Design of Automatic Beam Transport System at SPring-8 LINAC
Hironao Sakaki, Hiroshi Yoshikawa, Hideaki Yokomizo,
Takuya Sogo*, Kouji Kinoshita*, Norihiko Adachi*
SPring-8 Linac, Kamigori, Ako, Hyogo, 678-12, Japan
Division of Applied systems Science, Kyoto University, Kyoto, 606, Japan *Abstract
At a new accelerator, the best operating parameters have tobe found by trial and error. The operator must learn fromexperience, and it expends much time for operation because
the accelerator has many alignments and other errors whichare hard to measure. The SPring-8 Linac is also a new accelerator operated since 1996. It’s a 140m long, 1GeV electronmachine. The machine is used as an injector into the 8GeV
synchrotron. The synchrotron demands high energy stability, so the operator must search for the parameter by trial
and error. Even after the parameter is fixed, it is possiblethat the energy is fluctuated by the temperature and various
other reasons, and the operator must engage in adjustment
continually[1].
Whenever a parameter is adjusted, the beam profile is also
checked on a screen which is made with alumina-ceramic(Desmarquest AF995R). Therefore we design an automatic
operation system using screen monitors. Firstly, we develop
an image processing system for the screen monitor. Next, wetry to do a preliminary automatic control using the system.
It is attempted for the electron beam transport.
This paper presents the image processing system of screen
monitor, and some results of a preliminary automatic control
experiment using it.

MMIF layer

EWS

X serverOptical Ether-net
JPEGVME#0~ #22

Machine Control
layer

RS-232Cfor Switcer
control
LINAC Hardware
Control Lines

CCD CAMERA#1~ #32

Video Signal
SwitcherPHICCD

φPM

Dummy

Dummy

1 Data acquisition system

Camera I/F&JPEG Compress(Q_value = 80)

Trigger

ACC tube

ACC tube

Q-MAG

1.1 Linac control system and screen monitor system

IPIP

For the data acquisition and low level control of devices, weadopt VME computers. The hierarchy of the control system has two layers. One is the Machine Control Processlayer (VME), another is the MMIF layer (EWS) [2]. Figure
1 shows a layout of the system in the Linac. These VMEs
have MVME147 boards (Motolora 68030 CPU) and run theOS-9 operating system. An EWS uses HP9000 series. TheVME system is located on the second floor which is called
the klystron gallery.
The 32 screen monitors are installed in the Linac. Themonitor is constructed with a CCD camera that sends an image by wire to the control-room. Usually, the image processing for getting the profile is done by shuttered CCD
camera[3]. However, we use non-shutter CCD Camera
based on NTSC (National Television System Committee)
regulation, because it is very expensive to install all screenmonitors. The CCD signal is inputed to a VME, and convert
to digital data.

Figure. 1. Layout of Linac control system and the screen
monitor system.

1.2 Digital converting
The image processing board works on VME bus, and theimage convert timing is shown figure 2. First, the image
measurement message is sent from EWS to the board. If
we want to get a few frame delay time, because of intensity saturation on the screen monitor, we can set the NTSC
frame delay time. The NTSC frame pulse is constantly generate every 16.6msec (60Hz). When the message and NTSC
frame delay time coincides with the injection beam trigger,the conversion is started by the board. It needs a few hundred
msec. Secondary, the VME board compresses the obtained
image data into a JPEG (Joint Photographic Expert Group)4Image convertingstart !!

NTSC
v-sync pulse

16.6 msec

Get message
from EWS

Beam

Frame wait !

wait !

(frame delay= 1 )1 sec

Beam trigger

PM2-LS

3NTSC
frame # 1

Beam Energy 1.0GeV
2x_position (mm)NTSC
frame # 0NTSC
frame # 60

Beam Current 13mA

10-1-2

Image convert timing

x_position
x_fit-3-4-20

Figure. 2. Digital convert timing on VME bus. This timing
coincide with the beam emission trigger.

-15-10-505101520

ST1-LS (A)Figure. 4. Movement of electron beam position using asteering magnet.

about 2.9mm on the screen. Figure 4 shows these measurement results. It is clear that the beam moves about 3.0mm
on the screen (at 15Ampere). As the system’s resolution isabout 0.3mm/pixel, this shows the high performance of thesystem. This system can measure not only the position but
also the beam profile.
2 Transport modeling

Figure. 3. Human interface of the screen monitor.

data. It needs also a few hundred msec. The JPEG Q-valueis 80, and it compresses 491k byte image data into a 3k byte
JPEG data. The compression is important for the LAN traffic. These all processes are written in OS-9 C-language on
VME bus. Figure 3 shows the human interface of the screen
monitor system. The image process on EWS was made from
JPEG library and OSF-MOTIF. JPEG data from the VME
is analyzed using this process, and shows the digital beam
position and profile.
1.3 Measurement data
An orbit of the electron beam is changed by the strength ofthe magnetic field. When a steering magnet just before thescreen monitor is adjusted, the beam move on the screen.
To use it, we can confirm whether the screen monitor works
with precision.
A steering magnet which is installed at the end of theLinac is 0.00123 (T m), 17Ampere, and the distance between the monitor and the magnet is 892.8mm. Therefore,
when the magnet operates at 15Ampere, the beam moves



Mathematical modeling of the accelerator can be used to calculate the optimum parameters. Generally speaking, there
are two types of modeling methods.
 Statistical approach
The regression model built from statistics, and thepresent condition is simulated by using it.
 Analytic approach
The accelerator is resulted by the model obtained theoretically.
It is difficult for the huge scale accelerator to use the Analycal approach, because of many kinds of complex error. If
we use this model for the optimization, it is hard to calculate
the optimum parameters. We aim principally at the calculation efficiency, and we select the statistical approach. The
statistical approach is usually expressed by using the lowlevel polynomial expression. So we assume that the beamtransport is expressed by the following quadratic expression.

f (I ) = 0 + 1 I1 + :::: + I + 11 I12 + :::: ++ 12 I1 I2 + ::: +,1 I ,1 I + "pp

where,p;ppp

ppI2p(1):

0 ; 11 ; 12 ; :::; p,1;p and " are constants, I1 ; I2 :::Ip are
the current parameters.
For getting this model expression, the displacement ofelectron beam position was measured by using 20 magnets.
And these data are approximated with the quadric model byleast square fitting based on singular value decomposition

701597/07/03 PM1-M18
Frame delay 5

97/07/03 PM1-M18
Frame delay 560

Base _current
x_0_optimize
y_0_optimize

10Magnet current (A)x position (pixel)

50

50-54030

2010x_25% _2
x_25% _3
x_cal _data

0-100102030405060Measurment counts

7080

90

100-100Figure. 5. The prediction data from the quadric expression
model and measurement data.

(SVD)[4]. Figure 5 shows measurement data and the prediction data from the quadric expression model. Measurement
data is horizontal displacement that the current value has manipulated respectively 5 times in 20 magnets. It has goodagreement, and the correlation coefficient is 0.927. Thismodel must be good for the optimization.

24681012Magnet numbers

14161820Figure. 6. Result of the optimization. A vertical axis is themagnet current value, a horizontal axis is equivalent to theelectromagnet which installed on the lower reach from ST1M8.

takes an objective view of the situation. It confirms that theoptimized parameter puts the beam to the screen center.
4 Conclusion

3 Optimization
Successive quadratic programming (SQP) is one of the best
methods for solving the nonlinear programming problem.
For solving the problem, a lot of numerical calculation software is avalible on market. One of these, MATLAB is ahigh-performance numerical calculation software, and it has
an SQP-library in the optimization tool-box[5]. We use thelibrary for solving the our transport model.
When we want to move the electron beam to the center ofscreen, x=0 and y=0, we solve the following minimization
problem with SQP.

minimize : (0 , f (I ) )2 + (0 , f (I ) )2xy:

For automatic operation, a screen monitor system has beendeveloped with image processing. The system works very
well, we can get precise beam profiles. To use this system,
the prospects which could be used for the optimized adjustment of the beam transport were given. We will proceed withthe full automatic transport using this concept.
Acknowledgements
We would like to thank Mr.Akimoto and Mr.Hori for comments and cooperation. And we also thank the operators, allof SES member, for the good LINAC operation.

(2)

ReferencesAnd if x=0 only,:[1]

Figure 6 shows the results of the optimization. The solidline is the electric current value when it is adjusted manuallyby the operator. This value is used as a starting point of theSQP calculation. The solid line with circles is a result ofSQP that fires the electron beam to a center of the horizontal
position on the screen, and the solid line with box is a resultof the center of vertical position. The results point out thatthe eighth magnet is adjusted to make each a zero. Whenwe would like to make each a zero in the human operation,
we image that the magnet which is close to the monitor isadjusted. This result shows that the optimized calculation[2]

minimize : (0 , f (I ) )2x

(3)

[3]
[4]

[5]

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