40 × 12 cm

Largest sample size

supported by MPEX 

10 MW/m2

Heat flux produced, similar

to what spacecraft

experience reentering

Earth's atmosphere

2.5 T

Magnetic field can

be reached in

MPEX

•

~30,000,000°C

Temperature fusion

materials will need to

withstand

MPEX: Materials Plasma 

Exposure eXperiment

OAK RIDGE NATIONAL LABORATORY

Oak Ridge National Laboratory's (ORNL's) Materials Plasma Exposure eXperiment (MPEX) 

is a next-generation linear plasma device that will advance research on the way plasma 

interactions with materials and components needed for future fusion reactors.

Generating fusion energy requires heating 

subatomic particles to temperatures 

hotter than the center of the sun and 

containing them in magnetic fields 

hundreds of thousands of times stronger 

than the Earth’s. When these particles 

escape the magnetic field and are incident 

on surrounding materials, the resulting 

interactions can change their structure 

entirely. 

Currently, only a few linear plasma 

devices are able to expose neutronactivated materials. Other devices cannot 

reach extreme plasma temperatures 

nor separately control electron and ion 

temperatures. MPEX will have all these 

capabilities, making it integral to efforts to 

prepare materials for a fusion pilot plant 

and ultimately for fusion power plants.

The project has awarded contracts for 

long-lead procurements and the facility 

is being prepared for installation. Device 

assembly is projected to begin in 2023.

“MPEX is expected to exceed the conditions of any current device. 

It can go all the way to fluence levels in DEMO—the machine after 

ITER—which are relevant for a prototype fusion reactor.”

 —MPEX Project Director Phil Ferguson

The prototype of the Materials Plasma Exposure 

eXperiment (Proto–MPEX) explores plasma–material 

interactions under conditions similar to those on the 

sun's surface.
CONTACT:

Phil Ferguson

MPEX Project Director

fergusonpd@ornl.gov

865-241-5702

One Bethel Valley Road

Oak Ridge, TN 37831

www.ornl.gov

Oak Ridge National Laboratory is managed by UT-Battelle LLC for the US Department of Energy January 2023

A New Breed of Fusion 

Materials

MPEX will advance the science of plasma–material interactions (PMI), 

which is essential for a viable path to fusion energy. ORNL brings to 

this challenge a long history of materials science leadership and the 

largest US effort in fusion materials. 

Currently, no plasma-facing materials and components are qualified 

for fusion reactors. Such materials will need to be strong enough 

to withstand the harsh radiation and erosion conditions of steadystate fusion reactors running over a long period of time with hightemperature environments and high ion and neutron fluences.

Hot Target 

Using MPEX, scientists will strive to advance the science of PMI and 

the technology of plasma-facing components for fusion reactors. MPEX will also enable researchers to understand how extreme 

conditions affect the divertor—considered the power and particle exhaust system of a fusion reactor—along its length. To achieve 

these goals, MPEX is being developed in collaboration with ORNL’s capabilities in plasma physics, radio frequency heating, and high heat 

flux engineering. 

Collaboration at Its Finest 

ORNL resources and expertise will help MPEX deliver high-impact science. Potential plasma-facing material samples will be exposed in 

ORNL’s High Flux Isotope Reactor to relevant neutron damage before cooldown and transfer for subsequent plasma exposure in MPEX. 

By pairing these facilities, ORNL has a unique opportunity to simulate fusion reactor conditions.

The Oak Ridge Leadership Computing Facility’s high-performance computing capabilities will also be particularly important during this 

process because it will be used to model MPEX performance and analyze surfaces of materials exposed to high-fluence MPEX plasmas.

ORNL also will initiate collaborative PMI research collaborations with other partners to study the effects of radiation damage and to 

develop diagnostic capabilities.

Proto-MPEX officially completed its research operations in 2021, after almost 

7 years of service and delivering multiple first-of-a-kind demonstrations key 

for MPEX success.