US-hosted Linear Collider Options A study commissioned by

US-hosted Linear Collider Options: A study commissioned by the US Linear Collider Steering Group G. Dugan Laboratory for Elementary Particle Physics Cornell University Ithaca, NY 14853 TESLA Collaboration Meeting May 26, 2003 US-hosted LC Options

Initial Charter for the US Linear Collider Steering Group The U. S. Linear Collider Steering Group leads universities and national laboratories working toward U. S. participation in an international high-energy, high-luminosity, electron-positron linear collider. The establishment of such a body was recommended by the HEPAP Subpanel on Long Range Planning. While the functions of the Steering Group are expected to evolve with time, the initial U. S. Linear Collider Steering Group will: …… Provide an evaluation of options for building the linear collider involving factors such as scientific requirements, technical feasibility, risk, cost, initial facility parameters, upgradability of alternate technologies, and the implications of different sites; Prepare the elements of a U. S. bid to host the linear collider; US-hosted LC Options 2

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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) 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. US-hosted LC Options 4

US LC physics requirements specified by the USLCSG Physics/detector Subcommittee • • • initial energy 500 Ge. V c. m. upgrade energy: at least 1000 Ge. V c. m. electron beam polarization > 80% an upgrade option for positron polarization integrated luminosity 500 fb-1 within the first 4 yrs of physics running, corresponding to an average luminosity of 2 x 1034 cm-2 s-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 Ge. V c. m. with luminosity scaling with Ecm US-hosted LC Options 5

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. • A fifth will be formed to provide risk assessment US-hosted LC Options 6

Task force membership DESY points-of-contact: Cost/schedule and siting: Franz Peters Design: Stefan Choroba US-hosted LC Options 7

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. US-hosted LC Options 8

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 Te. V 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 Ge. V, instead of the conventional positron source • At the subsystem and component level, specification changes to facilitate comparison with the cold LC option. US-hosted LC Options 9

Cold option reference design The major changes to be made to the TESLA design are: • An increase in the upgrade energy to 1 Te. V (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 Te. V (c. m. ) upgrade as for 500 Ge. V (c. m. ) operation • The choice of 35 MV/m as the initial main linac design gradient for the 500 Ge. V (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 Ge. V electron beam, facilitating operation over a wide range of collision energies from 91 to 500 Ge. V • 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. US-hosted LC Options 10

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 major design variants to be considered, in order of priority, are: • A single main linac tunnel architecture for the cold option. • The use of DLDS pulse compression for the warm option and superstructures for the cold option. • An initial (500 Ge. V c. m. ) main linac design gradient of 23. 4 MV/m for the cold option, and an initial (500 Ge. V c. m. ) main linac design gradient of TBD MV/m for the warm option. US-hosted LC Options 11

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Electron main linac US-hosted LC Options 14

Linac layouts US-hosted LC Options 15

Cold Option Beam Delivery System A TESLA linac lattice is matched into an unmodified NLC beam delivery system via a ~200 m 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 US-hosted LC Options 16

Linear Collider Final Focus - concept NLC-style IR: 20 mrad X-ing angle 20 mm 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 (1 nm !), adjustability, interaction with the solenoid, field stability (5 ppm), radiation resistance and a 11 (22) MW disrupted beam. US-hosted LC Options 17

Cost and schedule task force: Charge and Interpretation Charge “The Cost and Schedule (C&S) 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. • Follow U. S. DOE costing processes and procedures. US-hosted LC Options 18

Costing Assumptions/Bases • LC will be Built in the U. S. • U. S. DOE Financial Practices Apply • Scale of Project is Such That: – As Much Scope as is Reasonable will be Contracted Out • 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 • Escalation Will Not be Included (Same for Either LC) • A common WBS structure, with labor/materials/equipment breakdowns, will be used for both options • Costing Risk Calculation will be Monte-Carlo-Based US-hosted LC Options 19

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 US-hosted LC Options 2 of 6 Kuchler 20 04. 14. 03

Two-tunnel configuration US-hosted LC Options 21

Availability design task force: Charge • Establish top level availability requirements needed to achieve the specified integrated luminosity, 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, using estimated MTTR, MTBF for major components, collated in a computer simulation. • As time allows attempt to balance availability specs. to minimize risk and cost. • Compare required subsystem availabilities to data from existing accelerators US-hosted LC Options 22

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 to carry out this risk assessment. Draft goals for this effort are the following: Consider performance metrics of energy, design luminosity, availability, and cost. Do high-level (major system) analyses (FMEA) of potential failure modes for each of the technical design options. Identify those failure modes that are most germane to the key choices between the technical design options. Assess the relative risk of failure in performance metrics of each technical design option. US-hosted LC Options 23

Schedule for task force work • Jan. 10: Charge to Accelerator Subcommittee from USLCSG Executive Subcommittee • April 14: Joint task force meeting #1 • April 16: Status report to USLCSG Exec. Comm • June 15 -16: Joint task force meeting #2 • July 13: report on work at Cornell ALCW meeting • Late August: Final joint task force meeting, to review the final draft of the work, possibly with observers from DESY and CERN invited for comments and suggestions. • September : Completion of task force work US-hosted LC Options 24

Conclusion • A study of two options for a US-hosted linear collider is underway, sponsored by the US Linear Collider Steering Group (USLCSG). • These options are specified to meet the physics requirements specified by the USLCSG. • The study is based on reference design options similar to those of JLC/NLC and TESLA. • The study will include evaluation of cost/schedule issues and availability, and will include risk assessments. • We hope to complete the study, and deliver a report to the USLCSG Executive Committee, by the end of September. US-hosted LC Options 25