1. NuFACT06, Irvine 27. August 2006 The Front End Test Stand (FETS) is a collaborative project, between CCLRC (ISIS & ASTeC) and UK universities (Imperial College London and Warwick University), to design and construct a test stand for demonstrating key technologies for the front end of next generation high power accelerators. The FETS team: Status of the Front End Test Stand at RAL J. Pozimski NuFACT06 27. August 2006 John Back (Warwick) Aaron Cheng (Imperial) Christoph Gabor (ISIS/ASTeC) Mike Clarke-Gayther (ISIS) Dan Faircloth (ISIS) Simon Jolly (Imperial) Ajit Kurup (Imperial) David Lee (Imperial) Alan Letchford (ISIS) Ciprian Plostinar (ASTeC) Jürgen Pozimski (Imperial/CCLRC) Peter Savage (Imperial) Chris Thomas (ISIS)…..

2. NuFACT06, Irvine 27. August 2006 Motivation : Beam loss after injection into rings Some of the beam is not trapped by the RF. Untrapped beam leads to loss, and activation limits beam power. Chopping the linac beam gives little or no beam in the gap and can lead to near 100% trapping efficiency. => Demonstrate the production and clear chopping of a beam as required for high power proton accelerators of the MW range.

3. NuFACT06, Irvine 27. August 2006 The linac macro pulse is composed of beam bunches at the linac RF frequency – typically 100s MHz. Few ns Unchopped beam Chopper pulse Chopped beam Partially chopped bunches lead to loss in the linac Chopper pulse must rise between linac bunches To achieve perfect chopping a very high speed (<2 ns) chopper is required

4. NuFACT06, Irvine 27. August 2006 A frequency of 324 MHz has been chosen for FETS, as a suitable high power pulsed klystron is available off-the-shelf from Toshiba - E3740A, 3 MW peak power. A klystron has been ordered for delivery in the 4 th quarter of 2006.

5. NuFACT06, Irvine 27. August 2006 FETS main components: RFQ, 324 MHz, 3 MeV MEBT, chopper Ion source 70 mA, 2 ms, 10 % dc 3 Soleniod LEBT

6. NuFACT06, Irvine 27. August 2006 Ion source development Penning H- ion source Surface Plasma Source 35 mA through 0.6  10 mm aperture (  600mA/cm2) 200-250  s, 50 Hz  1% duty cycle 0.17  mm mrad (@ 665 keV, 35 mA) Double output current : 35mA → 70mA  Increase pulse length : 200μs → 2 ms  Improve emittance Maximize lifetime Parameters of the ISIS source: Development goals : D. Faircloth 70mA, 1.2 ms

7. NuFACT06, Irvine 27. August 2006 Initial particle distribution – source emittance D. Faircloth S. Jolly J. Back Measurement – pepper pot scanner Artificial distribution based on slit scanner Measurement – slit scanner MAFIA simulation (  x,rms =0.81  mmmrad;  y,rms =0.97  mmmrad) (  x,rms =0.25  mmmrad;  y,rms =0.25  mmmrad)

8. NuFACT06, Irvine 27. August 2006 Magnetic LEBT John Back Optimisation of the magnetic design is nearing completion. A 3 solenoid magnetic LEBT is being designed, based on the successful ISIS RFQ injector. An electrostatic LEBT has been rejected due to the close proximity of the caesiated ion source.

9. NuFACT06, Irvine 27. August 2006 An initial beam optics design has been completed. Further optimisation will be carried out based on the results of the pepper-pot measurements. John Back Simon Jolly Beam trajectory plot and transverse phase space distribution at the RFQ entrance for an artificial input distribution based on slit scanner results. Transverse phase space distribution at the RFQ entrance based on the results of a pepper pot measurement. (  x,rms =1.21  mmmrad;  y,rms =0.93  mmmrad) (  x,rms =0.33  mmmrad;  y,rms =0.33  mmmrad)

10. NuFACT06, Irvine 27. August 2006 324 MHz RFQ – cold model production A 0.5 m, 324 MHz 4-vane RFQ cold model design is done. Machining and brazing tests have been successfully completed. The cold model contains all the significant features of the final 4 m long design and is nearly finished. 2 copper “quadrants” of the cold model waiting for brazing. Aaron Cheng Ajit Kurup Alan Letchford Peter Savage Juergen Pozimski Design of the 4 vane Cold model Aluminium machining model

11. NuFACT06, Irvine 27. August 2006 Aaron Cheng Design of the beat pull measurement system. Set up of the beat pull measurements system at Imperial College. 324 MHz RFQ – RF properties measurements A computer controlled bead pull system is currently tested with a pillbox cavity and will be used to perform cavity field measurements on the cold models. Next measurements: September – old ISIS 4 rod RFQ cold model. October – new FETS 4 vane RFQ cold model. Comparison between measured and simulated field distribution using a pillbox cavity. TM 010 Frequency (MHz) unloaded Q, Q 0 Predicted572.60120941 Measured573.4714484

12. NuFACT06, Irvine 27. August 2006 An initial beam dynamics design has been completed for the FETS RFQ Alan Letchford The RFQ was optimized for a Waterbag input distribution (0.25  mmmrad, 60 mA) and showed negligible emittance growth and 94% transmission. For the generated data transported through the LEBT the transmission drops to ~83%. (  x,rms =0.35  mmmrad;  y,rms =0.35  mmmrad;  z,rms =0.19  degMeV) For the measured data transported through the LEBT the transmission drops further to ~47%. (  x,rms =0.62  mmmrad;  y,rms =0.62  mmmrad  z,rms =0.21  degMeV)

13. NuFACT06, Irvine 27. August 2006 High speed beam chopper A novel tandem chopper technique has been developed at RAL to overcome the conflicting requirements of fast rise time (< 2ns) and long flat-top (up to 100  s). Mike Clarke-Gayther Ciprian Plostinar A ‘fast’ chopper creates a short, clean gap in which a ‘slow’ chopper can switch on. The fast pulser is limited in flat-top but can switch between bunches. The slow pulser cannot switch between pulses but can generate the required flat-top. Chopper 1 (fast transition) Chopper 2 / Beam dump (slower transition) BEAM Fast and slow chopper modules

14. NuFACT06, Irvine 27. August 2006 Three chopper line optics designs are under investigation. A short line keeps the emittance growth low but makes chopping harder and requires some challenging technology. A long line is ‘easier’ but controlling the emittance is more challenging. The short ‘ESS’ solution will require novel, compact, high gradient quadrupoles and DTL- like cavities. Hybrid permanent and electromagnetic quads are being investigated. Mike Clarke-Gayther Ciprian Plostinar

15. NuFACT06, Irvine 27. August 2006 Diagnostics David Lee Jürgen Pozimski Christoph Gabor Accurate diagnostics are essential for FETS to be successful. In addition to more usual diagnostic devices, non-destructive laser stripping techniques will be employed. Photo detachment Detection of distribution Charge separation                   - - - - - - -  “no” momentum transfer I(t,y,x)-> 2 D profile, transv.  magnetic dipole I(t,y)-> profile, long.  (TOF)

16. NuFACT06, Irvine 27. August 2006 Beam is not cylindrically symmetric –So need tomography Measure profiles from different angles –Only 180° coverage required (symmetry) Transverse beam particle distribution will be determined by the use of a laser wire profile measurement device. David Lee Jürgen Pozimski Christoph Gabor Multiple profile measurements under different angles allow investigation of the spatial beam ion density distribution After deflection of the detached electrons from the beam a FDC is used as integral detector. Design of the Laser beam path

17. NuFACT06, Irvine 27. August 2006 IAP Frankfurt laser transverse emittance measurement system will be adapted to the FETS requirements. Christoph Gabor Jürgen Pozimski Schematic drawing of the set up to determine non destructively the transversal beam emittance, using laser detachment technique. Distribution of the neutralized ions on the scintillating screen.

18. NuFACT06, Irvine 27. August 2006 Conclusion – Time table Substantial progress has been made on all sub tasks ! Ion source LEBT DIAGNOSTICS RFQ CHOPPER MEBT Construction & Commissioning Design 2005200620072008 2009