‘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

‘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


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


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


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.


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.


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.


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,


Magnetic Field Measurement vs. ANSYS Calculation

Problem: Reliable and precise

B-field measurements in small bores.


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.


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.


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.


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


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


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).


Symmetry by Positioning of Coils and Connections


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.


• 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


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.

Documents

‘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