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 meetingshttp://indico.hep.lu.se/categoryDisplay.py?categId=44

• 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)

352.2 MHz 704.4 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

RFQ 1 ~4 352.21

DTL 3 ~4 352.21

Single Spokes 24 3.9 (4 cavity, FODO) 352.21

Triple Spoke 32 6.1 (4 cavity, FODO) 352.21

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

LLRF

MOD KL

VECTORSUM

CAV ANT1 to 4

KL 5MWPK klystronCIR 1MWPK circulatorCL 100kWRMS circ. LoadPH hybrid (e.g. planar 90°)HL hybrid loadVM 1MWPK vector modulatorMP Mech. phase-shifter/switchMOD Klystron modualtor

Individual signalsfrom all cavities

CIR CL CIR CL CIR CL CIR CL

fATT

VM fATT

VM fATT

VM fATT

VM

HL HL HL

PHPHPH

1/41/31/2

1/2 2/3 3/4

MP MP MP MP

Option ConfigurationCost of 4 cavity (K-

Euro)For Against

1 Four cavities per Klystron2420 Fewest power sources

Complexity, bulk, power overhead, fault tolerence

2 One Cavity per Klystron 2880

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 IOT 2520As above, perhaps cheaper & more compact

HPSPL would need doubling of IOTs, or larger rating IOTs

3 Two cavities per Klystron 2520 Half the number of klystronsNeed full hardware set, associated R&D, Power overhead, Reduced flexibility wrt option 2

3-VM Two cavities per KlystronWithout VMs

2370Half 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, 1.0-2 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-

10-50 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

19

=0.35

=0.15

Spoke resonatorsSpoke resonators

Two prototypes @ 352 MHz (Two prototypes @ 352 MHz ( 0.15 and 0.15 and 0.35) fabricated and 0.35) fabricated and

tested.tested.

Half-wave resonatorsHalf-wave resonators

Two prototypes @ 352 MHz (Two prototypes @ 352 MHz ( 0.17 and 0.17 and 0.31) fabricated and 0.31) fabricated and

testedtested

Synergies for linac

ALL SUCCESFULLY TESTED !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