R.F. Control System For Indus-1
Pravin S. Fatnani, B. J.Vaidya
Accelerator Controls Centre For Advanced Technology ( CAT )P.O. CAT, Indore,M.P., India 452 013
Email : fatnani@cat.cat.ernet.in Internet : http://www.cat.ernet.in
1 Introduction
Indus-1 is India's first synchrotron radiation source(SRS) nearing completion. It consists of a 20 MeV
Microtron injector, a 700 MeV Booster ring and a 450
MeV Storage ring. later, the same booster will inject 700
Mev electrons to a 2 GeV storage ring Indus-2. The R.F.
control system for this facility has been operational for
more than two years now. This system is integrated into
the overall control system for Indus-1.
2 Architecture of indus-1 control system
Indus-1 control system follows a two layer, loosely
coupled, modular and distributed architecture as depicted
in fig 1. This architecture was chosen for it’ ssimplicity;
simplicity of the machine and relative inexperience of thedesigners at that time. Another important consideration
was the use of the same system for commissioning as well
as for normal machine operation. The top layer orcontrol room layer consists of IBM-PC clones used as
operator consoles. These control room computers support
the networking environment consisting of Novell Netwareas the network operating system and Ethernet
communication standard with TCP/ IP as the network
protocol. Functional subdivision at this layer has resulted
in dedicating one PC for each subsystem like RF, Power
Supply, Timing, Vacuum, Beam Diagnostics, Radiation
monitoring etc. Each sub-system PC is connected overserial links to Equipment Interface Units ( EIU ) which are
VME crates running inexpensive and powerful 16 bit
Motorola 68000 processors. The operating environment at
this level consists of basic monitor firmware for the fastest
response times. Software development for this VME level(cross development) has been carried out at the control
room PC level with the help of cross compilers, crossassemblers and terminal emulation utilities. The machine
control software development at the control room layer
has been done using C compilers and netware API SDKs.

Control Room Layer

File Server (Netware)

Operator Consoles
PCPCPCPC

Ethernet

Serial Links =>Equipment Interface Layer

EIU
VME Crates

Accelerator Field Devices / Equipments
Fig. 1 Schematic Of Indus-1 Control System
3 Overview of R.F. system
The R.F. system has three major components - Booster
ring cavity, Storage ring cavity and Ion clearing electrodes
for storage ring. Both booster ring and storage ring rf
systems are similar except for the power levels.

4.0 KW RF Amplifier for booster ring cavity
10 KW RF Amplifier for storage ring cavity
100 W RF Amplifier for Ion clearing electrodes
Common frequency reference of 31.613 MHz exists forboth Booster and storage ring cavities. Fig 2 shows the RF
system schematic.

Three analog control loops receive reference SET
signals from the control system Tuning ( Frequency) loop - Compensates for the beamloading effects and temperature changes using motor
activated plunger ( tuner ) and maintains the resonant
frequency of the cavity. It is possible to change theresonant frequency of the cavity using a tuning
compensation setting from the control interface.
Amplitude loop - Compares the RF Power Set value
and the value of the accelerating field in the cavity andcorrects the difference if any using the variableattenuator. RF Power Set from controls allows varyingof the rf power which consequently changes the cavitygap voltage.
Phase loop - Compares the phase of accelerating
voltage in the cavity with the frequency synthesizer
output signal and effects corrections if required using
the variable phase shifter. Phase Set from controls canbe used to change the phases of accelerating fields inbooster and storage ring cavities.

Phase SetFREQ.
SYNTH.

PHASE
SHIFTERATTENUATOR

SOLID STATEDRIVER - 150 W

PHASE
DETECTORAMPLITUDE
COMPARATOR

PHASE
DETECTOR

10 KW RFAMPLIFIER

Tun SetERRORAMPLIFIER
Power Set
S.M.
CONTROLLER

Fig. 2 Schematic of Indus-1 RF System4 RF control system
In addition to complete control of the rf system ofbooster and storage rings, the control system also allows
control of ion-clearing rf system for storage ring. The
various devices/equipments under control regime are two
rf cavities and eight ion-clearing electrodes, two highpower rf amplifiers of 4.0 and 10 KW, high voltage DC
power supplies, pre-amplifiers, phase-shifters, phasedetectors, stepper motor control units, cooling water
pumps & chillers, flow switches and temperature sensors
etc. The system monitors crucial RF parameters e.g.
forward and reflected rf power, rf phase, cavity gap
voltage, tuning error etc. Operator interacts with thesystem from the PC in the main control room. VME crate
as the equipment interface unit handles the actual physicalconnections with the R.F. system.
5 Salient features•Provides Recommended Start up and Shut down
Sequence for RF sub-systems.

•••

In case of operational problems, the control systemprovides the operator guidance for troubleshooting
and allows for complete manual operation.
switching off / stopping the control system
software and hardware does not affect the state (on/ off) of the RF system.
Local / Remote Mode
Provides local / remote mode operation for most of
the sub-systems. This is activated from equipment /sub-system panel L / R switch. Local mode
disables ON / OFF & SET operation of equipment/ subsystem from main control room. This is usefulfor safe system maintenance. Remote mode allows
access from main control room only and disables
ON / OFF & SET operations from local equipment
panel during normal operation.

6 System interlocks
Start up sequence interlocks prevent unsafe ( to system)
conditions.

* No Cavity Cooling Water Flow - Trip RF* DC Power Supply Overload- Trip RF,( Plate / Screen / Grid )Driver PS & HV
* Blower Off / HV PS Door Open / Main Water Flow Off - Trip RF & HV
* Power Supply Fault- Trip RF,
HV & Driver PS* Vacuum Fault- Trip RF
7 Software
The operator interface software is simple, menu driven
and has been optimised for minimum operator interaction.
Following are the salient features :•••
•
•••
•
•
•

screen. Also, operator interaction results in ON / OFF ,SET and MODE changes commands which are delivered
to the slave EIU. The status of execution of thesecommands is tracked and operator is informed in case ofnon-compliance or malfunctioning. The EIU works in theslave mode. It keeps looping, updating the system status,
polling for commands from the operator console computer( PC) and when valid commands are received, executes
them and sends the relevant data back to PC. Actions on
interlock failures and alarm conditions is initiated at theEIU level and the same is conveyed to the PC.
Optically isolated serial communication link between
the operator console PC and the equipment interface unitprevents ground loops.

Operator Console (PC) Program - written in C.
EIU Program - written in 68K assembly lang.
Distributed Online Database - managed at Consoleand EIU levels.
Remote EIU program downloaded at start up.
Three convenient screens - one each for booster
ring, storage ring and common ( B.R., S.R. and Ion- clearing).
Top Menu bar for menu based selection offunctions / actions.
Bottom message bar for operator assistance ~ 20 messages / screen.
No direct data entry - Coarse and Fine UP-Downcontrols for setting RF Power, Phase and TuningCompensation.
Vacuum interlock prevents switching ON of RF if
required value of vacuum is not achieved.
Total system shutdown following a recommended
sequence.

8 Communication / Protocol
The communication between operator console PC andEIU is command - response type because of the master slave mode of interaction between them. The PC is themaster which regularly sends commands to the slave EIU
for sending the latest data and refreshes the same on the9 Experiences with the system / conclusions
The system’ response and overall operation has beenquite satifactory during it’ operation for the last two years.
It is realised that the demands for changes / additions are
put forth frequently and sometimes entirely new
functionalities are demanded. This calls for the features
making the system easily extensible and flexible toincorporate extra and new types of inputs / functions.
An Object Oriented approach in software design would
help achieve the above with minimum side effects andcode reuse to ease the situation.
Porting to different hardware and software platforms isnecessitated because the machine life cycle is longer andthe technology changes are faster.
International standards in both software and hardware
should be followed as far as possible. The concept ofsoftware sharing with other labs of the world seems very
useful and attractive and needs proper investigation andsupport.
References[1]B. J. Vaidya, J. S. Adhikari, P. Fatnani, et al. - Control
System for Synchrotron Radiation Facility Indus-1,Proc. Of Intl. Conf. On Synchrotron Radiation
Sources, CAT, Indore, India, Feb 1992.
[2]S.A. Pande, M. Lad, et al. - RF System for The
Booster Synchrotron and Indus-1, Proc. Of Intl. Conf.
On Synchrotron Radiation Sources, CAT, Indore,India, Feb 1992.