A Polywell Fusion Reactor Designed for Net Power Generation
Joel G. Rogers
Published online: 1 December 2017
Ó Springer Science+Business Media, LLC, part of Springer Nature 2017
A brief history of Polywell progress is recounted. The present PIC simulation explains why the most recent Polywell fusion
reactor failed to produce fusion energy. Synchronized variations of multiple parameters would require DC power supplies,
not available in historic model testing. Even with DC power, the simulation showed that the trapping of cold electrons
would ruin plasma stability during start-up. A theoretical solution to this trapping problem was found in Russian literature
describing diocotron-pumping of electrons out of a plasma trap at Kharkov Institute. In Polywell, diocotron-pumping
required matching the depth of the potential-well to the electron-beam current falling on a special aperture installed in one
of the electromagnets. With diocotron-pumping the reactor was simulated to reach steady-state, maximum-power operation
in a few milliseconds of simulated time. These improvements, validated in simulating small-scale DD reactors, were scaled
up by a factor of 30 to simulate a large, net-power reactor burning p ?
B fuel. Power-balance was estimated from a
textbook formula for fusion power density by numerically integrating the power density. Unity power-balance required the
size of the p ?
B reactor to be somewhat larger than ITER.
Keywords Polywell fusion power reactor Á Scale-model testing Á Particle-in-cell (PIC) plasma simulation Á
Polywell continues to show promise as a design for fusion
power production. Scale model reactors of the Polywell
design have been built and tested in the Energy Matter
Conversion Company (EMC2), founded in 1987 by Poly-
well’s inventor, Dr. Robert W. Bussard. Table 1 summa-
rizes Polywell progress since the founding of the company.
Over the years that EMC2 was in operation, many
generations of scale-model Polywell reactors were
designed, built, and tested. The latest of these, named WB-
8, was designed to produce more fusion energy than its
predecessors, WB-6 and WB-7, which had already pro-
duced record levels of fusion output energy. For reasons
not fully explained, WB-8 produced no fusion energy at all.
After the failure of WB-8, EMC2 abandoned the Polywell
principle in favor of a new experimental design . The
new design omitted the high voltage bias on the magnets,
an essential feature of Bussard’s designs. This latest
‘‘Polywell’’ relies on high energy plasma injection instead
of high voltage electron beams for heating the plasma.
Without the bias on the magnets, the cusp losses of elec-
trons are expected to be impractically large.
Following a ﬁnal report from the Company’s CEO in
2014 , no further experimental work on Polywell has
been reported. Theoretical work has continued on several
fronts [7, 8, 10]. The additional theoretical analysis
reported here seeks to answer the following three ques-
tions: (1) What went wrong with the testing of model
reactor WB-8 that prevented it from producing energy? (2)
What new design features could be added to produce
energy from DD model reactors? (3) What are the pro-
spects for a net power, aneutronic reactor burning proton-
plus-boron (p ?
Particle-in-cell (PIC) simulation  is the most rigor-
ous method available for analysis of plasma conﬁnement
devices. The computer code used in this work is OOPIC
Pro, a commercial version  of a software program
developed over several decades at Berkeley . A public-
domain version of the software, called XOOPIC, is cur-
rently available from the University of Michigan .
& Joel G. Rogers
Journal of Fusion Energy (2018) 37:1–20