CERN Accelerating science

Neutron Sources

Why are neutrons special?

Neutrons were discovered in 1932 by Chadwick who noticed “a radiation with the more peculiar properties”. The research of materials using neutrons originated with studies by Bert Brockhouse and Cliff Shull, was recognized with the 1994 Nobel Prize in Physics. The advantage of neutrons as a probe comes from the fact that neutrons are low energy, non-damaging and penetrating, with a broad wavelength range.

Neutrons are therefore, excellent for probing materials on the molecular level – everything from motors and medicine, to plastics and proteins.

Neutrons show very different cross-sections (sensitivity) to elements compared with X-rays.

Neutrons Sources

Detailed studies are dependent on how many neutrons can be produced by a neutron source.

Neutron facilities – reactors and particle driven. Updated from Neutron Scattering, K. Skold and D. L. Price, eds. Academic Press, 1986.

Many of today’s leading sources are reactor-based and coming towards their end of lifetime. As old sources close, new sources are created, such as the European Spallation Source (ESS), as well as other existing facilities in Europe being upgraded. For example both, ISIS (Didcot, UK) and ILL (Grenoble, France) are significantly enhancing the range of instruments available. This renewal was the subject of the recent ESFRI report.

Neutron Science

Neutron scattering probes materials science using neutrons. Neutron science is the science of everyday life. It is important for the development of new and better computer chips, cosmetics, detergents, textiles, paints, fuels, drugs, batteries and plastics. Industrial drivers such as fuel cells, superconductors, innovative structural engineering, climate, transportation and food technologies, pharmaceuticals, medical devices and clean energy, are all dependent on advances in the capacity and capability of the science of neutron imaging. The many thousands of products created and improved through material science using neutrons are essential to our basic quality of life, and our economic growth.

As such, neutron scattering is about a very broad range of disciplines for materials science. The ones below are specific examples.

Detector technology challenges for the coming decade

Due to the end of the cold war 25 years ago, the isotope 3He has become increasingly rare, instigating the “Helium-3 Crisis” in 2009. This crisis consists in a large mismatch between global supply and demand for this resource. Since 2009, replacement technologies have been a very hot topic for detector development as a strategic priority.

Concept of a neutron detector

Future neutron detectors requirements:

Detector size cm2 – 80 m2
Pixel size Micron - cm
Radiation tolerance  >1014n/cm2
Time resolution <μs
Readout Capable of digital and analog modes
Neutron detection efficiency Nominal 50% thermal neutrons
Gamma sensitivity <10-7
Wave length 0,5-20 Å
Rate sample Up to MHz/mm2

State-of-the-art of the Neutron Detector Technologies

  • 3He based detectors are the gold standard for neutron detection

  • Scintillators based detectors (ZnS:6LiF(Ag), ZnS:10B2O3, Li-glass) is increasingly used for instruments.

  • 10B based detectors, will be largely used at ESS due to the unavailability of 3He gas and some challenging detector requirements such as pixel size or rate capability which cannot be fulfilled with the 3He technology.

Map with some of the major centres involved in the latest developments

The upcoming new centres expect to install >100 new scientific instruments over the next decade.

14 of the almost 50 neutron research facilities worldwide.

The large amount of new and improved instrumentation at high brightness sources means that the requirements of neutron detectors is well beyond present day state-of-the-art. This represents a significant challenge to meet for developments in detector technology.

Requirements challenge for Neutron Detectors: beyond the state-of-the-art.

Explore more at:

neutronsources.org

European Spallation Source - Detector Systems

Neutron Position Sensitive Detectors for the ESS