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<kazuro.furukawa@kek.jp>
ICALEPCS 2013

K.Furukawa, KEK, Oct.2013.

SuperKEKB Injector Feedback Challenges

SuperKEKB and electron/positron Injector Linacu Asymmetric e+/e- Collider for B-physicsv Flavor structure of elementary particles, and possibly new physicsu 40-times higher Luminosity compared with that of KEKB (WR)v Twice larger storage beamà Higher beam current at Linacv 20-times higher collision rate with nano-beam scheme³ à Low-emittance (even at first turn)à Low-emittance beam from Linac³ à Shorter storage lifetime(à Higher Linac beam current)u Linac challengesv Low emittance e³ with high-charge RF-gunv Low emittance e+³ with damping ringv Higher e+ beam current³ with new capture sectionv Emittance preservation³ with precise beam controlv 4+1 ring simultaneous injection

ICALEPCS 2013

40xLuminositye+ efficiency

2x beamcurrent

RF-gunK.Furukawa, KEK, Oct.2013.

2SuperKEKB Injector Feedback Challenges

Linac Upgrade for SuperKEKB
u Higher Injection Beam Currentv To Meet the larger stored beam current and shorter beam lifetime in the ring
Ir5Cev 4~8-times larger bunch current for electron and positronu Lower-emittance Injection Beamv To meet nano-beam scheme in the ringv Positron with a damping ring, Electron with a photo-cathode RF gunv Emittance preservation by alignment and beam instrumentationu Quasi-simultaneous injections into 4 storage rings (PPM)v SuperKEKB e–/e+ rings, and light sources of PF and PF-ARv Improvements to beam instrumentation, low-level RF, controls, timing, etc

SuperKEKB injector Linac	
high currentgun	

low emittanceRF gun	
3.5 GeV
10nC x 2 (prim. e-)
5nC x 2 (inj. e-)	Bunch
Compressor	

S-bandlinac	

e+ target &L-band+LAS
capture section	ICALEPCS 2013

1.1 GeV
Damping Ringcirc. 136 m	
Energy-spread
Compression System	
3TRF gun	FC

50 Hz (e+ or e-)pulse-by-pulse
mode switching 	PFPF-AR
LER 6.5 GeV e-2.5 GeV e0.1nC x 1	

4.0 GeV e+ 4nC x 2	ECS	C-bandmodules	

HER 7.0 GeV e5nC x 2	K.Furukawa, KEK, Oct.2013.

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KEKB

SuperKEKB Injector Feedback Challenges

Main features of controls at (previous) KEKBuEPICS as Main control Software Toolkit
vProvided a robust basis of equipment controlsvReduced software design efforts muchuScripting Languages for Operational SoftwarevSADscript/Tk, Python/Tk, Tcl/Tk used much
³Especially, SADscript as a bridge btw. Accelerator simulation,
Numeric manipulation, Graphic interface and EPICS controlsvBright new idea in the morning meeting could make theoperation much advanced in the evening³Great tool to optimize the operation

ICALEPCS 2013

K.Furukawa, KEK, Oct.2013.

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SuperKEKB

SuperKEKB Injector Feedback Challenges

SuperKEKB ControlsuInherit Good part of KEKB ControlsvEPICSvScripting languagesuEPICS Channel Access (CA) EverywherevEmbed EPICS control software (IOC) everywhere
possiblevReduce efforts on protocol design, testing, etcuDual Tier: Another layer in addition to EPICS/CAvEvent system helps EPICS with another channelvAdditional functionality, synchronization and speed
ICALEPCS 2013

K.Furukawa, KEK, Oct.2013.

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Dual-layer Controls

SuperKEKB Injector Feedback Challenges

Dual-tier ControlsuIOC controls via Conventional EPICS CA³Above 1ms, ordered controlsuFast FPGA controls via SFP/Fiber (MRF)³10ps ~ 100ms, 114MHz synchronous controls
OPI
Channel Access
IOCIOCIOCIOC

EVG

EVR

EVR

EVR

FPGA/SFPICALEPCS 2013

K.Furukawa, KEK, Oct.2013.

6

Dual-layer Controls

SuperKEKB Injector Feedback Challenges

Fast, Global, and Synchronous Controlsu MRF’s series-230 (and SINAP's) Event Generator / Receiversu VME64x and VxWorks v5.5 / v6.8
u114.24MHz event rate,u EPICS R3.14.x with mrfioc1/2
50Hz fiducial
u 18 event receivers in KEKB
u~200 dynamicu More Home-grown receivers
50Hz-analog/timing param.
Central"Event Generator"uMulti/single-mode fiberuTiming precision is < 10ps.
v < 1ps with external module.

SH_A1"
KL_B5/B6"

SB_B"

Injection"

SB_A"

96nse­	  Gun!
ARC!

e– BT (PF: 2.5GeV, 0.1nC)!

Cont-ABC">100ns

KL_51/52"
SB_C"

Configurationin 2010to be expanded
ICALEPCS 2013

SB_1"

SB_2"

SB_3"

SB_4"

SB_5"

e+ BT (KEKB: 3.5GeV, 2nC)!	  

e+	  Target
Cont-1"

Cont-2">100ns96ns

Cont-3"Cont-4"Cont-5"

Event Receivers"e– BT (KEKB: 8GeV, 2nC, !
PFAR: 3.0GeV, 0.1nC)!

K.Furukawa, KEK, Oct.2013.

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Dual-layer Controls

SuperKEKB Injector Feedback Challenges

Single Machine, Multiple Virtual Accelerators (VAs)u Pulse-to-pulse modulation (PPM), one of the VAs is active at a timeu Independent parameter set for each VA, ~200 parameters are switchedevery 20ms pulsee− Gun
ARC

PF Injection

Every20 ms

e− GunDamping ring

SuperKEKB-LER Injection

ARCEvent-based
Control Systeme– (2.5GeV, 0.2nC)

e– (3.5GeV, 10nC)

e+ (4GeV, 4nC)

e+ Targete− GunARC

SuperKEKB-HER Injectione– (7GeV, 5nC)
e− GunARC

ICALEPCS 2013

PF-AR Injectione– (6.5GeV, 5nC)
K.Furukawa, KEK, Oct.2013.

8Dual-layer Controls

SuperKEKB Injector Feedback Challenges

Two kinds of Virtual Accelerators (VAs)u Virtual Accelerator Models (VAs)u PPM VAs, that represent independent accelerator viewsfor different purposesv by using dual-tier controlsu Simulation VAs, that represent physics models ofaccelerators in simulation codesv by using SADscript codes through EPICS CA, normallyv even before the machine completion

ICALEPCS 2013

K.Furukawa, KEK, Oct.2013.

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SuperKEKB Injector Feedback Challenges(Offline) Orbit Correction Test in Sim. VA
Sugimoto et al.
Orbit before
correction
Orbit after
correction
Horizontal
displacement
Verticaldisplacement

Corrector K0

ICALEPCS 2013

K.Furukawa, KEK, Oct.2013.

SuperKEKB Injector Feedback Challenges

Beam Feedback Loopsu Equipment has inherent instabilities caused by manysourcesv 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 limitsv Scripts for prototypes, then ePID on IOCsu SuperKEKB with demanding beam specification may
require further considerationsv Emittance preservationv PPM VA handlinguSimulation VA may help organize the loops
ICALEPCS 2013

K.Furukawa, KEK, Oct.2013. 11

SuperKEKB Injector Feedback Challenges

Energy StabilizationuEnergy instability was sometimes foundv Closed feedback loops wereformedv Beam positions weremeasured where dispersion
function is largev RF phases at adjacentstations were changedv Loop parameters were beammode dependentv Energy spread feedback
using multi-electrode monitor
was also implemented

ICALEPCS 2013

K.Furukawa, KEK, Oct.2013. 12

SuperKEKB Injector Feedback Challenges

Simple Orbit StabilizationuIf Orbit became unstablevBeam positions were measured where betatron phases are90degree apartvCorresponding steering magnets are adjustedvIf the orbit fluctuation was large, weighed average of BPMs
based on response functions to beam kick or energy changevThe same method was applied to equipment stabilization

ICALEPCS 2013

K.Furukawa, KEK, Oct.2013. 13

SuperKEKB Injector Feedback Challenges

Emittance Preservationu If Device is off center of the beamv Focusing magnet (quad) kicks the beam bunchv Accelerating structure (cavity) excites wakefield, to bend the tailu Distorted bunch in banana shapev Emittance dilution or blow-upv Depending on the beam optics and the beam chargeu Orbit correction is crucial to preserve the emittance
Sugimoto et al.

BeamFocusing
MagnetAccelerating
Structure
Transverse distribution in time direction

ICALEPCS 2013

K.Furukawa, KEK, Oct.2013. 14

SuperKEKB Injector Feedback Challenges

Emittance Dilution
uOffset injection may solve the issueuOrbit have to be maintained precisely
Mis-alignment leads to Emittance blow-up

Orbit manipulation compensates it

100 samples
Sugimoto et al.
ICALEPCS 2013

K.Furukawa, KEK, Oct.2013. 15

Dual-layer Controls

SuperKEKB Injector Feedback Challenges

Multiple Closed Loop Controls Overlappedu Closed loops were installed on each PPM VA independentlyv Tested at KEKB

e− Gun!

e– BT (PF: 2.5GeV, 0.1nC)!

PF Injection

ARC!

e+ Target"e− Gun!

Event-based
Control System

ARC!

KEKB-LER Injection

Primary e– (4GeV, 10nC)

e+ BT (KEKB: 3.5GeV, 0.6nC)!

e+ Target"e− Gun!
ARC!

KEKB-HER Injection
e+ Target"e– BT (KEKB: 8GeV, 1.2nC)!

ICALEPCS 2013

K.Furukawa, KEK, Oct.2013. 16

SuperKEKB Injector Feedback Challenges

Event-based
Control Systemu Four PPM VAs at least
for SuperKEKB(maybe withadditional PPM VA
for stealth beam)

Every
20 ms

F.B
e− GunARC

F.B

PF Injectione– (2.5GeV, 0.2nC)

F.B
e− GunARC

Damping ring

SuperKEKB-LER Injection

F.B

e– (3.5GeV, 10nC)

F.B

e+ Targete+ (4GeV, 4nC)

e− GunARC

SuperKEKB-HER Injection

F.B

e– (7GeV, 5nC)
e− GunARC

F.B

PF-AR Injection

F.B
e– (6.5GeV, 5nC)

ICALEPCS 2013

K.Furukawa, KEK, Oct.2013.

SuperKEKB Injector Feedback Challenges

Feedback loop life cycleuInstallation of feedback loopsv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, etcvoften without knowing the origin of the instabilityuInstability hunting, and fixinguBeam study, or machine study using beamuIf fixed, remove corresponding feedback loop

ICALEPCS 2013

K.Furukawa, KEK, Oct.2013. 18

SuperKEKB Injector Feedback Challenges

System Construction
Display and Analysis

EPICS Controls
Multiple
Independent PPM
Parameters

Common Parameters

MultipleEvent SynchronousControls

PPM
Virtual Accelerators

Multiple
Simulation
Virtual Accelerators

Real Accelerator
ICALEPCS 2013

K.Furukawa, KEK, Oct.2013.

SuperKEKB Injector Feedback Challenges

Conclusionu SuperKEKB requires demanding beam parameters atinjector linacv Even under PPM

u Models of PPM VAs and simulation VAs may help design
feedback loopsvEnergy, orbit, energy spread, chargevEmittance preservation (via orbit stabilization)uWe should be prepared for full commissioning from2015u With Phronesis (Greek: Practical wisdom, Ability to understand theUniversal Truth), we believe we can achieve the goal
ICALEPCS 2013

K.Furukawa, KEK, Oct.2013. 20

SuperKEKB Injector Feedback Challenges

Mt. Tsukuba

Thank you
SuperKEKB
dual rings
PF-ARPFLinac

ICALEPCS 2013

K.Furukawa, KEK, Oct.2013. 21