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Beam Feedback System Challenges at SuperKEKB Injector LinacL-band+LAS capture section 50 Hz (e+ or...
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![Page 1: Beam Feedback System Challenges at SuperKEKB Injector LinacL-band+LAS capture section 50 Hz (e+ or e-) pulse-by-pulse mode switching S-band linac 2.5 GeV e- 0.1nC x 1 PF ... ARC! e+Target!](https://reader033.fdocuments.net/reader033/viewer/2022060715/607c039c797207030538652e/html5/thumbnails/1.jpg)
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Beam Feedback System Challenges at SuperKEKB Injector Linac
Kazuro Furukawa, Ryo Ichimiya, Masako. Iwasaki, Hiroshi Kaji, Fusashi Miyahara, Tatsuro Nakamura,
Masanori Satoh, Tsuyoshi Suwada
KEK, Japan
![Page 2: Beam Feedback System Challenges at SuperKEKB Injector LinacL-band+LAS capture section 50 Hz (e+ or e-) pulse-by-pulse mode switching S-band linac 2.5 GeV e- 0.1nC x 1 PF ... ARC! e+Target!](https://reader033.fdocuments.net/reader033/viewer/2022060715/607c039c797207030538652e/html5/thumbnails/2.jpg)
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
SuperKEKB and electron/positron Injector Linac u⯠Asymmetric e+/e- Collider for B-physics
vâŻFlavor structure of elementary particles, and possibly new physics
u⯠40-times higher Luminosity compared with that of KEKB (WR) vâŻTwice larger storage beam Ă Higher beam current at Linac vâŻ20-times higher collision rate with nano-beam scheme ă ÂłâŻĂ Low-emittance (even at first turn) Ă Low-emittance beam from Linac ÂłâŻĂ Shorter storage lifetime (Ă Higher Linac beam current)
u⯠Linac challenges vâŻLow emittance e- ÂłâŻwith high-charge RF-gun
vâŻLow emittance e+ ÂłâŻwith damping ring
vâŻHigher e+ beam current ÂłâŻwith new capture section
vâŻEmittance preservation ÂłâŻwith precise beam control
vâŻ4+1 ring simultaneous injection
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2x beam current
40x Luminosity
RF-gun
e+ efficiency
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Linac Upgrade for SuperKEKB u⯠Higher Injection Beam Current
vâŻTo Meet the larger stored beam current and shorter beam lifetime in the ring vâŻ4~8-times larger bunch current for electron and positron
u⯠Lower-emittance Injection Beam vâŻTo meet nano-beam scheme in the ring vâŻPositron with a damping ring, Electron with a photo-cathode RF gun vâŻEmittance preservation by alignment and beam instrumentation
u⯠Quasi-simultaneous injections into 4 storage rings (PPM) vâŻSuperKEKB eâ/e+ rings, and light sources of PF and PF-AR v⯠Improvements to beam instrumentation, low-level RF, controls, timing, etc
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4.0 GeV e+ 4nC x 2
3.5 GeV 10nC x 2 (prim. e-) 5nC x 2 (inj. e-)
1.1 GeV Damping Ring circ. 136 m
ECS
high current gun
Energy-spread Compression System
Bunch Compressor
7.0 GeV e- 5nC x 2
low emittance RF gun
SuperKEKB injector Linac
e+ target & L-band+LAS capture section
50 Hz (e+ or e-) pulse-by-pulse mode switching
S-band linac
2.5 GeV e- 0.1nC x 1
PF
HER
LER PF-AR 6.5 GeV e-
C-band modules
3T RF gun
Ir5Ce
FC
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Main features of controls at (previous) KEKB uâŻEPICS as Main control Software Toolkit vâŻProvided a robust basis of equipment controls vâŻReduced software design efforts much
uâŻScripting Languages for Operational Software vâŻSADscript/Tk, Python/Tk, Tcl/Tk used much ÂłâŻEspecially, SADscript as a bridge btw. Accelerator simulation,
Numeric manipulation, Graphic interface and EPICS controls
vâŻBright new idea in the morning meeting could make the operation much advanced in the evening ÂłâŻGreat tool to optimize the operation
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KEKB
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
SuperKEKB Controls uâŻInherit Good part of KEKB Controls vâŻEPICS vâŻScripting languages
uâŻEPICS Channel Access (CA) Everywhere vâŻEmbed EPICS control software (IOC) everywhere
possible
vâŻReduce efforts on protocol design, testing, etc
uâŻDual Tier: Another layer in addition to EPICS/CA vâŻEvent system helps EPICS with another channel vâŻAdditional functionality, synchronization and speed
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SuperKEKB
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Dual-tier Controls uâŻIOC controls via Conventional EPICS CA
ÂłâŻAbove 1ms, ordered controls
uâŻFast FPGA controls via SFP/Fiber (MRF) ÂłâŻ10ps ~ 100ms, 114MHz synchronous controls
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IOC
EVG
IOC
EVR
IOC
EVR
IOC
EVR
OPI
Channel Access
FPGA/SFP
Dual-layer Controls
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
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Fast, Global, and Synchronous Controls
uâŻ114.24MHz event rate, 50Hz fiducial
uâŻ~200 dynamic 50Hz-analog/timing param. uâŻMulti/single-mode fiber
uâŻTiming precision is < 10ps. v⯠< 1ps with external module.
u⯠MRFâs series-230 (and SINAP's) Event Generator / Receivers u⯠VME64x and VxWorks v5.5 / v6.8 u⯠EPICS R3.14.x with mrfioc1/2 u⯠18 event receivers in KEKB u⯠More Home-grown receivers
ARC!
e+ Target e+ BT (KEKB: 3.5GeV, 2nC)!
eâ BT (KEKB: 8GeV, 2nC, ! PFAR: 3.0GeV, 0.1nC)!
eâ BT (PF: 2.5GeV, 0.1nC)!
Event Receivers"
Event Generator"
e- Gun!
Cont-1"
KL_51/52"
SB_5"SB_4"SB_3"
Cont-5"Cont-4"Cont-3"Cont-2"
SB_2"
KL_B5/B6" SB_A"SB_B"
Central"
Cont-ABC"
SB_1"SB_C"
SH_A1" Injection"
96ns >100ns
>100ns 96ns
Dual-layer Controls
Configuration in 2010
to be expanded
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Single Machine, Multiple Virtual Accelerators (VAs) u⯠Pulse-to-pulse modulation (PPM), one of the VAs is active at a time u⯠Independent parameter set for each VA, ~200 parameters are switched
every 20ms pulse
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Dual-layer Controls
ARC eâ (2.5GeV, 0.2nC) eâ Gun
ARC
e+ Target
e+ (4GeV, 4nC)
eâ Gun
Event-based Control System
PF Injection
SuperKEKB-LER Injection eâ (3.5GeV, 10nC)
ARC
eâ (7GeV, 5nC)
eâ Gun
SuperKEKB-HER Injection
ARC eâ (6.5GeV, 5nC)
eâ Gun
PF-AR Injection
Damping ring Every 20 ms
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Two kinds of Virtual Accelerators (VAs) uâŻVirtual Accelerator Models (VAs)
uâŻPPM VAs, that represent independent accelerator views for different purposes vâŻby using dual-tier controls
uâŻSimulation VAs, that represent physics models of accelerators in simulation codes vâŻby using SADscript codes through EPICS CA, normally vâŻeven before the machine completion
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Dual-layer Controls
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
(Offline) Orbit Correction Test in Sim. VA
Horizontal displacement
Corrector K0
Orbit before correction
Orbit after correction
Vertical displacement
Sugimoto et al.
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Beam Feedback Loops uâŻEquipment has inherent instabilities caused by many
sources vâŻAt the beginning of the KEKB project, we had to install many
feedback loops for beam energy, orbit, charge, etc. vâŻSimple PID (mostly Proportional and Integral), with limits
vâŻScripts for prototypes, then ePID on IOCs
uâŻSuperKEKB with demanding beam specification may require further considerations vâŻEmittance preservation vâŻPPM VA handling
uâŻSimulation VA may help organize the loops
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Energy Stabilization
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uâŻEnergy instability was sometimes found vâŻClosed feedback loops were formed
vâŻBeam positions were measured where dispersion function is large
vâŻRF phases at adjacent stations were changed
vâŻLoop parameters were beam mode dependent
vâŻEnergy spread feedback using multi-electrode monitor was also implemented
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
uâŻIf Orbit became unstable vâŻBeam positions were measured where betatron phases are
90degree apart vâŻCorresponding steering magnets are adjusted
vâŻIf the orbit fluctuation was large, weighed average of BPMs based on response functions to beam kick or energy change
vâŻThe same method was applied to equipment stabilization
Simple Orbit Stabilization
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Emittance Preservation uâŻIf Device is off center of the beam vâŻFocusing magnet (quad) kicks the beam bunch vâŻAccelerating structure (cavity) excites wakefield, to bend the tail
uâŻDistorted bunch in banana shape vâŻEmittance dilution or blow-up vâŻDepending on the beam optics and the beam charge
uâŻOrbit correction is crucial to preserve the emittance
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Focusing Magnet
Beam
Accelerating Structure
Transverse distribution in time direction
Sugimoto et al.
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Emittance Dilution uâŻOffset injection may solve the issue uâŻOrbit have to be maintained precisely
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100 samples
Mis-alignment leads to Emittance blow-up
Sugimoto et al.
Orbit manipulation compensates it
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
uâŻClosed loops were installed on each PPM VA independently vâŻTested at KEKB
Multiple Closed Loop Controls Overlapped
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ARC!
e+ Target"
eâ BT (PF: 2.5GeV, 0.1nC)!eâ Gun!
ARC!
e+ Target"e+ BT (KEKB: 3.5GeV, 0.6nC)!
eâ Gun!
ARC!
e+ Target"eâ BT (KEKB: 8GeV, 1.2nC)!
eâ Gun!
Event-based Control System
PF Injection
KEKB-LER Injection
KEKB-HER Injection
Primary eâ (4GeV, 10nC)
Dual-layer Controls
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
ARC
eâ (2.5GeV, 0.2nC)
eâ Gun
ARC
e+ Target e+ (4GeV, 4nC)
eâ Gun
PF Injection
SuperKEKB-LER Injection eâ (3.5GeV, 10nC)
ARC
eâ (7GeV, 5nC)
eâ Gun
SuperKEKB-HER Injection
ARC
eâ (6.5GeV, 5nC)
eâ Gun
PF-AR Injection
Damping ring
Event-based Control System
Every 20 ms
F.B F.B
F.B
F.B
F.B
F.B
F.B
F.B
uâŻFour PPM VAs at least for SuperKEKB (maybe with additional PPM VA for stealth beam)
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Feedback loop life cycle uâŻInstallation of feedback loops vâŻfor beam properties like beam orbit, energy, energy
spread, bunch length, charge, dual-bunch equality, as well as device properties like llrf, timing, magnetic field, etc
vâŻoften without knowing the origin of the instability
uâŻInstability hunting, and fixing uâŻBeam study, or machine study using beam
uâŻIf fixed, remove corresponding feedback loop
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Real Accelerator
EPICS Controls
Independent PPM Parameters Common Parameters
Event Synchronous Controls
Simulation Virtual Accelerators
Display and Analysis
PPM Virtual Accelerators
System Construction
Multiple
Multiple Multiple
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Conclusion uâŻSuperKEKB requires demanding beam parameters at
injector linac vâŻEven under PPM
uâŻModels of PPM VAs and simulation VAs may help design feedback loops vâŻEnergy, orbit, energy spread, charge
vâŻEmittance preservation (via orbit stabilization)
uâŻWe should be prepared for full commissioning from 2015
uâŻWith Phronesis (Greek: Practical wisdom, Ability to understand the
Universal Truth), we believe we can achieve the goal 20
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K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
SuperKEKB dual rings
Mt. Tsukuba
Linac
PF-AR
PF
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Thank you