AN EVIDENCE OF ANOMALOUS DEPOSITION OF REB ENERGY TO THE LOW Z TARGET

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Submitted on 1 Jan 1979

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AN EVIDENCE OF ANOMALOUS DEPOSITION OF REB ENERGY TO THE LOW Z TARGET

K. Imasaki, S. Miyamoto, S. Higaki, S. Nakai, K. Nishihara, C. Yamanaka

To cite this version:

K. Imasaki, S. Miyamoto, S. Higaki, S. Nakai, K. Nishihara, et al.. AN EVIDENCE OF ANOMA-

LOUS DEPOSITION OF REB ENERGY TO THE LOW Z TARGET. Journal de Physique Colloques,

1979, 40 (C7), pp.C7-779-C7-780. �10.1051/jphyscol:19797376�. �jpa-00219373�

JOURNAL DE PHYSIQUE Colloque C7, suppldment au n07, Tome 4 0 , J u i l l e t 1979, pac-re C7- 779

A N EVIDENCE ff ANOMALOUS DEPOSITION OF REB ENERGY TO THE LOW Z TARGET

K. Imasaki, 5. Miyamoto, S. Higaki, S. Nakai, K. Nishihara and C. Yamanaka.

I n s t i t u t e of Laser Engineering, Osaka University, Suita, Osaka, 565, Japan.

The interaction between REB and solid target is one of the most important issues in REB-ICF research because the required REB power, pellet size and structure for break-even is strongly influenced by the interaction. We report here an evidence of enhanced coupling between REB and solid target.

The experiment has been performed using 'Reiden 111' REB generator. The operational power level of Keiden 111 is 500 keV, 100 kA. The pulse length is 80 ns. The beam is focused onto a solid target using the tungsten quide rod. The focal spot size is measured to be 1.5 mm in diameter. The 80 % of the total diode current is concentrated in the pinch region.

Using a N2 laser, 6 ns pulse length, an interferometry and shadowgraphy of two channels were performed to measure the density profile and velocity of the blow- off plasma from the solid target irradi- ated by the REB. Thin foils of Ni, Ta and

(CH2) were used as the target.

In the case of Ni foil target of 10 um in thickness, a symmetric blow-off was observed on both sides of the target.

This fact can be explained by uniform deposition of REB energy due to the binary

collision in the target. But for the polyethylene target of 100 pm in thickness symmetric expansion on the rear and front side was not observed, although the pt of the target was kept the same value with the Ni target, where p was the mass den- sity and t is the thickness of the target.

Figure 1 shows the result of the inter- ferometry of the polyethylene target.

This fact indicates the REB energy is

1 , '. 4- L L V J L ~ . . L ~ U L I U L C -

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region of the target and REB electron cannot penetrate the 100 um thick poly- ethylene. The same result was obtained when the polyethylene of 20 pm in thick- ness was used. In the case of high Z target as Ni, this anomalous effect is suppressed.

The dynamic behavior of the target was simulated using 1-D Lagrangian code.

The absorption of the REB energy to the target was assumed to be the simple clas- sical in high Z target and anomal.ous in low Z target. Figure 2 shows the result of the simulation comparing with that of the experiment. They correspond quite well to each other.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797376

Figure 1. The interferometry of poly- ethylene target. The photograph was taken at 100 nsec after the pulse rise. The blow-off of the rear side aid not observed in contrast with that of the front side.

l o r n .

0 100 200 NSEC

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Figure 2 . The simulation result with experimental data for the high Z and low Z target.