machine physics at isis proton meeting 24 th march 11 dean adams (on behalf of isis accelerator...
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Machine Physics at ISIS
Proton Meeting 24th March 11
Dean Adams (On behalf of ISIS Accelerator Groups)
Machine Physics at ISIS
• ISIS delivers ~ 225 µA, 800 MeV proton beam @ 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 = 3.125 ns = 71.8 MeV
Chop a 100 ns injector pulse (1/15th 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
Bea
m H
alf
wid
th (
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 ( 2/5th turn) measured on 2 ring position monitors
Horizontal Vertical
Injection Measurements vs ORBIT Simulations
2.5x1013 ppp
-0.3ms
-0.2ms
-0.1ms
-0.3ms
-0.2ms
-0.1ms
Anti Correlated Anti Correlated Correlated
Horizontal Vertical Horizontal Vertical Vertical
Coherent Tune Measurements
0.26
Pos
ition
(m
m)
Turns
Abs
(FF
T)
Freq(n-Q)
Fractional Tune Measurement available:
During injection with chopped beams
During Acceleration with fast magnetic kickers
0 0.2 0.4 0.6 0.8 1 1.2 1.43.7
3.71
3.72
3.73
3.74
3.75
3.76
3.77
3.78
3.79Coherent Vertical Q vs Intensity Per Bunch at 3 ms
Intensity Per Bunch E13
Ve
rtic
al
Q
Vertical Q vs Intensity per bunch at 3 ms
Intensity per bunch E13
Measurement of Beam WidthsISIS Q law
π m
m m
rad
Horizontal Profile Scan -0.4 – 2 ms
ORBIT 3d Simulation Results turns
Ring Closed Orbit and Envelope ControlClosed Orbits use 10 position monitors 7 steering magnets per planeMAD model and MICADO or SVD
Relative Beta Envelope Measurement basedon injected 600 ns chopped beam measuredon 10 position monitors per plane. Correction uses 20 Trim quadrupoles and MAD model – In comissioning phase.
Longitudinal Measurements (V = Vh=2 sin (φ))
Tomographic Reconstruction at 0 ms
Measure Position Monitor Electrode sum signal over acceleration
Split into turns wrt RF Phase
Phase
Turn
sProfile @ 0ms
ORBIT 1d Simulation
Longitudinal Measurements V = Vh=2 sin (φ) - Vh=4 sin (2φ+Ѳ)
Measure Position Monitor Electrode sum signal over acceleration
Split into turns wrt RF Phase
Profile @ 0ms
Tomographic Reconstruction at 0 ms ORBIT 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
Q13 -1.2m lattice
MAD Lattice Models allow envelope and trajectory control on EPB1 (left) and EPB2 (bottom)
EPB1 Muon and Neutron Targets
Bea
m H
alf
wid
th (
mm
)B
eam
Ha
lf w
idth
(m
m)
EPB2 Neutron Target