EMMA: the first NS-FFAG

Roger Barlow

What is an FFAG?

Like a synchrotron

Strong Focussing (‘Alternating Gradient’)

Dipole field increases with particle energy

But through path variation not time variation

B/t not dB/dt

Orbit changes with energy

RF changes slightly

For and against

Advantages Magnets do not cycle• Cheaper, simplerHigh Repetition rate• ~kHz rather than ~Hz High duty cycle• Not quite DC, but…Rapid acceleration• Limited by RF not magnet Large acceptance• Useful for protons, vital for

muons

Disadvantages Limited dynamic

rangeMagnets

complicatedLimited experienceAbandoned in

1950’s?

FFAG renaissance

• Improved Magnet and RF technology

• Materials, modelling

• Proton FFAG built and working in KEK, Japan

• Plans for proton, electron, muon FFAGs

The NS-FFAG

‘Scaling’: constant orbit shape

Gives constant betatron tuneAbandon scaling principle – lose control of

tune. Fall into resonance?

Argument

If the tune changes rapidly, resonances don’t have time to destroy the beam.

Rapid acceleration: Big turn-to-turn variationPlausible but needs verifyingAdvantages (if it works)• Very small (~zero) RF change needed• Simpler magnets (BR not ln B R) • Smaller beam pipe

EMMA

Proof of principle machine

10 to 20 MeV electrons

42 cells

~16m circumference

RF every other cell

1.3GHz, TESLA frequency

magnets ~ 5cm x 2.5cm

EMMA at Daresbury

EMMA

More EMMA details

Slides following taken from talk by Rob Edgecock

CF MagnetsCF MagnetsEMMAEMMA

Flux lines at maximum dipole and quadrupole currents. Dipole coil (blue),Quadrupole (red).

RF SystemRF SystemEMMAEMMA

1.3GHz ELBE-like RF Cavities

20cm slot length

Few 10-4 variation in frequency to

allow acceleration

mode changes

Low frequency system for

further resonance

crossing studies

Initial design and cost estimate

done

Non-Scaling Electron ModelNon-Scaling Electron ModelEMMAEMMA

EMMAEMMA

Bid to UK “Basic Technology” Programme

BASROC=British Accelerator Science, Radiation and Oncology Consortium

Request funding for

• EMMA construction (£3.8M + £1.8M)

• Design of proton R and D machine (PAMELA) (£0.8M)

• Applications from Archaeology to Zoology (£0.4M)

The Consortium

• CCLRC+Cockcroft – EMMA Construction

• Manchester/Cockcroft – Coordination

• Liverpool/Cockcroft – Magnets

• Oxford/John Adams – PAMELA design

• Oxford/Gray Cancer Institute + Birmingham + Imperial + Glasgow – PAMELA and Hadron therapy applications

• Surrey+Leeds – general applications

Decision

This is still unofficial

Plan

• Project start 1 April 2007, last 3.5 years• Build and study EMMA• Design and seek funding for PAMELA• Build up portfolio of FFAG applications

– Hadron therapy– Cell irradiation studies– Solar wind simulator– Accelerator Driven Thorium Reactors– Proton drivers for muon/neutron sources– Muon accelerator for neutrino factory

• Enlarge project through linked activities