7.7.1 Experimental Result
Experiments mainly aiming at the effect of the foam layer to the accelerated proton
beam energy from the contamination layer have been carried out with 1 PW laser
system at IBS, Korea [19, 21]. At first, it is reported that the maximum energy of
accelerated protons shown in Fig. 7.25 with PIC code is well reproduced in the
experiment [19]. The value of the maximum energy of 30 MeV is well confirmed
experimentally for 8 mm thick foam target [Fig. 5 in Ref. 19]. The maximum proton
energy is compared for different polarization and intensity cases with 8 μm thick
foam layer and aluminum foil targets experimentally [21]. The experimental result is
shown in Fig. 7.30. It is surprising that the solid lines for the case with three different
polarization irradiations on the foamed targets result almost the same maximum
proton energy scaling to the intensity. This suggests the laser-matter interaction
becomes independent of the laser polarization because the porous structure of foams.
The dotted line data of aluminum foil targets without foam layer, however, show
strong dependence of the polarization configuration on the solid aluminum surface.
We have discussed about the maximum energy of accelerated electrons in the
case with foam layered targets. Specifically, Fig. 7.26 was used to evaluate the
accelerated energy of electrons by the longitudinal electric field. The hot electron
energy spectra are observed in the experiment with the Gemini laser at RAL, UK
[22]. The laser condition is that the pulse duration 50 fs, f/2 plasma mirror, focal spot
30
25
20
Maximum proton energy (MeV)
15
10
5
0.5 1.0 1.5
Intensity on target (10
20 W/cm
2
)
2.0 2.5 3.0 3.5 4.0 4.5
Fig. 7.30 Role of laser polarization and intensity. The maximum energy of measured protons as a
function of laser intensity with s- (blue squares), p- (red triangles), and c-polarization (black circles)
for solid target (empty symbol) and the double-layer target with 8 μm thick foam (full symbol).
[Figure 3 in Ref. 21]
7.7 Enhanced Coupling with Foam Layered Targets
271
Experiments mainly aiming at the effect of the foam layer to the accelerated proton
beam energy from the contamination layer have been carried out with 1 PW laser
system at IBS, Korea [19, 21]. At first, it is reported that the maximum energy of
accelerated protons shown in Fig. 7.25 with PIC code is well reproduced in the
experiment [19]. The value of the maximum energy of 30 MeV is well confirmed
experimentally for 8 mm thick foam target [Fig. 5 in Ref. 19]. The maximum proton
energy is compared for different polarization and intensity cases with 8 μm thick
foam layer and aluminum foil targets experimentally [21]. The experimental result is
shown in Fig. 7.30. It is surprising that the solid lines for the case with three different
polarization irradiations on the foamed targets result almost the same maximum
proton energy scaling to the intensity. This suggests the laser-matter interaction
becomes independent of the laser polarization because the porous structure of foams.
The dotted line data of aluminum foil targets without foam layer, however, show
strong dependence of the polarization configuration on the solid aluminum surface.
We have discussed about the maximum energy of accelerated electrons in the
case with foam layered targets. Specifically, Fig. 7.26 was used to evaluate the
accelerated energy of electrons by the longitudinal electric field. The hot electron
energy spectra are observed in the experiment with the Gemini laser at RAL, UK
[22]. The laser condition is that the pulse duration 50 fs, f/2 plasma mirror, focal spot
30
25
20
Maximum proton energy (MeV)
15
10
5
0.5 1.0 1.5
Intensity on target (10
20 W/cm
2
)
2.0 2.5 3.0 3.5 4.0 4.5
Fig. 7.30 Role of laser polarization and intensity. The maximum energy of measured protons as a
function of laser intensity with s- (blue squares), p- (red triangles), and c-polarization (black circles)
for solid target (empty symbol) and the double-layer target with 8 μm thick foam (full symbol).
[Figure 3 in Ref. 21]
7.7 Enhanced Coupling with Foam Layered Targets
271