advanced photon source upgrade project: injection design and … · 2018. 11. 21. · advanced...

Advanced Photon Source Upgrade Project:The World’s Leading Hard X-ray Light SourceInjection design and

beam test results for the APS-MBA upgrade

Aimin XiaoAccelerator physicistArgonne National Laboratory

For the Fast Injection Kickers Task Group

Topical Workshop on Injection and Injection Systems28th - 30th August 2017, BESSY, Germany

2A. Xiao, TWIIS, August 2017, BESSY, Germany

Group members*

J. Carwardine – group leaderF. Lenkszus (retired) – previous group leaderPhysics Team –

M. Borland, C-Y. Yao (retired), A. Xiao

Engineering Team – A. Barcikowski, A. Brill, T. Clute, A. Cours, Z. Conway, R. Keane,L. Morrison, X. Sun, J. Wang, F. Westferro, M. Abliz

Oversees by managementG. Decker (associate project manager- accelerator), J. CarwardineH. Cease, U. Wienands

* System is highly integrated with other systemsInput, comments, … from many colleagues outside the group

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Outline

Introduction Specifications Simulation study* Beam testing results Other pulser technology Summary

* Simulation study used ANL/LCRC blues cluster

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Reasons to choose on-axis swap-out vertical injection

APSU is a 42-pm1 low emittance storage ring (M. Borland and Y. Sun)– Strong nonlinear effects – limited machine acceptance– Use current APS injector system

• Large injected beam emittance• Delivers one bunch per cycle

→ On-axis injection only, the weakest stored bunch is swapped out

Minimum required beam separation (D) at septumD = R(stored chamber) + 2mm(Septum sheet) + 3σ(inj) + MarginD(H) = 4 mm (R) + 2 mm + 2.15 mm (3σ) + MarginD(V) = 3 mm (R) + 2 mm + 0.66 mm (3σ) + Margin ← less kick strength

→ Vertical injection

5A. Xiao, TWIIS, August 2017, BESSY, Germany

Extraction/Injection region layout

Stripline Kicker

Magnets

S38 S40

…

S39

LambertsonA:M1 Beam Dump

Stored Beam

Injected BeamExtracted Beam

Side View

HHC

High stored bunch power density would damage swap-out dump:pre-kicker required to inflate the projected beam size (see J. Dooling's talk)

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Layout of the on-axis injection section

Injection kickers (4)

Injected beam trajectory

Septum

Q2 Q1

Horizontal Plane

Vertical Plane

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Q1 cross section (Courtesy A. Donnelly)

95 mm

Gap: ±8 mmBSC: ±6.5mm

Tilting of Septum magnetInjected beam chamber

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Specification – Septum

Septum (1T, 1.78 m)

BTS dipole

BM1 Q2 Q1

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Optimization of stripline kickers

S

IK1

Septum

IK2 IK3 IK4

M2 M1

PA (8 cm)

5 cm 10 cm

y

Beam size: ±3σ @εy=20 nm (sketched plot)

Aperture clearence– M1: +3σ of injected beam to top blade of IK1– M2: -3σ of injected beam to bottom edge of injection beam chamber in

septum Stripline: voltage / gap / length – optimization objects

– Optimal condition: M1=M2

10A. Xiao, TWIIS, August 2017, BESSY, Germany

Blade voltage – Septum strengthBlade length

M1 (positive slope): clearance at kicker

M2 (negative slope): clearance at Septum

Optimal point(same clearance)

Scan parameters

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Optimization results – balance risk/challenge between stripline kicker and septum design Blade voltage –

Septum strength

L: 0.54 m (high E field)

L: 0.72 m(Low E field)

M1,

M2

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Pulser timing requirements

Flat top – provide uniform kick to injected/extracted bunch– T_top > 2L/c + 6σinj/stored + Δt

Rise/fall time – no excessive kick to neighboring stored bunch– Minimum bunch spacing 11.4 ns (324 bunch fill)– T_rise (T_fall) < 11.4 - 2L/c - 6σstored – Δt

Total waveform width– T_full < 22.8 – 2L/c – 6σstored – Δt

L = 0.72 m; σinj = σstored =100 ps; Δt (max peak to peak) = 0.5 ns

T_top > 5.9 ns; T_rise (T_fall) < 5.5 ns; T_full < 16.9 nsL

T_topT_rise T_fall

T_full

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Injected beam loss simulation (1)

Include optical mismatch: BTS line Quad strength error 1% Longitudinal mismatch: energy and timing (very conservative) Trajectory error: simulation and measurement

(rms)

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Injected beam loss simulation (2) 50 storage ring post-commissioning ensembles (V. Sajaev) Injected beam parameters: σδ=0.12%, σt=100 ps

– εx=60 nm, εy=16 nm

– εx=75 nm, εy=20 nm

– εx=90 nm, εy=24 nm

Uniformly distributed bunch with weight from Gaussian distribution Tracking for 1000 turns

HSCU (6x6 mm) HGSCU (6x6 mm)

COLCOL

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Beam test with FID pulser1,2,3,4

1 C. Yao et al., IPAC 15,3286.2 C. Yao et al., NAPAC16, 9523 X. Sun et al., NAPAC16, 943.4 A. Xiao et al., AOP-TN-2017-027

y

Cosmotec Inc.

ANL Phy. Division

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Measured FID* pulser waveform * FID Gmbh, www.fidtechnology.com

Flattop: main kick and width

Waveform tail: residual kick

After pulses: residual kick

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Measurement results

Results show (backup slides)– Maximum kicker angle agrees with designed value– Flattop width satisfies requirement– Waveform tail (rise/falling time) satisfies requirement– After pulse strength (~5%) is larger than specified tolerance (3%),

investigation is underway

Adjusted FID pulser trigger delay – measure beam deflection at different part of waveform

18A. Xiao, TWIIS, August 2017, BESSY, Germany

Other pulser technology?

Sydro (Kentech) Technologies Inc. proposed pulser w/pseudo-Gaussian waveform*

*Waveform courtesy Sydro Tech.

V0MaxV0Spread

V1Max

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Study of voltage (kick strength) variations

Simulations assume– Injected bunch length: ±300 ps (6σ)– Stored bunch length: ±300 ps (6σ)– Stored bunch center: -11.4 ns and +11.4 ns– Timing jitters (random): σ

t=100ps, 3-σ cut-off

– Systematic error (injected bunch center relative to waveform center): 0.0 ps and 100 ps

Measures of performance shown in histograms (following slides)– V0Max: max effective voltage to injected bunch– V0Spread: effective voltage variation over injected bunch length– V1Max: max kick to the neighboring stored bunch

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Distribution of maximum kick strength to injected beam

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Max spread 1.8% Didn't include amplitude variation

from pulse to pulse Total kick strength variation: ≤ 2.5%

Distribution of kick strength variation to injected beam

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Distribution of maximum kick strength to stored beam

Max kick strength 0.72% Specification: ≤ 3% A slightly wider pulse waveform

(giving smaller V0Spread) may be tolerable

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Summary On-axis swap-out extraction/injection will be used for APS-U Injection section optimization balances risks and challenges of

different systems (kicker, septum) Injection simulation results shows good injection performance

under specified error tolerances Beam test was performed using

– A prototype stripline kicker module including feed-through– Two FID pulsers: 20kV-pulser up to 15 kV; 30 kV-pulser up to 30 kV– Measured kicker strength agrees with designed value– Measured flattop width, tails are satisfied– Measured after pulse strength higher than tolerance specifications

• Investigation is underway

A pseudo-Gaussian waveform pulser was studied– Simulation results show kick strength variations are under error

tolerance specification– Looking forward beam testing with such a pulser

Backup Slides

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Required nominal kick strength

Measured maximum kick strength of FID pulser

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Measured flattop width of FID pulser

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Measured tail strength of FID pulser

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Residual kick tolerance

Measured after pulse kick strength

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Issues creating flattop

Ideally, can combine two Gaussian waveforms, one triggered at -Δt, another triggered at Δt to make a flattop

Differential mode timing errors → larger V0 variation

Conclusion: Δt=0 is preferred