Apr 2, 2007

Los Alamos scientist: X-ray machine right on schedule

April 2, 2007

LOS ALAMOS, N.M. (AP) _ A Los Alamos National Laboratory scientist leading a team in rebuilding an X-ray machine aimed at checking the reliability of nuclear weapons says it should be operational before its first full-fledged test next year.

The Dual Axis Radiographic Hydrotest facility, better known as DAHRT, was completed in 2003, but scientists discovered part of the machine did not work.

The machine, which had not been tested at full power, failed under the tremendous voltages required to generate an X-ray pulse powerful enough to make a four-frame movie of the dense metal at the heart of an exploding mock nuclear bomb.

Ray Scarpetti said he and his team have rebuilt the parts that failed and tested them to the breaking point. An independent review commissioned by the federal government recently concluded that there is ''high confidence'' the fix will work.

The machine cost more than $300 million to build. Another $90 million has gone into fixing the problems that have prevented it from fully working.

The machine is being rebuilt in the accelerator hall of the lab's DAHRT building. At the back end of the hall, a device fires a burst of electrons. They pass down the middle of a row of giant doughnut-shaped, high-voltage cells that accelerate the electrons to close to the speed of light.

It is those 17,000-pound cells that failed the first time around. Scarpetti's crew has lined up 26 of the new cells and fired an electron beam down the middle to test them. The crew also pushed them to 15 percent more voltage than they were designed for, to make sure the failure that doomed their performance in 2003 has been fixed, Scarpetti said.

The rest of the 74 doughnut-shaped cells should be installed by this summer, giving Scarpetti and his team time to adjust the X-ray machine's performance before it's tested next year.

''It's really just a matter of tweaking,'' he said. ''We know it's going to work.''

[View the JASON report on DARHT here.]

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