May 20, 2007

DARHT ushers in new era

By Kevin N. Roark
May 17, 2007

Facility conducts fully contained hydrotest

The Dual Axis Radiographic Hydrotest facility successfully fired a first ever fully-contained, high-explosive experiment on Tuesday inside a steel containment vessel.

This test marks the beginning of an era of fully-contained tests at DARHT as virtually all future testing at the facility will be conducted inside huge steel vessels, eliminating nearly all environmental hazards.

"This hydrotest was the culmination of almost a decade of work, and required the dedicated efforts of a large cross-section of the Laboratory," said David Bowman of Radiographic and Pulse-Power Systems (HX-6). "Excellent teamwork by all involved resulted in a return of very high quality data."

The experiment, number 3643, and called a "dynamic core punch" test, was the first to occur inside a containment vessel to prevent releasing the explosion's by-products, including pieces of metal shrapnel, to the environment. Post-test sampling and monitoring confirmed that the experiment was completely contained, according to Bowman.

One of the major issues at DARHT is the time between experiments due to the clean-up requirements at the firing point after all tests. With the move to fully-contained experiments, program managers hope that not only will the Laboratory gain from a more environmentally responsible stance, but also will be able to conduct more tests in less time.

This also was the first DARHT hydrotest to utilize a unique "Bucky Grid" camera system. This camera system significantly improves the quality of the radiographic data and enhances the ability to perform quantitative radiographic analysis. Simple Bucky Grids already are used in medical X-ray imaging, and are basically devices that produce highly parallel beams of X-rays--thereby reducing scatter and improving image quality.

Hydrodynamic tests are high-explosives-driven experiments that produce radiographs and other data from implosions of mock nuclear weapons components that are used to confirm, support, and inform computer models and weapons codes.

This experiment involved DARHT's highly reliable first axis, an electron beam accelerator used to create a single pulse of high-energy X-rays. The facility's second axis will undergo full energy commissioning later this summer, and is designed to produce a four-pulse beam of X-rays at a 90 degree angle from axis one, allowing scientists to capture short movies of experimental implosions and to create three dimensional images. Axis two is scheduled for completion in 2008.

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