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