The leader of a proposed compact fusion reactor project says that Lockheed Martin’s decision to lift the lid on its secret effort is an attempt to build a scientific team and find partners.

Speaking yesterday at a press conference at the company’s facility in Palmdale, California, Tom McGuire defended the project’s scientific merits: “We think we’ve invented something that is inherently stable,” McGuire told reporters. But he acknowledged that “we are very early in the scientific process.” He said he has been working with a team of five to 10 people for the past 4 years and hopes to expand the team now that the project is in the open.

He said that their magnetic confinement concept combined elements from several earlier approaches. The core of the device uses cusp confinement, a sort of magnetic trap in which particles that try to escape are pushed back by rounded, pillowlike magnetic fields. Cusp devices were investigated in the 1960s and 1970s but were largely abandoned because particles leak out through gaps between the various magnetic fields leading to a loss of temperature. McGuire says they get around this problem by encapsulating the cusp device inside a magnetic mirror device, a different sort of confinement technique. Cylindrical in shape, it uses a magnetic field to restrict particles to movement along its axis. Extra-strong fields at the ends of the machine—magnetic mirrors—prevent the particles from escaping. Mirror devices were also extensively studied last century, culminating in the 54-meter-long Mirror Fusion Test Facility B (MFTF-B) at Lawrence Livermore National Laboratory in California. In 1986, MFTF-B was completed at a cost of $372 million but, for budgetary reasons, was never turned on.

Another technique the team is using to counter particle losses from cusp confinement is recirculation. “We recapture the flow of particles and route it back into the device,” McGuire said. The team has built its first machine and has carried out 200 shots during commissioning and applied up to 1 kilowatt of heating, but McGuire declined to detail any measurements of plasma temperature, density, or confinement time—the key parameters for a fusion plasma—but said the plasma appeared very stable. He said they would be ramping up heating over the coming months and would publish results next year.

McGuire acknowledged the need for shielding against neutrons for the magnet coils positioned inside the reactor vessel. He estimates that between 80 and 150 centimeters of shielding would be needed, but this can be accommodated in their compact design. Researchers contacted by ScienceInsider say that it is difficult to estimate the final size of the machine without more knowledge of its design. Lockheed has said its goal is a machine 7 meters across, but some estimates had suggested that the required shielding would make it considerably larger.