harmonic rf kicker development for ccr/erl cooler...harmonic rf kicker development for ccr/erl...

Harmonic RF Kicker Development for CCR/ERL Cooler

Haipeng WangThomas Jefferson Lab

EIC Accelerator Collaboration Meetingat BNL, Upton, New York,

October 10-12, 2017

• CCR concept, strip-line kicker, LDRD, new numerologyAndrew Hutton, Edward Nissen, Amy Sy, Andrew Kinber, Andrew Dotson

• Harmonic RF cavity kicker design, prototype, elegant BD simulation, cavity bench measurement,

+Yulu Huang, PhD 2016 (JLab/IMP) from Lanzhou, ChinaHaipeng Wang, Robert Rimmer, Shaoheng Wang, Jiquan Guo

• Prototype cavity fabrication+Jim Henry, Larry Turlington, Bill Clemens, Damon Combs, Jim Follkie…

• Time domain measurement improvement, frequency domain wire-stretching measurement for e-center on the HK cavity+Sarah Overstreet

• New cavity design, RF-thermal analysis+Gunn-Tae Park, Fredrik Fors

• “Straight” merger, beam test plan, other applications like EIC, LCSL-II, CLS+all

Outline and Contributions

EIC Collaboration Meeting 2 Oct. 10-12, 2017, Upton, New York

From ERL Cooler to CCR/ERL Cooler


L1

L2

L3

L4

L5

From Strip-line Kicker to RF Harmonic QWR

EIC Collaboration Meeting 4

500 Times more total RF power needed for strip-line than RF kicker for a given kicking angle and a waveform (JLab-TN-15-040)

Oct. 10-12, 2017, Upton, New York

4-Cavity Model Based on Flat-Top Scheme

5EIC Collaboration Meeting Oct. 10-12, 2017, Upton, New York

QWR-based Deflecting Cavities

6

∫∞

∞−

+= dzzzcBzzEVn

ynn

xntn )]2sin()()2cos()([λπ

λπ

∑=

++=N

nntnt tnVVV

100 )cos( ϕω

The effective transverse kick voltage of the nth harmonic mode can be calculated from:

The electron bunches traveling through the cavity will be deflected by both the transverse electric and magnetic fields.

The total kick voltage from all harmonic modes is:

• Kick can be in both +x/-x direction by using odd harmonics only

• Higher harmonics always help the flatness of bunch kick

• Harmonic mode number N can have as least as half of CCR turn

NM ≤−12

For odd+even scheme, the relationship between cavity number M and maximum harmonic number N can be supported as:

EIC Collaboration Meeting Oct. 10-12, 2017, Upton, New York

Harmonic Kicker Waveform Synthetization

7

Ref: Y.Huang, H.Wang, R.A.Rimmer, et al. Phys. Rev. ST Accel. Beams 19, 084201 (2016)

• Correct the pulse curvature of the Least-Mode

• Reduce the harmonic number to half

Kick every 10th bunch as example


Pre-distortion (De-chirp) and Post-distortion (Re-chirp) Kickersto Compensate the Kicking Pulse Curvature



Tracking result with Kicker 3,1,2

f 0 0.1, 952.6..:= (MHz) Design value: L 821:= (mm)

0 86.6 173.2 259.8 346.4 433 519.6 606.2 692.8 779.4 866 952.62−

1.3−

0.7−

0

0.7

1.3

2

2−

1.3−

0.7−

0

0.7

1.3

2

=2pifZ0Cg g=35mm=2pifZ0Cg g=70mm=2piZ0Cg g=100mm=0=cot(2pifL/clight)

5-harmonic QWR design by graphic solution

Frequency (MHz)

=2*p

i*Fr

eq*Z

0*C

g

=cot

(2*p

i*Fr

eq*L

/clig

ht)

• Cavity length is sensitive to all odd harmonics

• Stub tuning will fine tune each mode on resonance

• Gap distance has less effect on the harmonic tuning

Analytical Model of Harmonic Kicker Cavity Design from Text Book


Half Scale of 476.3MHz Copper Prototype

10

31.5 inch

6 inch2 inch

Beam pipeInput coupler port

Stub tuners

Pickup port

“Half scale” copper prototype with 5 odd harmonic mode

95.26 MHz285.78MHz476.3MHz

666.82MHz857.34MHz



Ref: Yulu Huang, PhD thesis in 2016, IMP/JLab, JLAB-ACC-16-2444

Straight Tapers and Stub Tuners Design

11

• With the taper design, the frequencies of all harmonic modes can be optimized to exact odd multiple harmonics, the errors are within +/- 0.001% from their targets.

• Manufacturing errors and other errors can be tuned back by the stub tuners with a similar process.

• Stub tuners insert 25mm as the baseline of taper to get a bi-directional tuning range.



Fabrication and EBW Details

12

Alignment of EBW of the outer conductor with the

tuner pipes

EBW of the inner conductor to the magnetic end flange

EBW of the outer conductor with electric end flange

stub tuners assembly

inner conductor cap threaded to the inner conductor bar

Loop coupler and pickup for bench measurement antenna


Resonant Frequencies and Tuning Process

13

−+−+−−++−−−−−−+−−++−++−−−

=

1.42233.140.40117.976.4045.26508.2025.748.2165.1533.1042.1502.1809.12609.47

134.93.100583.807.33803.4370.9465.380.1793.2626.31

tunerM

Tuning matrix from measurement, mij is the 1rst order (linear) frequency response of mode i to tuner j in units of kHz/mm.


Measurement after fabrication without tuning

S-parameters, Unloaded Q Measurements



Setup of Harmonic Summation and New Measurement Techniques

New: Sarah, 2017, Summer Intern ReportOld: Yulu, PRAB 19, 122001 (2016)

• Sample sum voltage on stretched wire than pickup probe

• HP/LP filters built for noise reduction of the wire-stretching measurement from motor and RF source

• Retune the cavity with new bump and with the wire

• Wire-scanning for e-center and multiple analysis

Also Yulu Huang PhD Thesis, JLAB-ACC-16-2444Or DOE/OR/23177-4174

stub tuning

5-harmonic spectrum

Time-domain waveform

wire x-scan

New technique


Distribution of EM Field Components along the Beam Axis from CST

16

• The dominant Field component is the deflecting electric field Ex

• The longitudinal field Ez is much smaller than the deflecting field(maximum 10% in magnitude squared).

• The magnetic field Hy is much weaker, and much smaller for the lowest harmonic mode (0.1% in magnitude square) and relatively larger for the highest harmonic mode (6% in magnitude square).

Ex Ez Hy


Bead-pull Results Compared with the CST Simulation Results

17

• Dielectric sphere (left), metallic sphere (right) to measure Eabs• Very good agreement after carefully calibration of beads with a pill-box cavity• The longitudinal electric field and the magnetic field are too weak to be

separated out.



Harmonic Kicker Frequencies for JLEIC and UITF/LERF Test

952.64𝑀𝑀𝑀𝑀𝑀𝑀11 = 86.6𝑀𝑀𝑀𝑀𝑀𝑀

CEBAF/UITF/LERF RF

PEP-II or JLEIC e-ring RF

harmonic kicker base RF

CCR turns

• 5 Odd harmonic frequencies of RF kicker: 86.6 MHz x1, x3, x5, x7, x9, +DC=86.6MHz, 259.8MHz, 433.0 MHz, 606.2 MHz, 779.4 MHz, +DC• CCR harmonic number can NOT be multiple of 11• More even harmonics help the kick pulse flatness and reduction of slopes of zero crossing

JLEIC i-ring/ERL RF frequency

136.1 𝑀𝑀𝑀𝑀𝑀𝑀11 =

86.6 𝑀𝑀𝑀𝑀𝑀𝑀7 = 12.37 𝑀𝑀𝑀𝑀𝑀𝑀

photo cathode laser reprate in UITF/LERF test 1497 𝑀𝑀𝑀𝑀𝑀𝑀

11 = 136.1𝑀𝑀𝑀𝑀𝑀𝑀

kicked beam reprate in UITF/LERF test

1497 𝑀𝑀𝑀𝑀𝑀𝑀 ×7

2 × 11= 476.32𝑀𝑀𝑀𝑀𝑀𝑀

2 × 476.32𝑀𝑀𝑀𝑀𝑀𝑀 = 952.64𝑀𝑀𝑀𝑀𝑀𝑀

476.32𝑀𝑀𝑀𝑀𝑀𝑀11

= 43.3𝑀𝑀𝑀𝑀𝑀𝑀 Baseline JLEIC ERL gun laser reprate


Old/New CCR/ERL Beam Dynamic Parameters Comparison

New: from S. Benson’s Status Report, July 2017

Old: from Y. Huang’s PhD thesis, Dec. 2016Parameter Old Value New Value Unit

Electron energy 55 20-55 MeV

Charge per bunch 3.2 2.0 (3.2) nC

Bunch length at CCR 3 (rms) 2 (tophat) cm

Bunch distribution Gaussian Beer can

Bunch / cavity highest frequencies 476.3/476.3 476.3/952.6 MHz

Normalized transverse emittance at cooling channel 1.074 (non-mag) 36 (mag, drift) mm mrad

Normalized vertical emittance at cooling channel 1.074 (non-mag) 36 (mag, drift) mm mrad

Energy spread (uncorr) 3E-4 3E-4

Recirculation turns 10 11 No.

Kick angle 1 2.5 mrad

Total kick voltage 55 137.5 kV

Beam-stay-clear aperture on kicker cavity (dia.) 70 >70 mm


Old/New CCR Turns and Harmonic Numbers Comparison

Old: Dec. 2016

CCR turns: 10Cavity harmonics: 10 (5 odd, 5 even)Cavity base frequency: 47.63MHzCavity number per side: 4


CCR turns: 11Cavity harmonics: 5 odd + DCCavity base frequency: 86.60MHzCavity number per side: 1

New: Jul. 2017

New ¼ λ11 Length Stub Symmetrizer to Minimize Beam Loading

Old 2016

New, July 2017

Symmetrizeroptimization by Yuluin her thesisDec. 2016

Standing wave of Er on inner conductor surface

• Both simulation (CST) and measurement studies for this modification• 5-Stub tuners could not turn higher harmonics back to targets• Fixed stub length can only symmetrize e-center on one of harmonic

but not lower and higher ones• Only 952.6 MHz mode (and 476.3MHz) needs zero beam loading

Ex & Ez vs z

z

Ex

Ez

Slice & Mirror Boolean


CST Simulation Result with New Stub on Old Cavity

(TE11s in stub plane Z)

2

3

(TE11s in plane Y)


CST Simulation Result with New Stub on Old Cavity

• Increase the stub length by 16.1mm will see the e-center of 857.6MHz (HM5) instead of 1047.9MHz (HM6)

• Need fine tune both stub and cavity lengths for new cavity design

• Need to suppress TE11s higher than HM6, Freqcutoff ≅clight/[π(a+b)], more difficult for larger (a+b)

(TE11s in stub tuner plane Z)

(TE11s in plane Y)

(starts degenerate to TE11s)

(TE11s in plane Y)

(TE11s in stub tuner plane Z)

(TE11s in plane Y)


Analytical Model of Harmonic Kicker Cavity Design from Text Book

+ capacitance due to the fringe field

Disk capacitance

fringe field enforcement factor, new! not in exact format yet

𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑇𝑇2

Normalized transverse shunt impedance


Scaling Calculation of 5-Odd 5-Even Harmonic Kicker Cavity Design for 952.6MHz


476.5 MHz cavity design

Scaling Calculation of New 5-Odd Harmonic Kicker Cavity Design for 779.4MHz


New Cavity Design Estimate and Initial Mechanical Analysis

• Cavity Long Side Length (down): ~820mm

• Cavity Short Side Length (up): ~83mm (with symmetrizer) ~50mm (without Symmetrizer)

• Cavity OD: ~332mm Cavity inner conductor OD: ~117mm

• Cavity Beam-Stay-Clear Aperture (dia.): (70mm, 6.25kW); (100mm, 20kW)

• Less thermal problem to handle 7kW• More problems to bring 6th Odd in.

i.e. on the HOM (TE11s) suppression• Less efficiency of 6th mode on its

beam voltage to RF power• Max temp. 54oC on Stub houses for

1.56kW RF power deposition with inner and outer conductor water cooling. Inlet 35oC, outlet 40oC. No cooling optimization yet

vacuum stress analysis

RF-thermal(ANSYS) analysis for 1.56kW Power deposition


Oct. 10-12, 2017, Upton, New YorkEIC Collaboration Meeting 28

Summary• Beam dynamic (Elegant) simulation have demonstrated that a pair of

Harmonic Kickers (Injection + Extraction) and (De-chirping + Re-chirping) can do the CCR beam circulation without degradation of both kicked and un-kicked beam emittance

• Half scale copper cavity have been prototyped for the bench measurement, no any technical difficulty has been found

• The bead-pull and wire-stretching measurement fully agrees with simulation result and electric center prediction

• The “half-scale” cavity could become a true scale of cavity for the CCR beam in future and its next vacuum type cavity can be used for the beam test at UITF or LERF injector test facility

• Larger beam aperture (>70mm), 86.6MHz base frequency, suppression of TE11 modes for the 5-Odd+DC scheme are all at the cost of higher RF power

• HKC concept and its development will have many benefits to other small emittance conservation application: like “straight” merger, future LCLS-II beam switching and delivery system, CEBAF positron source, etc

• SRF application using least modes option for the high energy beam deflection or crabbing (like EICs here)

Thanks!

Backup Slides


Challenges and Solutions

30

~ns ~10 of nsFew kV

Few mrad

Pulsed power supplies, especially with these characteristics are beyond state of the art.

An alternative driving method is summing simple cosine waves at sub-frequencies of the final beam repetition frequency to generate a continuous waveform.

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 614

12

10

8

6

4

2

0

2

4

6

8

10

12

14

2π0 s

Oct. 10-12, 2017, Upton, New YorkEIC Collaboration Meeting

Multi-Cavity Kick-Drift Modeling in Elegant

31

X’X

1 mrad

Incoming bunch

Outgoing bunch

Recirculating bunch


32

Monitor 1Monitor 2 Monitor 3

Multi-Cavity Kick-Drift Tracking in Elegant


33

Monitor 1

Monitor 3Monitor 2

Monitor 1

Monitor 2 Monitor 3

Multi-Cavity Kick-Drift Tracking in Elegant


BD Simulation in ELEGANT for CCR Using Two Sets of Harmonic Kickers

34

With two kickers separated 180 degree inBetatron phase advance, emittance growth dueto the residual wave slopes between the kickingpulse can be totally cancelled.

Emittance growth mainly comes from theinjection and ejection process, which is onlydetermined by the kicking pulse curvature.



BD Simulation in ELEGANT Using Four Kickers and Kick-Drift Models

35

Kicking pulse curvature can becompensated by a pre Kicker 3 toKicker 1 for CCR and a post Kicker 4to Kicker 2. for ERL with phaseadvance of π.

Emittance growth sensitive to thepath length, voltage and phase errorshas been summarized in followingtable



HOM Power Deposition Analysis


• for 5-Odd+5-Even HK scheme

• No bump symmetrizer• Up to 100 HOMs have

been calculated• Safely avoid CCR beam

excitation with no bunch train gap structure

• Only 8.21W of HOM power on the 5-odd mode copper cavity without damping couplers

• Need to study for new cavity design and the beam spectrum with CCR+ERL and ion clearing gap structure


Gaussian vs Beer Can bunch spectrums


Multiple Field Analysis for Beam Dynamics

• All odd and evens mode cavities without symmetry bumps have been analyzed with CST

• Up to b5 terms in both normal and skew terms have been calculated

• Elegant tracking study shows that only an observable emittance grow due to an artificially increase of sextuple component amplitudes by three-orders

• Wire-stretching technique to measure the multiple field is under the study and the test on the prototype cavity


harmonic rf kicker development for ccr/erl cooler...harmonic rf kicker development for ccr/erl...

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