1. Accelerators 2007 Wakefields and the nsFFAG Roger Barlow

2. Manchester Christmas Meeting Roger Barlow - AcceleratorsSlide2 Wakefields Leading particles affect trailing particles through induced charges and currents Simulation in Merlin and other programs Investigate through EM codes

3. Manchester Christmas Meeting Roger Barlow - AcceleratorsSlide3 From bunches to point particles Bunch wake (modes 1-4) Delta wake (modes 1-4) Fourier Deconvolution

4. Manchester Christmas Meeting Roger Barlow - AcceleratorsSlide4 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 ) d r =b 0 +  a k sin(kr  /N) +  b k cos(kr  /N) Or d=b 0 +S a + C b To have d r =0 for all (-N+1)<r<0 requires a =( 2 / N ) ( S b 0 + S C b) To have d -N =0 requires b 0 =b 1 -b 2 +b 3 -b 4 … For any b, the causality requirement uniquely specifies b 0 and a

5. Manchester Christmas Meeting Roger Barlow - AcceleratorsSlide5 FFAG Progress Like a synchrotron Strong Focussing (‘Alternating Gradient’) Dipole field increases with particle energy But through path variation not time variation dB / dt not   B /  t Orbit changes with energy RF changes slightly

6. Manchester Christmas Meeting Roger Barlow - AcceleratorsSlide6 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

7. Manchester Christmas Meeting Roger Barlow - AcceleratorsSlide7 EMMA Future Present

8. Manchester Christmas Meeting Roger Barlow - AcceleratorsSlide8 EMMA Progress Production Magnets ordered RF prototypes ordered Main components on site Summer 2008 Assembly 2008-9

9. Manchester Christmas Meeting Roger Barlow - AcceleratorsSlide9 Other FFAG stuff PAMELA – design for hadron therapy machine Applications – Medical/Biological (Surrey) Neutron source (Leeds) ADSR (Manchester/Leeds)

10. Manchester Christmas Meeting Roger Barlow - AcceleratorsSlide10 Plan Work on ILC - insofar as we are allowed Work on CLIC (much in common) Build and run EMMA Look at other nsFFAG uses