Los Alamos National Laboratory

Confinement

Dennis Royer and Wendy Vogan Mc Neil

Dennis Royer (left) and Wendy Vogan McNeil inside an enclosure sitting atop the confinement chamber.

"Prior to 2007, experiments at DARHT were executed outside in the open air. The explosive shots were often spectacular, thrilling events, but they were also very loud, and the shot setup and cleanup were long, complicated, and expensive processes. Sometimes it would take weeks to clean up the firing site and the surrounding area. And while measures were taken to mitigate impacts to the environment, there were limits to what was possible.

"So in 2007 DARHT was reconfigured to use a confinement system. The test device is now placed in a hexapod alignment fixture [central can in the illustration] that can be positioned to sit precisely at the intersection point of the two pulsed x-ray beams. The hexapod is surrounded by a thick-walled steel vessel [green], which is surrounded by another thick-walled steel cylinder [gray]. Now, when the explosion goes off, it is completely confined. You hear virtually nothing, just a deep "pong," like someone hitting the bottom of a cooking pan with a big spoon. The thrill is also gone, but we made a commitment to the environment and we've stood by it."

—Dennis Royer, DARHT firing site coordinator

Confinement Pic

The DARHT facility, home to two x-ray sources (axes) and a confinement vessel, took nearly 20 years to design, build, and get running. X-ray pulses are produced by first accelerating a pulse of electrons to nearly the speed of light with a linear accelerator. DARHT's first-axis accelerator (red) became operational in 1999 and produces a single, very intense electron pulse. The second-axis accelerator (blue) uses a magnetic "kicker" to chop its 1.6-microsecond-long electron pulse into four pulses of variable duration. The electron pulses enter a conversion region and are focused onto a tantalum foil. Whenever an electron scatters from an atom on its way through the foil, it radiates x-rays. The x-rays pass through a collimator then into the confinement chamber. Facing page: The large confinement chamber that holds the test device.

 

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