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Instrumentation Lessons from

High Energy Physics Carl Haber

Physics Division

Lawrence Berkeley National Lab

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Main Points • HEP has a long history of detector development.

o It is very much in the culture of the field. o Instrumentation absolutely enables new science. o Developments are typically science driven. o Mostly done in collaboration

• Not always easy to find enough support for R&D. • The national labs have had a significant role. • It is important to recognize timescales. • Precision semiconductor detectors will be my primary example

o Survey subtopics to illustrate the technical experience gained from HEP • Disclaimer: I have borrowed heavily from the work of a variety of

groups, experiments, and projects. I have tried to indicate the credit wherever possible and I apologize for any omissions.

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770 microns15 microns

15 microns

n=1.59n=1.49

n=1.42

fiber

cladding

track

mirror

scintillating section clear section photon detector

Pre-WWII 1950’s-70’s 1960’s-70’s

1970’s-today

1980’s -1990’s 1990’s-present

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All of these were developed to address the fundamental physics agenda

• Precision optical metrology

• Film scanning machines

• Large scale data processing • Wire winding machines

• Scintillators

• Wavelength shifters

• Superconducting magnets

• Pure cryogenic liquids

• Radiation resistant silicon • Custom ASIC design

• High density packaging

• Thermal/mechanical materials

• Multichannel photon counters

• Photographic emulsion

• Ionization counter

• Bubble chambers

• Multiwire chamber

• Calorimeter • Scintillator, crystal

• Gas

• Cryo and warm liquids

• Compensating

• Drift and time projection chamber

• Velocity sensitive particle ID • dE/dx, TOF, Cerenkov

• Position sensitive solid state sensors+integrated readout

• Scintillating fibers

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Generalities

• Funding agencies have made big investments in the construction, operation, and maintenance of experiments and facilities

• It has been relatively more difficult to support the R&D which leads to the experiments before approval as bona fide projects.

• How does R&D get supported? o Limited funds for technology, FOA’s, LDRD, startup $, SBIR

• Both R&D and construction require special facilities and capabilities o The national labs have invested heavily in these o But how to maintain these with some sort of constant support between

projects? • From the researcher’s perspective, would like to see more support of

advanced instrumentation R&D in recognition of the role Fit plays. • Find a balance between new ideas and a strong physics driven

instrumentation agenda aligned with potential future facilities.

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Lab’s have been key players…

• Culture: in the USA, academia rewards physics analysis over instrumentation, labs have been a home for instrumentation

• LBNL o The cyclotron, bubble chambers, TPC’s, pixel detectors, fully depleted CCD’s

• Brookhaven o Liquid argon calorimetry, fast electronics, ion collider

• SLAC o Solenoidal detectors, e+e- colliders, DIRC (particle ID), track triggers, 3D sensor

• Fermilab o Superconducting accelerators & solenoids, DAQ, hadron calorimeters

• Argonne o Large scale scintillating calorimeters

• CERN

o Multi-wire proportional and drift chambers, Ring Imaging Cherenkov, hadron colliders, beam cooling

Incomplete list….

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Laboratory Facilities and Infrastructure • Unique capabilities serving the national community originating out of HEP

• LBNL: Micro Systems Lab focused on scientific CCD development and fabrication; Composites Facility focused on high performance thermal/mechanical structures

• BNL: Semiconductor Detector Laboratory: novel and radiation resistant sensors

• Fermilab: SiDet Facility focused on the assembly and fabrication of large precision tracking and imaging systems

• ASIC design groups exist at all the labs

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Transformation

• An important lesson is to think of transformation. There are many examples in HEP of this paying off.

• In the 1980’s HEP turned to precision semiconductor sensors + ASICs, but development was initially met with considerable skepticism

o Little experience to build on

o High risk

o Long design and iteration cycle

o Expensive and required new investments in staff and facilities

o Physics benefit was questioned

• But the investment paid off heavily in science, capabilities, and benefits to other fields.

• Continues to pay off

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Historical Timescales • CDF vertex detector R&D 1985-1989 = 4 years

• Construction 1990-1991

• Beam 1992

• LHC detector R&D 1990-1997 = 7 years

• LHC detectors Technical Design Report 1997

• Construction 1998-2004

• Beam 2008

• High Luminosity LHC detector R&D 2006-2015 = 9 years

• Construction 2017-2020

• Beam 2022 (?)

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Precision Semiconductor Detectors • A mainstay of HEP since the late 1980’s • The basic principles and structures have remained the same yet these

detectors continue to scale and function over a luminosity range of “~106” • Built on a significant and evolving technology base

o Application specific integrated circuits o Design and simulation tools o Wafer size 4”,…....,8”; decreasing feature size, circuit performance o Interconnections, wire and bump bonding o High density electronic packaging o Advanced power management, fault tolerance o Composite mechanics o Advanced thermal/mechanical materials o Precision optical metrology o Highly parallel DAQ with embedded processing (FPGA’s)

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Evolution of Electronics

2011 ATLAS FEI4 Chip 26880 pixels, 30 mW/pixel 3000 transistors/pixel

20 mm

~1980 single channel of discrete hybrid pre-amp, a few transistors, 14 mW/channel

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Collider Detectors

generation year luminosity DT chan/area dose readout

1 CDF SVX

1990 1029 3.5 ms

3.5 ms

128 ns

25 ns

25 ns

50K/ 0.68 m2 25 Krad 3 mm CMOS

2 CDF SVX*

1995 1030 50K 100 Krad 1.2 mm RHCMOS

3 Run 2

2000 1032 600K / 5 m2 1 Mrad, 1013/cm2

0.8 mm RHCMOS

4 LHC

2009 1034 5 x106 / 68 m2 108 pixels

10 Mrad 1015

0.25 mm CMOS RH Bi-CMOS

5 HL-LHC

2020 1035 108 / 200m2 109 pixels

100 Mrad 1016

65 – 130 nm CMOS SiGe, Commercial

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The Design Process

• Sensor • thin: lower voltage • thick: increased signal • smaller segment: less

capacitance, leakage, more channels

• Electronics • fast: high power, noise • readout architecture

• Cooling • Mechanical Support

• Physics Goals • Design Parameters

– Resolution – Layout – Segmentation – Mass – Rate, L

• Radiation exposure

Simulation tools play a critical role in all of these aspects

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Simulation • Detector performance

• GEANT, Fast MC’s, physics sims • Radiation fields

• FLUKA • Sensors

• Field and signal calculations • Analog IC

• SPICE • Digital IC

• Design tools, layout, verification

• Thermal/Mechanical • ANSYS, etc

• DAQ, queuing

0

20

40

60

80

100

120

0.1 0.2 0.3 0.4 0.5

Ther

mal

Con

duct

ivity

-W/m

K

Foam Density-g/cc

FEA 130ppi cell array

130ppi foam test data

curve fit to new data

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Technology Cross Section

• ASIC’s

• Packaging

• Sensors

• Large systems

• High performance materials

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ASICs

l Motivation was miniaturization of electronics to read solid state sensors close to the interaction or densely packed l This motivation still exists today

l Intimate connection of sensor element with readout electronics results in small capacitance. This enables: l High speed l Low Noise l Low power

l Prime example is hybrid pixel detector

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1988 1990 1996 1998 2003 2011

Commercial rad-soft

Military rad-hard

Commercial full custom (rad-hard)

Commercial synthesized (rad-hard)

3.0 mm 11K transistors

1.2 – 0.8 mm 0.25 mm 0.13 mm 90M transistors

2 cm

65nm

Top quark discovery

Precision Standard Model and quark Mixing matrix

Higgs boson candidate discovery

Future LHC discoveries

LBNL Vertexing ASIC’s only

SVX FE-IX

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The Impact of Feature Size

• We are at 130 nm and are moving to 65 nm

• Industry and academia are already a few gen’s ahead

• Can now conceive of significant processing per pixel

• But the impact of these very deep sub-m processes for the digital aspect can be as huge as ASICs were in 1990.

• But this has an effect on the design process as well

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How is ASIC Design Practiced?

l Not the same design process that is used in industry l Industrial chip makers have designers specialized by task l Assembly-line design, one does only place and route, another

only timing analysis, another design rule checking, etc. l Designers working on HEP chips see full subsystem design &

need a broader set of skills, longer learning curve for each new process

l Today’s ASIC design collaborations in HEP are large l Originally 1 or 2 engineers and a few scientists “SVX”

l Simple design and simulation tools, few10K transistors

l Order 10 engineers + order 10 scientists or more “FE-I4” l Sophisticated software tools with technical overhead, ~100M transistors

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The ASIC development cycle is changing

l For earlier processes or for applications of a process to a new use (eg. achieving radiation tolerance) several prototype iterations were necessary l Prototypes themselves were relatively inexpensive

l Simulation models were not always accurate

l Simulation tools and computers to run them were limited

l For a current CMOS process a chip should work exactly as designed the first time (see next slide example) l This front-loads the work into more design verification and simulation

instead of prototyping cycles.

l Prototypes in current CMOS processes are expensive

- 10 mm2 in a .35mm legacy process can cost around $10k - 10 mm2 in 65nm costs $80k

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Inside a Pixel Readout Chip

PHOTO

LAYOUT

100mm

10k transistor digital block every 4 pixels

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Power of modern design tools

Simulation type Power (avg) [uW]

ETS1 42.28 Spectre2 25.19 Ultarasim(s)2 24.69 Ultarasim(a) 2 24.73

Ultarasim(ms) 2 35.12 HSIM1 27.64 HSIM2 30.98

Digital column pair layout (30K transistors shown)

300um slice

Range of measured power: 20-30 mW

Power per 4-pixel block at 400 MHz/cm2 hit rate

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ASIC Design Opportunities • Significant IC design resources exist within the labs because

ASIC’s are so central to HEP today.

• These resources are eager to collaborate on non-HEP projects, because having a diverse customer base can keep a specialized effort viable in the long term. Many groups already design IC’s for use in photon science, but these are typically home grown initiatives: "what can we do that is of general interest outside of HEP".

• A significant opportunity is there for reversing this flow.

• Think big. Think about what could one do with massive high speed processing in photon/neutron science ASICs that would open up a new scientific window, and come with specifications to an HEP IC design group and willingness to get involved.

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Is Architecture Important? • A typical front end consists of a charge amplifier, signal

processor, storage, digitization, and readout. • There are many ways to implement this as long as you

can maintain the required S:N, power, bandwidth o Fully analog, n-bit ADC, binary o Technology vs performance

• Different pulse processing solutions can work for the same application.

• Part of debate may stem from what information you are convinced you need to keep.

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2 Approaches to the Same Problem

Maximalist

Minimalist

Both recently observed a new boson with a mass of about 126 GeV/c2

Application was silicon strip detector readout….

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High Density Packaging

• Electronic packaging is often the only “reducible” part of the detector mass

• Advances in packaging have allowed us to integrate increasing complexity into denser footprints

• Maintain necessary thermal performance with minimized mass and high reliability but also a vulnerable point

• Key technologies are based upon commercial processes • Avoid the homemade syndrome but push the limits…and, • Follow established testing and qualification protocols • Test under realistic conditions

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Key Technologies

• Surface mount technology (SMT), pick & place • High density multilayer PCB and flex

o Trace widths/space approaching 25 mm • Large area flexible circuits > 1 meter length • Chip on Board (COB) and Chip on Flex • Thin film on ceramic, glass, and polyimide • Thick film on ceramic, BeO and AlN substrates • Lamination onto high-TC carbon substrates • Wire and bump bonding • Adhesives and dispensing • Encapsulation

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Technology Examples

Sensor w. 5120 wirebonds

Readout ASIC

4 Layer Polyimide/Cu Hybrid (Liverpool)

Module Control Chip (SLAC)

Power Control Circuit (BNL)

1.3 meters

BeO/Au/Ag Hybrid

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Material Reduction

• This is a 2 sided sensor readout structure with integrated precision support and cooling

• Total material/unit is in the range 2.0-2.5% Xo

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Big Companies/Small Companies

• Working with industry is essentially required for the packaging aspect

• Large companies have invested heavily in cutting edge packaging for their in-house needs but they are unwilling to collaborate

• Small startups to do advanced packaging usually fail, beware!

• There exist only a small number of domestic “prototyping houses” who are willing to do reasonable projects for us and try to push the envelope. It is a good idea to work with them!

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Pushing the Boundaries

• Industry is good at developing reliable and robust technologies but their perception of limitations is driven by large scale manufacturing

• Can sometimes push the specs in a limited domain o A good example is wirebonding, exceed the pitch limits o Learn how to camp

• However inventing a new packaging technology can lead to grief o Material interactions can be a serious problem o Only do it if there is no other choice

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Wirebonding

• Mainstay of microelectronic interconnection

• Requires particular control of materials, cleanliness, and process

• Automated (5 bonds/sec) machines are commercially available and at labs now

• Now in widespread use in the HEP and related communities

• 75 mm pitch is achievable with good process control, a typical HEP “module” might contain ~5000 bonds, but this often exceed industrial specifications

• But things can still go terribly wrong….

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Many Lessons

• Interconnections are the Achilles Heal of detector systems

• Wirebond encapsulation and thermal stress

• Resonant excitation of wirebonds

• Cleanliness & surfaces

• Wirebond QA and testing

• Adhesives

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Sensors

• Ubiquitous silicon

• Processing complexity vs simplicity

• Limited vendors, market share

• Not made in the USA

• Radiation hardness

• High voltage

• New materials

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30 Years of Development by Many Groups Worldwide

Segmentation

Spee

d

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Simple vs Complex

• To date, earliest structures continues to overwhelmingly dominate the application to HEP and related fields. o Single sided silicon microstrip detector (SS SMD)

• Why? o It’s good enough to do the science o Inexpensive and relatively easy to fabricate o Robust to radiation and high voltage operation o Even the hybrid pixel detector is based upon SS SMD

• But does this lesson apply to the particular needs of the photon and neutron science community?

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Limited Vendors/Market Share/ USA

• In spite of the size of the USA semiconductor industry, no silicon strip/pixel detectors are manufactured commercially in the USA

• Worldwide the market is dominated by one vendor, for large scale applications there is a near monopoly situation

• Prior to the LHC era a second vendor made important contributions to the HEP market but now focuses on niche applications

• There are a handful of other small vendors, all in Europe, some with emphasis on the smaller niche applications

• Important to understand this situation in the context of future needs for photon and neutron science.

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Radiation Hardness

• This has been a key issue for HEP, not clear what the photon/neutron science overlaps are.

• Over the past 25 years this has been studied in great detail and a variety of effects have been characterized and even discovered. It is essentially a full time job.

• Silicon has continued to outpace any alternative over the “x106” range

• The solution has included materials, processing, electronics, structures, and operating protocols.

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Effects and Control

Gregor Kramberger, Ljubljana

M.Moll RD48

S.Parker

Bulk leakage: temperature, volume, integration Type inversion: materials, temperature

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Large Systems • Scaling • Mass production • Minimize the parts count • Services – still large gains to be made • Reliability and redundancy • Robotics • Calibration and monitoring • Why things don’t work: usually because they did not get

tested first.

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Scaling

• In the past, HEP has relied heavily on a scaling hypothesis which allowed us to extrapolate from a very small number of prototypes to a large array.

• To an extent we are departing from that with intermediate “multi-modular” substructures. But this is also driven by the bottleneck of final assembly

X 4000 each individually mounted

x1000

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Mass Production

• To fabricate and test 4K-20K sensor units “modules” requires an efficient, multi-institutional/multi-year coordinated project

• Achieving this may run counter to political or institutional values.

= 200 m2 Silicon

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Minimize the Parts Count

• Most anyone who has been through one of these projects will agree that minimizing the parts count and variety of elements is an important lesson.

• Achieving this may run counter to political or institutional values.

LHC CMS Tracker

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Services • Services refers to supply of current, signals, and coolant

to a detector.

• With the confidence of a generation of successful projects, this has been recognized as an opportunity for dramatic improvements. Also driven by granularity.

• Discard the principle of sensor isolation.

• Synergistic with emerging commercial and academic interest in efficient power management of new CPU’s.

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Power Architectures

Hybrid current = I Number of hybrids =n Total current = nI Power lines = n

Hybrid current = I Number of hybrids =n Total current = I Power lines = 1

…… Constant current source

Constant (high) voltage source

Hybrid current = I Number of hybrids =n Total current = n(I/r) Power lines = 1

……

……

1 2 3 4 5 6 n-1 n

1 2 3 4 5 6 n-1 n

1 2 3 4 5 6 n-1 n

…… + -

Individual power

Serial power

DC-DC power

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Serial Power

• Many variations on this have been studied in the R&D efforts, custom ASICs exist and are in development

• Large systems (>30 drops) have been operated with AC coupling

• Stable, low noise behavior obtained

• Failure recovery and control circuits have been tested (Brookhaven)

• Most efficient when current per module is uniform

BNL

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DC-DC Conversion

• DC-DC converters require high frequency clocks

• Realistic circuits have been operated in close proximity to sensor/modules with excellent noise performance, when adequately shielded.

• Main concern is the mass and size of required components

Buck converter with custom air core inductor CERN

Charge pump

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High Performance Materials

• HEP puts a big premium on low mass precision support structures and thermal management.

• Not completely clear how significant is the overlap with photon/neutron science needs but….?

• Have partnered successfully with small companies to o Create innovative and useful new materials o Develop detailed understanding and modeling of properties

• The fabrication of novel support and cooling structures has developed more as an in-house capability. o Would otherwise turn to aeronautics industry – too expensive

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Advanced Materials • Processed carbons

o Carbon-Carbon: CF reinforced C by pyrolysis

o Pyrolytic Graphite: TC>1000

• Graphite Foams: of varying density, conductivity

o Pocofoam

o Allcomp foam

• Boron Nitride: fillers

o Varying particle size, shape

• Thermal adhesives: rigid, compliant, radiation hard

• Silicon Carbide: solid, foam, also an electrical material

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Y STAR and Phenix Nuclear Physics Upgrades

ATLAS pixels

PROJECT R&D PROJECT

Conductive foam

Pixel staves & I-beams

Strip integrated structures

R&D PROJECT

Ultimate mass reduction

Pixel integrated structures

Final strip prototypes

ATLAS Hi upgrades

2007 2011-2 2013 2015

Your new R&D project here?

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Intelligent Tracking • So what would be a frontier application for HEP?

• Gather hit patterns from nearby sensors together in near real time to calculate momentum vectors.

• Requires fast data xfer, local processing, interconnects, precision support and alignment….

• Plus many variants involving, ie: 3D integration, etc…

TOP

BOTTOM

Correlator

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Unintended Consequences

• In the late 1980’s DOE funded the SSC Detector R&D program. o Significant aspects of today’s technology germinated there and in

the early CERN “RD” collaborations.

• An idea was to see if the front end electronics could be fabricated on the same silicon as the sensor o A monolithic rather than a hybrid approach.

• This was part of original justification for the LBNL MSL.

• S.Holland (LBNL) developed a CMOS compatible sensor fabrication process. By adding a gettering layer to the bulk substrate, high temperature steps could be included.

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Cont. • While the process was demonstrated the

approach was abandoned in HEP, because o The hybrid pixel detector was much more flexible. FE electronics

could keep pace with the commercial technology curve. Rad-hard and alternative sensor approaches were accommodated

o Then CMOS MAPS, which collect charge from thin undepleted regions, emerged as natural alternative for some applications

• But it was quickly realized that now CCD’s could be fabricated on high resistivity silicon leading to a deep fully depleted CCD with significant advantages for astronomical imaging.

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Principle of the Fully Depleted CCD

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Result

• Now regularly fabricated in a mixed Lab/Industrial process, tested and packaged for science application. o But this required the National Lab R&D infrastructure and

commitment which originated with HEP

• The development coincided with the great convergence of particle physics and precision cosmology which occurred in the 1990’s: dark matter, dark energy, supernovae, large scale surveys, lensing studies…..

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Deployed on Scientific Cameras

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Conclusions

• HEP has taken the initiative and the risk to invest in advanced instrumentation R&D.

• The scientific payoffs have been huge.

• This is in spite of a system which is not 100% supportive.

• It is a challenge to maintain key capabilities as projects cycle in and out. Quite open to work with others.

• Big ideas and transformative approaches are still to be found, particularly in relatively new research domains.

• If you don’t test it, it probably won’t work.

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Extra slides

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Historical Note • First silicon tracker for a hadron collider was proposed ~1985 by the INFN Pisa

group for CDF at Fermilab the “SVX” – 4 layers of silicon microstrips, 2-7 cm radii – 50K channels – Expected luminosity was 1029 (100 nb-1), (dose ~few KRad) – Primary purpose was to discover top by (real) W’tb – Not expected to do any significant B physics

• Many were skeptical about this application – “it will flood the rest of the detector with secondaries” – “it will be impossible to maintain required mechanical precision” – “it will be inefficient” – “it will burn up due to radiation” – “it will be unreliable or never work at all” – “anyway there is no physics to do with it…”

• This device was crucial to the discovery of the top quark by CDF and opened up the field of precision B physics at hadron colliders.

• All collider detectors now include silicon tracking • 2008 APS Panofsky Prize to Menzione and Ristori

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Bump or Flip Chip Bonding

• Wirebonding is impractical for large 2D arrays

• ATLAS pixel cell is 50 x 250 mm

• At this density FE interconnect is made with a conductive “bump”

• This is an industrial process and requires expensive technology, therefore has not become “in-house”

Xray of bumps 16 chips. 46,080 bump bonds

Sensor (below) ICs 6.3cm

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Bump Bonding Processes SOLDER BUMPING INDIUM BUMPING

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Emerging Interconnects

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Electrical Materials

material Resistivity (mWcm)

dielectric constant

Xo(cm) Thermal C. (W/moK)

CTE (ppm)

Silicon 11.9 9.37 149 2.6 Aluminum 2.65 8.9 237 23.9 Copper 1.67 1.43 398 16.6 Gold 2.44 0.335 297 14.2 Carbon 1375 19.32 varies Kapton 3.4 28.4 0.2 ~20 SiO2 3.9 10 1.1 BeO 1021 6.6 14.4 230 8.3 AlN >1020 9 8.4 170 4.3 Al2O3 >1020 9.0 7.55 24 7.2 G-10 4.7 19.4 0.2

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Miniaturization in Cosmology (recent)

DEC-CAM 60 2k x 4k CCDs

SNAP 1/2 size demonstrator camera (32 3.5k x 3.5k CCDs)

Huge (and heavy) boxes of conventional CCD readout electronics

ASIC electronics on back (in same footprint)

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Carbon Foams: Low density, hi conductivity

68 0

20

40

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80

100

120

0.1 0.2 0.3 0.4 0.5Th

erm

al C

ondu

ctiv

ity-W

/mK

Foam Density-g/cc

FEA 130ppi cell array

130ppi foam test data

curve fit to new data

• Developed in collaboration with industry through SBIR and other support.

• Now qualified for radiation tolerance and thermal/mechanical performance, will be used for pixel and strip stave fabrications.

• FEA modeling of thermal and mechanical properties.

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Technology Drivers • Scalable • Large Systems • Precision • Low Mass • Fast Electronics • Low Power • Low Temperature • Inaccessible • Radiation Hard • High Voltage