Accelerators 2007 Wakefields and the nsFFAG Roger Barlow

Accelerators 2007

Wakefields and the nsFFAG

Roger Barlow

Manchester Christmas Meeting

Roger Barlow - Accelerators Slide2

Wakefields

• Leading particles affect trailing particles through induced charges and currents

• Simulation in Merlin and other programs

• Investigate through EM codes



From bunches to point particles

Bunch wake (modes 1-4) Delta wake (modes 1-4)

Fourier Deconvolution



Fourier Fact

The Fourier Transform of a ‘Causal Function’ – f(x) which is zero for all x<0 – can be written explicitly

Write series as (r goes from –N to N )dr=b0+ak sin(kr/N) + bk cos(kr/N)

Or d=b0+S a + C bTo have dr=0 for all (-N+1)<r<0 requires

a =(2/N) ( S b0 + S C b)To have d-N=0 requires

b0=b1-b2+b3-b4…For any b, the causality requirement uniquely specifies

b0 and a



FFAG Progress

Like a synchrotron

Strong Focussing (‘Alternating Gradient’)

Dipole field increases with particle energy

But through path variation not time variationdB/dt not B/t

Orbit changes with energy

RF changes slightly



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

FuturePresent



EMMA Progress

Production Magnets ordered

RF prototypes ordered

Main components on site Summer 2008

Assembly 2008-9



Other FFAG stuff

PAMELA – design for hadron therapy machine

Applications –

• Medical/Biological (Surrey)

• Neutron source (Leeds)

• ADSR (Manchester/Leeds)



Plan

Work on ILC - insofar as we are allowed

Work on CLIC (much in common)

Build and run EMMA

Look at other nsFFAG uses

Documents

Accelerators 2007 Wakefields and the nsFFAG Roger Barlow