Nuclear fusion with polarized fuel

Springer Proceedings in Physics 187

Giuseppe Ciullo
Ralf Engels
Markus Büscher
Alexander Vasilyev Editors

Nuclear
Fusion with
Polarized
Fuel


Springer Proceedings in Physics
Volume 187


The series Springer Proceedings in Physics, founded in 1984, is devoted to timely
reports of state-of-the-art developments in physics and related sciences. Typically
based on material presented at conferences, workshops and similar scientific
meetings, volumes published in this series will constitute a comprehensive
up-to-date source of reference on a field or subfield of relevance in contemporary
physics. Proposals must include the following:
–
–
–
–
–

name, place and date of the scientific meeting
a link to the committees (local organization, international advisors etc.)

scientific description of the meeting
list of invited/plenary speakers
an estimate of the planned proceedings book parameters (number of
pages/articles, requested number of bulk copies, submission deadline).

More information about this series at />

Giuseppe Ciullo Ralf Engels
Markus Büscher Alexander Vasilyev
•

•

Editors

Nuclear Fusion
with Polarized Fuel

123


Editors
Giuseppe Ciullo
Dipartimento di Fisica e Scienze della Terra
Polo Scientifico e Tecnologico
Ferrara
Italy

Markus Büscher
Forschungszentrum Jülich

Peter Grünberg Institute
Jülich
Germany

Ralf Engels
Forschungszentrum Jülich
Institute for Nuclear Physics
Jülich
Germany

Alexander Vasilyev
National Research Centre “Kurchatov
Institute”
Gatchina
Russia

ISSN 0930-8989
Springer Proceedings in Physics
ISBN 978-3-319-39470-1
DOI 10.1007/978-3-319-39471-8

ISSN 1867-4941

(electronic)

ISBN 978-3-319-39471-8

(eBook)

Library of Congress Control Number: 2016942029

© Springer International Publishing Switzerland 2016
This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part
of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,
recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission
or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar
methodology now known or hereafter developed.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this
publication does not imply, even in the absence of a specific statement, that such names are exempt from
the relevant protective laws and regulations and therefore free for general use.
The publisher, the authors and the editors are safe to assume that the advice and information in this
book are believed to be true and accurate at the date of publication. Neither the publisher nor the
authors or the editors give a warranty, express or implied, with respect to the material contained herein or
for any errors or omissions that may have been made.
Printed on acid-free paper
This Springer imprint is published by Springer Nature
The registered company is Springer International Publishing AG Switzerland


Foreword

Energy in a wider sense is what drives human efforts to ensure not only survival of
a growing world population, but survival under human conditions. Especially, as
long as the population growth cannot be contained, this inevitably means a growing
energy demand for a long time on a world scale. On the long run limited energy
resources such as coal or hydrocarbons and even fuel for nuclear fission energy
production will be exhausted. Only “sustainable” energies such as from solar and
wind resources, as well as from nuclear fusion with its large amounts of available
fuel, will remain viable options. A host of problems connected with energy production and living under human conditions has not yet been addressed: storage of
energy to maintain its continuous flow, agriculture and production of sufficient food
for all, increase of the amount of partly poisonous waste, climate changes by rising

world temperatures, etc. To all solutions of these interconnected problems, fusion
energy could contribute substantially if realized. An example could be desalination
of seawater to fertilize arid African areas thus preventing large-scale population
migrations. The radioactive waste from fusion processes will not cause unmanageable problems. Despite the admittedly slow progress of approaching the energetic break-even, there is a hope that the different paths towards this goal, magnetic
(“tokamak” or “stellarator”) or inertial (e.g., “laser”) confinement fusion, will be
successful. An old and somewhat forgotten or postponed idea is that with the use of
spin-polarized fuel particles (D, T, and 3He) the yield of the nuclear fusion reactions
could be enhanced, in the cases of the T(d, n)4He and 3He(d, p)4He reactions even
by up to 50 %, thus suggesting, for e.g., a lower break-even threshold and/or lower
required input power. A number of other parameters of the fusion plasma, such as
the emission directions of reaction products, could also be controlled by preparing
the spin states of the fuel particles accordingly. The technologies and the

v


vi

Foreword

understanding of the production of spin-polarized beams or targets have reached a
stage from which promising developments of spin physics towards fusion energy
applications can start. This, however, would require new efforts and resources in the
field. The status of the field and the new ideas have been summarized in this
volume.
Cologne

Prof. Dr. Hans Paetz gen. Schieck

Contents

1

Polarized Fusion: An Idea More Than Thirty Years Old!
What Are We Waiting For? . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Giuseppe Ciullo

2

Spin Physics and Polarized Fusion: Where We Stand . . . . . . . . . .
H. Paetz gen. Schieck

3

The PolFusion Experiment: Measurement of the dd-Fusion
Spin-Dependence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Alexander Vasilyev, L. Kochenda, P. Kravtsov, V. Trofimov,
M. Vznudaev, Giuseppe Ciullo, P. Lenisa, Ralf Engels
and H. Paetz gen. Schieck

4

5

Hyper-Polarized Deuterium Molecules: An Option to Produce
and Store Polarized Fuel for Nuclear Fusion? . . . . . . . . . . . . . . . .
Ralf Engels, G. Farren, K. Grigoryev, M. Mikirtychiants,
F. Rathmann, H. Seyfarth, H. Ströher, L. Kochenda, P. Kravtsov,
V. Trofimov, Alexander Vasilyev, M. Vznudaev

and H. Paetz gen. Schieck
A Polarized 3 He Target for the Exploration of Spin
Effects in Laser-Induced Plasmas . . . . . . . . . . . . . . . . . . . . . . . . .
I. Engin, Markus Büscher, P. Burgmer, K. Dahlhoff, Ralf Engels,
P. Fedorets, H. Feilbach, U. Giesen, H. Glückler, F. Klehr,
G. Kukhalashvili, A. Lehrach, T. Leipold, W. Lesmeister, S. Maier,
B. Nauschütt, J. Pfennings, M. Schmitt, H. Soltner, K. Strathmann,
E. Wiebe and S. Wolf

1
15

35

45

55

6

Relevant Spatial and Time Scales in Tokamaks. . . . . . . . . . . . . . .
F. Bombarda, A. Cardinali and C. Castaldo

69

7

Depolarization of Magnetically Confined Plasmas . . . . . . . . . . . . .
R. Gatto

79

vii


viii

Contents

8

Ion Polarization in Magnetic Fields. . . . . . . . . . . . . . . . . . . . . . . . 107
S. Bartalucci

9

Prospects for Direct In Situ Tests of Polarization Survival
in a Tokamak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
A.M. Sandorfi and A. D’Angelo

10 DD Fusion from Laser Interaction with Polarized HD Targets. . . . 131
J.P. Didelez and C. Deutsch
11 Polarization of Molecules: What We Can Learn
from the Nuclear Physics Efforts?. . . . . . . . . . . . . . . . . . . . . . . . . 139
D.K. Toporkov, D.M. Nikolenko, I.A. Rachek and Yu.V. Shestakov
12 RF Negative Ion Sources and Polarized Ion Sources . . . . . . . . . . . 145
N. Ippolito, F. Taccogna, P. Minelli, V. Variale and N. Colonna
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

Contributors

S. Bartalucci INFN - Laboratori Nazionali di Frascati, Frascati, Rome, Italy
F. Bombarda ENEA, Frascati (Rome), Italy
P. Burgmer Peter Grünberg Institut, Jülich, Germany
Markus Büscher Peter Grünberg Institut, Jülich, Germany; Institut für Laser- und
Plasmaphysik, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany
A. Cardinali ENEA, Frascati (Rome), Italy
C. Castaldo ENEA, Frascati (Rome), Italy
Giuseppe Ciullo Istituto Nazionale di Fisica Nucleare (INFN) of Ferrara and
Physics and Earth Science Department, University of Ferrara, Ferrara, Italy
N. Colonna INFN, Bari, Italy
A. D’Angelo Università di Roma Tor Vergata, Roma, Italy; INFN Sezione di
Roma Tor Vergata, Roma, Italy
K. Dahlhoff Zentralinstitut für Engineering, Elektronik und Analytik, Jülich,
Germany
C. Deutsch LPGP, Université Paris-Sud (UMR-CNRS 8578), Orsay, France
J.P. Didelez IPN, CNRS/IN2P3 & Université Paris-Sud (UMR-CNRS 8608),
Orsay, France
Ralf Engels Institut für Kernphysik, Forschungszentrum Jülich, Julich, Germany
I. Engin Institut für Kernphysik, Jülich, Germany
G. Farren Institut für Kernphysik, Forschungszentrum Jülich, Jülich, Germany
P. Fedorets Institut für Kernphysik, Jülich, Germany

ix


x

Contributors

H. Feilbach Peter Grünberg Institut, Jülich Centre for Neutron Science, Jülich,
Germany
R. Gatto Sapienza University of Rome, Rome, Italy
U. Giesen Zentralinstitut für Engineering, Elektronik und Analytik, Jülich,
Germany
H. Glückler Zentralinstitut für Engineering, Elektronik und Analytik, Jülich,
Germany
K. Grigoryev Physics Institute IIIB, RWTH Aachen University, Aachen,
Germany
N. Ippolito INFN, Bari, Italy
F. Klehr Zentralinstitut für Engineering, Elektronik und Analytik, Jülich,
Germany
L. Kochenda Laboratory of Cryogenic and Superconducting Techniques, National
Research Centre Kurchatov Institute B.P. Konstantinov Petersburg Nuclear Physics
Institute (PNPI), Gatchina, Russia
P. Kravtsov Laboratory of Cryogenic and Superconducting Techniques, National
Research Centre Kurchatov Institute B.P. Konstantinov Petersburg Nuclear Physics
Institute (PNPI), Gatchina, Russia
G. Kukhalashvili Institut für Kernphysik, Jülich, Germany
A. Lehrach Institut für Kernphysik, Jülich, Germany
T. Leipold Peter Grünberg Institut, Jülich Centre for Neutron Science, Jülich,
Germany
P. Lenisa Istituto Nazionale di Fisica Nucleare (INFN) of Ferrara and Physics and
Earth Science Department, University of Ferrara, Ferrara, Italy
W. Lesmeister Zentralinstitut für Engineering, Elektronik und Analytik, Jülich,
Germany
S. Maier Peter Grünberg Institut, Jülich, Germany
M. Mikirtychiants Institut für Kernphysik, Forschungszentrum Jülich, Jülich,
Germany

P. Minelli CNR-NANOTECH, Bari, Italy
B. Nauschütt Peter Grünberg Institut, Jülich, Germany
D.M. Nikolenko Budker Institute of Nuclear Physics, Novosibirsk, Russia
H. Paetz gen. Schieck Institut für Kernphysik, Universität zu Köln, Cologne,
Germany


Contributors

xi

J. Pfennings Zentralinstitut für Engineering, Elektronik und Analytik, Jülich,
Germany
I.A. Rachek Budker Institute of Nuclear Physics, Novosibirsk, Russia
F. Rathmann Institut für Kernphysik, Forschungszentrum Jülich, Jülich, Germany
A.M. Sandorfi Physics Division, Thomas Jefferson National Accelerator Facility,
Newport News, VA, USA
M. Schmitt Zentralinstitut für Engineering, Elektronik und Analytik, Jülich,
Germany
H. Seyfarth Institut für Kernphysik, Forschungszentrum Jülich, Jülich, Germany
Yu.V. Shestakov Budker Institute of Nuclear Physics, Novosibirsk, Russia;
Novosibirsk State University, Novosibirsk, Russia
H. Soltner Zentralinstitut für Engineering, Elektronik und Analytik, Jülich,
Germany
K. Strathmann Peter Grünberg Institut, Jülich, Germany
H. Ströher Institut für Kernphysik, Forschungszentrum Jülich, Jülich, Germany
F. Taccogna CNR-NANOTECH, Bari, Italy
D.K. Toporkov Budker Institute of Nuclear Physics, Novosibirsk, Russia;
Novosibirsk State University, Novosibirsk, Russia
V. Trofimov Laboratory of Cryogenic and Superconducting Techniques, National

Research Centre Kurchatov Institute B.P. Konstantinov Petersburg Nuclear Physics
Institute (PNPI), Gatchina, Russia
V. Variale INFN, Bari, Italy
Alexander Vasilyev Laboratory of Cryogenic and Superconducting Techniques,
National Research Centre Kurchatov Institute B.P. Konstantinov Petersburg
Nuclear Physics Institute (PNPI), Gatchina, Russia
M. Vznudaev Laboratory of Cryogenic and Superconducting Techniques,
National Research Centre Kurchatov Institute B.P. Konstantinov Petersburg
Nuclear Physics Institute (PNPI), Gatchina, Russia
E. Wiebe Zentralinstitut für Engineering, Elektronik und Analytik, Jülich,
Germany
S. Wolf Zentralinstitut für Engineering, Elektronik und Analytik, Jülich, Germany


Acronyms

2DS
ABS
BRP
COP
CPA
DEMO
DWBA
ECR
EMP
ENEA
FTU
GFMC
GPD
GSI

ICF
ICRF
ICRH
IEA
IKP
ILE
INFN
INTOR
IPI
IPNO
ITER
IUCF
JET
KVI
LSP
MCF
MEOP

2 Degree Scenario
Atomic Beam Source
Breit-Rabi Polarimeter
Conference of the Parties
Chirped Pulse Amplification
DEMOnstration power plant
Distorted Waves Born Approximation
Electron Cyclotron Resonance
ElectroMagnetic Pulse
Ente Nazionale per l’Energia Atomica
Frascati Tokamak Upgrade
Green’s Function Monte Carlo

Gas Discharge Polymer
Gesellschaft für SchwerIonenforschung
Inertial Confinement Fusion
Ion Cyclotron Resonance Frequency
Ion Cyclotron Resonance Heating
International Energy Agency
Institut für KernPhysik
Institute of Laser Engineering
Istituto Nazionale di Fisica Nucleare
INternational TOkamak Reactor
IGNITOR Pellet Injection
Institute de Physique Nucléaire Orsay
International Thermonuclear Experimental Reactor
Indiana University Cyclotron Facility
Joint European Torus
Kernfysisch Versneller Instituut
Lamb-Shift Polarimeter
Magnetic Confinement Fusion
Metastability Exchange Optical Pumping
xiii


xiv

MHD
MRI
NCSM
PHELIX
PNPI
POLAF

POLIS
PST(P)
QSF
RCNP
RF–ICP
RGM
RHIC
SEOP
TFTR

Acronyms

Magneto HydroDynamics
Magnetic Resonance Imaging
No-Core Shell Model
Petawatt High-Energy Laser for Heavy Ion EXperiments
Pietersburg Nuclear Physics Institute
POlarization in LAser Fusion
POLarized Ion Source
Polarized Source, Targets (and Polarimetry)
Quintet Suppression Factor
Research Center for Nuclear Physics
Radio Frequency Inductively Coupled Plasma
Resonating Group Method
Relativistic Heavy Ion Collider
Spin Exchange Optical Pumping
Tokamak Fusion Test Reactor


Chapter 1

Polarized Fusion: An Idea More
Than Thirty Years Old! What
Are We Waiting For?
Giuseppe Ciullo

Abstract The present status of the fusion research is strictly connected to government investments on the corresponding research projects like ITER, or the proposed
IGNITOR and DEMO reactors. The production of energy by nuclear fusion is a perfect option that could give “breath” to the planet. Recent agreements on limiting the
global climate change and plans for our future life on the planet require the reduction of energy production by carbon-based resources. But even the use of nuclear
resources by fission implicates a non negligible risk for our civilization, either by
disasters like in Chernobyl or in Fukushima, or by the release of the fission products
into environment. CO2 emissions into the atmosphere and the growing and developing population urgently require to put more effort into fusion programs worldwide.
An additional option for any fusion program could be the use of polarized fuel. It
still requires intense effort on the development of the necessary technologies, but it
is a realistic option to increase the energy output of different types of fusion reactors
and to increase the cost efficiency. First of all we would like to give an overview on
the current situation in energy production and recent climate development. Secondly,
we would like to provide an introduction to the contents of this volume, devoted to
nuclear fusion using polarized fuels.

1.1 The Climate Policy Paradigma
The population growth has always been and is still driving the energy demand,
along with economic and social developments. More comfortable lifestyles lead to
increased (electrical) energy consumption as observed in the growing and developing
countries. The increasing energy demand is mainly satisfied due to exploitation of
coal and other fossil fuels. The world energy report from 2013 [1] issued by the
World Energy Council (WEC) analyzed the situation from 1993–2011 and provided
forecasts for 2020.
G. Ciullo (B)
Istituto Nazionale di Fisica Nucleare (INFN) of Ferrara and Physics and Earth Science

Department, University of Ferrara, Via Saragat 1, 44122 Ferrara, Italy
e-mail:
© Springer International Publishing Switzerland 2016
G. Ciullo et al. (eds.), Nuclear Fusion with Polarized Fuel,
Springer Proceedings in Physics 187, DOI 10.1007/978-3-319-39471-8_1

1


2

G. Ciullo

From 1993 to 2011 the global population growth was 27 %, the Total Primary
Energy Supply (TPES) usage increased in the same period by 48 % while the electric
energy production is increases by 75 %. As a result the total CO2 emission has
increased by 44 %.
Current forecast on expected CO2 emissions are dramatic, though considering an
increase in usage of renewable resources (except hydropower resources) of 300 %
(from 1993 to 2011 it increased by 1000 %), the CO2 emissions are still expected
to increase by 40 % in comparison to 2011. The behavior of the global temperature
on earth surface and emission of the CO2 and other GreenHouse Gases (GHGs) into
the atmosphere (Fig. 1.1) are strictly related. The correlation is also confirmed by
paleo-climate studies [2]. The renewable energy production in the year 2011 was 1/8
of the hydropower production and is expected to reach 1/2 in the year 2020. Forecasts
for hydro and nuclear energy production predict an increase by 18 and 58 % with
respect to 2011, so that both will reach the same absolute level.
Renewable resources have their own problems like periodicity, they require large
investments in grid connection, and still the possibilities to store large amounts of
the produced electric power are missing. In parallel, the WEC demands reduction

of government subsidies for fossil fuels, as even the forecasts will not be fulfilled
without reducing the attraction of conventional power generation. One should also
note that this forecast, which can be considered an optimistic outlook, still predicts an
increase. Figure 1.1 shows the annual temperature difference and averaged difference
over a period of five years with respect to the average temperature of the period from
1951–1980. Nine out of ten warmest years in record appeared since 2000. The year
2015 is the warmest year since 1880, when humans started to measure the aver-

Fig. 1.1 Development of the relative global temperature per year (∗) and averaged temperature
over a period of 5 years (dotted line), temperature scale on the left y-axis, with respect to the
average temperature from 1951 to 1980. In addition, the development of the CO2 concentration
in the atmosphere is shown for the last 60 years (solid line and scale on the right y-axis). The
correlation is quite clear (Source NASA/GISS [3])


1 Polarized Fusion: An Idea More Than Thirty Years Old! …

3

age world temperature and the trend is still continuing in 2016. Carbon dioxide, a
heat-trapping GHG, is released through human activities, e.g. burning fossil fuels
or deforestation, as well as through natural processes, e.g. respiration or volcanic
eruptions. The actual carbon dioxide concentration in the atmosphere has reached
the highest level for the last 650 000 years. Previous reconstruction of paleo-climate
temperatures and CO2 and other GHGs concentrations [2] are in first order comparable to 1880. This level of about 300 ppm is the so called pre-industrial level, which
is nowadays used as a reference for the health of the Earth.

1.1.1 The 2 Degrees Scenario: 2DS
An actual report on CO2 emissions from fuel combustion in 2015 [4] by the International Energy Agency (IEA) provided an overview on the most recent state of climate
change. It was published in the forefront of the 21st Conference of Parties (COP21)

of the United Nation Framework Convention on Climate Change (UNFCCC) held
in Paris in December 2015. Despite the growth of non-fossil energy (hydro, nuclear,
renewable), fossil sources account for 82 % of the total TPES in 2013. The GHG
emissions increased respectively from 2011 to 2013 as reported in [1]: Coal by 68 %,
Oil by 25 %, and natural gas by 62 %. According to another IEA report CO2 emissions from energy production of the developing countries (Annex I / see [5]) accounts
for three quarters of the anthropogenic GHGs emissions and 60 % of global emissions. Industrial countries in Europe and North America (Annex II) show a decrease
in the total emissions from electricity generation between 2000–2013 [4]. Nations
of Annex II should not just fulfill the Kyoto protocol on their own boundaries, but
they should also be involved in investments on new technologies to help developing
countries on low carbon and low emission projects.
The most prominent result of the COP 21 is the agreement that human activities
strongly influence global climate, resulting in the urgent need to limit global warming
to an increase of less than 2 ◦ C by the end of this century.
The electricity and heat production worldwide depends mostly on coal. Except
the Annex I countries, almost all countries show a huge increase in the CO2 emission
due to electric power generation. For example, Asia doubled the emission, China
itself quadrupled them compared to 2000.
To overcome this problem the global community has to develop the vision of a
low-carbon world. This also means to find an agreement between developed and
developing countries, which seems to be very difficult due to the opponent interests.
Most scientific societies [6] have express their position on how to contain the CO2
emissions, hoping to be able to address the major technological issues related to this
vision due to long-term sustained investments in research.


4

G. Ciullo

1.1.2 Energy Panorama Requires Nuclear Resources: Most

Comfortable Solution Is Nuclear Fusion
The global energy consumption is increasing more and more with growing and
developing populations. During the last 20 years the increase has always exceeded
the most pessimistic forecasts [1]. Investments in new resources and more efficient
technologies may help to satisfy this demand partly, but the development is rapidly
speeding up and cheap access will lead to additional use of fossil fuels, which will
counter act a decrease in CO2 emissions and reinforce the anthropogenic influence
on earth’s climate.
For this century the oil and gas resource peak problem seems to be solved due
to new technologies of extraction. Nevertheless, fossil resources are limited [1] and
other solutions must be found. Otherwise, energy prices will rise to unpredictable
values.
Nuclear energy is one possible part of the solution for the energy supply and surely
for fighting the climate change. Fission energy has become a well established technology, but it encounters strong public reservations about operation and final waste
disposal. Especially, the Fukushima accident influenced the public view negatively,
but countries in the Middle East and Asia are still increasing fission capacity.
In the technology road map for nuclear energy of the IEA [8] 72 new reactors are
mentioned to be under construction, with China accounting for the largest increase on
nuclear capacity in the next years. Based on the present consumption the resources
of uranium will cover the next hundred years [1]. In its road map the IEA has
deemed fusion not considerable before at least 2050. The same position was brought
forward in the US Government’s energy strategy from 1982, which also postponed
commercial use of fusion energy to at least 2050 [9].
There is no more time to postpone the problem. We are not only facing an energy
resource problem within the next century, but it is even a problem of present global climate change: we have to stop temperature increasing as rapidly as shown in Fig. 1.1.
Thanks to the proposal of Kulsrud et al. [10] on polarization preservation of polarized fuel in a tokamak reactor, 1982 was an important year for nuclear fusion, which
gave new hope for the production of energy by fusion. Newspapers and journals from
that time optimistically expressed the hope to enter the stage of energy production
by nuclear fusion before 1995 [11].
Why have several scientific programs and studies been stopped?

It is never easy to reconstruct the past. On a recent paper J. Sheffield [12] tries to
give a possible reason for the discontinuation of several fusion programs around the
world: according to Sheffield, most US programs and facilities, were not equipped
with proper diagnostics and, therefore, mostly were closed, without even being able
to perform critical tests.
The use of nuclear fusion for power generation is a challenge, which involves
massive scientific as well as technological efforts, and also funding and, therefore,
political will. But it can be expected to have an important social and economical
impact. Fusion can have an enormous impact for all societies: the necessary resources,


1 Polarized Fusion: An Idea More Than Thirty Years Old! …

5

deuterium and lithium for the production of tritium, are available everywhere and,
therefore, wars for resources are unlikely. In contrast there have been several conflicts
in the past, which have been directly connected to oil. The possible increase of
availability of electric power worldwide provides new options for heating and electric
cars avoiding CO2 emission. The need of deuterium extraction will drive new markets
and technologies. Another important social impact is due to the technologies used
for desalinization of water [13], which can also be useful for the water supply of
coastal areas.
The development of polarized targets at different accelerators for fundamental
nuclear physics might give new impulses to the idea of polarized fusion, as they
propose a way to produce polarized fuel.
Fusion needs impulses from different fields. There are several international efforts
on developing fusion reactors for energy production. Nevertheless, as an example the
operation of ITER (International Thermonuclear Experimental Reactor), the world
largest and most advanced fusion experiment, has been repeatedly postponed. In

2000, it was assumed to start in 2016, then said to begin operation between 2020–
2027, and in June 2016 there will be a official update on the estimated delay for the
begin of operation.
DEMO, the first tokamak, which will be designed for energy production based on
the technical experience of ITER, was once foreseen for 2021–2030, now operation
is planned for 2050.
Is the use of polarized fuel still an interesting option? For sure, it will be a flywheel
for fusion.
Polarized fuel for fusion, even tough already discussed in the 60 and 70s, gained its
first worldwide resonance after the proposal of Kulsrud [10]. Thereafter, there were
many papers on this field, in favor and also in a conservative critical approach of its
use in the fusion environment. In the next year a dedicated workshop on “polarized
fusion” took place where the polarized target community was included [14], but at
that time the production of a reasonable amounts of polarized fuel, as needed for first
tests in a tokamak, was not possible.
Now, after more than thirty years of technological progresses in the polarized
target production, scientific interest is directed back into this field.

1.2 Towards Nuclear Fusion with Polarized Fuel
The starting point for research on nuclear fusion with polarized fuel is the development of polarized targets for nuclear fundamental physics studies. Most of the
achievements are reported in a series of dedicated workshops “PST(P) (Polarized
Sources, Targets (and Polarimetry))”, which have been organized for more than 30
years, moving between Europe, USA and Japan [15].
The isotopes of hydrogen (except tritium) and 3 He, which are useful as polarized
fuel, are under investigations at different accelerators, e.g., as “frozen spin” solid
state targets or as gas targets in so-called “storage cells”. Nowadays, polarized 3 He


6

G. Ciullo

can be produced in large amounts and is used commercially, e.g. for NMR scans of
the lunge.

1.2.1 Fusion with Polarized Fuel: Advantages
The most favorable reactions for fusion are sequentially organized with respect to
the energy required to start the reaction [16]:
1st generation D + T → n (14.1 MeV) + 4He (3.5 MeV),
2nd generation D + D → n (2.45 MeV) + 3He (0.82 MeV) (50 %),
→ p (3.02 MeV) + T(1.01 MeV)
(50 %),
3rd generation D +3 He → p (14.7 MeV) + 4He(3.6 MeV) Neutron free reaction,
but with DD neutrons in a plasma.

The first generation is the most favorable and is planned as fuel for ITER. The
second generation provides less energy at higher plasma temperatures and, therefore,
it is more difficult to achieve. On the other hand, the necessary fuel for this reaction
is available everywhere and the amount of neutrons with lower energy is reduced,
which will increase the lifetime of the reactor blanket, which will reduce the costs
and the amount of radioactive waste. In first order, the third generation is neutron
free, but due to the presence of deuterium the D + D-reactions are contributing,
unless there reactions can be suppressed by using polarized fuel. Unfortunately, the
necessary fuel, i.e. the 3 He, is a rare isotope on earth and the necessary amount will
be expensive.

1.2.1.1

Polarized Fuel Made of Spin 1 and Spin 1/2 Nucleons

The advantages of polarized fuel including spin 1 as well as 1/2 particles, which are
needed for the 1st and 3rd generation reactions, are:
i Reaction cross-section gain:
Considering the statistical weight of the reaction spin channels for spin 1 and
spin 1/2 particles of the 1st (D + T) or of the 3rd (D + 3 He) generation, there is
an improvement of the cross-section by a factor of 1.5 when using polarized fuel
with respect to the use of unpolarized fuel. More details are reported by H. Paetz
gen. Schieck in this volume [17].
ii Control over the angular distribution of the reaction products:
For reacting spin 1 and spin 1/2 particles and both spins aligned along the magnetic
field axis, the products will have an angular distribution proportional to sin2 θ ,
where θ is the angle between the ejectile’s trajectory and the magnetic field. If
only the deuteron spin is aligned orthogonal to the field and tritium is unpolarized,
then the products will have an angular distribution proportional to 1+3cos2 θ . In


1 Polarized Fusion: An Idea More Than Thirty Years Old! …

7

this case, the total cross section is unchanged. This was already demonstrated by
scattering experiments for the spin equivalent reaction of the 3rd generation and
can be useful for the first generation tokamak.
iii Neutron lean reactors:
If the D + D reaction into n + T can be suppressed or, at least, reduced due to
polarized fuel used for the 3rd generation, it might be possible to have neutron
free or maybe at least lean reactors.
The reaction of the first and third generation, at the relative energy (or temperature) for
fusion, is dominated by S-wave interaction, in which case the law of conservation of
angular momentum will allow direct observation of the process and easier estimation

of the fusion environments.
From the nuclear point of view these assumptions were proven in 1971 [20],
confirming a dominating S-wave reaction (at least 96 %) through the spin 3/2 channel
and only a tiny amount through the remaining spin 1/2 channel. This was proven for
the case of the 3rd generation, which requires higher energy for fusion, but can also
be applied to the 1st generation.
The increase of the cross section will allow less stringent requirements for fusion,
which might allow to achieve third generation reactions in less constrained temperatures, using a more compact reactor and thereby, higher magnetic fields with less
power consumption [21].
The possibility to handle the angular distribution allows to design reactors, where
less parts of the wall are bombarded by neutrons, allowing improved, more cost
effective designs.
As an example, it is of particular interest that already a priori a mirror tokamak
can be implemented by the use of polarized fuel [22].

1.2.1.2

Spin 1 on Spin 1: Challenges for Fusion and Fundamental
Physics

The only spin 1 nucleon of interest for fusion reactions is the deuteron, which appears
in any of the three fusion reactions reported here. It can be found in abundance in
water (≈33 gm−3 [23]), and is virtually inexhaustible [16].
There are no measurements on the spin dependency of the cross sections for
the double-polarized D + D reactions. Furthermore, predictions on cross–section
gain and angular distributions by spin alignment are contentious. The estimations
are unreliable due to the presence of P- and D-waves and their interferences [17].
The absence of data does not allow to compare it with the different predictions to
understand the nuclear reaction behavior.
The ability of producing and manipulating nuclear targets, which involve deuterium, lead the communities, working in the field of polarized targets and sources,

to study the possibility of producing polarized fuel for testing in fusion programs. For
example, the residual polarization of recombined molecules was studied in polarized
atomic accumulation cells [24, 25], starting from where the PolFusion collaboration


8

G. Ciullo

has reached promising results in finding an appropriate procedure to recombine deuterium on special surfaces and measure its polarization, as reported by R. Engels in
this volume [26].
Deuterium is a test bench also for fundamental nuclear physics, which can provide
data for the four-nucleon interaction models [17].
The spin dependent cross-sections are also required to explain the so called Quintet
Suppression Factor (Q S F), which accounts for the difference in cross-sections of
aligned spin reactions, σ11 , and unpolarized cross-sections σ0 , i.e. Q S F = σ11 /σ0 .
If this ratio is zero, in case of aligned deuteron spins, the reaction is not permitted,
which would theoretically allow neutron free reactors.
These measurements are still missing, and are one of the challenges addressed by
the PolFusion collaboration due to an experiment with two crossed beams, discussed
in this volume by A. Vasilyev’s contribution [27]. Understanding the spin dependence
of deuterium cross-sections will reveal more possibilities for future designs and test
of new reactors.
The literature does not provide much experimental data on the D + D spin dependent cross-sections, although the formalism of interacting spin 1 particles has already
been well described in the 70s, as reported in this well organized review [28]. The
few measurements on spin dependent cross-sections are limited to analyzing powers,
obtained by polarized beam interaction with unpolarized targets, see e.g. [29, 30]. The
QSF is derived indirectly and the conclusions are contentious [31, 32]. These papers
still require double-polarized experiments, which can be performed with target and
projectile both polarized. Two papers [33, 34] report a well structured scheme of a

theoretical formalism and an experimental approach in order to access the complete
set of data, as also accessible by an experiment with two crossed beams.
The PolFusion collaboration is looking forward to gather the most interesting
data in an experiment with two crossed beams, discussed in dedicated workshops
[35, 36]. Thanks to the improved technologies in the area of polarized sources since
1982, spin correlation-coefficient experiments are finally possible nowadays. This is
due to an increase in intensity and polarization for atomic beam sources as well as
ionic beam sources by orders of magnitude compared to the 1980s [27].

1.2.2 The PolFusion Collaboration Challenges on D:
Towards Polarized Fuel and Spin Dependent Cross
Section
The PolFusion project [26, 27] started from the preliminary idea of increasing the
density of polarized gas-targets by looking for a possibility to keep the nuclear
polarization preserved in molecules (hyper-polarized molecules), obtained by the
recombination of polarized atoms.
Also, this development is of great interest for fundamental studies on spin dependent observables in nuclear and subnuclear physics, which support development and


1 Polarized Fusion: An Idea More Than Thirty Years Old! …

9

research on more dense nuclear targets [18]. Therefore this was successively discussed with larger audiences of scientists, involved in this field [19]. The PolFusion
collaboration takes part in the development of new technologies capable of producing more dense polarized gases to be used in nuclear fusion. The collaboration faces
the following challenges:
I producing D2 polarized fuel useable in fusion experiments;
II investigating the D + D polarized–crossed-beams interactions, in order to get
a minimum of information necessary for the understanding of the reaction of
deuterium as function of the spin alignments;

III preparing first fusion experiments in MCF or ICF environments, properly
equipped for the diagnostics and manipulation of polarized fuel.
The experience in the production of polarized atomic beams and its accumulation
is now oriented in the recombination on proper surfaces, capable of preserving the
nuclear polarization. Followed by investigation on freezing recombined molecules
and finally manipulate them for their use in fusion environments.
Studies of the surface dependent recombination have reached an advanced status
as reported in this volume [26].
There is also another idea discussed in this volume, which proposes to exploit the
advanced technology of superconducting atomic beam sources, which could directly
allow manipulation of nuclear spins in molecules in longer and more powerful superconducting magnets [37].

1.2.3 Fusion with Polarized Fuel: Open Questions
After being proposed in 1982 [10] there have already been discussions on difficulties,
which come along with the possibilities of polarized fuel for nuclear fusion:
i Is it possible to inject the polarized fuel without loss of polarization?
ii Can polarization survive in fusion environments?
This questions need to be carefully addressed and considered with respect to the
recent developments in plasma and fusion physics. As a consequence new studies on
RF wave propagation and their interaction with polarized fuel are currently foreseen.
These can be supported by experiments with polarized fuel in the plasma, which will
be discussed by F. Bombarda [38]. The investigation in this volume is based on the
constraints given at ITER and IGNITOR. Various effects causing depolarization or
polarization preservation are taken into account [38–40].
The difficulties in polarization preservation in confined fusion plasmas are being
reviewed, starting from the two best known papers on this argument [10, 41]. Most
recent developments in this field are reported by R. Gatto [40] in this volume.


10

G. Ciullo

1.2.4 Correlated Activities of Interest for Polarized Nuclear
Fusion
New ideas and technologies were developed since 1982, i.e. laser induced fusion.
Whether the use of polarized fuel is helpful for energy production with this method,
is under investigation [42]. The question, whether nuclear polarization is preserved
in the laser-induced plasma, is under investigation in M. Büscher’s group [43] and
part of this volume. By laser acceleration of polarized 3 He ions from polarized 3 He
gas the necessary conditions for polarization preservation will be investigated. This
technology may also provide an option to produce polarized 3 He2+ ions for further
use in accelerator studies in fundamental research. As soon as hyper-polarized D2
molecules are available [26], both ingredients are at hand to test the second and third
generation fuel in laser-induced fusion.
The problem of fuel injection into tokamaks is also discussed in connection with
RF ion sources and the post-neutralization of their ion beams before injection into
the tokamak. The technology can be implemented for polarized fuel injection as
reported in [44].
Studies and experimental tests of the persistence of the nuclear polarization are
presented by J.P. Didelez [45] for ICF environments and by A.M. Sandorfi et al.
[46] for MCF environments. The polarized solid HD target technologies were able
to achieve significantly higher densities and polarization values during the last years
compared to the possibilities at the time of the workshop on polarized fuel for nuclear
fusion in 1983 [14]. Present technologies would allow to perform advanced tests of
polarized fuel in fusion reactions.
New ideas often emerge while developing new technologies. Just recently it was
suggested to use an atomic beam source for the production of polarized hydrogen
and deuterium in parallel and produce hyper-polarized HD molecules due to recombination [47]. By using a dual radio-frequency cavity, developed for the Breit–Rabi
polarimeter [48] of the PAX experiment (Proton Antiproton experiment) [49], this

method allows to produce enough polarized HD molecules by recombination of the
polarized atoms for further tests in fusion reactors. With this method the polarization
of the HD molecules will be higher than for the solid HD targets [45, 46]. In parallel,
it is a ideal test bench for the handling of polarized DT molecules as fuel for first generation reactors. In addition, the production of polarized H2 , D2 and HD molecules
is even interesting for (laser-) spectroscopy experiments of these molecules.
A schematic view of the idea is shown in Fig. 1.2. With a dual strong-field cavity
and two medium field cavities, one for H and another one for D, the atomic beam
source can simultaneously produce polarized D and H. This setup would enable
feeding of the cell with hydrogen atoms in the hyperfine state |1 >, which has a
+1/2 nuclear spin, and the state |1 > of deuterium, which has a spin +1 nuclear
polarization. The Breit–Rabi polarimeter, which measures the polarization of the
injected H and D atoms, has already been commissioned with a dual cavity to be
used in the TRIC experiment [50]. The system allows to test if both hyperfine states
are preserved after injection in the accumulation cell by measuring the remaining


1 Polarized Fusion: An Idea More Than Thirty Years Old! …

11

Fig. 1.2 Possible modification of the PAX target and diagnostics for further studies of the injection
of polarized H and D atoms in parallel. This setup requires minor modifications on the existing
apparatus: the implementation of a dual Strong Field Transition (SFT Dual for D and H), similar to
the one already present (SFT D&H) and commissioned in the Breit–Rabi polarimeter

polarization of the atoms. Then, if the simultaneous production of H and D is proven,
the source of H and D polarized atoms can be implemented in the hyper-polarized
recombination device [26].
If the technology to freeze hyper-polarized D2 molecules is successful, it will
also be possible to recombine polarized H and D atoms for the production of hyperpolarized HD molecules. They can be used as solid HD targets in fundamental nuclear

research or, again, as test bench for the handling polarized DT ice.