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The Gossamer Tracker: A Novel Concept for a LC Central Tracker. Bruce Schumm SCIPP & UC Santa Cruz UC Davis Experimental Particle Physics Seminar June 3, 2002. Fall 2001 recommendation of the High Energy Physics Advisory Panel (HEPAP) to the Department of Energy’s Office of Science:. - PowerPoint PPT Presentation
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The Gossamer Tracker: A Novel Concept for a LC
Central Tracker
Bruce SchummSCIPP & UC Santa Cruz
UC Davis Experimental Particle Physics Seminar
June 3, 2002
“We recommend that the highest priority of the U.S. program be a high-energy, high-luminosity
electron-positron collider, wherever it is built in the world. This facility is the next major step in the
field, and should be designed, built, and operated as a fully international effort.”
Fall 2001 recommendation of the High Energy Physics Advisory Panel (HEPAP) to the Department of Energy’s Office of Science:
The LC group at SCIPP has been re-energized by this endorsement, and has continued to bolster its efforts with both public outreach and international cooperation.
TESLA
NLC
Linear Collider Physics
At leading order, the LC is a machine geared toward the elucidation of Electroweak symmetry breaking. Need to concentrate on:
• Precision Higgs Physics
• Strong WW Scattering
• SUSY
Reconstructing Higgsstrahlung
+
-
Haijun Yang, Michigan
M for p/ p
2= 3x10-5
Strong WW Scattering
Absent Higgs Sector, something else must act to renormalize W couplings
Diagrams: Wolfgang Killian, Karlsruhe
This physics will be produced via the t-channel will tend to be forward
W/Z Separation
Henri Videau; Ecole Polytechnique
Jet energy resolution requires energy-flow technique: excellent track/cluster matching to allow charged track energies to come from tracker
jetjet EE 60.0 jetjet EE 30.0
Precise Reconstruction of SUSYHaijun Yang; Michigan
Precise recon-struction of sparticle masses relies on precise determination of endpoint
p/ p2= 2x10-5
But does not establish as tight a requirement as Higgs physics
The North American Detectors
L Design: Gaseous Tracking (TPC) Rmax = 190cm 3 T Field Conventional (Pb/Sci) Calorimeter
S Design: Solid-State Tracking Rmax = 120cm 5 T Field Precise (Si/W) Calorimeter
The Trackers
The SD-MAR01 Tracker
Tracker Performance
SD Detector burdened by material in five tracking layers (1.5% X0 per layer) at low and intermediate mo-mentum
Code: http://www.slac.stanford.edu/~schumm/lcdtrk.tar.gz
Idea: Noise vs. Shaping Time
Min-i for 300m Si is about 24,000 electrons
Shaping (s) Length (cm) Noise (e-)
1 100 2200
1 200 3950
3 100 1250
3 200 2200
10 100 1000
10 200 1850
Agilent 0.5 m CMOS process (qualified by GLAST)
The Gossamer TrackerIdeas:• Long ladders substantially limit electronics readout and associated support• Thin inner detector layers• Exploit duty cycle eliminate need for active cooling Competitive with gaseous
track-ing over full range of momentaAlso: forward region…
TPC Material Burden
Pursuing the Long-Shaping Idea
LOCAL GROUPSCIPP/UCSC• Optimization of readout & sensors• Design & production of prototype ASIC• Development of prototype ladder; testing
Supported by 2-year, $95K grant from DOE Advanced Detector R&D ProgramSLAC• System performance studies (backgrounds, pattern recognition, vees, etc.)• Mechanical considerations
PRC MeetingDESY, Hamburg, May 7 and 8,
2003
SilC: an International R&D Collaboration to develop Si-
tracking technologies for the LC
Aurore Savoy-Navarro, LPNHE-Universités de Paris 6&7/IN2P3-CNRS, France
on behalf of the SiLC Collaboration
The SiLC CollaborationThe SiLC Collaboration
Brookhaven
Ann Arbor Wayne
Santa Cruz
Helsinki
Obninsk Karlsruhe
Paris
Prague Wien Geneve
Torino
Pisa
RomeBarcelonaValencia
Korean Universities
Seoul&Taegu
Tokyo
EuropeUSA
ASIASo far: 18 Institutes gathering over 90 people from Asia, Europe & USAMost of these teams are and/or have been collaborating.
Roles in the Larger Community
Discussions with Aurore Savoy-Navarro (LPNHE Paris)• Finite element (thermal, mechanical) modelling• Development of mechanical systems• Collaboration on ASIC development
University of Michigan• Interferometric alignment systems
The SCIPP/UCSC Effort
Faculty/Senior
Alex GrilloHartmut Sadrozinski
Bruce SchummAbe Seiden
Post-Doc
Gavin Nesom
(half-time LC postdoc from
1999 program)
Student
Christian Flacco
(will do BaBar thesis)
Engineer: Ned Spencer (on SCIPP base program)
SCIPP/UCSC Development Work
Characterize GLAST `cut-out’ detectors (8 channels with pitch of ~200 m) for prototype ladder
Detailed simulation of pulse development, electronics, and readout chain for optimization and to guide ASIC development (most of work so far)…
Pulse Development Simulation
Long Shaping-Time Limit: strip sees signal if and only if hole is col- lected onto strip (no electrostatic coupling to neighboring strips)Charge Deposition: Landau distribution (SSSimSide; Gerry Lynch LBNL) in ~20 independent layers through thickness of deviceGeometry: Variable strip pitch, sensor thickness, orientation (2 dimen-sions) and track impact parameter
Uncorrelated Sampling Check
Carrier Diffusion
)(21
exp),(0
2
ttDr
trPq
Hole diffusion distribution given by
Offest t0 reflects instantaneous expansion of hole clouddue to space-charge repulsion. Diffusion constant given by
hq qkT
D
Reference: E. Belau et al., NIM 214, p253 (1983)
sec65.00 nt
h = hole mobility
Other ConsiderationsLorentz Angle:
18 mrad per Tesla (holes)
Detector Noise:
From SPICE simulation, normalized to bench tests with GLAST electronics
Can Detector Operate with 167cm, 300 m thick Ladders?
• Pushing signal-to-noise limits• Large B-field spreads charge between strips• But no ballistic deficit (infinite shaping time)
Result: S/N for 167cm Ladder
At shaping time of 3s; 0.5 m process qualified by GLAST
Result: S/N for 132cm Ladder
At shaping time of 3s; 0.5 m process qualified by GLAST
132cm Ladder 300m Thick
Not Yet Considered
• Inter-Strip Capacitance (under study; typically ~5% pulse sharing between neighboring channels)
• Leakage Current (small for low-radiation environment)
• Threshold Variation (typically want some headroom for this!) But overall, 3 s operating point seems quite feasible proceed to ASIC design!
Analog Readout Scheme: Time-Over Threshold
(TOT)
i-min
thresh
e
e
nn
i-min
pulse
e
e
nn
r
TO
T/
/r
/te
etr
TOT given by differencebetween two solutions to
(RC-CR shaper)
Digitize with granularity /ndig
Why Time-Over-Threshold?
4
2
6
10
8
TO
T/
101 1000100
Signal/Threshold = (/r)-1
100 x min-i
With TOT analog readout:
Live-time for 100x dynamic range is about 9
With = 3 s, this leads to a live-time of about 30 s, and a duty cycle of about 1/250
Sufficient for power-cycling!
Single-Hit Resolution
Design performance assumes 7m single-hit resolution. What can we really expect?
• Implement nearest-neighbor clustering algorithm
• Digitize time-over-threshold response (0.1* more than adequate to avoid degradation)
• Explore use of second `readout threshold’ that is set lower than `triggering threshold’; major design implication
RMS
Gaussian Fit
RMS
Gaussian Fit
Readout Threshold (Fraction of min-i)
Trigger Threshold167cm Ladder
132cm Ladder
Resolution With and Without Second (Readout)
Threshold
Lifestyle Choices
Based on simulation results, ASIC design will incorporate:
• 3 s shaping-time for preamplifier
• Time-over-threshold analog treatment
• Dual-discriminator architecture
The design of this ASIC is now underway.
But Can It Track Charged Particles?
1 100.1
Energy (MeV)
z (cm)
Photon Distributions at R = 25 cm
Photon Interactions in Silicon
(Thanks to Takashi Maruyama, SLAC)
Converted electrons can come out of Si B = 5
Tesla E < 0.1 MeV
0.1 < E < 0.5 MeV
0.5 < E < 1 MeV 1 < E < 10 MeV
(Thanks to Takashi Maruyama, SLAC)
Photon Conversion Probability
0.1 1 10 0.1 1 10
Energy (MeV) Energy (MeV)
Edep > 50 keV
60°
75.5°
82.8°
86.4°
(Thanks to Takashi Maruyama, SLAC)
No. of Hits
0.1 1 10Energy (MeV)
Edep > 50 keV
Normal incident
(Thanks to Takashi Maruyama, SLAC)
No. of hits: 68 strips/train 69 strips/train 106 strips/train
Occupancy: 0.27% 0.28% 0.42%25k channels
Tracker Layer 1 Simulation Photon flux: 241 photons/4 bunches 5784 photons/train Use 241 photons 1000 times to
increase statistics.
(Thanks to Takashi Maruyama, SLAC)
Seem tractable at this level.
Where Next?
We’ve just begun the process of fleshing out the design of this `Gossamer Tracker’
In the 3-year R&D window, we need to:
• Demonstrate ability to read out long ladders• Demonstrate resolution and dynamic range • Demonstrate passive cooling (data transmission is an issue!)• Develop ultra-light, rigid mechanical systems• Demonstrate need for low-mass tracker (central, forward)• Prove that such a tracker will perform well in integrated tracking system
Some (Very Preliminary) Roles
Santa Cruz
Develop prototype front-end ASICTest bench results with `makeshift’ ladderTest-beam studies (S/N and resolution as a function of whatever
SLAC
Explore occupancy, pattern recognition issuesExplore mechanical designs
Paris
Mechanical/thermal finite element analysisASIC `Back-end’ architectureExplore mechanical designs
Roles (continued)Michigan
Interferometric alignment systems
New Group? Could begin with simulation…
Calorimeter-assisted tracking (Vees, kinks)Track/cluster matchingPhysics signals
Or not…
Procurement/construction of more appropriate ladder Test beam preparation and executionThermal and mechanical systems
Summary
An ultra-light silicon-strip tracker may well be feasible at a high-energy electron-positron Linear ColliderLooks reasonable on paper, but much work must be done over next 3 years to prove the principle, show needAn international collaboration (SiLC) is forming to explore this and other silicon-tracking option for the LCWork on `Gossamer’ Tracker currently focussed at SCIPP and SLAC, but we expect this to expand