ESS linac Mats Lindroos, Cristina Oyon and Steve Peggs

ESS facility technical objectives: 5 MW (upgrade 7.5 MW) long pulse source ≤2 ms pulses ≤20 Hz Protons (H+) Low losses High reliability, >95%

ESS-Bilbao WORKSHOP PARTICIPANTS The workshop brought together more than 160 experts from across the world, leaders in the fields of high power proton accelerators, beam dynamics and targets, in a format and infrastructure that promoted open discussion, while maintaining the focus of documenting clear recommendations for future collaborative R&D efforts. Design update: ESSB Preparatory work

Reference group meetings RG1: CERN, 6 February 2009 Present: 7 people (ESS, CERN, BNL, CEA) Theme: Recent progress in SCRF technology and what implications this has on the ESS (2003) linac design Main outcome: Tentative parameter list for ESSS linac proposal RG2: Lund, 25 February 2009 Present: 9 people (ESS, CERN, BNL, CEA, TSL, MSL, FNAL) Theme: Develop the tentative ESSS linac design from RG1 Main outcome: PAC09 contribution RG3: CERN, 5 June 2009 Present: 20 people Theme: What can we learn from SNS and the SPL study? Main outcome: Demonstrated the necessity to prototype and perform (cold) acceptance tests of all structures. Decision to work on strong links to both SNS and CERN-SPL RG4: Århus, 9 October 2009 Present: 30 People Theme: Transition (energy) from NC to SC structures RG5: Bilbao, 23 November 2009 Present: 35 People Theme: Beam losses and operational simulations

Design update: ESSS Preparatory work Work with expert group (the ESSS linac reference group) MHz MHz

Many cavities! Approx. 200 cavities, RF distribution is a major part of budget! Minor default => Major problem, big risk Can we keep RF source and distribution budget under or at level with the 2003 design value? Structure Number of Tanks or Cavities Tank or Period Length Frequency RFQ1~ DTL3~ Single Spokes243.9 (4 cavity, FODO) Triple Spoke326.1 (4 cavity, FODO) Elliptical (0.65)40 (SPL : 42)6.2 (4 cavity, Doublet)704.4 Elliptical (0.92)96 (SPL : 200)12.8 (8 cavity, Doublet)704.4

In lay-out pictures

Lay-out of the full segmented linac

RF distribution Option Configuration Cost of 4 cavity (K- Euro) ForAgainst 1 Four cavities per Klystron 2420Fewest power sources Complexity, bulk, power overhead, fault tolerence 2 One Cavity per Klystron2880 Reduced hardware inventory, minimum R&D, fully independent control, minimum RF power overhead, best fault tolerance, easy upgrade to HPSPL Number of power sources 2a One cavity per IOT2520 As above, perhaps cheaper & more compact HPSPL would need doubling of IOTs, or larger rating IOTs 3 Two cavities per Klystron2520Half the number of klystrons Need full hardware set, associated R&D, Power overhead, Reduced flexibility wrt option 2 3-VM Two cavities per Klystron Without VMs 2370 Half the number of klystrons, more economical than Option 3 Risk for higher intensity?

RF test stand in Uppsala

ESS Guidelines (adopted by ESS STC) Starting point is the 2008 ESFRI Roadmap specification Performance parameters Neutron production 30 times SNS today Peak neutron flux 30 times ILL´s average flux Time-averaged flux equal to ILL Electrical power supply 32 MW to 38 MW Accelerator key parameters A proton linac Proton energy range: 1 to 2.5 GeV Pulse frequency range: 10 to 20 Hz Pulse length range: 0.8 to 2 msec Beam power nominal: 5 MW Beam on target: > 95 % reliability Beam loss: ~ 1 W/m Target station key parameters A single target station Cold and cold-thermal moderators A liquid metal target: mercury or lead-alloys, Solid rotating target as fall-back 22 beam ports (11 North, 11 South) or 11 beam ports South and 22 neutron guides North.

Base line for ESS – v0 Technical Design Report with cost to completion for the end of 2012: Proton linac: 5 MW, protons, ms pulse, 20 Hz at 2.5 GeV Aim for 1.0 ms pulse length Priority: i) power couplers (>1.2 MW?), ii) additional cryomodules and/or iii) higher energy Final decision on pulse length to be taken for the TDR Upgradable for higher power (repetition rate or pulse current) and for H MeV Higher energy: Size of moderator Distribution and direction of hadronic cascade

Examples of risks to be addressed High losses in the linac Action: Comprehensive studies of beam dynamics (simulations and theory) Poor reproducibility in cavity performance Action: Quality control during manufacturing and prototyping of a sufficient large number of cavities Limits in cavity performance due to field emission Action: Prototyping and comprehensive tests of complete cryomodule Lower power limit than expected of power couplers Action: Prototyping, sufficient conditioning facilities and contingency in linac design

Writing Group Project plan for the linac design update and prototyping Design Report for the end of 2012 Prototyping will run longer Responsibilities within WG S.Peggs – Beam physics C.Oyon – project planning M. Lindroos – coordination R. Duperrier – System WG schedule and milestones Status report 3 February STC Presentation of project plan 23 April STC Review and audit of Project plan before STC in October

Collaboration model for linac design! Work Package (work areas) 1. Management Coordination (ESS) 2. Accelerator Physics (ESS) 3. Infrastructure Services (Tekniker, Es) 4. SCRF Spoke cavities (Orsay, Fr) 5. SCRF Elliptical cavities (CEA, Fr) 6. Front End and NC linac (INFN, It, TBC) 7. Beam transport, NC magnets and Power Supplies (ÅU, Dk) 8. RF Systems (UU, Se)

Collaboration model: Required A collaboration to share interesting R&D, assure an all European effort and kick start the ESS work A strong Coordination Team in Lund to take the intellectual ownership of the design, to follow the work, to assure good project cost control, and to be responsible for project integration A collaboration board to assure good coordination and to address poor performance Use of common standards, web based documentation, regular reporting and appropriate costing tools Regular reviews of critical path deliverables and even milestones of large work packages (if at a single institute)

Synergies with SPL project at CERN 18

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 =0.35  =0.15 Spoke resonators  Two 352 MHz (  0.15 and  0.35) fabricated and tested. Half-wave resonators Half-wave resonators  Two 352 MHz (  0.17 and  0.31) fabricated and tested Synergies for linac ALL SUCCESFULLY TESTED !

Conclusions The ESS linac project plan In progress… But at a stage when new partners can join! Looking forward to work together with new and old friends in Portugal