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Progress at the RAL Front End Test Stand J. Pozimski Talk outline :

Progress at the RAL Front End Test Stand J. Pozimski Talk outline :. Overview Ion source development LEBT RFQ Beam Chopper MEBT. Ion source 70 mA, 2 ms, 10 % dc. 3 Soleniod LEBT. RFQ, 324 MHz, 3 MeV. MEBT, chopper. Overview – Experimental Parameters.

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Progress at the RAL Front End Test Stand J. Pozimski Talk outline :

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  1. Progress at the RAL Front End Test StandJ. PozimskiTalk outline : • Overview • Ion source development • LEBT • RFQ • Beam Chopper • MEBT

  2. Ion source 70 mA, 2 ms, 10 % dc 3 Soleniod LEBT RFQ, 324 MHz, 3 MeV MEBT, chopper 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)

  3. Ion sourceD. Faircloth - ISIS Parameters of the ISIS source • 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) Development Goals : • Double output current : • 35mA → 70mA • Increase pulse length : • 200μs → up to 2 ms • Improve (preserve) emittance • Maximize lifetime

  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 1750μsachieved 70mA beam current !

  5. no of successful runs LEBT length [m] LEBTJ. Back – Warwick; S. Jolly - Imperial 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.

  6. Electromagnetic modelling of the RFQ using Mafia(A. Letchford – ISIS; A. Kurup, S. Jolly – Imperial) Theoretical Q value of the 4 vane RFQ ~12000 Theoretical Q value of the 4 rod RFQ model ~6400 • 4-rod or 4-vane ? • 4- rod 324MHz ? • start of particle dynamics calculations Model of the 4 rod RFQ and electric field distribution of the quadrupole mode near the electrodes Distribution of the magnetic fields of the quadrupole mode in the 4 vane RFQ.

  7. Beam Chopper(M. A. Clarke-Gayther – ISIS) To avoid a partial chopped beam, the fast chopper (t<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

  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 (t<2ns).

  9. MEBTFG - 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

  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

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