Shielding for ambitious neutron experiment

July 24, 2008

In science fiction stories it is either the inexhaustible energy source of the future or a superweapon of galactic magnitude: antimaterial. In fact, antimaterial can neither be found on Earth nor in space, is extremely complex to produce and thus difficult to study.

In order to nevertheless track down the origin of material and antimaterial in the universe, a European research group is measuring the power of the electrical dipole moment of neutrons, which represents a measure for the different physical properties of material and antimaterial.

The prerequisite for further, still more accurate measurements is a perfect insulation against electrical and magnetic radiation from the environment. Magnetically soft mumetal serves as a material of the new shielding - the design, testing and set-up of which the Physikalisch-Technische Bundesanstalt is responsible.

Neutrons are electrically neutral particles, when observed externally. As the neutron contains both positively and negatively charged quarks, it would be conceivable that there exist equally large positive and negative charges at a minimal spatial distance from one another in its interior. The neutron would then be an electrical dipole with two oppositely charged poles.

At the Institut Laue-Langevin (ILL) in Grenoble, a European research group is attempting to measure the magnitude of the electrical dipole moment of neutrons (nEDM) with high accuracy. In these experiments, the behaviour of extremely slow neutrons, so-called ultra cold neutrons (or abbreviated as UCN), is investigated in magnetic and electrical fields.

Due to the fact that neutrons possess a spin and thus have a magnetic moment, they are also subject to electromagnetic interaction. If an additional electrical field is applied, the neutron, if it possesses an electrical dipole moment, would have to slightly change its properties in a magnetic field.

So far, experiments have shown no sign that would indicate an appreciable electrical dipole moment. Due to the fundamental physical significance it is interesting, however, to further restrict the magnitude of the possible electrical dipole moment. The electrical dipole moment of the neutron is namely a measure of how strongly matter and anti matter differ from one another in their physical properties. In order to significantly improve the measurement uncertainty, a new setting up of the experiment at the Paul Scherrer Institut (PSI) with a stronger UCN source and a better magnetic shielding is planned.

As valuable know-how has been collected at the PTB during the assembly of the best-shielded magnetic cabin worldwide, this expertise is now to be used for the construction, testing and assembly of the new shielding of the neutron experiment. The measuring systems available at PTB will be used for the preliminary investigation of facility components. Of particular importance is the expertise at PTB for detecting even the slightest magnetic impurities.

Provided by PTB

Explore further: Miniaturizable magnetic resonance: Microscopic gem key to new development in magnetic lab-on-a-chip technology

Related Stories

Magnetic monopoles in spin ice crystals

November 12, 2015

Today one of the major goals of physicists is to unify the forces of nature into a Grand Unified Theory that could portray a more elegant and comprehensive representation of the Universe. One step towards this big theory ...

Frustrated magnets point towards new memory

September 23, 2015

Theoretical physicists from the University of Groningen, supported by the FOM Foundation, have discovered that so-called 'frustrated magnets' can produce skyrmions, tiny magnetic vortices that may be used in memory storage. ...

Jupiter's moon Ganymede

October 16, 2015

In 1610, Galileo Galilei looked up at the night sky through a telescope of his own design. Spotting Jupiter, he noted the presence of several "luminous objects" surrounding it, which he initially took for stars. In time, ...

Researchers transform slow emitters into fast light sources

October 22, 2015

Researchers from Brown University, in collaboration with colleagues from Harvard, have developed a new way to control light from phosphorescent emitters at very high speeds. The technique provides a new approach to modulation ...

Engineers refine protection system for LHC magnets

September 4, 2015

This week, the Large Hadron Collider (LHC) was switched off for its second scheduled technical stop since starting to run at the new high energy of 6.5 teraelectronvolts (TeV) per beam. These regular stops allow engineers ...

Recommended for you

Exploring the physics of a chocolate fountain

November 24, 2015

A mathematics student has worked out the secrets of how chocolate behaves in a chocolate fountain, answering the age-old question of why the falling 'curtain' of chocolate surprisingly pulls inwards rather than going straight ...

Biomedical imaging at one-thousandth the cost

November 23, 2015

MIT researchers have developed a biomedical imaging system that could ultimately replace a $100,000 piece of a lab equipment with components that cost just hundreds of dollars.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.