Ideally, proton and ion therapy require very small, intense and mono-energetic beams. The energy is particularly important, as this controls the depth at which the main energy deposition takes place. In general, the protons used for this therapy are

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Proton and Ion Cancer Therapy
Radiotherapy forms a major component in the
treatment of cancer, with 40-50 of patients
being treated in this way. Photons, in the form
of X- or gamma rays, are most commonly used but
have the problem that much of the energy is
deposited in healthy tissue surrounding the
tumour, rather than in the tumour itself.
Ideally, proton and ion therapy require very
small, intense and mono-energetic beams. The
energy is particularly important, as this
controls the depth at which the main energy
deposition takes place. In general, the protons
used for this therapy are accelerated using
cyclotrons, which can only give a single proton
energy. To produce the correct energy, this must
be degraded using absorbers and this can produce
an undesirable spread.
FFAGs, on the other hand, can produce particle
beams with a variety of energies. A prototype
under test in Japan is designed for three, but
more may be possible. This will reduce, if not
eliminate, the need for absorbers. Furthermore,
FFAGs produce very intense particle bunches, so
in principle it will be possible to select from
these intense bunches of exactly the right
characteristics
Protons and light ions, on the other hand,
deposit most of the energy at one place which
depends on the energy of the proton or ion. In
addition, beams of these particles can be steered
and focused, making them ideal for radiotherapy.
As a result, proton and ion therapy, in
particular with carbon ions, have been both
studied and employed for cancer treatment over
many years, in laboratories all over the world.
Both have proved very successful, protons
particularly in the treatment of tumours for
which conventional radiotherapy presents an
unacceptable risk, for example cancer of the eye,
the brain and the prostate. Carbon ion therapy is
proving beneficial in the treatment of certain
cancers which are resistant to conventional
radiotherapy with photons, for example in the
liver, pancreas and parotid gland.
Boron Neutron Capture Cancer Therapy
Accelerator Driven Systems
BNCT is a possible method for treating one of the
deadliest forms of cancer, a type of brain tumor
called a "glio-blastoma multiforme". This
afflicts 12500 people in the USA each year, for
example, and is always fatal. In BNCT, a compound
containing boron-10, a non-radioactive isotope,
is introduced into the brain and preferentially
absorbed by the tumour. This is then exposed to
intense neutron beam which causes the boron-10 to
fission, releasing an alpha particle and lithium
nucleus. Both of these have a very short range
and hence destroy the malignant cells that the
boron is in without damaging healthy cells.
ADS address two main, but related, issues to do
with nuclear power generation. The first is to
drive sub-critical nuclear reactors based on
thorium-232 (Th-232). There has been interest in
using thorium for many years as it is 3 times
more abundant in the Earth's crust than uranium
and in principle all of it can be used in a
reactor, compared to 0.7 of natural uranium. It
works be absorbing a neutron to become Th-233
which decays to U-233, which fissions. The
problem is there are insufficient neutrons
generated to sustain the reaction. In ADS, a high
intensity proton accelerator is used to generate
the neutrons required to sustain the reaction by
spallation. It has a big advantage over
conventional reactors, in addition to burning
thorium if the accelerator is turned off, the
reactor stops without the need to employ
moderators to absorb neutrons.
BNCT has been investigated in a number of
countries with very positive results. Most
studies have employed reactors as the neutron
source, which is not practical treating many
patients on a day-to-day basis. FFAGs provide a
possible solution for producing enough neutrons
to treat patients in hospital and a study of this
has recently started in Japan.
Tests of BNCT have employed nuclear reactors, but
these are impractical for large scale
day-to-day treatment. An FFAG could provide the
neutrons rather than a reactor.
The second issue is the transmutation of
radioactive waste. Along with safety, the
disposal and storage of the waste is one of main
problems of nuclear power generation. In
transmutation, the long-lived waste is bombarded
with neutrons which in most cases causes fission
and gives (in general) short-lived products. This
also generates energy and transmutation could be
combined with a sub-critical reactor.
FFAGs are ideal for this application due to the
high beam intensity and rapid cycling. A five
year project started at Kyoto University Research
Reactor Institute in 2002 to develop an FFAG and
a reactor to test the feasibility of this form of
energy generation and nuclear waste transmutation.
A drawing of an ADS scheme using a linear
accelerator. There are a number of benefits to
using an FFAG for the proton acceleration instead.
What still needs to be done ?
Physics research applications currently under
study for FFAGs
? high power proton drivers FFAGs are being
considered in relation to a number of future,
high power proton drivers. ? eRHIC a 10 GeV
electron FFAG is being investigated as part of
the project to create electron-ion collisions at
the Brookhaven Laboratory.
The current Neutrino Factory layout in the USA.
A magnet for the prototype 150 MeV scaling FFAG
built at KEK. The magnets for a non-scaling FFAG
could have a 10 times smaller aperture, making
the magnets smaller and cheaper.
The orbit shape in a scaling FFAG cells is the
same at each energy, but varies with non-scaling
machines. This allows the apertures of the
magnets to be much smaller in the latter,
reducing the cost for the same performance.
We are seeking collaborators to work with us on
the development of this novel form of accelerator
for any of the potential applications!