The Joint Actinide Shock Physics Experimental Research (JASPER) facility recently surpassed 200 full-containment experimental shots, marking more than two decades of precision operations, scientific advancement and collaboration in support of the National Nuclear Security Administration's (NNSA) stockpile modernization programs.
Since its first actinide experiment in 2003, JASPER, operated jointly by Lawrence Livermore National Laboratory (LLNL) and the Nevada National Security Sites (NNSS), has played a central role in advancing understanding of plutonium under extreme conditions. Data from its experiments help refine models that ensure the safety, reliability and performance of the U.S. nuclear deterrent.
"JASPER is one of only two impact launchers in the United States where we can study the dynamic properties of plutonium, and the only one capable of reaching the extreme pressures required for these studies," said David Bober, LLNL's JASPER experimental team leader. "Our ability to execute this work safely and precisely for more than 22 years has produced a vast body of high-quality data that the stockpile modernization community depends on."
When JASPER was first proposed in the late 1990s, conducting gun experiments on plutonium inside a fully contained chamber was still considered ambitious. Physicist Neil Holmes, who helped conceive and guide the project, played a key role in making it a reality.
"After more than 200 shots, we tend to view JASPER operations as routine, but try to imagine being in the room when it was first proposed or in the program's early development," Bober said.
To date, JASPER has completed 201 full-containment experiments: 92 using actinide materials and 109 non-actinide developmental shots. Its 65-foot, two-stage gas gun propels projectiles up to 8 kilometers per second, or about 18,000 miles per hour, creating pressures millions of times greater than atmospheric pressure for less than a microsecond. These experiments reveal how plutonium and other dense, radioactive materials respond to shock compression.
JASPER experiments address a range of objectives central to maintaining and modernizing the nation's stockpile. Certification experiments assess the behavior of newly manufactured plutonium material, including those supporting the W87-1 Modification Program, to help validate the performance of modern warhead components. Non-actinide "confirmatory" experiments use surrogate materials to validate experimental methods and diagnostics under the same extreme conditions applied in plutonium studies. Aging experiments examine how plutonium changes over time, providing critical data for assessing legacy materials.
Over its history, JASPER researchers have built a detailed experimental record using carefully characterized reference materials and high-precision laser and X-ray diagnostics. This data serves as a benchmark for new studies and enables scientists to compare aged plutonium from surveillance operations with newly produced material from the PF-4 pit production facility at Los Alamos National Laboratory. These comparisons help verify the quality of new material for future deterrent systems.
Precision science and evolving capability
Nathan Barton, who leads research integration for JASPER, said surpassing the 200-shot mark is less about the number than what it represents.
"It reflects a long-term culture of reliability, repeatability and scientific excellence," he said. "We're measuring things about plutonium that have never been measured before, and those data directly inform our models. Every shot strengthens our predictive capability and our confidence in the stockpile."
Barton explained that the program's capabilities have expanded well beyond the Hugoniot measurements for which the facility was originally designed.
"The program continues to adapt to new questions, and that evolution is what keeps JASPER relevant today," he said. Early work focused on generating and quantifying specific thermodynamic states, but today JASPER supports a broader range of dynamic materials science, including temperature, strength and release-wave studies.
Ricky Chau, JASPER's execution lead, said the facility's continued success reflects its ability to evolve.
"JASPER was originally designed to collect one type of data, and that initial campaign met its goals years ago," he said. "Now we're well beyond that original mission and continuing to expand into new kinds of experiments the program couldn't have envisioned two decades ago."
He credited the facility's precision and longevity to a culture of rigor and teamwork.
"We have the lowest error bars, and people actually believe our error bars," Chau said. "Every time we close the loop with the workforce, and they see how their data mattered to the nation, you can see the pride. That's why we do it."
Partnership and progress ahead
JASPER's nested confinement systems, a primary target chamber sealed by an ultrafast closure valve within a secondary steel vessel, ensure safety and environmental protection during each experiment. The facility's design, location and operational discipline have enabled more than 20 years of secure, fully contained plutonium experiments.
The program also reflects a lasting partnership between LLNL and NNSS. Livermore scientists lead the experimental design, diagnostics and data analysis, while NNSS helps operate and maintain the gas gun facility, manages many of the diagnostics systems and oversees post-shot waste handling.
"Each shot is a choreographed, multi-organization effort, and that partnership is a big part of why JASPER keeps delivering," Bober said.
As JASPER moves beyond its 200th shot, the facility remains a cornerstone of science-based stockpile modernization - reliable, precise and continually evolving. New diagnostic tools and experimental campaigns keep it at the forefront of high-pressure research.
"We're fielding experiments that use more diagnostics and more sophisticated systems than ever before," Chau said. "Each one expands what we're able to measure and deepens our understanding of plutonium."
