AN OPERATOR ASSISTANCE SYSTEM FOR BEAM ADJUSTMENT OF
JAERI AVF CYCLOTRON
T. Agematsu†, K. Arakawa, S. Okumura, Y. Nakamura and S. Tajima, JAERI Takasaki, JAPANbeam current values represented by various
colored dots, are superimposed on the FSRs.

Abstract
A computer-based operation system for AVF cyclotron
which assists inexperienced operators has been developed.
The system has been installed at JAERI (Japan Atomic
Energy Research Institute) AVF cyclotron. The systemprovides a CRT display: the cyclotron beam trajectories,
feasible setting regions, search traces and the beamenvelopes designed to optimize beam parameter
adjustment. The evaluation experiment for the system
was carried out and the operation time to reach required
beam conditions of the injection region of the cyclotron
was reduced by approximately 65%. Also the system isvery useful to study the problems on the beam transport
such as beam trajectory, envelope, beam profile, spot sizeand so on.

1 INTRODUCTION

2 VISUAL INTERFACES
The visual assistance system provides three functions ofhuman interfaces for beam parameter adjustment:• Beam trajectories and envelopes are rapidly
calculated and graphically displayed whenever theoperators change the cyclotron parameters.
• Feasible setting regions (FSRs) of the parameterswhich satisfy beam acceptance criteria of thecyclotron are indicated.
• Search traces, which are historical visual maps of___________________________________________†agematsu@taka.jaeri.go.jp

Beam Behavior

Assistance
SystemTrajectory
Display

Simulator

Parameter
Setting
FSR
Display

FSR
Calculation

Search Trace
Display

Search Trace
MemorySetting Regions
Sensitivity

Cyclotron

Setting

Status MapEquipment
Setting
Beam
Trajectory

Mutual Relation
Measure-ment

BeamCurrent

Figure 1: Block diagram of information flowin the operator assistance system.
Fig. 1 is block diagram of the information flow between
the operator, assistance system and the cyclotron. The
beam adjustment interface calculates the beam
trajectories/envelopes using actual parameters anddisplays them on a CRT. This display shows a historicsummary of the simulated beam's trajectories/envelopes
after any parameter has been adjusted by an operator.
Operators can refer to either display, correct thedifferences between them, and search for the optimum set
point which provides desirable beam envelope/trajectories.
Therefore, operators are able to quickly gain valuable
operation experience which ultimately leads to a
reduction of the time necessary to reach the specific beamcondition.
BeamTrajectory

Deflector

Exit

Phase Slit
DesignedTrajectory
Inflector
Dee

Simulated Trajectory2) Central Region Block

3) Extraction Block

Magnets (Q,BM,ST)
Deflector

Beam Envelope and Trajectory4) Beam Transport Block

Inflector
GL1
GL2
GL3
GL4

GL4Glaser Lenses

Cyclotron start-up operations require dozens ofadjustable parameters to be tuned to maximize extracted
beam current.
Experienced operators perform thisprocess through trial and error using their experience andintuition.
However, the process is difficult for
inexperienced operators because operator need to adjust
parameters using little information such as measured
beam data, alarm, status of components, and so on.
A cyclotron design requires a large number of physicaltheories, calculation codes and analysis of the beam
trajectory. These codes and analyzed results have notbeen used in actual operation for cyclotron. For a
cyclotron control technique, we have developed a newcomputer-based visual assistance system for JAERI AVF
cyclotron operation by using an applicable theoreticalequations and numerical simulations.
A new computer-based operation system which assists
inexperienced operators has been implemented for JAERIAVF cyclotron. The reliability of the system wasevaluated by comparing the result of the simulation withactual operation [1,2,3]. The system can use to search thebeam trajectory and envelope, when an operator has adifficult time in cyclotron operation.

Operator(Mental Model)

FSR
GL3

AVF cyclotron

1) Axial Injection Block

Figure 2: Schematic drawing of AVF cyclotron andexample of beam trajectory display in the four blocks.
1) Axial injection block 2) Central region block3) Extraction block 4) Beam transport block.
The system has been applied to four blocks of thecyclotron as shown in Fig. 2: the axial injection, thecentral region, the extraction and the beam transport.
This system is constructed by the language of C andworks on the workstation.

2.1 Axial Injection Block

3.1 System Evaluation

The axial injection block is a region between thebottom of the cyclotron yoke and the inflector. There are
four Glaser lenses (GL1,2,3,4) with adjustable focallengths. The beam is led into the cyclotron by adjustingthese lenses through a small gap of the inflector entrance.
The resultant envelopes are calculated with in four lenses
and the magnet field distribution using the transfer matrix
method. The FSRs are limited mainly by the geometry of
the inflector entrance.

To evaluate system effectiveness, the search timerequired to reach maximum beam current conditions wasmeasured at the axial injection block [1]. Typicaloperation display and operation is shown in Fig. 3. Inaddition, system operability was evaluated using written
questionnaires. Nine operators (1 expert, 4 trainees, and 4novices) were asked to obtain maximum beam current byperforming adjustments of the axial injection block bytuning the four lenses using three different interface
modes:• Mode 1: Using the existing console with four dials
and a beam current meter.
• Mode 2: Using the assistance system without theFSR display.
• Mode 3: Using the full assistance system.

2.2 Central Region Block
The central region block follows the axial injectionblock. The first turn of the beam trajectory is determinedin this block. The adjustable parameters in this region aredee voltages, trim coil currents and the phase of beam
buncher voltage. These parameters are adjusted so thatthe beam passes through two sets of phase slits. The
beam trajectory is calculated as functions of theseparameters and magnetic and electric field data. TheFSRs are limited mainly by the geometrical condition of
the phase slits.

2.3 Extraction Block
The beam in the final turn is led into the deflector andthe magnetic channel, deflected from the circular orbit,
and is finally extracted from the cyclotron. In this block,the system simulates the deflected beam trajectory. At
the first step, the beam trajectory entering the deflector iscalculated on the basis of the magnetic field data and two
beam positions detected by the main and the deflector
probes. At the second step, the beam trajectory in thedeflector and the magnetic channel is simulated on thebasis of the deflector position, the deflecting field and themagnetic channel field. The FSRs are determined asfunctions of the above parameters, and the clearance ofthe deflector and the magnetic channel.

2.4 Beam Transport Block
The extracted beam from cyclotron is led into the target
port through the beam line. In this block, the systemsimulates the beam envelopes and the beam trajectory.
The beam is led into the target port by adjusting thesequadrupole, bending and steering magnets through gapsof the element's structures.

Table 1: Summary of search times
using three interface modes
Operator
Mode 1Mode 2
Level*
1
E
1.0
1.07
2
T
1.0
0.76
3
T
1.00.68
4T
1.00.975T
1.00.676N
1.00.92
7N
1.00.95
8N
1.00.65
9N
1.00.47
Median1.00.76* Level: E; Expert, T; Trainee, N; Novice

Mode 3
0.59
0.86
0.63
0.73
0.46
0.85
0.80
0.42
0.34
0.63

Table 1 summarizes the resultant search times for thethree modes and give their medians. All values werenormalized by mode 1. In mode 2, the average searchtime was reduced by ~80% of that in mode 1. This
improvement in operation is attributed to the search trace
display and the ability to make beam settings using amouse. Operational improvements were increased an
additional 15% using the full assistance system (mode 3),i.e., the search time was reduced by ~65% in comparison
to mode 1. The FSR display decreased the search time
because an operator searches a smaller parameter area
than without the display; thus more quickly reaching thedesired optimal setting even though the theoretical model
does not exactly represent the actual cyclotron conditions.

3 SYSTEM EVALUATIONThe reliability of this system was evaluated [1,2,3]. In
this paper, we report the system as operation tool.

Table 2: Questionnaire results on the effectivenessof the operator assistance system
Function(1) Trajectory display(2) FSR display(3) Search trace display(4) Display layout(5) Operation by mouse

Figure 3: Typical operation display and operation
at the axial injection block.

Ave.
Score
4.29
4.00
4.14
4.71
4.14

522
3
52

Histogram
432532324
1

1

Table 2 summarizes the results of an operator
questionnaire survey given to 7 operators (1 expert, 4
trainees and 2 novices) to evaluate system effectiveness.

Five system functions are considered and scored from 1(not effective) to 5 (very effective). Since scores ranged
from 4.0-4.7, the operators highly evaluated theeffectiveness of system operability.

3.2 Correction of The Beam Line Level
The JAERI AVF cyclotron has dedicated to various
applications as biotechnology, material science, radiation
chemistry, nuclear science and radioisotope production.
The ion micro beam is available to study the change ofcellular structure and function by single ion hit and todevelop a cell surgery technique in the field ofbiotechnology. A specific site of living cell is exposed toion beam collimated around 10µm in diameter. To form
the micro beam, there are three sets of the narrowcollimators after the vertical bending magnet in the beamline. First collimator size is 5mm in diameter, second
0.5mm, third 10µm. It was very difficult to pass throughbeam into the three sets of narrow collimators because thebeam is meandering through beam duct. An operator
need to adjust the parameters for steering and quadrupole
magnets.
To evaluate the meandering of the beam envelope, wesimulate the beam trajectories using the visual assistancesystem as shown in Fig. 4. If we set up the operated
actual parameter to simulator, the beam trajectories break
down on the way. The beam, however, is transported byusing the same parameter in the actual operation. Whenthe beam trajectories simulated by changing the initialconditions from center of beam axis to +3mm on thevertical axis, it is show that the beam trajectories be able
to transport with operated actual parameters. Finally, we
found that the cause of beam off centering is thedifference from the beam axis level between the beamline and the cyclotron. The level of beam line changed
about 3mm by down flower level during thirteen years.
We corrected the vertical level of magnets in the beamline [4].

4 CONCLUSION
The characteristic of the system is shown in next.
• Easy adjustment by visualized information.
• He can be understanding about the behavior ofbeam, when he is adjusting.
• It can effective adjustment, because the systemcover physical knowledge and poor experience ofhim.
• Quickly training of operators.
The evaluation experiment for the system was carriedout and the operation time to reach required beam
conditions of the injection region of the cyclotron wasreduced by approximately 65%. Also the system is very
useful to study the problems on the beam transport suchas beam trajectory, envelope, beam profile, spot size andso on.

Figure 4: Examples of simulated beam trajectories withactual operating parameters.
Solid lines show the trajectories of offcentered beam by +3mm.
Dotted lines show the trajectories of centeredbeam. The beam trajectories are crash into thebeam duct.

5 REFERENCES[1] T.Okamura, T.Murakami, T.Tachikawa, T.Agematsu,S.Okumura, and K.Arakawa , Proc. 13th Int. Conf. on
Cyclotron and Their Applications, Vancouver, Canada,pp.644-647(1992).
[2] T.Agematsu, K.Arakawa, and S.Okumura, Proc. 14thInt. Conf. on Cyclotron and Their Applications, CapeTown, South Africa, pp.284-287(1995).
[3] T.Agematsu, K.Arakawa, Proc. 15th Int. Conf. on
Cyclotron and Their Applications, Caen, France, pp.232235(1998).
[4] Y.Nakamura, et al , JAERI TIARA Annual Report
2000, JAERI-Review 2001-039, pp293-235