CBM Technical Challenges

1
CBM Technical Challenges

• Walter F.J. Müller, GSI, Darmstadt
• for the CBM Collaboration

2
Observables ? Detector Requirements
Capabilities
Observables
Momentum measurement Hadron ID Lepton ID e or
µ Photon detection Vertex reconstruction
event-by-event fluctuations flow excitation
function strangeness production K, L, S, X, W
low-mass vector mesons ?,?, f hidden charm J/?
Capacities
High track density ? highly granular
detectors Large integrated luminosity high
interaction rates (10 MHz) ? fast detectors
(100 kHz/ch) ? efficient event selection
several month/year beam ? radiation hard
detectors
open charm D0, D,Ds
3
CBM Setup
Capabilities
Momentum measurement Hadron ID Lepton ID e or
µ Photon detection Vertex reconstruction
Capacities
High track density ? highly granular
detectors Large integrated luminosity high
interaction rates (10 MHz) ? fast detectors
(100 kHz/ch) ? efficient event selection
several month/year beam ? radiation hard
detectors
4
Driving Factor 1 Rare Probes
D ? 106 int/sec
J/? ? 107 int/sec
Integrated Luminosity 1014 int/lifetime for
some sub-systems
5
High Multiplicity
Central AuAu collision at 25 AGeV URQMD
GEANT 160 p 170 n 360 ?-
330 ? 360 ?0 41 K 13 K-
42 K0
6
Driving Factor 2 Hit Densities
For Au Au _at_ 25 A GeV central collisions
at Vertex Detector
at end of STS
at ToF Wall
horz. planevert. plane
up to 1 hit/mm2/evt
10-2 hit/cm2/evt
up to 1 hit/cm2/evt
x 1014 int/life ? 2.5 MRad
replace Vertex Detectorafter one run
25 KHz/cm2/sec
7
CBM Event Selection Requirements
assume archive rate few GB/sec 20 kevents/sec

• In-medium modifications of hadrons
• ? onset of chiral symmetry restoration at high
  ?B ? measure ?, ?, ? ? ee- or µµ -
  open charm (D0, D)
• Strangeness in matter
• ? enhanced strangeness production ? measure
  K, ?, ?, ?, ?
• Indications for deconfinement at high ?B
• ? anomalous charmonium suppression ? ?
  measure D0, D -
• J/? ? ee or µµ -
• Critical point
• ? event-by-event fluctuations
• ? measure p, K

offline
trigger
trigger ondisplaced vertex
offline
drives FEE/DAQarchitecture
trigger
trigger
trigger on high pt ee- or µµ- pair
offline
8
Driving Factor 3 Tracking Trigger

• Example D0 ? K-? (3.9 c? 124.4 ?m)
• reconstruct tracks
• find primary vertex
• find displaced tracks
• find secondary vertex

target
few 100 µm
5 cm

• high selectivity because combinatorics is reduced

first two planesof vertex detector
9
DAQ Event Selection

• Challenge
• no conventional first level trigger
• first decision level requires tracking and
  vertexing
• hard to do in a limited decision time
• straight forward to use farming to achieve
  throughput
• Solution
• build a system that is throughput limited, not
  latency limited
• use self-triggered front-ends

10
DAQ Data Push Architecture
Detector
Self-triggered front-end Autonomous hit detection
time distribution
FEE
No dedicated trigger connectivity All detectors
can contribute to L1
Cave
Shack
Highbandwidth
DAQ
Large buffer depth available System is
throughput-limitedand not latency-limited
Some Programmable Logicand mostly CPU's
Use term Event Selection
Archive
11
Front-End for Data Push Architecture

• Each channel detects autonomously all hits
• 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
  concentrators)
• Association of hits with events done later using
  time correlation
• Typical Parameters
• with few 1 occupancy and 107 interaction rate
• some 100 kHz channel hit rate
• few MByte/sec per channel
• whole CBM detector 1 Tbyte/sec

12
Vertex Detector

• Challenge
• 30 x 30 µm pixel size
• cope with 1 Mhz interaction rate
• stand at least 1012 interactions
• low material budget (0.2-0.3 X0)
• Solutions
• Active pixel sensors (MAPS)
• DEPFET sensors

13
Vertex Detector MAPS Development

• Base technology like STAR Heavy Flavor Tracker
  (HFT)
• Working on
• faster readout
• column-parallel read-out
• short columns
• 10 MHz pixel rate _at_ 1 mW/column
• radiation hardness
• 1 MRad and 2x1012 neq/cm2 demonstrated so far
• low mass support structure

M. Winter, IPHC, StrasbourgJ. Stroth, Uni.
Frankfurt
14
Silicon Tracker

• Challenges
• Sensor
• radiation hard (must stand 1014 interactions)
• 50 µm pitch, double sided, 150 stereo,
  ladderable
• Read-out
• self-triggered, 128 ch, radiation tolerant
• Support Structure
• low mass
• likely need cooled sensors

15
Silicon Tracker FEE Development

• Start with N-XYTER chip from DETNI Collaboration
• 128 channels, self-triggered (designed for
  neutron detectors !)
• 2 ns time stamp accuracy
• 32 Mhit/sec readout bandwidth
• will be used in 2007/2008 prototyping
• Next steps
• lower power fully digital interface
• radiation hardness
• Strategy
• use same architecture also for read-out of highly
  granular gas detectors (e.g. GEM) ? variants with
  adapted preamps

16
N-XYTER Architecture
Front-end targeted for Silicon strip (pos
neg) GEM's and MSGC's
S. Buzzetti, Uni HeidelbergDETNI Coll.
17
Fast Gas Tracking Detectors
Needed in many places
e-e- setup
µ-µ- setup doinghadronic observables
MUCH detector
18
Fast Gas Tracking Detectors

• Challenges
• hit density 10-2 up to 1 hit/cm2
• hit rate 25 kHz up to 2.5 MHz/cm2
• fluence 1012 up to 1014 part/cm2 ( 1
  C/cm2)
• Solution
• up to a few 100 kHz/cm2 (TRD or intermediate
  Tracker)
• high-rate MWPC'sseveral 100 m2 needed for TRD or
  intermediate trackersignificant RD done in the
  last years
• above a few 100 kHz/cm2 (parts of Muon system)
• GEM, Mircomegasrequirements depending on
  detailed MUCH layoutwork just starting within CBM

19
Time-of-Flight Wall

• Challenges
• Size 150 m2
• hit density 10-2 hit/cm2
• hit rate 25 kHz/cm2
• System time resolution lt 80 ps
• Solution
• Multigap RPC Counters with 'low' resistivity
  electrodes

20
RPC Development

• Example Ceramic electrodes
• controlled resistivity alumina109 O cm at room
  temperature
• efficiency drop
• 9 /100 kHz in single gap
• 2 _at_ 200 kHz for 4 gaps
• Also under investigation
• warm glass
• semiconductive glass
• Outlook
• 25 kHz/cm2 rate is achievable
• challenge is to control ageing

Single gap
P. Fonte, LIP, Coimbra
For ? pairs expect 60 ps for MIPS
21
Summary

• Hit rates and densities seem feasible
• Main challenge is
• control radiation damage / ageing
• ? long-term and comprehensive testing
• system integration
• ? build complete sub-system prototypes

22
CBM collaboration
India (cont) Univ. Varanasi IIT
Kharagpur 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  
Croatia RBI, Zagreb China CCNU, Wuhan USTC,
Hefei 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
Portugal LIP Coimbra 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
23
The End
Thanks for your attention
24
The End
Spares
25
Conventional FEE-DAQ-Trigger Layout
Detector
fbunch
FEE
DAQ
L2 Trigger
Archive
26
Fast Gas Detector Development

• MWPC Example Double-sided pad plane HCRTRD
  chamber for TRD
• 3mm max. drift 12 mm Xe
• stable up to 200 kHz/cm2
• p rejection of gt100 can be achieved with 6 layers
  and foil radiator

M. Petrovici, NIPNE, Bucharest
27
Straw Detector with Segmented Anode
Glass joint with 2 anode wiresand a read-out
wire
Feed-Through
Joint plus spacer unit
V Peshekhonov, JINR, Dubna