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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
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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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3A. Xiao, TWIIS, August 2017, BESSY, Germany
Outline
Introduction Specifications Simulation study* Beam testing results Other pulser technology Summary
* Simulation study used ANL/LCRC blues cluster
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4A. Xiao, TWIIS, August 2017, BESSY, Germany
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
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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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6A. Xiao, TWIIS, August 2017, BESSY, Germany
Layout of the on-axis injection section
Injection kickers (4)
Injected beam trajectory
Septum
Q2 Q1
Horizontal Plane
Vertical Plane
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7A. Xiao, TWIIS, August 2017, BESSY, Germany
Q1 cross section (Courtesy A. Donnelly)
95 mm
Gap: ±8 mmBSC: ±6.5mm
Tilting of Septum magnetInjected beam chamber
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8A. Xiao, TWIIS, August 2017, BESSY, Germany
Specification – Septum
Septum (1T, 1.78 m)
BTS dipole
BM1 Q2 Q1
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9A. Xiao, TWIIS, August 2017, BESSY, Germany
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
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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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11A. Xiao, TWIIS, August 2017, BESSY, Germany
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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12A. Xiao, TWIIS, August 2017, BESSY, Germany
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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13A. Xiao, TWIIS, August 2017, BESSY, Germany
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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14A. Xiao, TWIIS, August 2017, BESSY, Germany
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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15A. Xiao, TWIIS, August 2017, BESSY, Germany
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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16A. Xiao, TWIIS, August 2017, BESSY, Germany
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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17A. Xiao, TWIIS, August 2017, BESSY, Germany
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
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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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19A. Xiao, TWIIS, August 2017, BESSY, Germany
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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20A. Xiao, TWIIS, August 2017, BESSY, Germany
Distribution of maximum kick strength to injected beam
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21A. Xiao, TWIIS, August 2017, BESSY, Germany
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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22A. Xiao, TWIIS, August 2017, BESSY, Germany
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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23A. Xiao, TWIIS, August 2017, BESSY, Germany
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
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Backup Slides
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26A. Xiao, TWIIS, August 2017, BESSY, Germany
Required nominal kick strength
Measured maximum kick strength of FID pulser
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27A. Xiao, TWIIS, August 2017, BESSY, Germany
Measured flattop width of FID pulser
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28A. Xiao, TWIIS, August 2017, BESSY, Germany
Measured tail strength of FID pulser
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29A. Xiao, TWIIS, August 2017, BESSY, Germany
Residual kick tolerance
Measured after pulse kick strength
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30A. Xiao, TWIIS, August 2017, BESSY, Germany
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