HEP by linzhengnd


									ATLAS at the Super-LHC
                Phil Allport

          Representing ATLAS UK

 • Examples of Expected Physics Gains
 • ATLAS Upgrade Requirements
 • Proposed UK Programme
 • Resource Requirements
 • Conclusions
           Examples of Expected Physics Gain
• Physics case for 10× luminosity much better known after
  first significant high energy data from the LHC
• However we can expect:
         Improved mass reach for discovery by ~500GeV
           (50%) with increased luminosity
         Greatly increased statistical precision on rare or
           very high energy processes
• Because of statistics and mass reach, SLHC is to a large
  degree complementary to the ILC − only LHC/SLHC can
  pair produce particles with mass ≥ 0.5 TeV.

                                       Dark Matter?                  Requires 5 years of SLHC

                                   Measure coupling of neutralino to Higgs.
                                   Determine its higgsino component.
      Examples of Expected Physics Gain
                         See Eur. Phys. J. C39(2005)293

• Precision Standard Model physics with 10 × data (sensitive to new physics)
    • Higgs couplings
    • Triple and quartic gauge couplings
    • Strongly coupled vector-boson scattering (if there is no Higgs)
    • Rare top decays through FCNC
• Extended mass reach for new particles (by ~0.5 to 1 TeV):
    • Heavy Higgs-bosons, extra gauge bosons, resonances in extra-dimension
      models, SuperSymmetry particles (if relatively heavy).
• SuperSymmetry (if relatively light, already discovered at LHC)
    • complete the particle spectrum
    • access rare decay channels and measure branching ratios
    • improve precision (e.g. to test against WMAP results)
        Examples of Expected Physics Gain
                                        In absence of clear Higgs at LHC,
                                        SLHC statistics could be needed to
                                        probe the W, Z scattering process
                                        which has diverging cross-section in
                                        SM without Higgs.
                                        It is therefore particularly sensitive to
                                        whatever new physics must exist to
                                        keep this process finite.
       Requires several years of SLHC

                         LHC                                           SLHC
Even with 300fb-1 many potentially important channels can be statistics limited
 Examples of Expected Physics Gain

                      ADD X-dim@9TeV                       SUSY@3TeV


                                                            200 fb-1/yr

                  fb-1/yr          80 fb-1/yr                             600 fb-1/yr

           2009             2011        2013        2015                  2017          2019
  First physics run: O(1fb-1)
       ATLAS Upgrade Requirements
To keep ATLAS running more than 10 years the inner tracker will need to be
replaced. (Current tracker designed to survive up to 730 fb-1)
For the luminosity-upgrade the new tracker will have to cope with:
• much higher occupancy levels
• much higher dose rates
To build a new tracker for 2015, work needs to start now.
• R&D until 2009 leading into a full tracker Technical Design Report (TDR)
  in 2010
• Construction phase to start immediately TDR completed and approved.
This proposal deals with the tracker upgrade programme only. It concentrates
on a part of the new proposed barrel detector region facing particular
challenges, but where the UK has special expertise.
The intermediate radius barrels are expected to consist consist of modules
arranged in rows with common cooling, power, clocking and cooling.
The aim of this proposal is to prototype the smallest unit for these radii
(a “super-module”) that can operate independently, testing all subsystems. This
may or may not also be a mechanically self-supporting object (a “stave”).
The ATLAS Silicon Central Tracker
         UK led project: all 4 barrels and 9 disks of EndCap-C assembled in UK
                                UK leadership on sensors, irradiation studies, module
                                prototyping and production, optoelectronics, data
                                links, final alignment systems, data acquisition and
                                engineering components.

                         Current Inner Tracker Layout
                                                                                             ID TDR



                                                               Pixels: 2 m2, ~80M channels
                                                               SCT: 60 m2, ~6.3M channels    Mean Occupancy in
                                                                                             Innermost Layer of
                                                               TRT straws: ~400k channels
                                                                                             Current SCT
Pixels (50 m  400 m): 3 barrels, 2×3 disks                    4.7cm < r < 20cm
• Pattern recognition in high occupancy region
• Impact parameter resolution (in 3d)
Radiation hard technology: n+-in-n Silicon technology, operated at -6°C
Strips (80 m  12 cm) (small stereo angle): “SCT” 4 barrels, 2×9 disks
• pattern recognition                                  30cm < r < 51cm
• momentum resolution
p-strips in n-type silicon, operated at -7°C
TRT 4mm diameter straw drift tubes: barrel + wheels             55cm < r < 105cm
• Additional pattern recognition by having many hits (~36)
• Standalone electron id. from transition radiation
     WP1: Physics and Layout Studies

Note: numbers based on factor 10 increase in luminosity but still 25 ns bunch crossing.
Would be worse for longer (50 ns) bunch crossing time.
                   WP 1: Physics and Layout Studies
All Silicon Tracker Proposal
 Pixels:                                           r=5cm, 8cm, 12cm              z=±40cm
 Very short -strips:                              r=24cm                        z=±40cm/100cm
 Short (3cm) -strips (stereo?):                   r=32cm, 46cm, 60cm            z=±100cm
 Long (12 occupancy-strips (stereo layers):
           cm) (3 SS + 2 LS)                       r=75cm, 95cm                  z=±100cm


     1                                      mean


          0   20   40       60   80   100
                   radius (cm)

vs radius
(25 ns)

                                                           Including disks this leads to:
                                                           Pixels: 2 m2, ~150,000,000 channels
                                                           Very short strips: 1.2/3m2, ~2.4/6,000,000 channels
                                                           Short (3cm) strips: 60 m2, ~25,000,000 channels
                                                           Long strips: 120 m2, ~13,000,000 channels
WP2: Radiation Background Benchmarking and
Simulations at the SLHC
• Understanding radiation
      background issues at SLHC crucial
      for successful design and operation
      of inner tracker.
    → Radiation degrades performance of
      detector and readout systems
    → High levels of activation will require
      careful consideration for access and

• UK played leading role at LHC and
     has unique expertise in this area.
•    Programme proposed for SLHC, led
     by UK, divided into two main areas:       Quarter slice through ATLAS inner tracker
                                               Region, with 5cm moderator lining calorimeters.
    1) Radiation background simulations.
                                               Fluences obtained using FLUKA2006, assuming
    2) Benchmarking of the Monte Carlo         an integrated luminosity of 3000fb-1.
       simulation codes with LHC data.
WP2: Radiation Background Benchmarking and
Simulations at the SLHC
 1) Radiation simulations                           2) Benchmarking
 • New moderator design and predictions         • Radiation monitor installation and
    for inner tracker.                             analysis of data.
     • Moderator reduces neutron energy             • Collaboration with several institutes
        making them less damaging to silicon.           established (Ljubljana, Arizona,
 • Beamline activation studies.                         Prague).
     • Access and maintenance to inner              •   Different monitoring technologies
        tracker impossible with current                 being installed in and around
        beamline. New design needed.                    ATLAS experiment.
 • Machine interface studies.                       •   Measurements of fluences (pion,
     • Increased integration between                    neutron, 1Mev-eq. etc.) and doses.
        machine and experiment inevitable.      • Minimum-bias measurements for
        For example machine magnets are            benchmarking of event generators
        being proposed near tracker.               (eg Pythia).

    Programme reviewed and endorsed by ATLAS Upgrade Steering Group.
    Seek support to take on a leadership role in this programme.
              Super-Module/Stave Concept
WP7: Engineering                   WP8: Data Acquisition and Off-detector Readout

                                    WP5: Optoelectronics
                                    Readout System

                                                           WP4: FE Electronics and

         WP6: Power
Distribution Schemes

                       WP3: Sensor Research
Current Barrel
                          and Development
    WP3: Sensor Research and Development

For LHC doses:
• Main failure mode is when full depletion voltage grows beyond breakdown
voltage. Undepleted region low field → poor charge collection.

For the SLHC doses (r=27cm: 1015neq/cm2=1.8×1015p/cm2):
• Will not be able to operate (conventional) silicon fully depleted (VDEP >> 1000V)
However, p-type silicon with n-strips (collecting electrons) can work as the
undepleted region is semi-insulating after heavy irradiation.
• Trapping is dominant radiation effect on sensor performance.
Optimize for charge collection efficiency CCE not for VDEP
• High currents threaten stable operation (thermal runaway)
Require robust cooling to reduce currents and remove heat
         WP3: Sensor Research and Development
ATLAS UK lead the programme which has                     Full-size LHCb sensors
developed detectors able to withstand > 4 times           prototyped by UK on p-type                  neutron
the expected 27cm radius dose at SLHC                                                              irradiated
                                                          Miniature micro-strip detector
The target for SLHC micro-strips is survival to           now neutron irradiated by UK
~1.8 ×1015p/cm2 (1015neq/cm2) with S/N > 10.              ~3×1015neq/cm2 =5.5×1015p/cm2
(Requirements quoted in 1MeV neutron                Prototyping on p-type now by
equivalent dose, by convention, but actual          many international groups
irradiation is mostly charged hadrons at low radii)


                         p-type 1cm detector
                         after 7.5×1015p cm-2
                         (2MGy)                                                 10,000e

                              UK designed,
                              irradiated and

                                                        This technology is promising for
Pulse height distribution of a miniature n+-in-p
detectors with 106Ru β-source, after exposure at the
                                                        replacement silicon, but need full-size
CERN-PS to 7.5×1015p cm-2 with LHC speed electronics.
                                                        commercially manufactured sensors
      WP4: FE Electronics and Interconnects
• Final design specifications of ABC-next SLHC 0.25μm CMOS microchip
• Procurement and evaluation of ABC-next
   Sensor (WP3), optoelectronics (WP5), powering (WP6), super-module prototyping (WP7)
    and read-out (WP8) studies all rely on an many hundreds of ASICS for UK R&D
• Prepare design for 3cm kapton hybrid and fabricate              ASIC    Die-attach/flip chip

• Evaluate first modules
                                                       sensor     Diode strip
• Identify candidate MCM-D process                              Routing layer

• Carry out thermo-mechanical tests to see if MCM-D
  can be integrated with detector
• Fabricate MCM-D hybrid on silicon for 3cm option
• Make transition to shorter strips
1) Sensor wafer

    2) Add dielectric and open vias

          3)Add metal layers
          and pattern

              4) Dice sensor

                  5) Flip-chip ASICs

                    to hybrid

                    … or make
                    this also part
                    of MCM-D
    WP5: Optoelectronics Readout System

Radiation tolerance determination of current readout components
•   Step index multi-mode and graded index fibres,
•   ATLAS lasers, p-i-n diodes for commercial packaging
•   other COTS (custom off-the-shelf)
•   future custom-made devices (if necessary).
Develop and test connecting link infrastructure for suitability in the
SLHC environment in close collaboration with other work-
Deliver suitable optoelectronic components for the UK ‘super-
module’ prototype for the on and off detector parts.
Test for SEU (single event upset) and long-term reliability of
candidate high-speed optical readout systems.
                                    WP5: Optoelectronics Readout System

                 2.5                                                                   Threshold shift of VCSEL lasers
         Threshold [mA]
ΔTh [mA]

                5 2                                            SLHC
                                                                                       • All VCSEL alive after annealing
                 1.       1.5
                                    LHC                                                • Promising result BUT failures
                 5 1                                                                     developed after long term operation

                0.5                                                                    • Long term reliability needs to be
                           0                                                             investigated with more tests.
                                0   1  2    3     4     5     6     7     8   9   10
                                0    1 2    3     4     5     6     7     8   9   10
                                           Fluence 10^15 [n(1 MeV)/cm2]
                                        Fluence 1015 [n (1MeV)/cm2]

                                                                                         Step index multi-mode fibre
                                                                                           irradiation up to 100 Mrad

                                                                                         • 1.33% performance loss/m
                                                                                           – very good
                                                                                         • Graded index fibre radiation
                                                                                           tests needed
           WP6: Power Distribution Schemes
•   Solution of power distribution problem is key for Tracker Upgrade
•   RAL was awarded a £50K (incl. effort) seed-corn grant for serial powering.
    R&D is very well within schedule. Grant runs out in summer 2007
•   Grant allowed us to obtain lead in powering distribution R&D in ATLAS
•   Understanding of serial powering has greatly increased and results are well
    received at conferences (LECC 2005, Hiroshima 2006, IEEE NSS 2006)
•   Must now increase pace of R&D and make transition from generic studies to
    engineering of SLHC prototypes
•   Power distribution is closely intertwined with ASIC and hybrid design;
    supermodule electrical and mechanical design; etc. Power distribution
    should be ahead of these in order avoid additional iterations
•   Requested effort for powering distribution R&D is escalated from actual
    seed-corn expenditure, is well-known, and modest in comparison.

             WP6: Power Distribution Schemes
•   Noise performance and grounding and shielding issues for large structures
•   Power consumption of regulators
•   Operation of serial powering systems with many modules (20)
•   Alternative sensor bias voltage schemes

• ABC-Next operation voltages and power variation
• Regulator specifications and design
• AC-coupling schematics                                            board
• Low voltage buffer design
• Need for DC-balanced protocol
                                          SP Test with Current
•   Risk of single-point failure analysis ATLAS modules
•   Over-current protection schemes
•   Communication with regulators
•   Slow control information on module currents
                WP6: Power Distribution Schemes

                                                           Analog and digital
           IP           M1         M2          M3

      Serial powering and parallel power bus with DC-DC conversion

                                                         Constant current for both
           SP             M1         M2          M3      analog and digital power
                                                            + local regulators
 Parallel powering
 with DC-DC               M1            M2          M3

Note: Parallel powering without DC-DC conversion is problematic due to low
                      power efficiency and large IR drops                  22
                       WP7: Engineering
                                   Engineering issues pose some
                                   of the greatest challenges

                                                      Sensor dimensions,
                                                      hybrid design/technology
                                                      substrate (with integrated
                                                      cooling?) data links,
                                                      connectors, supports etc
                                                      …all to be defined
Final detector
array will have to
occupy same
volume as current
tracker and use       Limited time to build
same services        much larger and more
routing                 demanding system
                         WP7: Engineering

The UK is uniquely placed to implement the lessons from the current SCT in any
future build
For R&D, we propose to concentrate on thermal management, low mass tapes
(LMTs) and connectors
• The radiation effects will require the silicon sensors to run 15OC cooler than at present
  Need optimised module design and lower temperature coolant
• The powering, communications and read-out will require radically different solutions
  Attention to LMTs and connectors needed now to achive reliability and drive large-scale
We intend in this, and previous work-packages to ensure (with international
colleagues) that all elements are in place to allow design and manufacture of a
super-module prototype before the TDR is required, and to prove mass
production, affordable construction of the entire tracker is feasible
It is to this end, that we are proposing a programme of prototyping of mechanical
and thermal structures along with electrical prototyping and testing
                     Thermal Management
SCT experience C3F8 evaporative cooling system                        12.5°C

• constant temperature throughout cooling lines
• high cooling capacity (limited flow)                                     0


• successful thermal separation hybrid and sensors.


Challenges for the SLHC:
• more modules / more power dissipation
• may need to keep silicon temperature at -25°C.
    • strong constraint on thermal separation hybrid and sensor
Proposals for study:
• sensors on high thermal conductivity spine/base (TPG,CC, other)
• Use two-phase cooling again. Limited number of coolants available
     • C3F8 (current system)
     • CO2 (high cooling capacity with very thin pipes)
                     WP7: Engineering
A key part of the request is to employ a senior project engineer, able ot play
a pivotal role in the ATLAS Upgrade Project Office at CERN

The UK project engineer will:

•ensure that the UK effort is coherent
•coordinate the distributed UK engineering effort
•ensure UK engineering effort is efficient and focussed
•work with colleagues in the ATLAS Project Office, to fully optimise the
 upgrade tracker design

The outputs of all the previous work-packages and WP8 are needed if the goal of a
prototype super-module/stave is to be realised by 2010 and the experience and
appropriate infrastructure is to be developed to make subsequent pre-production
and finally production units
     WP8: DAQ and Off-detector Readout
•   UK groups are responsible for current ATLAS SCT DAQ and major
    parts of off-detector electronics
    • SLHC requires re-design for data-rate, volume, new ASICs, new
    • All existing ATLAS UK expertise gathered together in this work
•   Two necessary paths:
    1. Developments from existing (all UK) SCT lab DAQ and readout
        • To provide vital, timely, support for other SLHC R&D activities
    • Needed now in order to:
        • Test features of new ABC-Next ASIC (WP4)
        • Read out sensors with existing and new ASICs (WP3)
        • Read out modules during early stages of super-module
    • Developments must be underway in 2007 and completed in 2008
WP8: DAQ and Off-detector Readout
2.    R&D towards longer-term readout solutions
•     Needed from 2007 in order to:
     • Provide input to design features of ASICs (WP4), optical
          protocols (WP5), powering scheme protocols (WP6)
     • Produce a prototype DAQ chain capable of reading out
          400-ASIC super-module at end 2009
          • Super-module cannot be tested electrically without
             this development
          • Test-bed for scalability studies of DAQ
•     Will start by studying potential of generic PC-based
      components for use in this application
•     If found inadequate, return to custom VME-based solutions
       ATLAS Tracker Upgrade Summary
Likely date for SLHC luminosity upgrade to 1035 cm-2s-1 is around 2015.
Preparations for required inner tracker replacement already urgent.

Simulation: urgently needed to define layout and operation constraints
Sensor technology: solutions may exist but urgently require commercial prototyping
Front-end electronics: deep sub-micron rad-hard technologies needed
Interconnect Technologies: integrated with ASIC design and required granularity
Optoelectronics: very radiation hard and much higher bandwidth
Powering: individual power to each hybrid/sensor not an option
Engineering: issues may be the biggest challenge:
• require integrated design of module/stave with full services incorporated
• need to work on cooling, electrical power distribution and optical read-out
DAQ: programme not possible at each stage without read-out

Limited time to build large tracker requiring many innovative technologies
     The European strategy for
          particle physics

        “The LHC will be the energy frontier machine for the
     foreseeable future, maintaining European leadership in the
  field; the highest priority is to fully exploit the physics potential
   of the LHC, resources for completion of the initial programme
have to be secured such that machine and experiments can operate
     optimally at their design performance. A subsequent major
      luminosity upgrade (SLHC), motivated by physics results
    and operation experience, will be enabled by focussed R&D;
 to this end, R&D for machine and detectors has to be vigorously
     pursued now and centrally organized towards a luminosity
                      upgrade by around 2015.”
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