Proceedings of IBIC2012, Tsukuba, Japan

MOPB75

REAL-TIME BEAM PROFILE MEASUREMNT SYSTEM USINGFLUORESCENT SCREENS
Takahiro Yuyama, Yosuke Yuri, Tomohisa Ishizaka, Ikuo Ishibori, and Susumu Okumura
Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency
1233 Watanuki-machi Takasaki, Gunma, Japan, 370-1292
An irradiation technique of a large-area uniform ion
beam formed by multipole magnets is developed at theTIARA azimuthally-varying-field (AVF) cyclotron
facility in Japan Atomic Energy Agency (JAEA). It is
indispensable to perform uniform-beam tuning in realtime for efficient operation. Therefore, we developed areal-time beam profile measurement system, composed of
CCD cameras, fluorescent screens and an image analysis
program based on LabVIEW. In order to measure thetransverse intensity distribution of the beam through thefluorescence map converted from a camera image, theirradiation response of two fluorescent screens, DRZHigh (Gd2O2S:Tb) and AF995R (Al2O3:Cr), were
investigated using several species of ion beams. The
available fluence rate of the screens was found in thepresent system. The relative transverse intensity
distribution could be obtained from the fluorescence inreal time. It was also confirmed that the intensity
distribution measured in this system agreed well with therelative intensity distribution obtained with a Gafchromic
radiochromic film.

thin metallic foil, is transformed into a uniform beam on
the target by folding the beam tail the by the nonlinear
magnetic field. It is possible to irradiate the whole of alarge-area sample uniformly at a constant fluence rate.
It is indispensable to form and evaluate the beam
quickly for the efficient utilization of the uniform beam.
The real-time measurement system of the beam profile
based on the beam fluorescence was, therefore,configured and tested.

SYSTEM CONFIGURATIONThe real-time beam profile measurement system iscomposed of CCD cameras and fluorescent screens. The
fluorescent data is processed using a computer (PXI,National Instruments) with LabVIEW. Two different
types of fluorescent screens, DRZ-High (Gd2O2S:Tb, 0.5
mm thick, Mitsubishi chemical) and AF995R (Al2O3:Cr, 1mm thick, Desmarquest) have been chosen. The activelayer (310 Pm thick) of DRZ-High is put on a 190-Pm
plastic base. The DRZ-High screen is more sensitive andhas lower afterglow as compared with AF995R. The main
devices used in the present system and their layout are
shown in Table 1 and Fig. 1, respectively.
INTRODUCTION
The fluorescent screen is mounted on the target in avacuum
chamber where the large-area uniform intensity
The JAEA AVF cyclotron with a K number of 110 MeV
distributionof the beam is formed by octupole magnets.
accelerates and provides various species of ion beams atThetargetsize is as large as 20 cm square at thedifferent energies for researches in the fields of biologicaland materials science, such as plant breeding, production maximum. When the large-area screen is monitoredof functional polymers and radiation hardness tests of diagonally using a camera, the distortion of thespace-use devices [1]. Various irradiation techniques have fluorescent image is inevitable. As shown in Fig. 1, thebeen developed for providing useful beams. In recent camera A (B), therefore, monitors the screen from theyears, a large-area uniform beam irradiation technique below (from the right side) diagonally for the horizontal
using the nonlinear focusing force of octupole magnets
has been developed [2]. In the technique, a Gaussian-likebeam, obtained by multiple Coulomb scattering through aTable 1: Main Components of the Real-time Beam Profile
Measurement System
ChassisCPU
Image capture
Image analysis device
PC (PXI)
ChassisCPU
Image capturedeviceAl2O3:Cr
FluorescentscreenGd2O2S:Tb

FluorescencescreenPXI-1031
PXI-8106
PXI-1411
PXI-1042Q
PXI-8106

NationalInstruments Co.

PXIPXICamera A

PXIe-8234
AF995R
DRZ-highHorizontal
ICD42VP
cameraVerticalscA1390-17gc
camera_________________________* E-mail: yuyama.takahiro@jaea.go.jp

Measurement
hardwareOctupole
magnetDesmarquest Co.
Mitsubishi
chemical Co.
Ikegami tsushinki
Co.
BASLER AG

Camera B

Figure 1: Schematic layout of the main components
for the real-time beam profile measurement. The CCD
cameras A and B monitor the beam fluorescence
vertically and horizontally, respectively.
ISBN 978-3-95450-119-9

Transverse Profiles, Screens & Wires Monitors1c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○AbstractMOPB75

Proceedings of IBIC2012, Tsukuba, Japan
2506040200-1

CASE1
CASE2
CASE3
CASE4
CASE5
CASE680

Intensity [pixel ]Beam current [a.u]

100

100
50

20020(vertical) profile of the beam.
The fluorescent light from the screen due to ion-beamirradiation is taken as an 8-bit image data of theluminance (fluorescent intensity) and processed in thePXI computer. The image data is analyzed for theevaluation of the beam intensity distribution in real time.

EVALUATION OF THE SYSTEM
In order to explore the available beam intensity i.e., toreveal the dependence of the fluorescent intensity on thefluence rate in this system, the beam irradiation
experiment was carried out using 10-MeV proton and520-MeV argon beams.

Beam Intensity Control Using a Beam Chopper
An electrostatic beam chopper, installed before thecyclotron, was used for the gradual control of the average
beam intensity. Figure 2 shows the scaled beam intensity
when the beam duty was changed by the beam chopper
working at 1 kHz. The beam current of 10-MeV protons
was monitored by a Faraday cup near the target. Six
different conditions of the beam are plotted. It was foundthat, using the beam chopper, the beam intensity could be
reduced within an error of 1%, independent of beam
conditions. Thus, the fluence rate can be controlled in awide range.

Irradiation Response of the Screen
Using the beam chopper, the fluence-rate dependenceof the screens was investigated on the target. The uniform
distribution of 40 ~ 50 cm2 was formed on the target sothat the transverse dimension of the beam could bedetermined easily. The fluence rate was determined fromthe beam cross-sectional area and current measured by theFaraday cup.
Figure 3(a) shows the dependence of DRZ-High andDesmarquest on the fluence rate of the 10-MeV proton

0991 102 103 10-2 -1
Fluence rate [cm s ]

94 10

9250
DRZ-High
AF995R

200-1

40
60
80
100
Duty ratio [%]Figure 2: Scaled beam current of 10-MeV proton
beams as a function of the duty of the electrostatic
beam chopper. The beam current has been scaled bythe value at a duty of 90%.

c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○0Intensity [pixel ]0DRZ-HighAF995R

1501501005000

77772 10 4 10 6 10 8 10-2 -1
Fluence rate [cm s ]81 10Figure 3: Fluorescent intensity of the two screens on
the fluence rate of ion beams. (a) 10-MeV proton
beams. (b) 520-MeV argon beams.
beam. The fluorescent intensity is proportional to thefluence rate of the beam at a low fluence rate and thensaturated. DRZ-High is available in the fluence rate on
the order of 108 cm-2 s-1, which is 15 times more sensitive
than AF995R.
The result on the 520-MeV argon beam is shown in Fig.
3(b). The available fluence rate is about one order ofmagnitude lower than that of 10-MeV protons for eachscreen. The difference of the sensitivity between the twoscreens is larger than that in Fig. 3(a). This might bebecause the argon beam stops fully in the active layer ofDRZ-High.

BEAM INTENSITY DISTRIBUTION
MEASUREMENT
The present system was applied to beam tuning of theuniform distribution formation using multipole magnets[2]. The transverse intensity distribution of the beam on
the target was measured based on the response
characteristics of the fluorescent screen The horizontal
scaled intensity distribution of the beam is shown as the
red line in Fig. 4, which indicates the flat-top intensity
distribution of 12-cm wide.

ISBN 978-3-95450-119-92Transverse Profiles, Screens & Wires Monitors

Proceedings of IBIC2012, Tsukuba, Japan

MOPB75

1

Scaled intensity [a.u.]

Fluorescence intensity
Optical density

0.80.60.40.20-100-50050
Horizontal length [mm]100For the verification of the intensity distribution
measured by the beam fluorescent, a Gafchromic
radiochromic film was irradiated with the same beam [3].
The scaled intensity distribution obtained from the opticaldensity of the Gafchromic film is given by the blue
dashed line in Fig. 4. As clearly seen in the figure, both
distributions agree well except for the noise included in
the beam fluorescence.

SUMMARY
The real-time beam profile measurement system wasdeveloped for the efficient formation of the uniform ionbeam. We investigated the beam irradiation response of
two fluorescent screens DRZ-High and AF995R for 10MeV proton and 520-MeV argon beams. The fluorescentintensity was proportional to the fluence rate of the beam
at low fluence rates for both screens in the present system.
The real-time analysis of the relative intensity distributionof the beam was carried out for the uniform beam
formation. It was confirmed that the relative intensity
distribution of the beam obtained from the fluorescenceagreed well with the relative intensity distribution
determined from the Gafchromic film, which verified themeasurement system developed.

REFERENCES[1] K. Arakawa et al., Proc. 13th International Conference
on Cyclotrons and their Applications, Vancouver,Canada, 1992, p. 119.
[2] Y. Yuri et al., Nucl. Instrum. Methods Phys. Res. Sect.
A 642 (2011) 10.
[3] Y. Yuri et al., in these proceedings, TUPB79.

ISBN 978-3-95450-119-9
Transverse Profiles, Screens & Wires Monitors

3c 2012 by the respective authors — cc Creative Commons Attribution 3.0 (CC BY 3.0)
Copyright ○Figure 4: Comparison between the relative horizontalintensity
distributions
from
theDRZ-Highfluorescence and the optical density of the HD-810
Gafchromic film. The HD-810 film was irradiated withthe 10-MeV proton beam of 15 nA for 10 s.