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Space charge in LEIR?

Michael BodendorferFebruary 27h, 2014

With the help of Django Manglunki, Maria-Elena Angoletta, Alan Findlay, Christian Carli, Sergio Pasinelli, Gerard Tranquille,

Jerome Axensalva and Maxim AndersenAnd many, many thanks to:

Elena Benedetto and Vincenzo Forte

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LINAC3 & LEIR

Overview

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MotiviationLEIR came from LEARPre-LHC era:

• Ion chain with new Linac3 for SPS fixed target ion operation (via Booster)

• Not suitable for LHC: large emittances and low brightness (brightness limited already at ECR ion source)

Proposals to increase brightness for LHC:• Laser-ion-source to increase brightness (Studied in the 1990s)• Accumulation in synchrotron with electron cooling

• Electron-Cooling fast at low energy and for “heavy” (high charge state) ions• Studied experimentally between 1994 and 1997 with LEAR• Chosen as viable solution, which can be ready on time for LHC

(expected around 2006)• Construction of LEIR, re-using most of the LEAR hardware• LEIR transforms several long low density pulses from Linac3 into dense short

bunches, useful for LHC in 2006

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LEIR – Low Energy Ion Ring

From LINAC3 & to PS

EcoolerBeam

Injection Extr. Septum

Extr. Kicker

RF

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OverviewMachine Output Energy Charge stateECR ion source 2.5 keV/n …,29+,…LINAC3 4.2 MeV/n 29+/54+LEIR 72.2 MeV/n 54+PS 5.9 GeV/n 54+/82+SPS 176.5 GeV/n 82+

LEIR Design Parameter

Value

Length 78mbrel.(Inj. & Ej.) 0.095 0.392grel. (Inj. & Ej.) 1.0045 1.087gtransition 2.84ε*

transv. (inj & Ej.) 0.65 μm 0.7μm

εlong. (Inj. & Ej.) 0.015eVs/u 0.1eVs/uTune (Hor. & Vert.) 1.82 2.72

LEIR

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E-Cooling

Extraction

D=10m

D=0

EjectionKicker 1Quadrupole

doublet

RF

D=0

InjectionBρ=1.14Tm

4.2MeV

Quadrupole triplet

EjectionKicker 2

D=10m

Optics Bρ=4.8Tm72.2MeV

Symmetry

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LEIR performance, 2013 and LIU IonsWhy upgrade?

Parameter Unit LEIR Pb84+

2013LEIR

baselineLEIR

full upgrade

Pb charge state [-] 54+Output Energy [GeV/u] 0.0722In/Out Bρ [Tm] 1.138 / 4.8Injections for next machine [-] 1

Bunches/ring [-] 2Total extracted charge Charges >5.4x1010 5.4x1010 8.6x1010

Charge at flat bottom Charges >6.0x1010 6.0x1010 1.1x1011

Space charge ΔQ on flat bottom

[-] 0.06(LHC design rep)

0.06…0.09(estim.)

0.13(estim.)

From: PERFORMANCE OF THE INJECTORS WITH IONS AFTER LS1D. Manglunki for the LIU-Ions team, CERN, Geneva, Switzerland, 2013

ALICE wants by 2035: 10nb-1

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A LEIR NOMINAL cycle (Qh=1.82; Qv=2.72)

7 inje

ction

s. Fir

st at

215m

s, th

en

spac

ed 20

0ms.

200μ

s lon

g. Extraction@ 2880ms(Master timer)

RF capture @ 1780ms

Continuous electron cooling

Magnetic ramp start @ 1823ms

Intensity in 1010 charges vs. cycle time: 0 to 3.6s

B-field

Up to 50% loss(Coasting beam)

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Electron beam shifts the ion beam in energy space

Less hot ions

Hot electronsCold electrons

Hot ions

Ekin_e=qe-(Uc+Ue+Ui) vele Δveli

Uc

Uground

Electron cooling

Cooling RF adjustFrevcorr

necessary

Ue

Ui

Uc = Cathode potentialUe = Space charge potential of electron beamUi = Space charge potential of ion beam

Δveli

Toroidal magnetIe >> Ii

Cooling rate:

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Tomoscope @ RF capture before

Tomoscope @ RF capture after

Higher accumulated intensity (before RF-capture) beam is lost at RF-capture Adjusting Frevcorr -> RF-capture successful

Trev.

Measurements from Nov. 29th, 2012

Waterfall diagram of Tomoscope analysis:

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Oracle output shows improvement:

Jan 21st, 2013

Frevcorr improved Frevcorr improvedoriginal original

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TWISS parameters (MADX)

Qx - Qy = -1 2Qx - Qy = 1 4Qy = 11 Qx + 3Qy = 10  3Qy = 8 2Qx + 2Qy = 9 

Tune measurement:

13 Pictures from: Low Energy Ion Ring LEIR, C. Carli, 14th March 2012

LEIR multi-turn injection (proposed by D.Möhl and S.Maury)

x

y

x

y

x

y

x

y

1st turn of incoming beam

After 3 turns

End of injection (71 turns)

After collapse of the bump

Mechanism:• Bumper moves orbit inwards• Momentum ramping moves orbit outwards Betatron amplitude for incoming beam

remains constant

Stack “parked” with negative momentum offset

CO remains fixed Closed orbit of

injected beamRange:

Δp/p=4x10-3

x

Towards machine centre()

timeD=10m

Inj. beamSeptum

DxΔp/p

Bump

Low momentum

High momentum

Bump+DxΔp/p

200μs (71turns)

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Longitudinal Schottky spectrumTi

me

Momentum

Center: 35MHzSpan: 330kHz

Center: 36MHzSpan: 313kHz

Den

se b

eam

1st inj.2st inj.

7st inj.

3st inj.4st inj.5st inj.

6st inj.

21. Nov. 20124.5*1010 charges

3. Feb. 20138*1010 charges

p-ramp: 4x10-3

Less

den

se b

eam

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Typical LEIR NOMINAL cycle (sampler output, Nov. 21st, 2013)

Den

se b

eam

1st inj.2st inj.

7st inj.

3st inj.4st inj.5st inj.

6st inj.4.5*1010 charges

Insufficient cooling and/or space charge?

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Where/when is there space charge in LEIR?

Den

se b

eam

1st inj.2st inj.

7st inj.

3st inj.4st inj.5st inj.

6st inj.

During multi-turn inj.?

During cooling?

At RF-capture?Coasting beam

Can S/C cravate detach from design tune?

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Findings so far:• Accurately modelling LEIR is a challenge (MADX-PTC: 90° BHN bending

magnets, design specifications inconsistent with actuallity,…)• Identified three potential origins for space charge, maybe more?

Simulation activities (actual and planed):• MADX-PTC optical model vs. machine parameters by LOCO-analysis• PTC-Orbit fit for ions? (may need source code modification)• PTC-Orbit flat-bottom, multi-turn injection, RF-capture and magnetic

ramp

Wanted:• Space charge during/after multi-turn injection?• Space charge at RF-capture?• Electron cooling simulation (effect)

Potential reward:• Compare LEIR with existing simulations (PSB,…)• Understanding better PTC-Orbit (Performance, stability, accuracy,

convergence behavior)

BIG THANKS to S/C WG ! ! !

Off to the movies!

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Additional slides…

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εlong = 10.8eVsPb54+/bunch = 5.1E8

εlong = 8.1eVsPb54+/bunch = 5.0E8

S. Hancock, 21.2.2013

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Positive vertical chromaticity in LEIR

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Electron cooler loss rates for different Pb charge states

Loss-rate coefficients measured for lead ions of different charge states and different machine settings.

Experimental Investigation of Electron Cooling and Stacking of Lead Ions in a Low Energy Accumulation Ring

J. Bosser, C. Carli, M. Chanel, CERN, CH{1211 Geneva 23, SwitzerlandApril 27, 1999

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Restricted maxima search

LEIR horizontal tune NOMINAL (6 injections)

Fractional tune

Cycl

e tim

e [m

s]

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ΔQ for programmed radial offset from-20mm to +20mm

-20mm

-15mm

-10mm

-5mm

5mm

10mm

15mm

20mm

1 time step: 20ms

Difference of Horizontal tune to reference tune (@ 0mm beam offset)

Cycl

e tim

e [m

s]

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YASP output

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Linear extrapolation:-20mm to +20mm radial offset

Measurement from +10mm programmed radial offset

Measurement from -10mm programmed radial offset

Linear extrapolation of Δp/p

Δp/p

Cycl

e tim

e [m

s]

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DispersionYASP MADX MADX

Dx/beta_rel Element delta Element DX_madx-108.6467794 UEH11 0.05 UEH11 -108.594631-108.6467794 UEV11 0.06 UEV11 -108.5916379-108.6467794 UEH12 0.19 UEH12 -108.4540057-108.6467794 UEV12 0.20 UEV12 -108.4510126

-29.7103708 UEV13 0.20 UEV13 -29.51327851-27.03419573 UEH13 0.21 UEH13 -26.82629815-3.659102848 UEH14 0.24 UEH14 -3.414974121-2.648617378 UEV14 0.24 UEV14 -2.409566799

2.74087E-12 UEV21 0.01 UEV21 0.0086070132.74027E-12 UEH21 0.01 UEH21 0.0078188312.72836E-12 UEH22 -0.01 UEH22 -0.007822682.72776E-12 UEV22 -0.01 UEV22 -0.008611838

-2.648617378 UEV23 -0.25 UEV23 -2.901496482-3.659102848 UEH23 -0.26 UEH23 -3.92239623-27.03419573 UEH24 -0.35 UEH24 -27.38481892

-29.7103708 UEV24 -0.35 UEV24 -30.06436595-108.6467794 UEH31 -0.17 UEH31 -108.8144791-108.6467794 UEV31 -0.16 UEV31 -108.8103844-108.6467794 UEH32 -0.02 UEH32 -108.6660674-108.6467794 UEV32 0.03 UEV32 -108.6164755

-29.7103708 UEV33 0.23 UEV33 -29.48507857-27.03419573 UEH33 0.25 UEH33 -26.78910043-3.659102848 UEH34 0.37 UEH34 -3.286295971-2.648617378 UEV34 0.37 UEV34 -2.27545835

2.69117E-12 UEH41 0.26 UEH41 0.2636268092.69184E-12 UEV41 0.26 UEV41 0.2606499942.72887E-12 UEV42 0.10 UEV42 0.0954367912.72953E-12 UEH42 0.09 UEH42 0.092459977

-2.648617378 UEV43 -0.16 UEV43 -2.804066827-3.659102848 UEH43 -0.17 UEH43 -3.825424558-27.03419573 UEH44 -0.28 UEH44 -27.31623092

-29.7103708 UEV44 -0.29 UEV44 -29.99979657

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