JAERI-Conf 95-021

3a3-2
DEVELOPMENTOFANIONI~LANTEDTHIN ALUMINA BEAM PROFILE MONITOR
Toshikazu KURIHARA, Hitoshi KOBAYASHI, Takao URANO, Tsuyoshi SUWADA,Ryuichi TANAKA*, Sohei OKADA*, Sin-ichi MAS UNO*, Yasushi AOKI*
Photon Factory, National Laboratory for High Energy Physics (KEK),Tsukuba, Ibaraki, Japan*Takasaki Establishment, Japan Atomic Energy Research Institute,Takasaki, Gunma, Japan

Abstract
It is very important to get a real image of thebeam from the injector linac. Therefore, it isdesirable to monitor the beam position and beamprofile as well as the beam current in the linac.
Alumina screen (Desmarquest AF995R, chromiumactivated alumina ceramics ), is often used as a beamprofile monitor for diagnosis of a linac beam.
Typical thickness of alumina phosphor screen isabout 1mm. Especially for the low energy beam partof the linac, scattered electrons in such a thick screen
produce enlarged beam profiles. A thin film
phosphor screen with chromium ion implanted
alumina has been designed and manufactured toproduce a high-precision beam profile monitor.
1. Introduction
The demand of a low-emittance electron
linac has increased in these years, for applications
such as the free-electron laser, coherent synchrotron
radiation, and others. It is very important to transport
and accelerate the beam emitted from the cathodewith negligible emittance growth.
There is some attempt to build up anemittance measurement system for a low emittancebeam 1). A plastic scintillator which is 10 J..Ull thinand has a fast scintillation characteristic has been
adopted to measure the beamlets' image with a hightemporal and spatial resolution. Silver (30 Angstromthin) was deposited on the scintillator surface byvacuum evaporation to avoid charge-up. This
experimental set up is for off-line use. An inorganic
scintillator with thin thickness is necessary for theinjector linac.
We try to make an oxide layer on aluminum
surface. With ion implantation technique, we could
get a polycrystalline ruby in oxide layer on aluminum
surface. As the first trial, we have made preliminary
experiments to show the possibility to make nearly
10 ~m thin oxide layer on aluminum and to makepolycrystalline ruby layer on alumina with chromium
ion implantation technique.
2. Experimental

The aluminum anodizing technique has been
established and is widely applied to metal surface
technology to coat or color the surface ofaluminum2,3). We applied this technique to produce
thin film scintillator.
Aluminum plates of purity SN were
electrically polished in a 3N NaOH bath at room
temperature with a de density of 500 mNcm2.
Reactions are as follows,
Anode2Al + 3H20 -> Al203 + 6H+ + 6eCathode
6H+ + 6e--> 3H2

The average direct anodic current was fixed at 20mNcm2. Thickness of alumina layer as a function ofoxidation time is shown in Figure 1.

.............,.....,,.....,...,:':

70..,........,..,..,.......,...,..,.,...........,..,.,-~"'T""""'"........,:!::!

50~ 400 ~~~~~~~~~~~
0

10 20 30 40 50 60 70
Time (min.)Fig. 1. Thickness of alumina layer as a function ofoxidation time.

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Compared with other method (for example, vacuum
evaporation technique or sputtering technique), one
could easily get a nearly 10 Jlm thin oxide layer withreasonable time by the aluminum anodizing
technique.
Alumina plate of thickness 0.125 mm
purchased from ASAHIKASEI Co. was prepared as astarting material. Purity of alumina was 99 .9wt.%
AI203. Specimen size was 20 mm.x 20 mm.
Specimens were implanted at room temperature with200 keV or 800 keV chromium to fluences in therange 1 X 1012 /cm2 - 1 X 1016 /cm2. Chromium
ion implantation profiles have been generated foralumina using the simulation code TRIM. Figure 2
shows the implantation profiles for 10 keY to 1 MeV
chromium ion in alumina.
- - B Electron- - C NuclearCron Al203- ..- - D

Projected--X-- E

LongitudinalStraggling. ·+·. F

LateralStraggling

I!'I

3. Results
Optical measurements were done withspecimens as implanted.
Compared with
Desmarquest AF995R, no light emission from
implanted alumina was observed yet. Naramoto eta1.4) pointed that in the temperature range of 1200 °C
to 1300 °C , substitutional damage recovery hastaken place in both the AI and 0 sublattices, and atthese temperatures, one begins to see significant Cr
incorporation into substitutional lattice sites.
Recovery process is necessary to get emission fromthis specimen.

References
1) Y. Yamazaki, T. Kurihara, H. Kobayashi, I. Satoand A. Asami, Nucl. Instrum. & Methods in Phys.
Res. A322 (1992) 139
2) M.Miyagi et al., Applied Optics Vol.26, No.6,(1987) 970
3) D.G.W.Goad and M. Moskovits, J. Appl. Phys. 49(5) (1978) 2929
4) Naramoto et al., J.Appl.Phys. 54 (1983) 683

200 ......-~,...--~,...--~.,....,.-~.,....,.-~.,....,.-....-.-, 5000
I

repetition rate. Emission from the specimen wastaken by CCD camera.

ij40001503000?1.g

100·········-r--· ·····r-~

I i':

2000

Iiso ... .... L..t. ...... L..........L.........L. .........;...........
i"iiii,~]:,::r::-:r::r::r

1000

0 E:.....L...L...L...._.._,_.L...._......._.L...............L.....-"-L.-'--'...~ 00
200 400 600 800 1000 1200
ion Energy (keV)

Fig. 2. Implantation profile of Cr in Al203.

Takasaki Ion Beam Implanter and Tandem
Accelerator were used for this implantation
experiment.
After implantation, specimens were mounted
on the specimen holder of the beam profile monitor
test bench in KEK. These specimens were irradiatedwith 150 keY electron beam from the linac. The
intensity of the linac beam was measured using thecurrent monitor. The peak current of the beam was
200 rnA. The beam was 5 J.l.S pulse width and 1Hz-432-