‘Single Non-linear Kicker for Top-Up Injection at BESSY II’
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Transcript of ‘Single Non-linear Kicker for Top-Up Injection at BESSY II’
‘Single Non-linear Kicker for Top-Up Injection at BESSY II’
O. Dressler, P. Kuske - Low Emittance Ring 2013 Workshop, Oxford, UK, July 8 - 10
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 2
Content
2
• Non-conventional Injection vs. 4 Kicker Bump
• Undisturbed Injection in Top-Up-Mode
• Commissioning of Non-linear Kicker System for BESSY II
• Multipole Injection Kickers for New Storage Rings- Limitations in Modern Accelerators- Technological Challenges- Technical details
• Summary and Outlook
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 33
Non-conventional Injection vs. 4 Kicker Bump
*Phys. Rev. ST Accel. Beams 10, 123501, ‘New injection scheme using a pulsed quadrupole magnet in electron storage rings’, K. Harada, Y. Kobayashi, T. Miyajima, S. Nagahashi, Photon Factory, 2007.
Non-conventional injection with one single non-linear kickerApplication of the two injection septa and one single pulsed non-linear kicker magnet outside the injection straight for special injection procedure in top-up-mode *.
Conventional layout of BESSY II Storage Ring Injection Two similar injection septa and four injection kickers in one (long) straight section, were two kicker magnets are powered in series by one pulse power supply respectively.
Oscillation from
injection point to
non-linear kicker
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 44
Undisturbed Injection in Top-Up-Mode
Aims: ‘Top-Up’ operation mode for the BESSY II storage ring, for constant beam current of 300mA,
with injection shots every 30s, high accumulation efficiency, without excitations of stored beam.
‘Non-linear’ refers to the characteristic distribution of induction in the magnet.
Advantages: Wide zero field region on axis, reliable zero crossing, flat By-max at certain distance.
Tasks for single non-linear kicker magnet system development:
Beam optics calculations, magnet system concept, magnetic field calculations, rf power loss
estimations, mechanical design, power electronics, control electronics, system integration, etc.
Magnetic field distributions:
Dipole Quadrupole Sextupole Octupole Non-linear
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 5
Conventional vs. Non-linear Kicker Injection
Local Orbit Bump InjectionNeighboring kicker magnets (K1 + K2 and K3 + K4) are powered in pairs to form a local pulsed orbit bump for beam accumulation.
• 4-kicker injection bump optimized for small excitation.
• Injection efficiency ~ 80%• rms orbit perturbation
horizontal ~ 1.000mmvertical ~ 0.500mm
• Standard injection, beam current 300mA• Perturbation of the stored beam in both planes
Turn-by-turn measurement of horizontal and vertical beam oscillations due to kicker schemes.
• Single non-linear kicker injection, not completely optimized.
• Injection efficiency ~ 80%• rms orbit perturbation
horizontal ~ 0.060mmvertical ~ 0.015mm
• Injection up to a beam current of 300mA possible
Non-linear Kicker Magnet InjectionOne pulsed non-linear kicker magnet located outside the injection straight at an effective phase advance of 45° in reference to the injection point.
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 6
Commissioning of Non-linear Kicker magnet (1)
Methodology of Measurements: The kicker magnet was excited by its nominal current (4 x 700A). The kicker timing relative to the storage ring injection was changed stepwise [µs]. The kick strength [kick/µrad] into either horizontal or vertical direction, measured at a particular horizontal / vertical geometric position (x / y [mm]) of the beam in the vacuum pipe, is shown in the plots.
Set-up: All 4 magnet coils were powered in parallel, on 2 transducers for upper and lower magnet half respectively. Maximal efforts for tuning of current symmetry were done.
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 7
Commissioning of Non-linear Kicker magnet (2)
Set-up: The 2 magnet coils magnet coils of top and bottom magnet half were connected in series, on 2 transducers for upper and lower magnet half respectively, and tuned for best current, and hence, magnetic field symmetry.
Result: • In both coil set-ups a minimum of beam excitation in horizontal direction can be detected.• While in the first case as minimum for vertical beam perturbations is far away from the
horizontal minimum, in the second case one finds much better agreement with the theory.• Assumption that only a series connection of all four kicker coils will achieve horizontal and
vertical minima at the same x / y position.
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 8
Direction of scalability of design. Vertical aperture required for storage ring is most limiting factor.
Measures in [cm]
Desired: 4 currents into one direction
The kicker magnet possesmirror symmetry on itshorizontal and vertical middle axis.
Final design with bore of vacuum pipe and titanized ceramics support.
Specifications: By max. ≥ 20 mT, depiction in [G], (1 G = 1•10-4 T)By max. at y = 0 and x = +10 mm By min. at y = 0 and x = -10 mm (symmetry condition)Bx = 0 along y = 0
Evolution of Design: 4 conductors,
with ceramics support
and vacuum pipe profile.
Non-linear Kicker Magnet, 2D B-Field Calculations
POISSON SUPERFISH, Report No. LA-UR-96-1834, 7 Feb. 2007, Los Alamos National Laboratory
4 coils,
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 99
Magnetic Field Measurement vs. ANSYS Calculation
Problem: Reliable and precise
B-field measurements in small bores.
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 10
Multipole Kicker Magnets - Limitations by Accelerator
10
Limitations of MIK Concept:
• Positioning of the MIK within the storage ring by
considering non-linear optics of modern accelerators.
Changes in optics may require to move kicker.
• Vertical aperture requirements limit positioning of the
kicker coils; injected beam at chosen position may not
be at By-field maximum of non-linear field distribution.
• Limitation for the excitation pulse length by revolution
time; injected beam only kicked once.
• Small emittance of injected beam required.
Advantages of MIK Concept:
• Non-disturbed stored beam in top-up injection mode.
• Octupole like field distribution with zero field on axis
and flat By-field maximum at a certain distance.
Only injected beam deflected.
Reference:S.C. Leemann, Phys. Rev. ST Accel. Beams 15, 050705, ‘Pulsed sextupole injection for Sweden’s new light source’ MAX IV, 2012.
Multipole Injection Kicker (MIK) development at SOLEIL
for MAX VI is succeeding BESSY NL-Kicker design.
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 11
Multipole Kicker Magnets - Technological Challenges
11
Technological Challenges of MIK Concept:
• Precise wire positioning in alumina (1/100 mm).
• Sensitive vacuum system with welded flanges to
ceramics.
• Uniform coating of alumina with Titanium for
mirror current path and good rf containment.
• Low inductance pulse power circuit for required
high pulse currents at short pulse duration.
Reference:P. Lebasque, Magnetic and electric evaluation in transient mode of the Bessy-II MIK design … (collaboration report), March 2013.
Technical details:
• Eddy currents in neighboring metallic surfaces
cause field distortion, asymmetries and weakening.
• Proper contacting of coated surface to avoid rf
power loss and temperature rise of component.
• Pulsed PS outside the tunnel foreseen, to avoid risk
of radiation damage on switching power electronics.
• Now long cables are necessary with ‘pseudo
matching’ to keep load impedance low.
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 12
Pro:• High currents on small
load impedance.• High accuracy possible.• Low ripple on pulse top.
Con:• Small distance to magnet.• Foot width vs. pulse top
of half-sine pulse current.
Lumped Element Circuit
Traveling Wave Circuit
Comparison of Different Pulse Circuit Topologies
Pro:• Pulser unit in save distance to
magnet, therefore no radiation.exposure of power electronics
• Small attenuation by cable only.
Characteristic impedances:50, 25, 12.5Ω
Con:• Impedance matching required.• Small impedance mismatch by
load inductance deteriorates slew rate of pulse current.
• High charging voltage necessary because of system impedance.
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 13
Concept: Pulser / Transducer / Magnet
Transducer in saturation
CT1
CT2
Schematics of Linear Transducer
Scope picture as example for non-linearity and saturation of core material
Properties:• Primary and secondary stray inductance of
windings and connections• Non-complete coupling• Eddy current and hysteresis losses in core
material, possible saturation• Transformation ratio ≠ 1:1 causes
transformation (increase) of load impedances and hence longer current pulses
* Heinz Knoepfel, S. 143, Physical effects and generation methods concerning pulsed fields up to the megaoersted level, Verlag: North-Holland Publ. Co. (1970), ISBN-10: 0-444-10035-0
21 LLKM
01 21
11
0
1 dt
dIM
dt
dILLRIdtI
C S
t
0122
dt
dIM
dt
dILLM
(2)
(3)
(1)
01
111
2
ICdt
dIR
dt
IdLE
(5)MSE LLL
1
11 2
2
1 /K
L
L
(4)
(6)
2L
LL (7)
(3) in (2)
LE - Apparent inductance of pulser circuit, in (4)
β in (5)
α in (6)
Transformation ratio 1:1, only prim. + sec. stray inductance add on
M - Mutual inductance, K - coupling ratio
Schematics of Linear Transducer
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 14
MLS- and Diagnostic Kicker System
References: F. Marhauser, O. Dressler, V. Dürr, J. Feikes, ‘Impedances in Slotted-Pipe Kicker Magnets’, proceedings of the EPAC, Edinburgh, Scotland, 2006. O. Dressler, J. Feikes, ‘Diagnostic Kicker System as a Versatile Tool for Storage Ring Characterizations’, proceedings of the EPAC, Edinburgh, Scotland, 2006. O. Dressler, V. Pickert, C. Rediess, ‘IGBT Driver Circuit in Inductive Adder Technology for Pulsed Power Applications’, proceedings of the PCIM, Nürnberg, 2008.
VUC 1200
ÎP = 800 A half sineτ = 2.3µsfr up to 10 Hz
Amplitude stability 0.1 %
Thyratron pulser system for diagnostic kicker in BESSY SR
kVUC 15
ÎP = 4000 A half sineτ = 1.5µsfr up to 10 Hz
Slotted pipe kicker in MLS SR with solid state pulser attached
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 15
Four Kicker Coils
Realization of Magnet and Connections
Symmetryaxis
2D Magnet Model
Sectional View 3D Magnet Model
Schematics of Electrical Connections
Options for Coil Interconnections
• 2 coils in parallel on 1 transducer (top/bottom), 2 circuits in parallel.
• 2 top and 2 bottom coils in series using 1 transducer respectively (installed).
• 4 coils in series on 1 transducer (will be installed this August).
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 16
Symmetry by Positioning of Coils and Connections
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 17
Acknowledgement
We would like to acknowledge the efforts of the HZB project team:
P. Kuske, M. Dirsat, T. Atkinson and O. Dressler, H. Rast (TU Dortmund).
We also appreciate the prosperous collaboration of MAX VI and SOLEIL.
Especially to mention is the MIK development team of P. Lebasque at SOLEIL.
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 18
• Tests of NL-kicker in BESSY II storage ring for beam injection was successful.
• RF power loss was reduced by complete coating of surfaces with titanium.
• B-field amplitude stability is no issue since only one pulse power supply is used.
Injected beam needs to stay within dynamic aperture boundaries.
• Studies of beam excitation and injection efficiency show promising results. Further studies in top-up mode are ongoing.
• The series connection of all coils to reduce imbalance further is coming this summer.
Summary
LER Workshop, Oxford, UK, July 8 - 10, 2013 Olaf Dreßler 19
Outlook
• Development efforts by a collaboration of SOLEIL and Max VI to deploy
MIK concept for injection into modern accelerators.
• Higher integration of magnet functionality, e.g. the ceramics chamber is
becoming part of the magnet vacuum system to relax pulser requirements,
and also facilitate air-cooling.
• Advance from a ‘prove of principle’ component and test system to a highly
reliable injection kicker system for 24/7 operation.
• Development of a dedicated pulse power supply having smallest circuit
inductance, based on solid state technology and outside the storage ring.