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UWFDM-1303 Performance of a Low-Pressure, Helicon Driven IEC 3He Fusion Device WISCONSIN
FU
SI
ON
T
EC
HNOLOGY INSTITUTE
F U S I O N T E C H N O L O G Y I N S T I T U T E
U N I V E R S I T Y O F W I S C O N S I N
M A D I S O N W I S C O N S I N
Performance of a Low-Pressure, Helicon Driven
IEC
3
He Fusion Device
Gregory R. Piefer
December 2006
UWFDM-1303
Ph.D. thesis. Performance of a Low-Pressure, Helicon
Driven IEC
3
He Fusion Device
Gregory R. Piefer
Fusion Technology Institute
University of Wisconsin
1500 Engineering Drive
Madison, WI 53706
http://fti.neep.wisc.edu
December 2006
UWFDM-1303
Ph.D. thesis. Performance of a Low-Pressure, Helicon Driven IEC
3
He Fusion
Device



by

Gregory R. Piefer





A dissertation submitted in partial fulfillment of

the requirements for the degree of





Doctor of Philosophy

(Nuclear Engineering & Engineering Physics)




at the

UNIVERSITY OF WISCONSIN-MADISON

2006
i

Abstract


The study of the
3
He(
3
He,2p)
4
He fusion reaction is interesting for many reasons
ranging from nuclear physics to astrophysics to fusion energy. While this reaction has
been studied in particle accelerators, its behavior at low energy ( < 1 MeV) is not fully
characterized due to low accelerator beam currents (< 1 mA) and the low reaction
cross-section. The spherical recirculation of ions in an Inertial Electrostatic Confinement
(IEC) device offers the potential to explore these reactions at sub MeV energy levels, but
with ion currents as high as 100 mA or more. Such a capability would improve counting
statistics tremendously, and be a valuable tool for characterizing this reaction at these low
energies.
This dissertation focuses on the development of an IEC device toward this end,
with the final goal of detecting
3
He(
3
He,2p)
4
He reactions. Many facets of IEC
technology were enhanced to accomplish this, and these enhancements will also play a
major role in the development of IEC devices for near-term applications.

Some of the major enhancements at the University of Wisconsin IEC facility
were:
1.

the maximum operating voltage was increased from 55 kV to 170 kV
2.

the lifetime of insulators was increased from about 1 month to 6 months
3.

a gas recycle system was developed that allowed the reuse of
3
He gas after it flowed
through the system
4.

a helicon ion source was developed that allowed operation at 1/3 the previous
minimum pressure with seven times the current
5.

the same helicon ion source was developed to give independent control over the ion
current
6.

a proton detection system was developed that reduced the noise level in the detection
system by two orders of magnitude.

ii

These developments allowed for the detection of
3
He(
3
He,2p)
4
He reactions at the
rates of 144
± 44 reactions / sec at 124 kV, and 400 ± 67 reactions / sec at 134 kV, with a
maximum total reactivity of 1.1 * 10
3
reactions / sec. These results agree to within 50%
of the theoretical prediction from the combination of beam-background and beam-
embedded fusion, and represent the first time that
3
He-
3
He reactions have been observed
in an IEC device.
iii
Acknowledgements


Through the years spent on this work, there have been many people who have
played roles in shaping the work presented in this dissertation. Some of them have also
played a role in shaping my life, and I would very much like to thank them for their
influence.

I would like to issue a special thanks to Professor Gerald Kulcinski, for believing
in me since the day I first came to ask him about graduate school. He has had a profound
impact on my work, as well as my development as a scientist and a person. He taught by
instruction and by example, and my life would be quite different if I had chosen another
path. I would not have it any other way.

I extend my thanks also to John Santarius, who is quite possibly the most well
informed person in our field that I know. In addition to teaching me an uncountable
number of scientific methods, John taught me never to jump to conclusions, and to
always view things with a sense of humor. I would also like to thank John for his
patience and understanding when I would become too convinced by the wrong ideas.

Another person who played a key role in this work was Robert Ashley. I would
like to thank Bob for always being supportive, especially when it seemed things were so
bad I felt like quitting. He taught me never to give up, but just to step back and take a
deep breath when it looked like things couldnt get worse.

Id like to thank Harrison Schmitt, for being an inspiration to me. Hes been an
amazing person to work with, and his support can make one believe in even the most
impossible dreams. I am so grateful for this, and will always try to keep dreaming.
iv

Id like to thank Professor Noah Hershkowitz, for giving me the insights and
advice I needed to finish my work. His expertise is immense, and his enthusiasm for
teaching young minds unparalleled.

This work could not have been accomplished without the help of my fellow
students. Id like to thank Ross Radel, who has been with me from the beginning. Hes
been a great friend and co-worker and helped me get through it all. Id also like to say a
thank you to the other students who helped with wonderful ideas and endless hard work.
John Weidner, Ben Cipiti, Alex Wehmeyer, Tracy Radel, Kunihiko Tomiyasu, Krupaker
M. Subramanian, Dave Boris, Thad Heltemes, Brian Egle, Eric Alderson, Sam Zenobia,
and Chris Seyfert, thanks for everything, both the good times and the amazing work.

The staff of the FTI, particularly Joan-Welc Lepain and Dennis Bruggink have
been very helpful and even better become great friends. They have been instrumental in
making things happen, and I am grateful to have worked with them.

A special thanks goes out to Greg Winz and Paul Nonn, experts not associated
with our group who provided a tremendous amount of help out of love for the field.
When I didnt know how to do something, odds are they could come up with something
and I am glad they were there when those times came around.

Last, but probably most importantly, Id like to thank my family; my sisters
Kristin and Karen, and my brother Mark for always being there for me; and most
importantly my parents, Rick and Judy. They have given me all the opportunities I now
have, and made me open as many doors as I could. For believing in me, especially when
some said I could never do it, I owe them everything. I could not have asked for a better
family.
v

Finally, I would like to offer my thanks to the groups that have funded my work.
Without the generous support of the Grainger Foundation, Wilson Greatbatch, the
University of Wisconsin, and the Department of energy, this dissertation would not have
been possible. Their dedication to research and the advancement of mankind is without
question, and their support moves us all forward.
vi
Table of Contents
Abstract................................................................................................................................ i
Acknowledgements............................................................................................................. iii
Table of Contents ................................................................................................................vi
Table of Figures..................................................................................................................xi
Table of Tables...................................................................................................................xv
Chapter I Introduction......................................................................................................1
I.A
References................................................................................................................6
Chapter II Conceptual Approach ....................................................................................7
II.A
References ............................................................................................................10
Chapter III Previous Work.............................................................................................12
III.A
IEC ......................................................................................................................12
III.A.1
Summary ....................................................................................................12
III.A.2
Discussion ..................................................................................................17
III.B
3
He-
3
He Reaction Studies................................................................................... 18
III.C
References ...........................................................................................................20
Chapter IV IEC Theory ..................................................................................................23