions? corresponds to ?105 D mesons detected
  (already decent
  measurement!)
• Possible running conditions
• a) ?1 day detector lifetime at 107
  reactions/s, 100 events piled up, or
• b) ? 4 month detector lifetime at 105
  reactions/s, no pile-up events.

URQMD, AuAu 25 GeV/nucleon Fluence of 1 MeV
nequiv./cm2 in 1st MAPS station at z 5cm
?Kpn
What about retracting the 1st MAPS station from
the target?
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Benchmark for SVT and STS Performance D0
mesons, AuAu collisions at 25 AGeV

• realistic tracking in magnetic field,
• 2 MAPS, 2 Hybrid pixel, 4 Strip stations
• proton identification required

• D0 production cross section from HSD
• 25 AGeV AuAu from UrQMD
• minimum bias collisions

dose ¼ S/B ¼ ? no gain!!
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Summary - CBM

• CBM is a baseline experiment at FAIR. Running
  from 2014/15.
• CBM offers very interesting physics program on
  the QCD phase diagram.
• Unique features expected in CBM energy range
  First order phase transition, critical point
• As a 2nd generation experiment, CBM will be able
  to study rare probes, fluctuations and
  correlations!

• Detector development under way
• Increasingly realistic feasibility studies are
  performed
• ? Technical Proposal in 2007.

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Summary Silicon Detectors
The Silicon Tracking and Vertex Detection System
is the core of CBM. Detector concept
Tracker (Microstrips) Vertex Detector
(MAPS) RD activities - layout optimization
Ongoing. New and powerful tools available
for realistic detector/physics simulations. -
tracking studies Ongoing -
sensor development Ongoing - r/o
electronics development Ongoing - mechanical
studies Beginning Still may gaps
to fill, including - realistic sensor shapes,
support material in simulations. - realistic
FLUKA radiation study. - RD on module
prototypes Microstrips MAPS. - thin sensors,
low-mass r/o cables, low-mass support
structures. - ...
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Data-Push Architecture, Data Flow

• Each detector channel detects autonomously all
  hits? FEE design.
• An absolute time stamp, precise to a fraction of
  the sampling period, is associated with each
  hit.
• All hits are shipped to the next layer (usually
  data concentrators).
• Association of hits with events done later using
  time correlation.
• Typical parameters
• (few occupancy, 107 interaction rate)
• some 100 kHz hit rate per channel
• few MByte/sec per channel
• whole CBM detector 1 Tbyte/sec