Introduction

In 1992, the President of the United States

placed a moratorium on underground nuclear

weapons testing. As a result, alternate 

experimental methods for certifying the nation’s

nuclear weapons stockpile were implemented.

Among these experimental methods was the

Joint Actinide Shock Physics Experimental

Research (JASPER) Facility, located at the

Nevada Test Site. JASPER plays an integral

role in the certification of the nation's nuclear

weapons stockpile by providing a method to

generate and measure data pertaining to the

properties of materials (radioactive chemical

elements) at high shock pressures, 

temperatures and strain rates. These extreme

laboratory conditions approximate those 

experienced in nuclear weapons. Data from the

experiments is used to determine material

equations-of-state and to validate computer

models of material response for weapons 

applications. Experiment results are used for

code refinement, permitting better predictive

capability and ensuring confidence in the U.S.

nuclear stockpile.

Background

The Joint Actinide Shock Physics Experimental

Research (JASPER) Facility is a 

multi-organizational research facility hosting

Lawrence Livermore National Laboratory

(LLNL), Los Alamos National Laboratory, Sandia National Laboratories, the U.S. Department of

Energy’s National Nuclear Security Administration and National Security Technologies LLC. Lawrence

Livermore National Laboratory maintains the responsibility for overall project management, physics

definition, engineering, health and safety.

How It Works

JASPER experiments support the Stockpile Stewardship Program in several ways complementing 

subcritical experiments conducted at the Nevada Test Site. To achieve the high shock pressures, 

temperatures, and strain rates similar to that of a nuclear weapon, JASPER experiments utilize a 

two-stage gas gun.

The JASPER two-stage gas gun.

The JASPER gas gun chamber.

Secondary

confinement 

chamber

Primary 

target 

chamber
The basic concept of a gas gun is to propel a projectile into a target at extremely high velocities, often

exceeding eight kilometers per second. The JASPER gas gun is specifically designed to conduct

research on plutonium and other surrogate materials as targets.

The two-stage gas gun consists of a first-stage breech containing gunpowder and a pump tube filled

with hydrogen gas; and a second-stage evacuated barrel for guiding the high-velocity projectile to a

target containing radioactive material. Hot gases from the burning propellant drive a heavy piston

down the pump tube, compressing the gas. At sufficiently high pressures, the gas eventually breaks a

rupture valve and enters the narrow barrel, propelling a projectile, housed in the barrel, toward the 

target.

When the projectile hits the target, it produces a high-pressure shock wave. In a fraction of a

microsecond, the shock wave reverberates through the target. Diagnostic equipment, triggered by the

initial wave, measures the properties of the shocked material inside the target during this extremely

brief period. The target is disintegrated by the impact of the projectile and contained within the primary

confinement chamber. A second confinement chamber protects workers as a safety precaution in the

unlikely event that the primary system fails. The data from these experiments is used by the national

laboratories to further refine the computer codes used to certify the U.S. nuclear stockpile

Conclusion

Because of the well-controlled environment of the gas gun, JASPER provides scientists with more 

precise equation-of-state data than can be obtained from conventional, high-explosive experiments.

Nested confinement systems assure that radioactive materials are not released into the gas gun 

building or the environment after target impact. The primary target chamber houses the target 

material, and an ultra-fast closure valve system traps radioactive contaminants within the chamber

after the projectile enters. A secondary confinement chamber assures that if any material escapes

from the primary target chamber, it will not migrate into the building environment.

Pump tube

Piston

Hydrogen gas

Projectile

Primary target 

chamber

Target

Rupture valve

(open) Secondary confinement

chamber

Hot gases

A diagram of the JASPER two-stage gas gun.

Breech

For more information, contact:

U.S. Department of Energy

National Nuclear Security Administration

Nevada Site Office

Office of Public Affairs

P.O. Box 98518

Las Vegas, NV 89193-8518

phone: 702-295-3521

fax: 702-295-0154

email: nevada@nv.doe.gov

http://www.nv.doe.gov

DOE/NV - -1015

September 2004