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Work package 2: Collider design


WP Leader Participant 1 Participant 2 Participant 3 Participant 4 Participant 5 Participant 6


This work package will deliver a performance optimised machine design, integrated with the territorial requirements and constraints identified by WP 3, considering cost, long-term sustainability, operational efficiency and design-for-impact developed by WP 4. The work builds on two pedestals: (1) the conceptual baseline established in the FCC-ee report and (2) a documentation of the FCC-ee physics programme goals. Involving beneficiaries and partners, the work package has the following objectives:

  • Optimise the collider parameters and layout (CERN, CEA, DESY, IFJPAN, INFN, BINP, KEK, UOXF)
  • Develop and openly document the collider beam optics and lattice design, including the interaction regions (CERN, CEA, DESY, BINP, KEK)
  • Establish procedures for optics corrections. Determine the beam diagnostics requirements and develop the beam instrumentation. Design the optics corrections and emittance tuning (DESY, CERN, KIT, KEK, UOXF)
  • Establish the impedance budget for the collider and the booster and evaluate single-beam collective effects for different modes of operation (INFN, DESY, CERN)
  • Design the collimation system, develop the aperture model and develop the machine protection concept (CERN, DESY, INFN)
  • Develop the top-up injection scheme (CEA, CERN, KEK)
  • Develop and document the machine detector interface, final focus, stabilisation measures, background control and luminosity measurements (INFN, CERN, CNRS, KEK, UOXF)
  • Design and document the full energy booster (CEA, CERN)
  • Develop techniques for precision energy calibration, especially requirements and procedures for energy calibration using resonant depolarisation in the Z and W running modes, and benchmarking of techniques, like Compton scattering, to extend the energy calibration to higher energy (KIT, BINP, CERN)

Work description

Task 2.1: Work package coordination (lead: DESY, participants: CEA, CERN, CNRS, KIT, IFJPAN, INFN)

DESY, with the assistance from CERN, coordinates the tasks in this WP to ensure consistency of the work according to the project scope and plan. DESY organises the regular coordination meetings, workshops, manages the scope, reviews the progress, distributes information within the WP and manages the interfaces and collaborative with other WPs. IFJPAN coordinates the interfaces with theoretical and experimental physics communities. A specific person at CERN plans and follows up the documentation and open-access data publications concerning the experimentally tested beam optics at particle accelerators which are made available free of charge by the beneficiaries. DESY, CEA, CERN and KIT focus on the accelerator design coordination. INFN coordinates the work around the interaction region. CERN coordinates the interfaces with partners BINP and UOXF and for the territorial layout and placement requirements (DRRT, EdG). CERN allocates a person for the configuration management of the beam optics, lattice and the element database. CERN produces an open Product Breakdown Structure (PBS, M2.1) and disseminates data on Zenodo. The editing of the collider-related chapters of the design report (D5.5, WP5) is with CERN.

Task 2.2: Collider design (lead: DESY, participants: CEA, CERN, KIT, IFJPAN, INFN, partners BINP, KEK)

Develop the parameters and machine layout, starting from the physics programme requirements (D2.1) and iteratively ensure that the design matches the physics research requirements with tasks 2.1 and 2.3 (IFJPAN). Study different numbers of interaction points (IPs) and compare their respective performance (CERN). Analyse and mitigate impedance and single-beam collective effects in the collider rings (INFN). Develop the positioning concept (CNRS). Conceive an effective beam diagnostics architecture, specify the device functions and performance (KIT). Understand the measurement needs and the level of precision required for a layout of the longitudinal beam diagnostics system. Develop a diagnostics concept based on an electro-optical setup for bunch-by-bunch measurements of the longitudinal profile and centre of gravity of the bunches. Time-resolved measurements of the horizontal beam size in a dispersive section are proposed as an approach to measure the energy spread. Test (D2.4) prototype diagnostics at the KARA accelerator (KIT). Develop the concept for the global orbit control system. Verify optics correction and vertical emittance tuning procedures in beam tests (D2.4) at the PETRA III (DESY) storage-ring or, at VEPP-4M at BINP and at SuperKEKB (KEK) (D2.2). Integrate the findings in the main deliverable of the project (D5.6)

Task 2.3: Interaction region and machine detector interface design (lead: INFN, participants: CERN, CNRS, DESY, partners BINP, KEK and UOXF)

Ensure that the interaction region design meets the collider performance goals and develop an accelerator-detector interface coherently with task 2.2. Develop a 3D model of the interaction region, including final quadrupole and solenoid magnets, support structures, cooling schemes, and vacuum system. Develop heat-load budget and determine cooling requirements. Analyse vibration and stability. Develop and refine concepts for the luminosity measurement. Analyse and propose effective design measures to control the background and to protect the machine. Design the collimation system, develop a collider aperture model and develop an accelerator-detector protection concept. Review the SuperKEK IP feedback (KEK) architecture, performance, merits and limitations. Experimental beam studies (D2.4) exploring the sensitivity of the beam-beam performance to IP optics aberrations are planned at DAΦNE (INFN) and at SuperKEKB (KEK) with the crab-waist collision scheme. Document the interaction region design (D2.2) and integrate the findings in the main deliverable (D5.6).

Task 2.4: Full energy booster and top-up injection design (lead: CEA, participants: CERN, INFN, BINP)

Design a full-energy booster and integrate it with the collider using a top up injection scheme (D2.3). This work comprises optics design, including injection and extraction region and beam transfer to the collider rings, field quality and dynamic aperture at injection and during the ramp and collective effects. Determine the minimum acceptable injection energy. Integrate the findings in the projectís main deliverable (D5.6).

Task 2.5: Polarisation and energy calibration (lead: KIT, participants: CERN, partner BINP)

Develop and validate the optics correction and spin-matching procedures for establishing the transverse polarisation to achieve high-precision centre-of-mass energy calibration in cooperation with task 2.2 and 2.3. Refined energy calibration through resonant depolarisation with pilot bunches, polarisation wigglers and error assessment is an enabler for the extreme statistical precision and experimental accuracy at the Z pole and at the WW threshold. Plan tests (D2.4) with resonant depolarisation at KARA (KIT) and energy measurement at VEPP4M (BINP). Possibly study an alternative energy calibration using Compton backscattering, benchmark the two methods in low energy running modes, and extrapolate to higher energy. Document (D5.6) the design, including the elements and expected performance with a level of detail that permits starting the detailed technical design.

JulieHadre - 2021-08-24

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Topic revision: r3 - 2021-08-24 - JulieHadre
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