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For the first time in Europe, a team from
the Institut de Physique Nucléaire d’Orsay (Orsay Nuclear
Physics Institute, CNRS/IN2P3)(1) has successfully tested a new acceleration
device, a supraconducting cavity known as "Spoke". The cavity's
excellent performance opens up new possibilities for future linear accelerators
with intense high-energy proton beams (several million Watts) that could
eventually control nuclear waste incinerator reactors of the future for
the purpose of producing radioactive ion beams or even providing a source
of spallation neutrons(2).
The use of supraconducting technology for
accelerating cavities (3)has many advantages: limited operating costs
due to nearly negligible power dissipations, low activation (4) of structures
as a result of a wider opening of the tubes and, above all, increased
flexibility and reliability due to a modular structure (a power source
per cavity). In view of the enormous potential of this technology, the
Institut de Physique Nucléaire d’Orsay (IPNO) of the CNRS/IN2P3
initiated a research program that has become the European precursor in
its field. This choice has proven to be a total success.
The cavity's performance is based on a supraconducting device that operates
at -270°C and does not dissipate energy into its structure while making
it possible to obtain accelerations equivalent to 10 million volts per
meter. The cavity is built of solid niobium, a material that acts as a
supraconductor at low temperatures. Its particular shape, developed by
the IPNO using powerful simulation software, provides it with excellent
mechanical properties. Its manufacturing plans were entrusted to the Cerca
Company (Romans, in the France's Isère department) that produced
a high-quality prototype. The actual performance of this prototype was
evaluated in the Orsay cryodrome, a facility that makes it possible to
reach a supraconducting state while supplying the resonating cavity with
an accelerator frequency of 352 MHZ for which effective high-frequency
transmitters already exist.
This supraconducting technology has already been used for other types
of cavities known as "elliptical", recently developed through
a partnership between the IPNO and the French Atomic Energy Commission
(CEA), for the acceleration of high-energy sections of the accelerator
(above 100 MeV) (5) where accelerated particles reach a speed close to
that of light. At this time, the "Spoke" cavities make it possible
to extend the supraconductivity to sections in which particles are accelerated
at speeds much lower than the speed of light (from 5 to 100 MeV) or, in
other words, to the accelerator as a whole. Among other things, this will
make it possible to reduce the electrical power necessary for operating
the accelerator by half and will result in enormous savings in related
operating costs while providing a high degree of operational reliability
and robustness as well as extraordinary advantages, particularly in relation
to its use for the incineration of nuclear waste.
This experimental research is of major importance for the European PDS-XADS
project (24 partners including the CNRS), financed within the framework
of the European Union's 5th RDFP (Research and Development Framework Program),
in order to develop a European demonstrator for the incineration of radioactive
waste. During the 6th PCRD, whose funding requests are presently under
discussion, it will be necessary to finalize the research and development
program in order to be able to rapidly proceed with the construction of
this demonstrator which Belgium would like to sponsor under the name of
Myrrha.
1 - Institut National de Physique
Nucléaire et de Physique des Particules (National Institute of
Nuclear and Particle Physics).
2 - Spallation neutrons are neutrons produced when a target is bombarded
by a projectile. This bombardment actually produces multiple and chain-reaction
collisions between the nucleons at the center of the nuclei of the target,
causing some of them to be ejected.
3 - An accelerating cavity is an electromagnetic resonator limited by
conducting walls open at each end to allow for the passage of particle
beams. When it is subject to a radio frequency excitation at a frequency
corresponding to one of its resonator modes, a stationary wave is established,
presenting an axial electric field in the same direction as the beam propagation
axis and therefore capable of accelerating the charged particles.
4 - A material is said to be activated when some of these nuclei have
been transformed into radioactive nuclei under the effect of radiation.
5 - 1 MeV = 1 million electron-volts
Researcher
contacts:
IPN - Orsay
Dominique Guillemaud Mueller
Tel: +33 1 69 15 73 25
E-mail: guillema@ipno.in2p3.fr
IN2P3/CNRS contact:
Dominique Armand
Tel: +33 1 44 96 47 51
E-mail: darmand@admin.in2p3.fr
Press Contact
CNRS:
Martine Hasler
Tel: +33 1 44 96 46 35
E-mail: martine.hasler@cnrs-dir.fr
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