Initial study and design on ignition ellipraum

Abstract

An initial study and design on ignition elliptical hohlraum (ellipraum) is given by using the expended plasma-filling model with criterions. As a result, in an ellipraum with a smaller ratio of major-to-minor axis (a/b), the radius ratio of ellipraumto-capsule (b/R C ) should be larger (hence more sphere-like) to meet the criterions of plasma-filling and laser deposition, meanwhile the required laser energy and peak power are lower and the coupling between different modes is weaker. To produce a 300 eV radiation pulse to ignite a capsule of 1 mm radius, an ellipraum of a/b = 1.6 and b/R c = 2.8 is superior to a cylinraum with a length-to-diameter ratio of 1.81 and a cylinraum-to-capsule radius ratio of 2.54 in saving more than 10% laser energy and reducing 50% coupling between different modes.

High flux symmetry of the spherical hohlraum with octahedral 6LEHs at the hohlraum-to-capsule radius ratio of 5.14

“…More importantly, a very uniform flux from the hohlraum on the shell of capsule is mandatory because a small drive asymmetry of 1% [2] can lead to the failure of ignition. Actually, the small flux asymmetry will be magnified during the compression process due to the varied kinds of instabilities and results in a serious hot-cold fuel mixture that can dramatically lessen the temperature or density of the hot spot for ignition.Various hohlraums with different shapes have been proposed and investigated, such as cylinder hohlraum [1,2], rugby hohlraum [5-10] and elliptical hohlraum [11]. These hohlraums are elongated with a length-to-diameter ratio greater than unity and have cylindrically symmetry with two LEHs on the ends.…”

“…Various hohlraums with different shapes have been proposed and investigated, such as cylinder hohlraum [1,2], rugby hohlraum [5][6][7][8][9][10] and elliptical hohlraum [11]. These hohlraums are elongated with a length-to-diameter ratio greater than unity and have cylindrically symmetry with two LEHs on the ends.…”

First demonstration of improving laser propagation inside the spherical hohlraums by using the cylindrical laser entrance hole

“…Nevertheless, the plasmas entering the laser path are very thin and the deflection is small, and the laser energy is mainly absorbed at the initial pointing position in the experiment. Notice that the laser deflection might influence the time evolution and spatial distribution of capsule symmetry in the cylindrical, rugby [24] and elliptical hohlraums [25], and it should be considered in the target design. In contrast, for the octahedral spherical hohlraum, the influence of laser deflection on radiation asymmetry can be neglected since the radiation symmetry is insensitive to the laser spot movement [9,10].…”

Octahedral spherical hohlraum and its laser arrangement for inertial fusion

“…11,27 Shown in Fig. 9 is the initial design of laser energy and R H /R C by using the extended plasma-filling model.…”

“…Of course, the flux symmetry is strongly connected with the hohlraum geometrical structure. Up to now, various hohlraums with different shapes have been proposed and investigated theoretically and experimentally, such as cylinder hohlraum, 1,2 rugby hohlraum, 5-10 elliptical hohlraum, 11 and spherical hohlraums with 4 LEHs 12,13 or 6 LEHs. 14,15 Among all these hohlraums, the cylindrical hohlraums are used most often in inertial fusion studies and are chosen as the ignition hohlraum on The National Ignition Facility (NIF).…”