Inertial Confinement Fusion Program Research Articles

Damage resistance of coated optics

Successful application of high energy lasers to national needs in strategic defense, inertial confinement fusion and isotope separation is contingent on the development of optical coatings that can withstand very intense radiation. Significant progress has been made in the development of damage resistant coatings over the past 15 years to support the needs of the inertial confinement fusion and isotope separation programs. However, the requirements evolving from the Strategic Defense Initiative (SDI) are much more severe and demand dramatic improvements in the performance of optical coatings beyond the current state of the art. The approach taken at Los Alamos towards solving the problems of optical coatings for SDI is presented.

Development of the Antares Electron Gun

Antares is the Los Alamos National Laboratory 40 kJ, 1 ns, CO2 laser system, now operational. This laser system was developed for the Inertial Confinement Fusion (ICF) program and is being used for target experiments. The distributed circuit modeling, design, and operation of the large electron gun developed for the final laser power amplifier are reviewed. This gun is significant because of the large electron current area, 9 m2; the number of emitter blades, 48; the dual cathode current return; the coaxial geometry and grid control. Electron current density measurements of individual windows and over the entire length of the gun are presented. The gun components and their development are discussed. These include the emitter blades, the Kapton® /aluminum electron transmission windows (to provide an interface between gun vacuum and laser gas), the grid resistor and coaxial grid (to adjust and maintain constant electron current during the 5 μs pulse), the bonded stacked-ring insulator (to provide 500 kV hold-off for the grid and cathode), and the 15 m3 vacuum shell (operated at 1.3x1O-4 Pa). A unique pressure diagnostic used in the gun conditioning process is also discussed.

Light Ion Sources for ICF

PBFA II, Sandia National Laboratories' (SNLA) advanced light-ion accelerator [1] (now under construction), will deliver a 30-MV, 5 MA lithium ion beam to an Inertial Confinement Fusion (ICF) target. Although most ICF experiments have been performed with proton beams, lithium ions were selected for PBFA II for several reasons. The use of lithium enables a large anode-cathode spacing, resulting in less impedance change during the pulse. Lithium ions have less magnetic deflection in the diode, so they can be focused for a longer period of time. Also, since the ionization potential of Li+ is low, while that of L++ is very large, a Li+ source should be achievable without significant contamination from Li++ Ions heavier than Li+ would require operating voltages greater than 30 MV, or the ions would have to be accelerated in a multiple charged state. The selection of the lithium option for PBFA II has made the development of a suitable lithium source one of the highest priority areas in the light-ion ICF program. Following that decision in the fall of 1983, SNLA organized a comprehensive ion source program to develop an optimum lithium source for PBFA II and to understand near-term sources.

Fabrication of thin‐wall, freestanding inertial confinement fusion targets by chemical vapor deposition

To meet the requirements for plasma physics experiments in the inertial confinement fusion (ICF) program, chemical vapor deposition (CVD) in fluid beds was used to fabricate freestanding tungsten spheres and cylinders with wall thicknesses less than 5.0 μm. Molybdenum and molybdenum alloy (TZM) mandrels of the desired geometry were suspended in a carrier bed of dense microspheres contained in an induction‐heated fluid‐bed reactor. The mandrels were free to float randomly through the bed, and using the reaction WF6+3H2→723 KW +6HF, very fine‐grained tungsten was deposited onto the surface at a rate and in a grain size determined by temperature, gas flow rate, system pressure, and duration of the reaction. After coating, a portion of each mandrel was exposed by hole drilling or grinding. The mandrel was then removed by acid leaching, leaving a freestanding tungsten shape. Experimental procedures, mandrel preparation, and results obtained are discussed.

Particle Beam Fusion Acceleratr-I (PBFA-I)

The first Particle Beam Fusion Accelerator (PBFA-I) has recently completed its operational series of tests. It provided 30 TW into 36 power flow lines terminated in electron beam loads at the accelerator's center. The outputs were 2 MV at 15 MA for a 40 ns pulse which provided 1 MJ of output energy. During the accelerator develcpament, several ways of modifying and reconnecting this modular, few MV output pulsed power were discovered. The data from PBFA-I tests show the flexibility and reliability of pulsed power. This technology base could provide a 100 TW accelerator known as PBFA-II which will be the light ion beam test bed for breakeven experiments for the Department of Energy's Inertial Confinement Fusion Program. Pulsed power technology continues to be flexible and adaptable to a wide variety of basic research problems. It is a cost effective technology for producing large pulsed energy outputs.

Overview of the U.S. inertial confinement fusion program

Overview of the U.S. inertial confinement fusion program

A 12.5 MHz Heavy Ion Linac for Ion Beam Fusion

Argonne National Laboratory (ANL) is currently developing the injector of a heavy ion beam driver for the inertial confinement fusion program. The first phase of the program is to accelerate about 20 mA of Xe/sup +1/ from a 1.5 MV preaccelerator 11.4 MeV in a low-beta RF linac. The first section of the linac utilizes a single harmonic buncher and independently-phased short linac resonators with a FODO magnetic quadrupole focusing lattice. These are followed by two double-stub Wideroee linacs. A layout of the linac up to 6.4 MeV is shown. The operating parameters of the low-beta linac are given. This paper gives details of the low-beta linac design and results of low power measurements on the first accelerating cavity.