Shielding for ambitious neutron experiment

Jul 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: Used MRI magnets get a second chance at life in high-energy physics experiments

Related Stories

Direct visualization of magnetoelectric domains

Apr 27, 2015

A novel microscopy technique called magnetoelectric force microscopy (MeFM) was developed to detect the local cross-coupling between magnetic and electric dipoles. Combined experimental observation and theoretical ...

Quantum Criticality in life's proteins (Update)

Apr 15, 2015

(Phys.org)—Stuart Kauffman, from the University of Calgary, and several of his colleagues have recently published a paper on the Arxiv server titled 'Quantum Criticality at the Origins of Life'. The id ...

A new look at the sun's magnetic field

Mar 27, 2015

Sunspots, bursts of radiation and violent eruptions are signs that our sun is permanently active. Researchers have long known that this activity varies in a cycle of around eleven years' duration. Even if ...

Recommended for you

SLAC gears up for dark matter hunt with LUX-ZEPLIN

May 21, 2015

Researchers have come a step closer to building one of the world's best dark matter detectors: The U.S. Department of Energy (DOE) recently signed off on the conceptual design of the proposed LUX-ZEPLIN (LZ) ...

First images of LHC collisions at 13 TeV

May 21, 2015

Last night, protons collided in the Large Hadron Collider (LHC) at the record-breaking energy of 13 TeV for the first time. These test collisions were to set up systems that protect the machine and detectors ...

User comments : 0

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.