ICA Applied to Long Bunches

Jeff KolskiInformal workshop on ICS and High Intensity acceleratorsIndiana UniversityLos Alamos Nation Laboratory3/17/10LA-UR 10-01611

Outline

•A brief overview of LANSCE operations

•ICA applied to long bunches

•Single turn kick experiment

•Some interesting ICA modes

Los Alamos Neutron Science Center (LANSCE)

Los Alamos Neutron Science Center (LANSCE)

Ion SourcesSector J

Drift TubeLinac (DTL)(201 MHz)

TransitionRegion (TR)

Isotope ProductionFacility (IPF)

CoupledCavityLinac (CCL)(805 MHz)

Proton Radiography (pRad)

Ultra ColdNeutrons (UCN)

Switch Yard (SY)

Area A

LujanCenterWeapons

NuclearResearch(WNR)

Central Control Room (CCR)

Jeff’s OfficeBuilding 6

ProtonStorageRing(PSR)

Google Maps

Proton Storage Ring (PSR)

Skew Quad

Merging Dipole Stripper Foi l

C Magnets

Bump Magnets

Matching Section

Skew Sec tionSkew Quad

Final Bend

H-/H0 Dump Line

Circumference = 90m

Beam energy = 798 MeV

Revolution frequency =2.8 MHz

Bunch length = 290 ns (73 m)

Accumulation time = 625 μs

= 1746 turns

ES41y

ES43q

WM41 and WC41

RJM

Pinger

Ring Parameters

Circumference C 90.2 mBeam Kinetic Energy T 798 MeVBetatron Tunes νx, νy 3.19, 2.19

Transition γ γt 3.1

Phase Slip Factor η -.19Max rf Voltage Vrf 18KV

Buncher Harmonic, Freq h, f 1, 2.795 MHzSynchrotron Tune (10KV) νs .00042

Mean Pipe Radius b .05 m

Injection SchemeLinac frequency 201.25 MHz, 5 ns

PSR frequency 2.8 MHz, 358 ns

72.07 of the Linac frequency

Turn 1Turn 2Turn 3Turn 14Turn 15

ICA for long bunches

Nxxx

Nxxx

Nxxx

tx

BPMBPM

2)1(

21

21

2

222

111

• Instead of having several BPMs distributed around a ring, use one digitized BPM signal where each digitization bin is a time slice along the length of the beam.

• For ICA, the time slices are effectively BPMs along the beam length.

• The resulting spatial modes then describe the strength of the motion along the beam.

Setup for theSingle Turn Kick Experiment•Data taken by R. Macek in Oct. 2006.• Accumulate for 1225μs• Store for 200 μs• Give the beam a single turn kick ~400 turns

before extraction to induce coherent betatron motion.

•Capture digitized BPM data using wc41 and wm41 (vertical sum (vs) and difference (vd), horizontal sum and difference).

… And begins the Fishing Expedition

• ICA of the vd signal from wm41 yields modes containing transverse information. (coherent tune shift)

• ICA using the vs signal from wm41 yields modes containing transverse and longitudinal information. (transverse coherent tune shift, longitudinal motion, and injection structure).

• ICA of wc41 yields the same modes as using wm41vs except with a low frequency bias.

A Betatron mode•Mode

only appears after the transverse kick.

•Temporal part of mode FFT peaks at twice the tune.

ICA and Coherent TuneShift•Several ICA modesdescribe thecoherent tune shift.•In this example,there are only threedouble modes.•In principle there isan ICA tune mode foreach the time slice.•ICA yields the modes that most diagonalize the

time-lag covariance matrices

Another Betatron mode•Strongest

betatron modes show double FFT peak.

•Could transverse profile be non-symetric?

A “Noise” Mode•DC

temporal mode without much frequency

•The SV from the time lag correlations are very small.

“Scope” mode•Temporal

mode is DC

•Spatial mode even where beam is not.

•Mode FFT peak ~ the scope clock.

The “Injection” Mode • Mode only appears during injection.

• Mode FFT peaks at 72.07 (the injection sub-harmonic PSR).

• 54 peaks in the spatial mode, same number as the injected micropulses per turn.

CombiningInjection Modes

Late Injection?

•are

A Longitudinal Mode • Shoulder on the front of the cumsum of the spatial mode.

• If beam was injected late, does this mode describe the motion of the beam filling the front of the bucket?

Another Longitudinal ModeDelay

betweenthe cumsumof the spatialmode and thebeam current.

Anotherexample ofinjecting late?

Last Longitudinal Mode

•Spatial modes has three humps.

•Peaks at the synchro-nous phase and ± 90°.

Continuing Work

•Experimentally verify the ICA modes

•Understand how the number of turns, modes, time lags, and BPMs effect the ICA.

•Simple simulations

Acknowledgements

•A special thanks to

▫SY Lee and Xiaoying Pang (Indiana University)

▫Bob Macek and Rod McCrady (LANL)