KEKB Linac, Energy Feedback

Energy Feedback Systems
at KEKB Injector Linac
Kazuro Furukawa, KEK<furukawa@kek.jp>

KEKB Linac Commissioning GroupElectron Linac Control Group

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Introduction, KEKB Linac◆ Stable and Robust Operation of Linac
for Higher Experiment
Efficiency◆ Many Active Operation Parametersat Microwave Systems, etc.
◆ Frequent Switching between
KEKB e–KEKB e+,8GeV 1.2nC Single Bunch
3.5GeV 0.64nC Single(Primary e– 10nC)

PF e–
AR-PF e–2.5GeV 0.3nC Multibunch
2.5GeV 0.5nC Multibunch

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Linac Beam Parameters & Stability◆ Precise Tuning of the Beam Parameters
energy, orbit, emittance, energy spread,bunch profile, bunch charge, beam timing◆ Each Component of Linac was Designed to Satisfy
Predefined Values◆ Simultaneous Fluctuation ofElectric Power or Temperature◆ Interim Failure of Linac Equipment◆ KEKB Luminosity Degradation◆ Linac/Ring Equipment may be Damaged
K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Beam Parameter Fluctuation & Stabilization◆ If certain Instability was Observed
We have to Hunt the Source
to Fix the Problem (if possible) or to Form a Closed Loop
◆ To Find the Source, Correlation Analysis
and Singular Value Decomposition (SVD)◆ Often the Source is Attributed to the Linac Injector Section
where Many Devices Reside◆ Feedback Loop without Resolving the Real Source
Choosing certain Pair of Monitor & Tuner, Still Effective◆ (Instead of Simple Feedback, Sophisticated Method like
Downhill Simplex or Global Orbit Correction
But Important Defects may be Hidden)
K.Furukawa, Oct.1999.

KEKB Linac, Energy FeedbackBeam Monitors◆ Computer Readable Beam Instrumentation
Strip-line type Beam Position Monitors (BPM)
Streak Cameras for Beam Bunch Profile
Wire Scanners for Transverse Beam Profile◆ To Find the Beam Energy
BPM Readout where Dispersion is Large◆ Noise: External Electric Noise mainly from Klystrons
Integration; Resolution, Frequency, Dispersion◆ Noise: Beam Orbit Fluctuation (Betatron Oscillation)
Can be Derived from Orbit at Straight Section
Gun

ARC(R0)

BCS(17)
Targete--BT(PF)ECS(61)e--BT(KEKB,AR)

e+-BT(KEKB)

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Beam Energy Tuner & Feedback◆ Energy Tuner — Energy (Software) Knob
Microwave Phases at two Adjacent Klystrons(Voltage may change both Phase and Amplitude)
BeamFluctuation

Read Beam Position (x and δx)
at Reference Points
SP-BPM SP-BPM
Klystron

BeamKlystron––> Convert into RF Phases
for two Klystrons
Energy Knob
Beam Positionsat Measurement Points
SP-BPM's– Beam Fluctuation––> Convert into Energy
Average (Integration)
x Gain – Offset
Energy Feedback

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

MS-Windows Interface for Operation

Touch Panel for Operation
EPICS Gateway to KEKB-Ring

X-Window Interface for Commissioning

Main Network (FDDI, Ethernet)

Device Manager

Main Computer System (Unix)
Equipment Level Network (Optical Ethernet)

VME's (~25)(and Loop-3)

PLC's (~140)

CAMAC's (~15)

VXI's (~30)

PC / GPIB / RS232C

Beam Monitor
MagnetTrigger

Klystron
MagnetVacuumTrigger

RF Monitor

Gun
Beam Monitor
othersThere are many kinds of local controllers, but, they all communicate through UDP/RPC over switched
optical Ethernet segments.

K.Furukawa, Oct.1999.

KEKB Linac, Energy FeedbackLogical Configuration
Operation Application(Parameter Handling, etc.)

Scientific Application(Simulation, etc.)

Upper Layer Control Service(Klystron, Magnet, etc.)

Lower Layer Control Service(Loop3, PLC, CAMAC, etc.)
StaticDatabase

Engineering Application(Calibration, etc.)

Alarm andHistory Service

ArchiveDynamicDatabase

Field Control Hardware

Each lower layer software supports corresponding field controllers. Upper layer software hide differences between
controllers and serves accelerator equipment controls to clients. While UDP-based RPC protocol is used at lower layer,
upper layer make use of TCP-based one.

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Software Architecture◆ Client to Linac Control System via RPC
Written in Tcl Script Language to Maximize Flexibility
Employing Tk Widget to Enable Runtime Configuration◆ 1) Check Condition: Beam Operation Mode, Beam Charge◆ 2) Determine Monitor Value:Limit, Integration, Betatron Isolation, Post-process(Tcl)◆ 3) Calculate Feedback: Conversion, Gain, Frequency, Dead-band◆ 4) Tune: Pre-process(Tcl), Limit, Control thru Energy Knob
◆ 0) Controls: Flow Control, Error Check, Graph, Log,
Remote Control (Tcl/Tk send) from other Applications(ex. global orbit correction, status viewer)

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Other Feedback Loops◆ Simple Orbit Feedback
Monitor: Weighed Average of BPM's
over 1 Betatron Wavelength based on Steering Response
Tuner: Two Steerings with 90-degree phase advance(Difficult to Predict Orbit Because of Wake Fields)◆ Simple Device Feedback
As a Quick Fix
Voltage of two Guns
Amplitude and Phase of two Sub-Harmonic Bunchers (SHB)

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Example◆ Any Parameters can be Changed
at Any Time◆ Runtime Debugger to Test
Internal Variable/Routine

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback◆ Gun Voltage Change
after Power-on
which was not Expected in the Design◆ Orbit Daily Change,
Peaks at 6 o'clock,
Later Attributed to SB_C

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback◆ 7-min-Period Energy Change,
Later Attributed to Air
Conditioner at KL_A1◆ 40-min Period Orbit Change,
Later Attributed to SHB

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Discussions◆ GUI Improvement to Avoid Human Errors◆ Betatron Orbit Isolation is not Mature Enough
Need more Study on Beam Optics with Wake Field◆ 50-Hz BPM Readout (instead of 1-Hz)
at least to Make Numerical Integration Betterto Suppress Frequency Component Above 1Hz(50-Hz Phase Shifter is under Development)◆ Not only Energy Center Value but also Energy Spread
Improved Software for Wire Scanners
Not Linear but Quadratic: Optimization Feedback
K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Conclusions◆ Suppress Energy Fluctuation to a Half or a Third◆ Installed at 6 Locations and Used Routinelyfor 4 Beam Operation Modes◆ The Same Software was Applied to12 Orbit and 6 Equipment Feedback Systems◆ Is Possible to Install and Modify quickly
with the Script Language Tcl/Tk◆ Helps not Only Routine Operation
but also the Beam Commissioning Greatly
Primitive but Indispensable even to Carry Study
K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Linac Control System Overview◆ Rejuvenation in 1993
with a New Equipment-Oriented Design◆ Unix, VME, TCP/IP,
International and de-facto Standards◆ Old Field Controllers Kept Running◆ Redundant Unix Servers◆ Layered Software to Serve Equipment Services◆ Homemade RPC Protocol at both Internal / External◆ No Strict Standard for Field Controllers
but Diskless and UDP at Least◆ Upper Layer Software Hides Lower Layer Differences◆ Memory-Resident Hashed Database
and Cached Field Information
K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Control Network System◆ FDDI and 100Base-Tx/10Base-T Ethernet at Center(about 100 computers/controllers)◆ 10Base-FL (Optical) Ethernet at Fields
to Avoid Klystron Noises◆ About 200 10Base-FL Field Controllers◆ Layered Switches and Repeaters in Star topology◆ Redundant Configuration at Central Networkand Upper Field Network

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Layered Configuration in Control Systems◆ No Resources to Replace all Field Systems◆ At least two Layers to Manage each Componentsof Hardware and Software◆ Must Survive Long Termin spite of Technology Advance(already 15 years and maybe 10 years more)◆ Layered Architecture with well-defined Interface
is Necessary
K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

MS-Windows Interface for Operation

Touch Panel for Operation
EPICS Gateway to KEKB-Ring

X-Window Interface for Commissioning

Main Network (FDDI, Ethernet)

Device Manager

Main Computer System (Unix)
Equipment Level Network (Optical Ethernet)

VME's (~25)(and Loop-3)

PLC's (~140)

CAMAC's (~15)

VXI's (~30)

PC / GPIB / RS232C

Beam Monitor
MagnetTrigger

Klystron
MagnetVacuumTrigger

RF Monitor

Gun
Beam Monitor
othersThere are many kinds of local controllers, but, they all communicate through UDP/RPC over switched
optical Ethernet segments.

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Logical Configuration
Operation Application(Parameter Handling, etc.)

Scientific Application(Simulation, etc.)

Upper Layer Control Service(Klystron, Magnet, etc.)

Lower Layer Control Service(Loop3, PLC, CAMAC, etc.)
StaticDatabase

Engineering Application(Calibration, etc.)

Alarm andHistory Service

ArchiveDynamicDatabase

Field Control Hardware

Each lower layer software supports corresponding field controllers. Upper layer software hide differences between
controllers and serves accelerator equipment controls to clients. While UDP-based RPC protocol is used at lower layer,
upper layer make use of TCP-based one.

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Network Configuration of Linac Controls
SwitchRepeater

Console SystemsSwitch

Dual FDDI Network (Star)

Redundant
Transceiver

SwitchRepeater
SwitchSwitchSwitchRedundant Transceivers and Repeaters
Transceiver

Field Controllers

Controller

33 field network stations are connected with central switches on FDDI through redundant 10Base-FL
Ethernet. Each station is connected to 4 to 10 field controllers. All connections at fields use 10Base-FL
because of the klystron noises. Network traffic at important points are monitored via SNMP.

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Layered Configuration of RF Controls

Equipment Software on Unix Server
Network System

PLC-based
Controllers

VXI-based
MeasurementSystems

High-Power
Klystron / SLEDOld (Loop-2)
Controllers

High-Power
Klystron / SLED

About 30 new controllers (PLC-based), 40 old (microcomputer-based) controllers and 30 VXI-based
measurement systems are connected with the central control software, which is designed to hide local
differences.

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Layered Configuration of Magnet Power Supply Controls
Equipment Software on Unix Server
Network System
PC-based
Management
System
PLC-based
Controllers

PLC-based
Controllers

MagnetPower SupplyOld (Type1)
Controllers

Old (Type2)
Controllers

MagnetPower Supply

There are 4 types of local controllers for magnet power supply controls. Its central control software isdesigned to hide those differences.

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

EPICS Control System(KEKB Ring)

Other Control Systems

Portable CA-Server
as Gateway to EPICS

cdev and/or CORBA
Gateway

KEKB Linac Control System

Layers which are planned on top of the linac control system. Portable CA-Server is being installed. Theselayers will expand the linac control system and increase the interoperability.

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

TRANSPORT
Modeling SoftwareSADModeling SoftwareInterface
Software

Static Database forBeam Line, etc.

KEKB Linac Control System

An interface layer is provided to enable online accelerator modeling. Currently two software packages aremainly used. It is a kind of the operator interface, but with large specific database.

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

MS-Windows/Visual-Basicfor Simple Operation
Tcl/Tk on X-Window
for Commissioning

DOS based Touch Panelfor Simple Operation

Gateway

SAD/Tk on X-Window
for Commissioning
EPICSGateway

Linac RPC
Control Network Environment

Linac Control System

Script languages are utilized for graphical operator interfaces, while client codes for Linac remote procedure calls arewritten in C. The Linac is operated from the KEKB main control room, although the Linac control room is still active
mainly for Photon Factory injection. (SAD is an accelerator designing software developed at KEK, which now has its own
script language and X-Window interface through Tk.)

K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

Conclusions◆ Software resources can be shared easily between
Unix control system and Windows consoles
with small modification, and they provide
good performances.
◆ Shared libraries (DLL) could be built to generate
links to languages other than C/C++ like
Visual-Basic or Tcl, etc. That part was nottested much yet.
◆ This scheme provides an interim solution without
any loss.
K.Furukawa, Oct.1999.

KEKB Linac, Energy Feedback

K.Furukawa, Oct.1999.