Presentation on theme: "Imperial College 1 Progress at the RAL Front End Test Stand J. Pozimski Talk outline : Overview Ion source development LEBT RFQ Beam Chopper MEBT."— Presentation transcript:
Imperial College 1 Progress at the RAL Front End Test Stand J. Pozimski Talk outline : Overview Ion source development LEBT RFQ Beam Chopper MEBT
Imperial College 2 Overview – Experimental Parameters Aim is to demonstrate a 60 mA, 2 ms, 50 pps chopped beam at 3 MeV It is a collaboration of several physics institutes: RAL/ISIS (chopper, ion source, engineering) RAL/ASTeC (beam dynamics, RF cavities) Imperial College HEP group (engineering, RFQ, diagnostics, LEBT) Warwick University HEP group (LEBT) RFQ, 324 MHz, 3 MeV MEBT, chopper Ion source 70 mA, 2 ms, 10 % dc 3 Soleniod LEBT
Imperial College 3 Ion source D. Faircloth - ISIS Double output current : 35mA 70mA Increase pulse length : 200μs up to 2 ms Improve (preserve) emittance Maximize lifetime Parameters of the ISIS source Development Goals : Penning H- ion source Surface Plasma Source (SPS) 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, rms)
Imperial College 4 Ion source development -results In the experiments the nominal beam current of 70 mA was already reached and an pulse length of up to 1750μs achieved 70mA beam current !
Imperial College 5 A 3 solenoid LEBT like in ISIS will be used. The parameter space was scanned by the use of a envelope simulation to search for possible solutions which fulfil the RFQ input requirements for the given source parameters. Now further simulations with GPT for a more detailed analyses of the found solutions to further optimize the beam transport are planned. no of successful runs LEBT length [m] LEBT J. Back – Warwick; S. Jolly - Imperial
Imperial College 6 Electromagnetic modelling of the RFQ using Mafia (A. Letchford – ISIS; A. Kurup, S. Jolly – Imperial) Distribution of the magnetic fields of the quadrupole mode in the 4 vane RFQ. Theoretical Q value of the 4 vane RFQ ~12000 Theoretical Q value of the 4 rod RFQ model ~6400 Model of the 4 rod RFQ and electric field distribution of the quadrupole mode near the electrodes 4-rod or 4-vane ? 4- rod 324MHz ? start of particle dynamics calculations
Imperial College 7 Beam Chopper (M. A. Clarke-Gayther – ISIS) To avoid a partial chopped beam, the fast chopper ( <2 ns) removes 3 bunches while the slow chopper (t<12 ns) rises to its max voltage and then chops for 240 ns-0.1ms
Imperial College 8 Beam Chopper – Pulse generator - measurements Measurements show that the built fast pulse generator system already fulfils the requirements on the voltage and the rise- and fall time ( <2ns).
Imperial College 9 MEBT FG - AsTec Improvements compared to the ESS scheme : chopped beam from fast & slow chopper is collected in 2 dedicated beam dumps, designed to take full beam power (no need for 2 identical chopper sections) deflection of fast & slow chopper is optically increased by defocusing quadrupoles now only 30% of original plate voltage for the slow chopper is required (6 kV -> 2 kV), -> faster rise time for slow chopper larger apertures for all elements
Imperial College 10 Conclusions Encouraging progress at the ion source development Particle dynamics design of the LEBT will finish this autumn and mechanical design started Particle and electrodynamic design of RFQ started, cold models will be built next spring Design of beam chopper and MEBT develops strongly Electronics for the fast beam chopper on the test rig Definition of new beam diagnostics started