Ⅱ-8. Accelerator

RIKEN Accel. Prog. Rep. 47 (2014)

Creation of cocktail beam from alloy target with laser†
S. Ikeda,*1,*2, M. Romanelli,*3 D. Cinquegrani,*4 M. Sekine,*1,*2 M. Kumaki,*1,*5 Y. Fuwa,*1,*6 N. Munemoto,*2T. Kanesue,*7 Q. Jin,*8 M. Okamura,*7 and K. Horioka*2
Lasers can create many types of heavy ions from a solidtarget. Therefore, with the use of a laser and an alloy target,
an ion beam composed of several elements can be easily
created. The cocktail beam can be used to simulate cosmic
rays in a laboratory. A recent paper reported theenhancement of a plasma flux by mixing a few different
types of species with an original target.1) However, thecharge state distribution of each ion was not studied. To
create a controllable cocktail beam, we investigated thecharge state distributions of laser plasma from an alloy
composed of Al and Fe.

from the pure targets. As shown in the figure, they wereAl 1+: 0.5, Al 2+: 0.68, Al 3+: 0.58, Al 4+: 0.27, Al 5+: 0.27,Al 6+: 0.65, Al 7+: 0.84, Al 8+: 0.89, Al 9+: 0.34, Fe 1+: 0.72,
Fe 2+: 0.60, Fe 3+: 0.51, Fe 4+: 0.65, Fe5+: 3.5, Fe 6+: 15.
Total peaks up to a 4+ charge state of the Al and Fe ionsfrom the alloy targets were around half those from the puretargets. Hence, the ratios of the peak value were close to thestoichiometric ratio in the target material (Al:Fe =10:19).
On the other hand, the ratios of highly charged states werelarger than the composition ratio; in particular, Fe 5+ and Fe
6+ were much larger than those of the other ions.
The results showed that we can control the ratio of theflux of the Al to Fe ions, except for Fe 5+ and Fe 6+, as afunction of composition ratio of alloy. A large increase in Fe
5+ and Fe 6+ indicates that we can substantially increase thecharge state of a specific ion using an alloy.

Fig. 1. Schematic of experimental setup.
Figure 1 shows a schematic of the experimental setup.
We used a Nd:YAG laser (1064 nm, 6 ns, 615 mJ, and7.9×10-3 cm2 spot size) for ablation. As the targets, we usedpure Al, Fe sheets, and an alloy of Al and Fe(AL-FE-01-F.ALLY) with Al:Fe = 10:19 (number). The
chamber was evacuated to 5×10-4 Pa. The charge state
distribution was measured through a time-of-flight (TOF)
method using a cylindrical electrostatic ion energy analyzer.
The device was composed of two coaxial electrodes, with aslit
infrontof
theelectrodes,
anda
secondary-electron-multiplier detector (SEM) placed at 3.3
m from the targets. Only the particles with a specificvelocity and ratio of charge to mass could pass through theelectrode. In addition, we could determine the velocity ofparticle reaching the SEM from the time of flight.
Consequently, we could obtain the ratio of chare to mass
and identify the ion.
Figure 2 shows the experimentally obtained results ratiosof peak ion flux from the alloy target to the peak ion flux
from the pure targets. As shown in the figure, they were†Condensed from the article in Rev. Sci. Instrum. 85, 2 (2014)
RIKEN Nishina Center＊2
Department of Energy Science, Tokyo Institute of Technology＊3
School of Applied and Engineering physics, Cornell University＊4
Nuclear Engineering and Radiological Sciences, University ofMichigan＊5
Department of Nuclear Engineering, Waseda University＊6
Department of Physics, Kyoto University＊7Collider Accelerator Department, Brookhaven National Laboratory＊8
Institution of Modern Physics

Fig. 2. Ratios of peaks value of Al and Fe ion flux fromalloy target to those from pure targets＊1

References

1) A. Velyhan, J. Krasa, E.Krousky, L. Laska, D. Margarone,
M.Pfeifer, K. Rohlena, J. Skala, J. Ulischmied, A. Lorusso, L.
Velardi and V. Nassisi : 4th workshop on PPLA2009, Messina,
Italy, 165, 6-10 (2010), p488-494- 161 -