UShosted Linear Collider Options: A study commissioned by the US Linear Collider Steering Group

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US-hosted Linear Collider OptionsA study
commissioned by the US Linear Collider Steering
Group
G. Dugan Laboratory for Elementary Particle
Physics Cornell University Ithaca, NY 14853

• American Linear Collider Workshop
• July14, 2003

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Charge

• The Accelerator Subcommittee of the US Linear
  Collider Steering Group (USLCSG) has been charged
  by the USLCSG Executive Committee with the
  preparation of options for the siting of an
  international linear collider in the US.

Membership of the USLCSG Accelerator
Subcommittee David Burke (SLAC) Gerry Dugan
(Cornell) (Chairman) Dave Finley (Fermilab) Mike
Harrison (BNL) Steve Holmes (Fermilab) Jay Marx
(LBNL) Hasan Padamsee (Cornell) Tor Raubenheimer
(SLAC)
Also member of USLCSG Executive Committee
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US LC physics requirements specified by the
USLCSG Physics/detector Subcommittee

• initial energy 500 GeV c.m.
• upgrade energy at least 1000 GeV c.m.
• electron beam polarization gt 80
• an upgrade option for positron polarization
• integrated luminosity 500 fb-1 within the first
  4 yrs of physics running, corresponding to a peak
  luminosity of 2x1034cm-2s-1.
• beamstralung energy spread comparable to initial
  state radiation.
• site consistent with two experimental halls and
  a crossing angle.
• ability to run at 90-500 GeV c.m. with luminosity
  scaling with Ecm

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Charge

• Two technology options are to be developed a
  warm option, based on the design of the NLC
  Collaboration, and a cold option, similar to the
  TESLA design at DESY.
• Both options will meet the physics design
  requirements specified by the USLCSG Scope
  document.
• Both options will be developed in concert,
  using, as much as possible, similar approaches in
  technical design for similar accelerator systems,
  and a common approach to cost and schedule
  estimation methodology, and to risk/reliability
  assessments.

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Task forces

• To carry out the charge, the Accelerator
  Subcommittee has formed four task forces
• Accelerator physics and technology design,
• Cost and schedule,
• Civil construction and siting
• Availability design.
• Risk assessment will be carried out by a team
  formed from members of the other 4 task forces

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Task force membership
DESY points-of-contact Cost/schedule and siting
Franz Peters Design Stefan Choroba
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Guidelines for LC option design

• The reference designs for the warm and cold
  options will be similar to, but not identical
  with, the NLC design of the JLC/NLC collaboration
  and the TDR design of the TESLA collaboration.
  Major system-level changes from these designs
  will be limited to those which fall into the
  following categories
• Changes required to meet the machine
  specifications stipulated by the USLCSG
• Changes motivated by clearly-identified major
  cost reductions, or major reliability/operability
  issues.
• Technically benign changes which make the
  comparison between the options simpler and more
  straightforward.

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Warm option reference design

• New features of 2003 NLC configuration
• SLED-II pulse compression
• 2-pack modulator
• 60 cm, 3 vg HDS structures
• EM quads in linac
• Improved damping ring design
• Improved positron source
• BNL-style SC final focus doublet
• Low-energy IR reach improved to 1.3 TeV

• Differences between the warm option reference
  design and the 2003 NLC design
• The use of an undulator based positron source,
  utilizing the high energy electron beam at 150
  GeV, instead of the conventional positron source
• At the subsystem and component level,
  specification changes to facilitate comparison
  with the cold LC option.

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Cold option reference design

• The major changes to be made to the TESLA design
  are
• An increase in the upgrade energy to 1 TeV
  (c.m.), with a tunnel of sufficient length to
  accommodate this in the initial baseline.
• Use of the same injector beam parameters for the
  1 TeV (c.m.) upgrade as for 500 GeV (c.m.)
  operation
• The choice of 28 MV/m as the initial main linac
  design gradient for the 500 GeV (c.m.) machine.
• The use of a two-tunnel architecture for the
  linac facilities.
• An expansion of the spares allocation in the
  main linac.
• A re-positioning of the positron source
  undulator to make use of the 150 GeV electron
  beam, facilitating operation over a wide range
  of collision energies from 91 to 500 GeV
• The adoption of an NLC-style beam delivery
  system with superconducting final focus
  quadrupoles, which accommodates both a crossing
  angle and collision energy variation.
• At the subsystem and component level,
  specification changes to facilitate comparison
  with the warm LC option.

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Initial stage energy reach
Black warm option, structures qualified at
unloaded gradient 65 MV/m, loaded gradient 52
MV/m Red cold option, cavities qualified at max
gradient 35 MV/m, operating gradient at 500 GeV
(52/65)35 MV/m 28 MV/m
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Design variants

• Design alternatives will also be considered, as
  variants on the reference design. These variants
  offer the possibility of significant cost and/or
  risk reductions from the reference designs. The
  principal technical, cost, availability, and risk
  implications of these variants will be evaluated.
  
• The design variants to be considered are
• A single main linac tunnel architecture for the
  cold option.
• 35 MV/m initial stage gradient for the cold
  option
• The use of DLDS pulse compression for the warm
  option and superstructures for the cold option.
• For the cold option, reduction of the number of
  particles per bunch to 1.63x1010 corresponding to
  an initial peak luminosity of 2x1034cm-2s-1.
• Conventional positron sources for both options

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Cold LC option layout
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Linac layouts,500 GeV cm
Electron main linac, 250 GeV beam energy
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Cold Option Beam Delivery System

• A TESLA linac lattice is matched into an
  unmodified NLC beam delivery system via a 200m
  matching section.
• The NLC-like beam delivery system is then
  adjusted to give TESLA-like lattice functions at
  the IP using the matching section.
• This matching section is then used for the fast
  extraction (beam abort/ tune-up line) system.
• 2 separate dumps per beam

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Linear Collider Final Focus - concept
NLC-style IR 20 mrad X-ing angle 20mm incoming
aperture Outgoing beamline used for diagnostics
instrumentation Replace the permanent magnets
close to the IP with compact superconducting
ones Cold option gives flexibility optics
variation, energy variation, improved
correction scheme, etc.. Issues involve
mechanical stability (1nm !), adjustability,
interaction with the solenoid, field stability (5
ppm), radiation resistance and a 11 (22) MW
disrupted beam.
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Cost and schedule task force Charge and
Interpretation

• Charge
• The Cost and Schedule (CS) Task Force is
  charged to provide estimates of the TPC and
  schedule for completion of each of the machine
  configurations if entirely funded by the U.S. and
  built in the United States by U.S. labs and
  universities and global industries on a
  competitive basis.
• Interpretation
• Provide not Make
• Fully utilize existing work done by NLC/JLC and
  TESLA Collaborations.
• Fully utilize previous analysis of this work.
  (E.g. Fermilab-led restatement of costs from
  TESLA, and Lehman Review of the NLC.)
• Configurations provided by the Accelerator Design
  Task Force for the warm and cold technology
  options may (are) not exactly the official
  NLC/JLC or TESLA Collaboration configurations.

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Costing Assumptions/Bases

• LC Will be Built in the U.S.
• U.S. DOE Financial Practices Apply
• As Much Scope as is Reasonable Will be Contracted
  Out
• Currency conversion for TDR costs 1 Euro1 US
  dollar
• All the Civil Construction Will Be U.S. Content
• The Cost Impact (If Any) of In-Kind or
  Politically-Directed Contributions/Purchases Will
  be Ignored
• Common WBS structure used for both options
• Costing Risk Calculation Will be
  Monte-Carlo-Based

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United States Linear Collider Steering
Committee Conventional Construction and Siting
Task Force

• Overview of Goals and Key Issues
• Develop a Design Solution for Each of Four
  Options
• Cold and Warm in CA and Cold and Warm in IL
  Using a Twin Tunnel Configuration in all Cases
• Develop a Fifth Option for a Cold Machine Using
  a Single Tunnel Configuration
• Deliverables for Each Design Solution to
  Consist of a Written Configuration Summary,
  Schematic Design Drawing Set and Cost Estimate
• An Analysis of Construction Issues Related to a
  One-Tunnel vs Two Tunnel Solution for a Cold
  Machine is Also Included in the Work of this
  Task Group

2 of 6 Kuchler
04.14.03
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Availability design task force Charge

• Establish top level availability requirements
  such as
• Annual scheduled operating time
• Hardware availability
• Beam efficiency
• Consider 3 machines
• Warm,
• Cold in 1 tunnel
• Cold in 2 tunnels
• Allocate top-level availability requirements down
  to major collider systems.
• As time allows attempt to balance availability
  specs. to minimize risk and cost.
• Compare to data from existing accelerators

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Availability design task force Overall plan

• Write a simulation that given the MTBFs, MTBRs,
  numbers and redundancies of components, and
  access requirements for repair can calculate the
  integrated luminosity per year. Luminosity will
  be either design or zero in this simulation.
• Collect data on MTBFs and MTBRs from existing
  machines to guide our budgeting process
• Make up a reasonable set of MTBFs that give a
  reasonable overall availability.
• Iterate as many times as we have time for
  (probably once during this task force) to
  minimize the overall cost of the LC while
  maintaining the goal availability

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Risk assessment

• The USLCSG charge to the Accelerator
  Sub-Committee included a requirement to make a
  risk assessment of the LC options.
• A fifth task force will be formed, from members
  of the other 4 task forces.
• Each task force will identify issues and
  potential risks in their respective areas
• The risk task force will use this information to
  make an overall risk assessment for each option
• The overall assessment will be based on
  high-level performance metrics of energy, design
  luminosity, availability, and cost.

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Schedule for LC option evaluation

• Jan. 10 Charge to Accelerator Subcommittee from
  USLCSG Executive Subcommittee
• April 14 Joint task force meeting 1
• April 16, June 11, July 15 Status reports to
  USLCSG ExecComm
• May 22-23 Cost review meeting at DESY
• June 5-6 Design review meeting at DESY
• June 15-16 Joint task force meeting 2
• July 13 report on work at Cornell ALCW meeting
• mid-August 2nd cost review at DESY
• August 27-28 Joint task force meeting 3
• September Completion of task force work,
  writing of final report, and submission of report
  to the USLCSG Executive Committee presentation
  to observers from DESY, CERN, KEK