NNSA Reveals Quiet Contributions of Cygnus: A Dual Beam X-Ray Source for Radiography

Success provided significant benefits to the science-based stockpile stewardship mission focused on validating new 3-D ASC Models that will ultimately assess the reliability and performance of the U.S. nuclear weapons stockpile without nuclear testing.

November 17, 2009

The National Nuclear Security Administration (NNSA) recently celebrated a milestone quietly achieved at the Nevada Test Site (NTS). The dual beam Cygnus X-Ray source system completed its 1000th shot during the Barolo and Bacchus Subcritical Experiments (SCE). These are the latest in a series of experiments at NTS initiated in 1997 to gain data on the dynamic properties of plutonium and sample other special nuclear material.

Although a moratorium ended nuclear testing at the NTS in 1992, underground experiments still are conducted using highly-scientific equipment to measure reactions to weapons-grade plutonium as part of the nation’s Stockpile Stewardship program. The design intent of Cygnus was to provide the dual beam pulse powered penetrating flash x-ray source required to radiograph the Armando Subcritical Experiment in 2004. The radiographic results of the dynamic test were stunning, and it became clear to scientists that the dual Cygnus sources could prove very useful to the science-based stockpile stewardship mission.

As early as 2001, the need for a penetrating dual x-ray source came to the forefront, and NNSA teamed with Sandia National Laboratory, Naval Research Laboratory (NRL), and Los Alamos National Laboratory (LANL), NTS, and L-3 Pulse Sciences (L-3) to acquire Cygnus. These collaborators accomplished the design, fabrication, and testing of Cygnus-1 and 2 respectively at LANL and L-3. After proving sufficient dose and refining spot size, each x-ray source was relocated and integrated into the U1a Complex at NTS.

Initially, Cygnus was designed assuming a life cycle of only a couple hundred shots. But the collaborators developed a meticulous maintenance and operations protocol to sustain x-ray source integrity for future experimenters, leading to the successful milestone of 1,000 shots.

The difficulty of maintaining source integrity becomes clear with an outline of the architecture of Cygnus. Cygnus begins with state-of-the-art Process Controls allowing operation, monitoring, and cycling of the several subsystems; such capability requires highly-experienced operators and staff. The Data Acquisition and Triggering system requires dozens of specialized voltage/current monitors that feed into four racks of digitizers and digital trigger generators.

Cygnus has become an essential element to a long list of successful experiments i.e., Armando, Step Wedge, Thermos, Odyssey, and now Barolo and Bacchus, with even more experiments being planned. “Cygnus is a great NNSA investment and multi-agency success story highlighting the working relationships between NNSA, National Laboratories, the NTS M&O – National Security Technologies (NSTec), and private industry,” said Raffi Papazian, Missions and Projects Division manager for NSTec.

The Cygnus Dual Beam Radiography System remains quite viable and available for future experiments and research. The system continues to be the subject of published research on pulsed power, x-ray source characterization, and radiography. Cygnus is named after the famous x-ray emitting binary star formation in the constellation of the Swan. With proper attention the Cygnus swan song can be significantly delayed. Cygnus has potential to become a National User Facility.

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The Cygnus team: Front Row – Gene Ormond (Sandia), Mark Hanson (NSTec), Doug Good (NSTec), Dale Cain (LLNL), Dan Nelson (Sandia), John Smith (LLNL), David Henderson (NSTec); Back Row, Gilbert Peralta Jr. (NSTec), Monty Larson (NSTec), Vance Mitton (NSTec), Isidro Molina (Sandia), Michael Burke (Sandia).