The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

Development of Visual Beam Adjustment Method for the Beam Transport
Takashi AGEMA TSU, Kazuo ARAKAWA and Tetsuya OKAMURA*Advanced Radiation Technology Center, Japan Atomic Energy Research Institute1233, Watanuki-cho, Takasaki, Gunma, 370-12, JAPAN* R&D Center, Sumitomo Heavy Industries, Ltd.
63-30, Yuuhigaoka, Hiratsuka, Kanagawa, 254, JAPANAbstract
We have developed a computer-based visual beamadjustment method for the beam transport system at theJAERI A VF cyclotron. This system provides CRT displayof the beam trajectories and beam envelope in real-time.
1 Introduction
A cyclotron design requires a large number ofphysical theories, calculation codes and analysis of the beam
trajectory. These codes and analyzed results have not beenused in actual operation. For a new cyclotron control
technique, we have developed a computer-based visual beamadjustment system[l] for JAERI A VF cyclotron operationby using the above codes. This system provides CRT
display of the cyclotron beam trajectories, feasible setting
regions, and search traces which were designed to improve
beam parameter adjustment.
A new computer-based operation system whichassists inexperienced operators has been implemented for thebeam transport system at the JAERI A VF cyclotron. To
examine the reliability of this system, the simulation result
was compared with that of the actual operations.
2 Visual Intetfaces
Ion beams extracted from the cyclotron aretransported to a target point without any beam loss in thebeam ducts. The beam transport system consists of bending
and focusing magnets, beam monitors,· beam shutters, etc.
There are 9 bending magnets, 85 quadrupole magnets and 10
beam steering magnets in 10 horizontal and 4 vertical beamcourses which transport ion beam to 17 target ports on theways or at the ends of the beam courses located in 8 ionrooms. An achromatic and telescopic beam transportsystem was designed for high transmission efficiency of ion
beams and good adjustability of the magnet parameters

using
thebeamopticscalculation
program
TRANSPORT [2].
The ion beams extracted from an A VF cyclotron
have large emittance and energy variations. Beam transportsystem start-up operations require dozens of adjustableparameters to be finely tuned to maximize beamtransmission efficiency. Generally, the transportation ofaccelerated ion beam is efficiently realized by setting
quadrupole magnets at parameter for a magnetic field
gradient designed by TRANSPORT -code.
However
inexperienced operators have a difficult time because
operator consoles displaying measured beam parameters,
alarm information, component status, etc. do not provide
enough information to guide these new operators. There are
two ways of describing the ion transfer properties. One is
the ray tracing that is used to study the behavior ofindividual ion trajectories. The other is the phase space
ellipsoid method that treats the beam envelopes characterized
by the boundaries of the phase space volume.
The new computer-based operation system provides
two kinds of visual human interfaces to support the beamadjustment of the beam transport system as follow: i) beamenvelope and trajectory are rapidly simulated and graphicallydisplayed on a CRT whenever the operators change theexcitation current of the magnet, ii) historical display ofsimulating beam envelope and trajectory are superimposed
on CRT. For simulation the beam envelope/trajectory,these interfaces have special four functions as follow; i) themagnetic field of each magnets are calculated from exciting
current, which are operator adjustable parameter, considering
the effe,ct of the field saturation,ii) initial setting
parameters (energy, ellipse, etc.) for calculating the beamenvelope/trajectory can be changed at will, iii) all narrow
channels which are obstacles to pass through the beam in
the beam transport line are displayed, iv) beam ellipses canbe displayed whenever the operator changes the exciting
current of the magnets.

-446-The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997The simulation method of beam envelope is a
simplified transfer matrix method based on the phase space
The beam trajectories are calculated at fiveellipse.
positions on the ellipse including a center point as shown in
In order to reflect operators' action to theFig. 1.
simulation immediately, each elements of transfer matrix arelinked directly to a parameter database and the calculation isinvoked whenever change value event occurs. And for
reduction of simulation and display

time,

References[1] T.Agematsu, K.Arakawa, and S.Okumura, Proc. 14thInt. Conj. on Cyclotron and Their Applications, CapeTown, South Africa, pp.284-287(1995).
[2] K.L.Brown et al. , SLAC Report, No.91(1974).

historicalenvelope/trajectory are saved as bitmap data.
As the data which are necessary for simulation and display,such as layout data, initial beam conditions, magnet
characteristics, data base entry and so on, are described inx',y'x,yeditable definition files, it is easy to modify these data foraccurate simulation.

3 Examination of the System
In case of the ion which do not move close to thebeam axis, namely, the ion beam is not paraxial, the beam
We examined the beam
trajectories were simulated.
trajectories by the real beam operations of 45MeV H+. In
real beam operation, the beam axis was changed bychanging the field of steering magnet which is located at thecyclotron exit. The beam changes not only the position butFig. 1 The elliptical phase space and therepresentative five ion particles at the firstwaist point of the cyclotron exit.

also the profile on the target as shown in Fig. 2. The
typical simulated beam trajectories for 45MeV H+ are shownin Fig. 3. Fig. 3 (a) shows the simulated beam trajectories
in case of the ion move close to the beam axis. Fig. 3 (b)shows the simulated beam trajectories by setting excitation
current to+ lOA of a CSTE (horizontal steering magnet).
4. Conclusion
The beam adjustment interface calculates the beam
trajectories/envelopes using actual parameters and displaysthem on a CRT. This display shows a historic summary ofsimulated beam trajectories/envelopes after any parameter"setting" adjustment by an operator. Operators can refer toeither display, correct the differences between them, andsearch for the optimum set point which provides desirable
beam envelope/trajectories.
Since, operators are able to quickly gain valuable
operation experience which ultimately leads to a reduction of
the time to reach the planned beam transport condition.

Fig. 2 The change of beam profile on the almina
monitor at the target point LB2.
In actual operation, by changing fieldstrength of horizontal steering magnet
located at the cyclotron, the change ofprofiles is measured with 45Me V W.

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The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

..

a...

...

D.Di i..

X(a) Beam trajectories by standard condition, namely the ion beam move close to the beam axis.

g... g ......... i i.. a.
"'PJ

D,.,....

I(b) Beam trajectories by setting excitation current to +lOA of CSTE (the ion beam is not paraxial).
Fig. 3 Beam trajectory simulation for 45MeV H+ in the beam transport system of the cyclotron.

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