1. Accelerators 2006 Roger Barlow 1: Wakefields 2: The NS-FFAG

2. Wakefields in Collimators Leading particles affect trailing particles through charges and currents induced in beam pipe, apertures, and collimators. Collimator wakefields are important for the ILC. Similar but different to wakefields in cavities

3. What it’s about Effect expressible as sum over azimuthal modes Kick =  m ( r ) m ( r’ ) m-1 Cos (m  ) Most studies of transverse wakes just consider the m=1 (dipole) mode Going further and keeping the calculations sensible needs lots of (A-level) trignometry and some C++

4. Results:  y’ versus z nmodes 1 2 3 4 5 Offset.5mm 1mm 1.5 mm

5. Conclusions and future High order modes do matter when the beam passes close to the component surface Need to extend to more general cases – with and without axial symmetry

6. 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

7. For and against Advantages Magnets do not cycle Cheaper, simpler High 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 range Magnets complicated Limited experience Abandoned in 1950’s?

8. The NS-FFAG ‘Scaling’: constant orbit shape Gives constant betatron tune Abandon scaling principle – lose control of tune. Fall into resonance?

9. 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

10. EMMA at Daresbury EMMA

11. Successful 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)

12. Plan Project start 1 March 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