Post on 12-Jan-2016
description
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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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