Demonstration of Symmetry Control of Infrared Heated Deuterium Layers in Hohlraums

Abstract

Infrared smoothed deuterium ice layers inside capsules have been successfully demonstrated for capsules inside cylindrical hohlraums. Improved characterization methods and infrared illumination enables low mode control in both the axial and azimuthal directions. Experimental results agree well with computer models. Results of these experiments will be used to derive accuracy requirements for an infrared heating system for ice layers in hohlraums on NIF.

Low Mode Control of Cryogenic ICF Fuel Layers Using Infrared Heating

“…This power level is to be considered if the beneficial effects of increased layering rate and enhanced higher mode smoothing are desired. 3,4,7 This power is close to the maximum that can be removed through the hohlraum gas and cryogenic cooling rods. From Figure 5b, we find solutions for high power with beam 1 pointed near the limiting value of -2 mm and beam 2 in the range 0 -1 mm.…”

“…The parameters are specified for a number of incident angles, and interpolated for angles between the specified ones. The parameter values used in the present work have been taken from measurements of roughened gold surfaces 7 and are listed in Table II. In addition to the scattering model, we have implemented user specified IR absorption coefficients for each material, specifically for the fuel and capsule, and Fresnel reflections at material boundaries, according to user supplied index of refraction data.…”

“…In Figure 5 we show the contours of the beam power ratio, as determined by Eqs. (7)(8) to minimize the P 2 variation as well as the region of acceptable temperature variation. Figure 5a shows the case for W ir = 10 W β .…”

“…Recently, it was demonstrated that one can control the two lowest modes of D 2 thickness perturbations using two properly pointed IR laser beams. 6,7 Each beam was a ring, symmetric about the hohlraum axis. The beams irradiated a small annular surface area on the inside hohlraum wall.…”

Review on high repetition rate and mass production of the cryogenic targets for laser IFE

“…This technique is called joule (J) heating [23] . The second technique, infrared (IR) heating, uses monochromatic IR radiation to selectively excite rotational-vibrational bands of specific molecular hydrogen isotopes [23][24][25][26][27][28] . This technique causes a volumetric heating of the ice layer and is similar to the beta-layering smoothing technique.…”