1. Related poster [1] TPAG022: Slow Wave Electrode Structures for the ESS 2.5 MeV Chopper – Michael A. Clarke-Gayther Status Funding bids have been prepared and submitted to UK and EC organisations (the FP6 programme). Work is about to commence on a prototype beam chopper, in parallel with ion source, RFQ and DTL development. Detailed synchrotron studies continue as part of the UK Neutrino Factory Project. For more information contact: ISIS Accelerator Theory and Future Projects Group Email: C.R.Prior@rl.ac.uk Web: http://www.isis.rl.ac.uk/AcceleratorTheory Upgrade Proposals Development work for an improved H  ion source, and installation of a RFQ in the ISIS linac and a dual harmonic RF system in the synchrotron, should take the machine to 240 kW at the existing energy of 800 MeV. A second target station has recently been approved. To go to higher power levels requires a new ring and increased energy. Upgrade plans are proposed in three phases: Phase I Construction of a 1MW proton synchrotron with injection directly from ISIS. This could operate in two modes: a)at 3 GeV and 50 Hz as a ~1 MW neutron source; b)at 8 GeV and 16.7 Hz as a facility for bunch compression tests, studies of pion targetry and experiments with a proto-type muon front-end system, all essential for a neutrino factory. Phase II Development of the new synchrotron to 2.5 MW with a new injector comprising a 180 MeV linac and two 1.2 GeV, 50 Hz booster synchrotrons, replacing the existing ISIS linac and ring. Phase III Addition of a second high energy synchrotron stacked above the first and operating at 25 Hz. At 3 GeV this would provide an enhanced neutron source; at 6 GeV it could be used for a 5 MW neutrino factory. Introduction The ISIS spallation neutron source has been running successfully for more than 15 years and at 160 kW remains the most powerful source of its kind in the world. With machines due to operate at or near the MW level under construction in the US (SNS) and Japan (J- PARC), demand for neutrons in Europe remains high and an ISIS upgrade is an obvious possibility. Phase I: The New Synchrotron  The lattice is based on a racetrack design with superperiod 2, integer Q h in the arcs and long dispersion- free straights. Nominal tunes are Q h =11.7, Q v =7.2, with trim quads used to avoid 2Q v =14, 4Q v =28 resonances.  The use of sector dipoles avoids ripples in the vertical  - function.  Short central dipoles are included to limit the field to B~1.44T at 8 GeV and assist with dispersion control.  Main quadrupole gradients < 9.8 T/m.  The accelerating cycle uses a B-field chosen to minimise dB/dt and hence the RF required in the ring.  At 50 Hz and accelerating to 3 GeV, V peak = 570 kV. Simulation Phase II: A New Injector  Upgrade the new synchrotron to 2.5 MW with a new injector replacing the existing ISIS.  Build a 180 MeV linac feeding two 1.2 GeV, 50 Hz booster synchrotrons. The linac includes a 280 MHz fast beam chopper [1] to assist loss-free ring injection.  The transfer line to the rings contains a 180 o achromat with high normalised dispersion for longitudinal collimation. Horizontal and vertical collimators help prepare the beam for injection.  The two booster synchrotrons are designed for radius 39 m (half the radius of the main ring), will be stacked vertically and filled with 3 bunches each, one ring after the other.  Dispersion painting and energy ramping are used to ensure loss-free injection, and programmed ramping of the cavity voltages will minimise beam loss during trapping and acceleration.  At the same energy in both rings,1.2 GeV, all six bunches are extracted and transferred to the main synchrotron constructed in Phase I for final acceleration. Phase III: Addition of a Second Main Synchrotron With two main synchrotrons available, the aim is to:  fill the booster synchrotrons each with 3 bunches of 1.7  10 13 protons at 50 Hz;  transfer all six bunches into one main synchrotron, operating at 25 Hz; repeat for the second synchrotron;  extract on alternate cycles, thus recovering the 50 Hz;  with a top energy of 3 GeV, this could be used for a spallation neutron source;  at 6 GeV, bunch compression to ~1 ns rms would provide a 5 MW proton driver for a neutrino factory. ISIS Megawatt Upgrade Plans – Neutrons and Neutrinos for Europe C.R. Prior, D.J. Adams, C.P. Bailey, D.W.J. Bellenger, G. Bellodi, J.R.J. Bennett, I.S.K. Gardner, F. Gerigk, J.W. Gray, W.A. Morris, G.H. Rees, J.V. Trotman, C.M. Warsop CLRC Rutherford Appleton Laboratory, U.K. In the ISIS spallation neutron facility at the Rutherford Appleton Laboratory, U.K. a 70.44 MeV H  linac injects via charge exchange injection into an 800 MeV synchrotron operating at 50 Hz. Two bunches per pulse, each ~100 ns in duration, focus onto a spallation neutron target. Optical parameters for the ISIS upgrade lattice. Nominal tunes are Q h =11.7, Q v =7.2. Sextupoles are included to correct chromaticity. The corresponding dynamic aperture is large, equivalent to a normalised emittance of ~ 600  mm.mrad. Longitudinal simulations using TRACK1D of the ISIS pulse accelerated from 0.8 to 3 GeV (top left to bottom right). The final bunch length ~ 72 ns and  p/p ~ ± 3 10 -3. H - linac for Phase II. The design is based on studies for the European Spallation Source with an extended DTL to 180 MeV. Layout of the proposed new ISIS synchrotron. The mean radius is 78 m (three times the existing ring) and the overall dimensions are 184 m  107 m. Injection Extraction Time (ms) Energy (GeV) Volts (kV) -0.950.886.6 0.00.85422.4 2.01.21571.1 5.01.87495.2 7.02.31516.3 9.02.77432.1 10.953.0130.0 Two 25 Hz 3-6 GeV main synchrotrons, mean radius 78 m 180 MeV H  linac Two 50 Hz 1.2GeV booster synchrotrons, mean radius 39 m Transfer line and Achromat for momentum collimation and energy ramping