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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
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
v Flavor structure of elementary particles, and possibly new physics
u 40-times higher Luminosity compared with that of KEKB (WR) v Twice larger storage beam à Higher beam current at Linac v 20-times higher collision rate with nano-beam scheme ³ à Low-emittance (even at first turn) à Low-emittance beam from Linac ³ à Shorter storage lifetime (à Higher Linac beam current)
u Linac challenges v Low emittance e- ³ with high-charge RF-gun
v Low emittance e+ ³ with damping ring
v Higher e+ beam current ³ with new capture section
v Emittance preservation ³ with precise beam control
v 4+1 ring simultaneous injection
2
2x beam current
40x Luminosity
RF-gun
e+ efficiency
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Linac Upgrade for SuperKEKB u Higher Injection Beam Current
v To Meet the larger stored beam current and shorter beam lifetime in the ring v 4~8-times larger bunch current for electron and positron
u Lower-emittance Injection Beam v To meet nano-beam scheme in the ring v Positron with a damping ring, Electron with a photo-cathode RF gun v Emittance preservation by alignment and beam instrumentation
u Quasi-simultaneous injections into 4 storage rings (PPM) v SuperKEKB e–/e+ rings, and light sources of PF and PF-AR v Improvements to beam instrumentation, low-level RF, controls, timing, etc
3
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
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Main features of controls at (previous) KEKB u EPICS as Main control Software Toolkit v Provided a robust basis of equipment controls v Reduced software design efforts much
u Scripting Languages for Operational Software v SADscript/Tk, Python/Tk, Tcl/Tk used much ³ Especially, SADscript as a bridge btw. Accelerator simulation,
Numeric manipulation, Graphic interface and EPICS controls
v Bright new idea in the morning meeting could make the operation much advanced in the evening ³ Great tool to optimize the operation
4
KEKB
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
SuperKEKB Controls u Inherit Good part of KEKB Controls v EPICS v Scripting languages
u EPICS Channel Access (CA) Everywhere v Embed EPICS control software (IOC) everywhere
possible
v Reduce efforts on protocol design, testing, etc
u Dual Tier: Another layer in addition to EPICS/CA v Event system helps EPICS with another channel v Additional functionality, synchronization and speed
5
SuperKEKB
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Dual-tier Controls u IOC controls via Conventional EPICS CA
³ Above 1ms, ordered controls
u Fast FPGA controls via SFP/Fiber (MRF) ³ 10ps ~ 100ms, 114MHz synchronous controls
6
IOC
EVG
IOC
EVR
IOC
EVR
IOC
EVR
OPI
Channel Access
FPGA/SFP
Dual-layer Controls
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
7
Fast, Global, and Synchronous Controls
u 114.24MHz event rate, 50Hz fiducial
u ~200 dynamic 50Hz-analog/timing param. u Multi/single-mode fiber
u Timing precision is < 10ps. v < 1ps with external module.
u MRF’s 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)!
e– BT (KEKB: 8GeV, 2nC, ! PFAR: 3.0GeV, 0.1nC)!
e– 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
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
8
Dual-layer Controls
ARC e– (2.5GeV, 0.2nC) e− Gun
ARC
e+ Target
e+ (4GeV, 4nC)
e− Gun
Event-based Control System
PF Injection
SuperKEKB-LER Injection e– (3.5GeV, 10nC)
ARC
e– (7GeV, 5nC)
e− Gun
SuperKEKB-HER Injection
ARC e– (6.5GeV, 5nC)
e− Gun
PF-AR Injection
Damping ring Every 20 ms
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Two kinds of Virtual Accelerators (VAs) u Virtual Accelerator Models (VAs)
u PPM VAs, that represent independent accelerator views for different purposes v by using dual-tier controls
u Simulation VAs, that represent physics models of accelerators in simulation codes v by using SADscript codes through EPICS CA, normally v even before the machine completion
9
Dual-layer Controls
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.
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Beam Feedback Loops u Equipment has inherent instabilities caused by many
sources v At the beginning of the KEKB project, we had to install many
feedback loops for beam energy, orbit, charge, etc. v Simple PID (mostly Proportional and Integral), with limits
v Scripts for prototypes, then ePID on IOCs
u SuperKEKB with demanding beam specification may require further considerations v Emittance preservation v PPM VA handling
u Simulation VA may help organize the loops
11
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Energy Stabilization
12
u Energy instability was sometimes found v Closed feedback loops were formed
v Beam positions were measured where dispersion function is large
v RF phases at adjacent stations were changed
v Loop parameters were beam mode dependent
v Energy spread feedback using multi-electrode monitor was also implemented
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
u If Orbit became unstable v Beam positions were measured where betatron phases are
90degree apart v Corresponding steering magnets are adjusted
v If the orbit fluctuation was large, weighed average of BPMs based on response functions to beam kick or energy change
v The same method was applied to equipment stabilization
Simple Orbit Stabilization
13
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Emittance Preservation u If Device is off center of the beam v Focusing magnet (quad) kicks the beam bunch v Accelerating structure (cavity) excites wakefield, to bend the tail
u Distorted bunch in banana shape v Emittance dilution or blow-up v Depending on the beam optics and the beam charge
u Orbit correction is crucial to preserve the emittance
14
Focusing Magnet
Beam
Accelerating Structure
Transverse distribution in time direction
Sugimoto et al.
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Emittance Dilution u Offset injection may solve the issue u Orbit have to be maintained precisely
15
100 samples
Mis-alignment leads to Emittance blow-up
Sugimoto et al.
Orbit manipulation compensates it
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
u Closed loops were installed on each PPM VA independently v Tested at KEKB
Multiple Closed Loop Controls Overlapped
16
ARC!
e+ Target"
e– BT (PF: 2.5GeV, 0.1nC)!e− Gun!
ARC!
e+ Target"e+ BT (KEKB: 3.5GeV, 0.6nC)!
e− Gun!
ARC!
e+ Target"e– BT (KEKB: 8GeV, 1.2nC)!
e− Gun!
Event-based Control System
PF Injection
KEKB-LER Injection
KEKB-HER Injection
Primary e– (4GeV, 10nC)
Dual-layer Controls
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
ARC
e– (2.5GeV, 0.2nC)
e− Gun
ARC
e+ Target e+ (4GeV, 4nC)
e− Gun
PF Injection
SuperKEKB-LER Injection e– (3.5GeV, 10nC)
ARC
e– (7GeV, 5nC)
e− Gun
SuperKEKB-HER Injection
ARC
e– (6.5GeV, 5nC)
e− 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
u Four PPM VAs at least for SuperKEKB (maybe with additional PPM VA for stealth beam)
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Feedback loop life cycle u Installation of feedback loops v for 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
v often without knowing the origin of the instability
u Instability hunting, and fixing u Beam study, or machine study using beam
u If fixed, remove corresponding feedback loop
18
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
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
Conclusion u SuperKEKB requires demanding beam parameters at
injector linac v Even under PPM
u Models of PPM VAs and simulation VAs may help design feedback loops v Energy, orbit, energy spread, charge
v Emittance preservation (via orbit stabilization)
u We should be prepared for full commissioning from 2015
u With Phronesis (Greek: Practical wisdom, Ability to understand the
Universal Truth), we believe we can achieve the goal 20
K.Furukawa, KEK, Oct.2013. ICALEPCS 2013
SuperKEKB Injector Feedback Challenges
SuperKEKB dual rings
Mt. Tsukuba
Linac
PF-AR
PF
21
Thank you