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Status of the CMS GEM Project
Michael Tytgat on behalf of the CMS GEM Collaboration
RD51 Collaboration Meeting, October 16, 2013
Outline
IntroductionCMS Muon Trigger motivationDetector construction and testsProduction quality control Integration into CMSDAQ and ElectronicsTowards LS3
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 2
LS2
LS3
The CMS GEM Project
GE1/1
Install triple-GEM super chambers (double stations) in 1.6<|η|<2.1-2.4 endcap region:
GE2/1
• Restore redundancy in muon system for robust tracking and triggering during HL-HLC
• Improve L1 and HLT muon momentum resolution to reduce or maintain global muon trigger rate
• Ensure ~ 100% trigger efficiency in high PU environment
GEMs: R&D Project CMS 10.02; The LS2 ProjectOctober 16, 2013
M. Tytgat - RD51 Collaboration Meeting 3
OVER FOUR YEARS OF R&D • 2009-2010
– Small prototypes, bench tests; picked GEMs among MPGDs for further study– Established space and time resolution achievable– First Large-area GEM foils produced with Single Mask technology– First large-area GE1/1 prototype; beam test
• 2011– Second redesigned GE1/1 prototype (smaller gaps b/w GEMs)– “GEM Collaboration (GEMs for CMS)” constitutes itself in May CMS week (76 collab.
from 15 inst. )– Summer beam tests (including first test in CMS test magnet)– Established 100µm (300µm) res. with analog (binary) r/o chip– NS2 GEM foil assembly technique w/o spacers – Preliminary electronics design starts
Project Milestones
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 4
2012• Beam tests – Magnetic Field Operation and fine space and time resolution on
large size establishedWorking Groups • Detector Hardware • Physics Studies• Trigger Simulations• Detector Physics Group• Integration and Services• Electronics & DAQ• Online Operation
Collaboration Expanded 42 Institutions, 183 collaborators EOI, ~ 75 authors• 6 GE1/1 full size NS2 detectors produced• CMS approval for installation of GE1/1 demonstrator, i.e. 2 Super Chambers
covering a 20° sector in YE1/1 during LS2 (2x36 Super Chambers = 144 triple-GEMs)
• “Motivation” plots approved by CMS• GE1/1 TDR on track
2013
Project Milestones
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 5
GE-1/1 proposal for LS2– Proposal calls to instrument the part of first muon station closest
to the beam with a set of triple-GEM chambers:• Highest rates in the entire system
– Only CSCs, no redundancy• RPC coverage ends at |η|=1.6
ME1
/b
GE1
/1
ME1
/aEv
en c
ham
bers
Odd
cha
mbe
rs
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 6
CMS Muon Trigger Challenges Forward region |η|>1.6 trigger
relies entirely on the CSC system General trend is lowering efficiency
towards higher eta to compensate for higher background rates
Optimal operating point is a function of PU (7 and 8 TeV are different)
CSC is a superb system but it is not PU-proof: Efficiency losses grow with PU High L1 trigger rates in the very
forward region L1 trigger rates “flattening”
The period between LS2 and LS3 is the most difficult time: Current system at the edge and
the foreseen L1 Tracking Trigger is not yet online
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 7
Forward Muon Trigger Muon momentum from stub positions
ΔφXY=φ(ME-X)-φ(ME-Y)
Measurement driven by Δφ12: ME-1/1 “drives” precision (least scattering)
Slow turn-on: Efficiency plateau is 20-25% above L1
threshold “Flattening”: mismeasured soft
muons Soft muons scattering in the absorber
can occasionally have stubs aligned like for a high pT muon (rare, but lots of soft muons); tails in L1 momentum resolution
Only two handles on pT mismeasurements: Nstubs (out of 4) and ME-1/1 stub
presence; both are used to define quality of the CSC TF tracks (used in GMT)
Can’t push too far without large efficiency losses
PU reduces trigger efficiency by few %
91% plateau
Zero PU
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 8
L1 muon momentum resolution can be improved with a second muon system, allowing to measure the “bending angle”
A GEM detector in YE-1/1 (the least affected by scattering, largest B) Increase “lever arm” from
10cm to Δz=30-50cm (physical constraints)
Need ~2 mm or better trigger resolution to effectively discriminate 5 GeV from 20+ GeV muons
View from the top of CMS down
October 16, 2013
GEM-CSC “Bending Angle”
M. Tytgat - RD51 Collaboration Meeting 9
Detector Hardware
2010
Generation IThe first 1m-class detector ever built but still with spacer ribs and only 8 sectors total. Ref.: 2010 IEEE (also RD51-Note-2010-005)
2011 2012 2013
Generation IIFirst large detector with 24 readout sectors (3x8) and 3/1/2/1 gaps but still with spacers and all glued. Ref.: 2011 IEEE. Also RD51-Note-2011-013.
Generation IIIThe first self-stretched sans-spacer detector, but with the outer frame still glued to the drift. Ref.: 2012 IEEE N14-137.
Generation IVThe current generation that we have built two of at CERN so far, with four more to come from the different sites. No more gluing whatsoever. Upcoming papers from MPGD 2013and IEEE2013.
2013/14
Generation VThe upcoming detector version that we will install. One long and one short version. Optimized final dimensions for max. acceptance and final eta segmentation.
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 10
Full-size GE1/1 Detectors Developments in Time
2010 2011 2012 2013 2013/14
2014/15 2015/16 2016/17 2017/18 2018/19
Production and QC of detectorsFirst prototype of VFAT3
Slice installation
Slice and trigger commissioning
Full-production of chambers and electronics started
Full installation of GE1/1 with final electronics
QC of Production GE1/1 chambers with final electronics
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 11
Current GE1/1 Detectors
October 16, 2013
Single-mask & self-stretching techniques Gap sizes: 3/1/2/1 mm Sectors : 3 columns x (8-10) η partitions Strip pitch: 0.6-1.2mm 1D readout of up to 3840 channels 35 HV sectors
M. Tytgat - RD51 Collaboration Meeting 12
NS2 Self-Stretching Technique
October 16, 2013
External frame : Originally made of 8 pieces, glued together; gave problems to fit onto PCB, 2 days needed for gluing and hardening Present version made of 1 single piece, with special tool to dril lateral holes
Internal frames: Made of 8X4 pieces: 8 pieces for each of the 4 frames used to make the GEM stack Sandblasting and polyurethane to prevent dust problems
Detector Frames
October 16, 2013 M. Tytgat - RD51 Collaboration Meeting 13
October 16, 2013 M. Tytgat - RD51 Collaboration Meeting 14
GEM foil in inner frame assembly GEM foil with inner & outer frame
Inside of readout board with O-ring seal
-sector with 384 radial readout strips
Base pcb with drift electrode
No spacers in active volume
Current GE1/1 Detectors
M. Tytgat - RD51 Collaboration Meeting 15October 16, 2013
Strip side External side
vias
Readout board: metalized vias bring the signal to the other side of the board; panasonic connector with 128 entries is soldered on the stripsDrift board: HV spring contacts to connect foils to HV; 4 contacts per GEM (Top/Bottom + redundant connection)
GE1/1 Readout & Drift Board
HV filter
HV divider
Soldering spring
contacts
Cover
Connectors & FE Hybrids
Exploded GE1/1 View
October 16, 2013 M. Tytgat - RD51 Collaboration Meeting 16
Cooling
GE1/1 Triple-GEM Chamber
Position of HV Divider
GBT’s
DC-DC Converte
rs
GE1/1 Cooling System
October 16, 2013 M. Tytgat - RD51 Collaboration Meeting 17
VFAT power – 600mWVFAT chip dimensions ~10×10mmConnectors – 6mm high
44mm50
mmVFAT
PCB
The cooling system has been studied/simulated taking into account electronics power dissipation (based on VFAT)
The cooling system will ensure a chamber temp. uniformity of (20 1) 0C
3mm PCB
6mmCu
pipe
1mm Cu strip
VFAT chipCu pipe
6mm/8mmat 18o C
VFAT PCB
Panasonicconnectors
Soldered to the pipe
6.5mm
R/o strips
M. Tytgat - RD51 Collaboration Meeting 18
2700 2900 3100 3300 3500 3700 39000
2
4
6
8
10
12
HV (V)
Rate
GE1/1 Gain Uniformity
October 16, 2013
Gain measured per sector to probe uniformity across surface
M. Tytgat - RD51 Collaboration Meeting 19
Detector Simulation Studies
October 16, 2013
Ongoing simulation effort in several areas:
Standalone simulation of a triple-GEM cell, with GARFIELD and ANSYS or MAXWELL :• Detector gain • Response uniformity (check with X-ray
results)• Signal induction and timing studies • Gas gap variations
Background simulations (neutrons & photons) with GEANT4:• GEM sensitivity/response to neutrons
and photons• Effect on GEM muon trigger and
reconstruction performance
FastSim:• fast GEM simulation parametrized using
GARFIELD input
Aging test @ CERN GIF
20
lead
shi
eld
A CMS GE1/1 detector was installed in the CERN GIF; detector performance and environmental & gas parameters monitored: Ensure long-term operation inside CMS Understand effects of radiation on the
materials Understand ageing origin (if any) and
propose solutions
GEM settings:
Drift: 3 kV/cm, Others: 3.5 kV/cm Induction: 5 kV/cm
Gain: 8 x 103 – 104; Gas mix: Ar/CO2/CF4 (45:15:40)
CMS high-η GEM
max. integrated
chargeGain of 2x104
50 MHz/cm2 X-rays, 10 days = > 20 C/cm2 integrated
CMS prototype
October 16, 2013 M. Tytgat - RD51 Collaboration Meeting
LHCb
M. Tytgat - RD51 Collaboration Meeting 21
CERNFoil Production
and final detector QC
USA FIT
ItalyBariLNF
IndiaBARC
BelgiumGhent
University
Installation in CMS
CERN: 186
October 16, 2013
Possible Assembly Sites
M. Tytgat - RD51 Collaboration Meeting 22
GE1/1 Quality Control
October 16, 2013
Final detectors for installation in CMS will undergo strict Quality Control in the different assembly sites:
Measure the leakage current of the GEM foils before, during and after the detector assembly
Validate the readout board by verfiying the connections of the strips to the readout connector
Measuring the detector gain uniformity with Mini-X and SRS/APV system
Response to x-ray checked for each η sector
GE1/1 detector uniformity
M. Tytgat - RD51 Collaboration Meeting 23
Super Chamber Dummies3 Super Chamber dummies were produced earlier this year to optimize design and to perform trial insertion into CMS:
no detector and no electronics inside all positions for gas , cooling and
electronics connections at the right place
dimensions as a real super chamber
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 24
Trial Installation in CMS
October 16, 2013
2014: Final Detector Geometry
October 16, 2013 M. Tytgat - RD51 Collaboration Meeting 25
Final (?) GE1/1 version should extend as much as possible in |η| : 1.5-2.2
“long” and “short” super chamber versionSeveral integration issues to solve
Old version
new version
M. Tytgat - RD51 Collaboration Meeting 26
DAQ and Electronics
October 16, 2013
Global Requirements on electronics: provide necessary input from all GEM detectors to Muon Triggering and Tracking
GEM detectors: Design optimized for gas detectors, in particular GEMs
Triggering: Provide “Fast OR” trigger information with granularity of 2 or
more channels to send locally to CSC Trigger Mother Board Timing resolution <8ns
Tracking: Provide full granularity tracking data on receipt of a LV1A Be compatible with CMS trigger upgrade possibilities:
• LV1A latency < 20μs• LV1A rate < 1MHz Poisson
M. Tytgat - RD51 Collaboration Meeting 27
GBT protocolOr 8b/10b encoding ?
2 Bidir. optical link @ 3.2 Gbps
DAQ and Electronics
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 28
Front-End ASIC Options
October 16, 2013
VFAT3:
Front-end with programmable shaping time
Internal calibration Binary memory Interface directly to GBT @
320Mbps Designed for high rate
(10kHz/cm2 depending on segmentation)
GdSP:
Similar to VFAT3, except has an ADC for each channel instead of comparator
Internal DSP allows subtraction of background artifacts, enabling clean signal discrimination
Center of gravity is possible to achieve finer pitch resolution
M. Tytgat - RD51 Collaboration Meeting 29
VFAT3
October 16, 2013
VFAT3 chosen for GEM Demonstrator and GE1/1 full installation during LS2
VFAT3 analog discriminator will use CFD or TOT to correct time walk
VFAT3 STT version (Separate Tracking & Triggering) : different paths for triggering and full granularity information
M. Tytgat - RD51 Collaboration Meeting 30
Electronics System
October 16, 2013
GEM OptoHybrid
GEB = GEM Electronics
Board
M. Tytgat - RD51 Collaboration Meeting 31
Trigger Concerns for LHC Phase 2 Phase-2 muon Level-1 trigger will rely on tracking trigger and
muon candidate matching But, track trigger fake rate grows with η; maintaining reasonable
trigger rate causes severe inefficiencies for |η|>1.8-2.0 GE-1/1 is doing exactly what one wants it to do for |η| < 2.1: it
compensates for the weakening of the tracker’s suppression power at higher |η| by strengthening the muon system
How do we cover region |η|>2.15 ??
Muon gun pT>5 GeVEfficiency includes track finding only. No muon system inefficiencies
incorporated.
Reco’ed stubs pT>2Stubs from true particles w/ pT>2
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 32
Ideas for Phase-2 CMS Muon System
LS2
LS3LS3
October 16, 2013
Near tagger ME-0 at the back of present HE with trigger capabilities in |η|>2.1; can be integrated with the calorimeter if desired
GE-1/1 + GE-2/1 GEM stations RE-3/1 + RE-4/1 gRPC stations ?
M. Tytgat - RD51 Collaboration Meeting 33
Extending Muon Coverage
CMS is looking into a possibility to extend tracking to |η|~4.0o Forward pixel extension
A new “Near Tagger”: a large increase in offline acceptance up to |η|=4
ME0: o small area, but nearly doubles
CMS muon coverageo Can optionally be integrated
into the new forward calorimeter
o Match muon stubs and forward pixel extension tracks
o Muon system improves momentum resolution
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 34
Summary
October 16, 2013
Over 4 years of R&D initiated in 2009 within the RD51 Collaboration resulted in partial approval for installation of triple-GEM detectors in CMS
During LHC Year-End Technical Stop of 2015-2016 (?), two Triple-GEM Super Chambers will be installed in YE1/1
Awaiting further green light from CMS Management for full GE1/1 installation during LS2
Preparing GE1/1 Technical Design Report, ready for October 2014 GEMs are now also being considered as candidate technology for
further CMS upgrades during LS3 (ME-0 muon tagger, forward calorimetry)
See also CMS GEM talks in WG6/7 & WG2 sessions by J. Merlin, P. Barria, A. Zhang, A. Marinov
GE1/1 detector today @ FNAL test beam
Backup Slides
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 36October 16, 2013
A second detector with high spatial resolution in station YE-1/1 provides new powerful ways to improve forward muon triggering Much improved resolution eliminates the famous “rate flattening”
problem A factor of x5-10 reduction in the trigger rate in the region covered
by GEMs (1.6<|η|<2.1) When averaged over (1.1<|η|<2.1), effectively a factor of 2
reduction in muon trigger rate for the entire forward region Amplified improvement from combining the new handles with the
existing ones – a better final trigger system
While critical for the time period between LS2 and LS3, will remain very important beyond LS3 as L1 inner tracking trigger performance likely to be limited beyond |η|=1.8 Installing additional GEM stations (ME-2/1) in LS3 is expected to
allow efficient triggering beyond |η|=2.1
Summary of Effects on Trigger
M. Tytgat - RD51 Collaboration Meeting 37
Effect on Trigger & PhysicsExample of where GE1/1 (1.6<|η|<2.1) can
help:
Upgraded Muon TrackFinder alone only allows decreasing the threshold from 42 to 25 GeV (with 9% efficiency loss)
Using GEM-CSC “bending angle”, allows to lower pT threshold from 42 to 13 GeV while increasing the efficiency
Hττ μτhad signal: fast falling muon momentum spectrum requires low pT thresholds; loose half (!) of the acceptance every time pT threshold by 10 GeV
GEM+CSC yield improved background rejection and result in ~20% increase in acceptance
13
42
L1 upgrade
no L1 upgrade
GEM+CSC
October 16, 2013
M. Tytgat - RD51 Collaboration Meeting 38
Muon detectors in new endcap
• At back of present HE• Totally new calorimeter
– Existing structure too “hot”
• Coverage options:– Minimal (top), maximal
(bottom) shown on right– {1.5, 2.1, 2.4} < |h| < {3.5,
4.0}– Complement or replace
ME1/1
• “Integrated” option– Build all of HE with GEM
technology, for example
new HE
m
m
October 16, 2013