Transcript Feedback from Vertex 2002 Conference Chris Damerell 18 December 2002 RAL •10th anniversary – held every year since 1992 •Traditions: •Island or lakeside •Invite leading young physicists •Encourage.

Feedback from Vertex 2002 Conference
Chris Damerell
18 December 2002
RAL
•10th anniversary – held every year since 1992
•Traditions:
•Island or lakeside
•Invite leading young physicists
•Encourage discussion of tough problems
•~70 participants – no parallel sessions
•http://www.phys.hawaii.edu/vertex2002/
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
1
•Topics
•Existing detectors
•Future detectors (hadron colliders)
•Present/future heavy ion detectors
•Vertex detectors in trigger
•Future detectors (linear collider)
•Radiation effects
•Electronics and integration
•Simulation studies
•Present/future astrophysics
•Other non-HEP applications
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
2
This year’s venue was
exceptional ..
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
3
A little geography/geology
~3000km
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
we were here
4
V= 5~10 cm/year
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
5
Existing vertex detectors
•HERA-b, CLEO, BaBar,Belle, CDF, D0, H1, ZEUS
•All are using silicon microstrips
•Pixels, used for vertex detectors since 1985 in NA32
and SLD, have been dormant for past 4 years.
However, a major transition is imminent ..
•What lessons are still being learned regarding the
highly-developed microstrip-based systems (used as
vertex detectors)?
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
6
•HERA-b
•Detector working well for 3 yrs, despite high and
inhomogeneous irradiation (tested to 3.1014 mips/cm2
equivalent)
•Some irradiated sensors show long term degradation (cce
etc), but this could be related to storage conditions
•CLEO
•Double sided (for minimal material); unfortunately,
constructed with non-floating electronics, so cannot
overdeplete. Serious degradation (loss of n-side efficiency)
with low radiation dose (~5 krads)
•Will probably remove detector for future programme, where
‘vertex-quality’ precision is not needed
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
7
•BaBar
•5 layers, DS. Working well, will need to replace inner layer
by 2005 (1-2 Mrad/yr in bend plane)
•Type inversion after 2-3 Mrads: ‘unexpected’?
•Hygroscopic CF support: Δr 200 μm from dehumidification
•Belle
•SVD1.4 to be upgraded to SVD2.0 by next summer
•Better coverage, electronics for 20 Mrad cf 1 Mrad now
(0.85-0.30 μm CMOS), floating electronics, so will not be
killed by pinholes, which currently disable a few half-ladders
per year
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
8
•CDF
•L00 SS, then SVXII – 5 layers DS detectors
•Heroic effort, now operating well
•Main problems: noise/pickup in L00,
and wirebond failures due to Lorentz force on high
current wires (pulsed) in solenoid fld inducing
resonant vibration – was also a concern in SLD
•Pickup means L00 can’t be in the trigger, and
readout time may be a bottleneck
•Only 0.1 fb-1 so far: will replace SVXII after 4 fb-1,
will then be good for 15 fb-1 (end of Run 2b)
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
9
•D0
•Silicon Microstrip Tracker has 8 layers (4 with full Φ coverage)
mix of SS and DS from different manufacturers …
•Another heroic effort, 3 sq m silicon, 90% now operational
•Not-understood pedestal shifts during superbunch, and noise
on some sensors (manufacturer-specific)
•Due to radiation damage, will need to build a completely new
SMT for Run 2b. Lessons: change from DS to SS, and simpler
design (avoid 6 sensor types as they have now)
•New detector will include a ‘Layer 0’, similar to L00 of CDF,
with electronics and cooling out of the tracking volume (hence
reduced material)
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
10
•H1
•Central Silicon Tracker has 2 layers of DS detectors
•Working pretty well, some repairs needed in Spring
2003 shutdown
•ZEUS
•SS detectors, working well
•Some dead modules, some have cabling/connector
problems
•Main concern is high radiation background at HERA;
hoping to fix in Spring 2003 shutdown
•Readout chips OK for 300 krads, so far seen up to
80 krad; a cause for concern
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
11
Put the electronics onto the
bias level.
Free from the “Pin-hole”
nightmare!!
P strip
+40V
N strip
0V
-40V
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
Isolated by photo
couplers on the
repeater system
12
CDF assembly and installation
L00 Into SVXII
SVXII into ISL
Final Assembly
Vertex 2002 feedback - Chris Damerell
Installation
18 Dec 2002
13
CDF future: Run IIb
• ~4-5 fb-1 inner layers perish (2005?) 
Replace L00, SVXII
– Improved rad hardness to 15 fb-1
– Easier to build-fewer different parts
– New SVX4 Chip (M Garcia Scivarez,
Th 1:45), DAQ etc mostly same as
Run IIa
Silicon Sensors
4mm separation
Hybrid electronics
Peek Cooling channels
2.9 x 5.6 mm
Mini PC
Cooling
Mounts
Chips
Wing Cable
Hybrid
Pitch Adapter
Sensors
Vertex 2002 feedback - Chris Damerell
Mounting holes
18 Dec 2002
14
Future vertex detectors
•Almost universal transition to pixel-based systems
•Can be made ultra-fast and rad-hard (LHC)
•Can be made ultra-thin and fine-grained (LC)
•[but not both at once!]
•Major advantages in terms of pattern recognition
•Ideal for vertex trigger at Level 1 (BTeV)
•Synergy with imagers for other science & technology
•SNAP (600 Mpixels, CCDs and CMT HAPS)
•SR detectors at new bright sources
•StillVertexand
video cameras:
silicon pixels now dominant
2002 feedback - Chris Damerell
18 Dec 2002
15
Future detectors (hadron colliders)
•LHCb
•Retain microstrip technology, SS detectors measuring R and
Φ separately
•Max flux 1.3.1014 neq/cm2/yr, significant gradient (but tiny
compared to ‘Fred effect’ of NA32)
•n-on-n gives life expectancy of over 2 years (fully efficient
when underdepleted) [pixels would be more durable]
•Sensors in secondary vacuum – delicate ‘Roman pots’
•Sensor design finalised, first module being built, complete
detector In 2005 for startup in 2007
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
16
•BTeV
•Pixel based – immersed in high field dipole magnet
•Ultra-fast track finding in vertical plane, momentum defined as a
by-product
•B trigger at Level 1, based on summed imp param significance
•Extremely rad-hard, so can operate 6 mm from beam axis
(adjustable!)
•Another project which has switched to DSM FE readout chips
•Thin Aluminium RF screen, but can operate in main machine
vacuum
•Being reviewed for full approval (for the third time!)
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
17
•CMS
•Pixels 150x100 μm2
•n+ on low resistivity n (with p+ backplane) for max lifetime
•Operate at –10 C
•Need annual removal for beampipe bakeout (really??)
•First (production?) module (16-chip) due Nov 2002 – done?
•ATLAS
•Pixels 400x50 μm2
•Otherwise similar to CMS. High oxygen silicon (but see later)
•Get ‘lifetime dose’ (50 Mrads and 1015 n equiv) in 10 yrs at R=8
cm, so will need fairly frequent replacements of ‘B layer’
•Goal remains <2% X0 per layer. Still challenging, for HAPS
•Module production mid 2003 to end 2004, install Jan 2006
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
18
LHCb detector layout – total length 54 cm
Each of 21 stations has 2 R and 2 Φ SS sensors
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
19
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
20
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
21
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
22
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
23
Present/future heavy ion detectors
•All need high precision VTX systems for charm detection (hard probe
of QGP) in high density environments – challenging! (BNL wkshop)
•STAR
•SDD-based (first VTX with this technology) 3-layer
•Relatively thick – 1.5% X0 per layer
•Helps imp param resoln, but not dramatic. Need more for charm
•PHENIX (NA60)
•High hit density (L1 at R=2.5 cm would have 12% occupancy with
strips) so pixels essential
•Consider HAPS (modelled on NA60) in short term, CCD/MAPS in
long term (beyond 2005) – need <1%Xo per layer
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
24
•ALICE
•Ambitious Inner Tracking System inside TPC:
SPD, SDD and SSD
•100 particles/cm2 at R=4 cm (only 10% of LC level)
•50x425 µm2 pixels (adequate)
•1% X0 per layer will be adequate
•Expect only 250 krads in 10 yrs …
•Design frozen, install 2006
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
25
NA60 HAPS-based vertex detector starting life …
•3 planes installed, 8 ultimately
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
26
ALICE SPD half-stave
Each Stave is built of two HALFSTAVES, read out on the two
sides of the barrel, respectively.
Bus
Ladder: 5 chips+1 sensor
MCM
ALICE1LHCb chip
Silicon sensor
193 mm long
Grounding foil
Cooling tube
Carbon-fibre sector
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
27
SPD bus
2mm
2
4
3
11mm
SMD component
5
6
7
7
7
7
6
5
7 layer Al-Kapton flex
2
1
1
PIXEL DETECTOR
Aluminum
Polyimide
Glue
READOUT CHIP
COOLING TUBE
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
28
Benchmark: D0  K-p+
•
Initial S/B ~ 5 · 10-6
– Pb-Pb collisions at LHC with
dN/dy = 6000
– invariant mass and particle-id
cuts only
•
Final S/B ~ 0.1
– after vertexing and pointing cuts
•
Significance S/√(S+B) ≈ 35
– for 107 events
(~15 days data taking)
Vertex 2002 feedback - Chris Damerell
107 events, all cuts applied
total
bkgd-subtracted
18 Dec 2002
29
Vertex detectors in trigger
•Belle
•Will be used mainly to eliminate beam-gas background at L2
•D0
•CFT plus SMT determine imp param significance of trks
•L2 decision time 100 µs
•Based on state-of-art FPGAs (Xilinx Virtex 560 pin BGAs)
•Will increase b-bbar production yield by factor 6, and accept
Z to bb (valuable for mass scale calibration)
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
30
•CDF
•L2, combine tracks from Central Outer Tracker with SVX to
determine all track parameters in rΦ view, hence imp
parameter significance
•45 KHz to 300 Hz, 20 µs processing time (massively parallel,
deadtimeless)
•Many complications solved, such as movement of Tevatron
beam by ~20 µm during a store
•Pick up hadronic B decays with high efficiency
•Now fully operational
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
31
•LHCb
•Similar approach (Level 2) to measure imp parameters
•Momentum determined from ‘TT’ tracker (?) in small fringing
field [precision of momentum determination?]
•BTeV
•Standalone tracking and momentum determination in vertex
detector
•Level 1 trigger from farm of ~2500 processors
•Accept if GE 2 trks with imp param significance GE 6 σ
•Hadronic B efficiency typically 60% with 99% suppression of
minimum bias events
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
32
•CMS
•Explore what a few thousand commercial processors (2007
vintage) can do with L1 events, given the full tracker
information
•Implies about 50 ms per decision (500 ms with 2002 vintage)
•Additional challenges: multiple events/bunch crossing and
huge rate of ‘uninteresting’ events with Bs
•Restrict to anticipated physics channels, and (for example)
demonstrate that B selection in dimuon events is feasible
•I continue to worry (as an outsider) that LHC GPD triggers are
necessarily closely related to expected new physics
[Remember the non-discovery of J/ψ at CERN ISR]
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
33
Future detectors (linear collider)
•There will be one machine, and possibly two detectors
•Trigger not required or desired – in fact, forbidden! [a major
reason for LC being essential, in parallel with the LHC]
•4 main VTX technology options, all using silicon pixels
•Reasonable world-wide co-ordination of R&D
•Goals are prototype ladders by about 2010
•Technology choice(s) to be followed by world-wide detector
construction programmes [nobody need be left out]
•Warm accelerator cavity option (JLC and NLC) is detectorfriendly (readout in 5 ms is OK) whereas TESLA needs 50 µs
readout time
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
34
•International LC physics/detector workshops (LCWS) held every
few years since 1991
•First world-wide phone conference on LC vertex detectors, with
slides on web, planned for 8th January 2003
•Idea is for these meetings to evolve into proto-collaboration
meetings over next year or so
•UK situation strengthened by recent PPRP recommendations, and
SR2002 outcome:
•LCFI (£2.3 M)
•UK participation in CALICE
•LC accelerator R&D (£5.4 M in SR2002 Science Budget)
•A UK view: ‘Global PP community can afford one big build and
one big exploitation phase at any given time’
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
35
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
36
•CCD
•Talks from LCFI and JLC
•Both push for similar performance, except that JLC focuses on the
room temperature machine option
•JLC group starting important studies of radiation effects from ~100
MeV electrons
•MAPS
•‘Standard CMOS process’ so main signal from undepleted bulk
•However this isn’t obligatory – early S Parker developments with
300 µm fully depleted devices were highly successful
•Early results based on few mm2 devices and minimal in-pixel logic
•Recently, with 0.35 µm CMOS, increasing functionality planned
•CDS is so far restricted to full readout cycle time
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
37
•DEPFET
•Based on detector-grade high resistivity silicon, fully depleted
•Requirement of supporting CMOS chips on 2 sides may be a
significant limitation
•Has advantage (wrt current MAPS) of fast CDS, given promise of
pulsed clear of entire signal charge after each row readout, so
equivalent noise performance to CCD option
•HAPS (incl new SoI-inspired)
•Read 1 in N pixels, by analogy with capacitive charge division in
strip detectors
•Resolution tends to be unstable
•Implications for 2-track resolution?
•SoI approach could reduce material, but looks pretty complex (?)
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
38
•Physics studies
•Results confirm need for thinnest possible layers, and Layer 1 at
minimal radius [response to a contrary suggestion at US LC
workshop last January]
•Beginning to simulate complex events, where the sensitivity to
performance increases
•Healthy degree of cross-checking in some areas, notably
precision achievable in measurement of Higgs BRs
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
39
Conceptual design (almost technologyindependent)
•Small pixels (20x20 mm2)
-> precise point resolution
• thin detector(<0.1%X0)
-> less multiple scattering
• close to the IP (15 mm)
-> smaller extrapolation
error
• large polar angle coverage
|cos()|<0.90 with 5 hits
|cos()|<0.96 with 3 hits
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
40
• 5 layers
-> higher resolution
-> robust local alignment
-> effective gamma conversion
• fast readout (50ms/layer)
-> sustain high integrated
background
• gas cooled, low mass foam
cryostat
• minimal electronics (power +
few optical fibres)
-> little material at low angles
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
41
Clock traces and 55Fe spectrum
for low drive voltages
at 50 Mpix/sec
Radiation damage effects:
• beam background expected
about 50krad/year
(neutron 5x109/cm2/year)
• CTI should improve at fast
readout : to be verified
• CCD58 can be flexibly
clocked from 1 to 50 MHZ,
so it should be possible to
obtain good results for CTE
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
42
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
43
DEPFET pixel
MOS transistor instead of JFET
A pixel size of ca. 20 x 20 µm² is
achievable using 3µm minimum
feature size.
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
44
Proposed concept for TESLA
readout chips
matrix is read out
row-wise
520 x 4000 pixel
DEPFET-Matrix
(25 x 25 µm pixel)
steering chips
• thin detector-area
readout chips
first thinned samples:
down to 50µm
• frame for mechanical
stability carries readoutand steering-chips
[L.Andricek, MPI Munich]
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
45
DEPFET pixel matrix
Low power consumption
Fast random access to
specific array regions
- Read filled cells of a row
- Clear the internal gates
of the row
- Read empty cells
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
46
Hybrid Pixel Detector with Interleaved Pixels
Readout pixel
Interleaved pixel
Polyresistor
readout pitch = n x pixel pitch
Large enough to
house the VLSI
front-end cell
p+
Small enough
for an effective
sampling
n
Charge carriers generated underneath one of the interleaved pixel
cells induce a signal on the capacitively coupled read-out pixels,
leading to a spatial accuracy improvement by a proper signal
interpolation.
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
47
Charge Sharing Studies – Resolution

 parameterization allows a coordinate reconstruction and
resolution measurement
 function
•
Average resolution
Resolution vs. spot position
Resolution:
– Interleaved pixels (efficient charge sharing): 3 mm
– Readout pixels (min charge sharing): 10 mm
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
48
SOI Imager – Main Concept
Detector  handlable wafer
– High resistivity
– 300 mm thick
Electronics  active layer
– Low resistivity
– 1.5 mm thick
Detector: conventional p+-n, DC-coupled
Electronics: preliminary solution – conventional bulk MOS
technology on the thick SOI substrate
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
49
optimal vertex detector design is most
important, to reach final physics goal !
PRELIMINARY tagging purity vs efficiency
5 layers, 0.1%X0
Vertex 2002 feedback - Chris Damerell
4 layers, 0.2%X0
18 Dec 2002
50
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
51
Radiation effects
•RD50: Luminosity of upgraded LHC 10 times present design
•Also, radiation effects at future LC: high energy electrons
•NIEL provides too-simplistic description (known in case of CCDs
for 30 years)
•Oxygen story is more complex than first thought. The simple idea
is that high oxygen encourages VO and hence inhibits V2O
[V2O is a deep acceptor, induces negative space charge, so Neff
becomes p-type;VO a shallow donor, uncharged]
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
52
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
53
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
54
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
55
Conclusions
Nothing tends so much to the advancement of knowledge as the
application of a new instrument
- Sir Humphrey Davy (1778-1829)
•Detailed points:
•For DS detectors, float the n-side electronics and be able to
significantly overdeplete
•Encapsulate wire bonds only if you must (eg due to currentinduced stresses)
•Storage/operation: standardise on boiloff nitrogen [?]
•Beware of hygroscopic materials for mechanical structures
•Convenient access for upgrades and repairs (including radiation
damage)
is essential
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
56
•General points:
•Increased physics challenges are forcing an exponential growth
in the complexity of vertex detectors
•Special factors are handing the future for vertex detectors to
pixel devices, both in hadron and TeV-scale e+e- colliders
•[For tracking systems, microstrips have a bright future]
•[somewhat reminiscent of the struggle for CCDs to gain
ascendancy over electron tubes – vidicon etc – for video
cameras in the ’70s and 80’s]
•All pixel varieties represent a major escalation in complexity
(look at R&D timescales of SLD, ATLAS, CMS, BTeV, ALICE)
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
57
•How to approach the best industrial ‘corporate wisdom’ in our
disparate community?
•Maximise use of top-class industry (not just for sensors and FE
chips; bump bonding, module assembly, etc)
•[For NA32, we fortunately did not heed advice to ‘design your
own CCDs’]
•Formalise information exchange between participating groups
round the world? [explicit contact persons?]
•Problem of vast documentation on websites and publications
becoming ‘write-only memory’
•Community of young physicists and engineers is up to the task
•ANNUAL vertex conferences induce marvellous networking; main
justification for not going at a slower pace
•Vertex 2003, being held for the first time in UK, will be on shore of
Lake Windermere, 15-19th September 2003
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
58
The setting for the coffee breaks was even better than at RAL
Vertex 2002 feedback - Chris Damerell
18 Dec 2002
59