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

1. 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 American Linear Collider Workshop July14, 2003

3. 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

4. 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 > 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

5. 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.

6. 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

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

8. 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.

9. 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.

10. 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.

11. 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

12. 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

13. Cold LC option layout

15. Linac layouts,500 GeV cm Electron main linac, 250 GeV beam energy

16. 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

17. 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.

18. 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.

19. 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 Euro=1 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

20. 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

21. 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

22. 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

23. 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.

24. 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