Machine Physics at ISIS Proton Meeting 24 th March 11 Dean Adams (On behalf of ISIS Accelerator Groups)

Machine Physics at ISIS ISIS delivers ~ 225 µA, 800 MeV proton 50 Hz onto 2 neutron and 1 muon target for condensed matter and muon research. Accelerator chain consists of: – 60 mA H- Ion source – 665 KeV RFQ – 70 MeV Linac – HEDS transport line – 70 – 800 MeV RCS running at 50 Hz – 800 MeV beamlines feeding 2 neutron and 1 muon target. Beam diagnostics include : Intensity, position, profile, temporal and beam loss. Machine Physics measurements/simulations presented focus mainly on those which support ISIS operations.

Injector Machine Physics Two Beam pickups in the HEDS TOF dt = ns = 71.8 MeV Chop a 100 ns injector pulse (1/15 th turn) Inject into ring with RF off. Beam de-coheres over 100 turns giving dp/p

70 MeV HEDS beam line Envelope and alignment control based on MAD models and IDL front end software. Phase Space matching studies at foil Beam Profiles Measured using wire scanner monitor Horizontal envelope Vertical envelope Beam Half width (mm)

Synchrotron: Injection Painting H- charge exchange injection, 70 MeV, Accumulate ~3e13 ppp, 200 µs (133 turns) Injection Septum Vertical Sweeper Injection Dipoles Foil Injected Beam Closed Orbit Dispersive Closed Orbit Anti-correlated Painting Measured betatron amplitude Fitted betatron amplitude Measured closed orbit Fitted closed orbit 600 ns chopped beam ( 2/5 th turn) measured on 2 ring position monitors HorizontalVertical

Injection Measurements vs ORBIT Simulations 2.5x10 13 ppp -0.3ms -0.2ms -0.1ms -0.3ms -0.2ms -0.1ms Anti Correlated Anti Correlated Correlated Horizontal Vertical Vertical

Coherent Tune Measurements 0.26 Position (mm) Turns Abs(FFT) Freq(n-Q) Fractional Tune Measurement available: During injection with chopped beams During Acceleration with fast magnetic kickers Vertical Q vs Intensity per bunch at 3 ms Intensity per bunch E13

Measurement of Beam Widths ISIS Q law π mm mrad Horizontal Profile Scan -0.4 – 2 ms ORBIT 3d Simulation Results turns

Ring Closed Orbit and Envelope Control Closed Orbits use 10 position monitors 7 steering magnets per plane MAD model and MICADO or SVD Relative Beta Envelope Measurement based on injected 600 ns chopped beam measured on 10 position monitors per plane. Correction uses 20 Trim quadrupoles and MAD model – In comissioning phase.

Longitudinal Measurements (V = V h=2 sin (φ)) Tomographic Reconstruction at 0 ms Measure Position Monitor Electrode sum signal over acceleration Split into turns wrt RF Phase Phase Turns 0ms ORBIT 1d Simulation

Longitudinal Measurements V = V h=2 sin (φ) - V h=4 sin (2φ+Ѳ) Measure Position Monitor Electrode sum signal over acceleration Split into turns wrt RF Phase 0ms Tomographic Reconstruction at 0 msORBIT 1d Simulation

Beam loss Measurements Time (ms) Measured Sum Ring Beamloss ORBIT Simulated Loss with 2.5d space charge ORBIT Simulation, Adam Dobbs, Imperial) No Space Charge 39 ring beam loss measurements over ISIS Cycle

Dipole 2 Scintillators Collector system is made of 13 copper/graphite collectors used to stop ~ 5 KW of beam lost during ISIS trapping and acceleration. Beam not collected can be dumped in dipole 2 leading to RF screen damage. Array of 12 scintillators ~ 20hx10v cm inside dipole

800 MeV Beamlines to Target 1 and 2 Q m lattice MAD Lattice Models allow envelope and trajectory control on EPB1 (left) and EPB2 (bottom) EPB1 Muon and Neutron Targets Beam Half width (mm) EPB2 Neutron Target