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The BonnThe BonnElectronElectron Stretcher AcceleratorStretcher AcceleratorElectronElectron--Stretcher AcceleratorStretcher Accelerator
Wolfgang Hillert
Physics Institute of Bonn University
KETNovember WorkshopIAP / Uni Frankfurt
Nov. 13th – 14th, 2008
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Set up: 1953 – 1958Operation until 1984
First strong focusing synchrotron being operational in Europe!
500 500 MeVMeV SynchrotronSynchrotron
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Booster SynchrotronBooster SynchrotronBooster SynchrotronBooster Synchrotron50 Hz Operation, max. Energy 2.3 GeV (1.6 GeV)
B di R di
12 Combined function Magnets of type F/2 – D/2 in operation since 1967
Bending Radius:ρ = 7.65 m
Di l St thmax. Dipole Strength:Bmax = 1 Tesla
Fi ld I dField Indexes:nf = -22.26→gf = 29.2 T/mnd = 23.26→gd = 30.5 T/md d
Total Weight:m = 18.5 t (incl. girder)
Number of Windings = 36, Maximum Current = 1380 A
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ELSA: FODOELSA: FODO--LatticeLatticeELSA: FODOELSA: FODO LatticeLatticeQuadrupole Quadrupole
DipoleR = 10,987m
DipoleR = 10,987m
QF QD
0 57m1,73m
Bmax= 1,07 T @ I = 3100Agmax = 10 T/m @ I = 915A
5,1375m0,57m,
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Slow ExtractionSlow ExtractionSlow ExtractionSlow Extraction
QAmΔΔ∼
Extraction Sextupole-Magnets:excitation of a 3rd integer resonance
Extraction Quadrupole-Magnets:Extraction Quadrupole Magnets:tune-shift close to a 3rd integer resonance, feedback (TAG-OR) stabilizes the external current
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Hadron Physics ExperimentsHadron Physics ExperimentsHadron Physics ExperimentsHadron Physics ExperimentsCB /TAPS B1CB /TAPS B1
i i d iin operation under construction
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Facility ParametersFacility ParametersFacility ParametersFacility Parameters
External beams of Electrons:
Two (three as of 2009?!) experimental areasTwo (three as of 2009?!) experimental areas
Energy range: 1.0 GeV < E < 3.5 GeV
Current range: 10 pA < I < 1 nA
Polarized electrons available routinely
Tagged photon operation with linearly and circularlyTagged photon operation with linearly and circularly
polarized photons
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Research & DevelopmentResearch & DevelopmentResearch & DevelopmentResearch & Developmentatat
Accelerator control: control system developed in house
Stretcher operation: fast ramping and beam extractionStretcher operation: fast ramping and beam extraction
Polarized beams: generation (source) and post-acceleration
Beam diagnostics: position and intensity monitors polarimetryBeam diagnostics: position and intensity monitors, polarimetry
High current operation: single and multi bunch instabilities, feed-back
ELSA / Bonn is participating in the Helmholtz Alliance @ DESY:Physics at the Terascale: R&D in beam diagnostics and dynamics, electron sources
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“Fast” ramping Stretcher Ring“Fast” ramping Stretcher RingFast ramping Stretcher RingFast ramping Stretcher RingFlange for IGP
stainless steel(0.3mm)
i f i ib
Water Cooling
reinforcing ribs(1mm)
Ion Clearing“Fast” Ramping Operation:
E ≤ 7.5 GeV/s
B ≤ 2.1 Tesla/s
•
•
BPM
Water Cooling→ reduction of eddy currents
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Closed OrbitClosed OrbitClosed OrbitClosed Orbitvertical orbit displacement in the quadrupole magnets
vertical orbit displacement in the quadrupole magnetscorrection of the measured displacement by steerer magnets:vertical orbit displacement in the quadrupole magnets
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Orbit Correction on the RampOrbit Correction on the RampOrbit Correction on the RampOrbit Correction on the Ramp
Implemented since Oct. 2008
1.2 GeV 2.35 GeV
∆zrms ≤ 0.15 mm
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Source of polarised electrons @ ELSASource of polarised electrons @ ELSAp @p @Main features:• inverted structure• inverted structure• adjustable perveance• load-lock-system• pulsed 200 mJ Ti:Sa laserpulsed 200 mJ Ti:Sa laser
Main parameters:Beam energy: 48 keVBeam energy: 48 keVPulse current: 100 mARepetition rate: 50 HzPolarisation: ≈80%
Load-Lock upgrade:• short loading time• storage of ≤ 5 crystals Polarisation: 80%
Quantum-lifetime: >3000 hCathode: Be-InGaAs/AlGaAs
g ≤ y• hydrogen cleaning
Set up in 2009
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Low Energy Transfer LineLow Energy Transfer LineLow Energy Transfer LineLow Energy Transfer Line
Transmission > 99.5% @ I = 100mALife-time > 3000h during operation
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S i R t ti IS i R t ti ISpin Rotation IISpin Rotation IISpin manipulation
Spin Rotation ISpin Rotation ISpin Rotation IISpin Rotation II
( ) 21 sB se ds
⎛ ⎞= ⋅⎜ ⎟∫Focusing:
2ds
f p= ⋅⎜ ⎟
⎝ ⎠∫
( )2
sB se dsp
φΔ = ⋅ ⋅∫
Focusing:
Spin Rotation:Lamor Precession ( )2
0
11
se a B s ds
m cφ
γ+
Δ = − ⋅ ⋅ ⋅− ∫
2p∫Thomas Precession
0 1m c γ
aφ γ ϑΔ = ⋅ ⋅
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Depolarizing ResonancesDepolarizing ResonancesDepolarizing ResonancesDepolarizing ResonancesDepolarizing Resonances @ ELSA
imperfection resonances: ,a n n Zγ ⋅ = ∈
P Q Z±intrinsic resonances: ,za n P Q n Zγ ⋅ = ⋅ ± ∈
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Harmonic CorrectionHarmonic CorrectionHarmonic CorrectionHarmonic Correction(Imperfection Resonances)
B(s) = a sin(Q θ) + b cos(Q θ)B(s) = a ⋅ sin(Qsp⋅θ) + b ⋅ cos(Qsp⋅θ)
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Orbit Correction SystemOrbit Correction SystemOrbit Correction SystemOrbit Correction SystemNew corrector magnet & fast switching power supply
Beam pipe optimized for eddy current suppressionL = 260 mH
Programmable 4-quadrantpower supply with
microcontroller
20 kHz20 kHz
Implementation in 2009
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Orbit Correction SystemOrbit Correction Systemyy
10 9.8 mTm
5
d / m
Tm
3.2 mTm
0
ral B
fiel
d
-5inte
gr
-10
time / ms
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Tune JumpingTune Jumping
Tune-jump quadrupole
p gp g(Intrinsic Resonances)
j p q p
Panofsky-type quadrupolewith ferrite yoke
Vacuum chamber:
Resistivity:
Al2O3 ceramics with
10 µm titanium coating
(4.298 ± 0.001) mΩ (DC)Resistivity:
Inductivity:
Max. pulse current:
Max. field gradient:
(4.298 ± 0.001) mΩ (DC)
(9.0 ± 0.1) µH (DC)
500 A
(1.1241 ± 0.005) T/m
Rising edge:
Falling edge:
4 – 15 µs
4 – 20 µs
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Møller-Polarimeter
Compton-Polarimeter
Mott-Polarimeter
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Achieved PolarizationAchieved PolarizationAchieved PolarizationAchieved Polarization
CB/TAPS@ELSA data taking:November 4th – 12th, 2008
on /
%la
rizat
io
B
Pol
Beam energy:E = 2.35 GeV
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0.7 m
Compton Compton PolarimetryPolarimetrydi l di ldipole
quadrupoledipole
5.9 m
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CountingCounting MicrostripMicrostrip DetectorDetectorCountingCounting MicrostripMicrostrip DetectorDetectorCounting Counting MicrostripMicrostrip DetectorDetectorCounting Counting MicrostripMicrostrip DetectorDetector
∙∙∙∙∙∙
Detector: (BABAR 1) 6 front-end chips: amplifier shaper discriminator counterDetector: (BABAR 1)• 768 strips• 50 μm pitch
resolution 14 μm
6 front-end chips: amplifier, shaper, discriminator, counter• high rate acceptance (10 - 150 MHz, single channel!)• digital part built in LVDS technology• FPGA controlled
Developed in close collaboration with ATLAS pixel‐detector group of Prof. N. Wermes, PI Bonn
resolution 14 μm FPGA controlled
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Beam ProfileBeam ProfileBeam ProfileBeam Profile
i l ti― num. simulation(1.7 X0 converter)
• measurement(2.0 X0 converter)
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Tune Measurements and Tune Measurements and Stabilization on the RampStabilization on the Ramp
Excitation of coherent oscillationson the fast energy ramp:
ki k tkicker magnetsRF phase jumps
Design of tune kickersDesign of tune kickers(num. simulations with CST™)Tune kicker power supplies(in collaboration with co. PPT) − without correction of dyn. effects
− with correction of dyn. effects
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High Current OperationHigh Current OperationHigh Current OperationHigh Current Operation
simulation with CST Microwave StudioTMSingle and multi bunch operation:
investigation of instabilitiesinvestigation of instabilities
influence of cavity HOM’s
methods of HOM dampingmethods of HOM damping
multi bunch feed-back system
ion clearingg
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SFB/TR 16
New experimental area for testing of particle detectors
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Design Study Energy UpgradeDesign Study Energy UpgradeDesign Study Energy UpgradeDesign Study Energy Upgrade(Acceleration of I = 50 mA up to E = 5 GeV)
Superconducting RF Cavities in a fast ramping strecher:
two 5-cell resonators 500MHz JAERI-type: UCav ≤ 4.5 MV/mstandard parameters: Q0 = 2·109, Rs = 1011Ω, Qext = 4·106, β = 540generator power: Pg ≤ 260 kW, power input coupler: Pcp ≤ 130 kWmaximum detuning: Δf ≤ 3.5 kHz, overvoltage factor: q ≤ 50l b f HOM’ d b d d HOM l d i !large number of HOM’s need to be damped, HOM-coupler design!
Magnet Optics and Dynamic Aperture:Magnet Optics and Dynamic Aperture:geometric aperture sufficient for 5 GeVdynamic aperture ok, 4 additional sextupoles may be requiredy p , p y qdipole magnets have to be replaced by stronger ones (1.5 T)
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ConclusionsConclusionsOperation of ELSA for hadron physics experiments:p p y p
serves two experimental areas with large acceptance detectorsll i d 1 0 3 5 G Vwell suited energy range 1.0 – 3.5 GeV
polarized beams, high beam pointing stability
Accelerator Physics R&D at ELSA:
generation and acceleration of polarized electronsbeam dynamics in a fast ramping stretcher ringbeam dynamics in a fast ramping stretcher ringadvanced beam diagnostics and polarimetryoperation with high currents: ion clearing HOM’s suppressionoperation with high currents: ion clearing, HOM s suppression, multi bunch feed-back system