The development of target fabrication for the Fast Ignition Realization EXperiment (FIREX) Project is described in this paper. For the first stage of the FIREX Project (FIREX-I), the previously designed target has been modified by using a bromine-doped ablator and coating the inner gold cone with a low-density material. A high-quality bromine-doped capsule without vacuoles was fabricated from bromine-doped deuterated polystyrene. The gold surface was coated with a low-density material by electrochemical plating. For the cryogenic fuel target, a brand new type of aerogel material, phloroglucinol/formaldehyde (PF), was investigated and encapsulated to meet the specifications of 500 µm diameter and 20 µm thickness, with 30 nm nanopores. Polystyrene-based low-density materials were investigated and the relationship between the crosslinker content and the nanopore structure was observed.
Resorcinol/formaldehyde (RF) foam resin is an attractive material as a low-density target in high-power laser–plasma experiments because of its fine network structure, transparency in the visible region, and low-Z element (hydrogen, carbon, and oxygen) composition. In this study, we developed disk-shaped RF foam and deuterated RF foam targets with 40–200 μm thickness and approximately 100 mg/cm3 density having a network structure from 100 nm to a few micrometers cell size. By deuteration, the polymerization rate was drastically slowed down owing to kinetic isotope effects. These targets were used in high-power laser experiments where a megaelectronvolt proton beam was successfully generated.
In high energy density physics including inertial fusion energy using high power laser, doping tracer atoms and deuteration of target materials play an important role in diagnosis. For example, the low concentration copper dopant acts as an X-ray source for electron temperature detection while the deuterium dopant acts as a neutron source for fusion reaction detection. However, the simultaneous achievement of Cu doping, deuterated polymer, mechanical toughness and chemical robustness for the fabrication process is not so simple. In this study, we report the successful fabrication of a Cu-doped deuterated target. The obtained samples were characterized by inductively coupled plasma optical emission spectrometry (ICP-OES), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The simultaneous measurements of Cu K-shell X-ray emission and beam fusion neutron were demonstrated using a petawatt laser in Osaka university.
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