Neutron microscope

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A neutron microscope is a microscope that uses neutrons rather than light to produce enlarged images of objects. The concept of the neutron microscope was created in the early 1980s. It was then that the technical prerequisites for the deflection and storage of neutrons were created, which are necessary for the construction of such a microscope. The first working neutron microscope was invented jointly by MIT and NASA in 2013 .

Neutrons offer some unique advantages over currently used methods such as the electron microscope . Neutrons interact very strongly with hydrogen. Together with the ability to easily penetrate organic material, this could open up new methods of investigation, especially in biology, where the samples to be investigated contain high proportions of water and hydrocarbons.

construction

Similar to conventional microscopes, attempts are made to use (neutron) lenses to focus a beam of neutrons on the sample and to detect the interactions with the sample. Since a neutron interacts with the rest of the matter in a completely different way than photons or electrons , the neutron microscope sometimes uses fundamentally different techniques and material systems.

The neutrons used may only have a low thermal energy (approx. 2 · 10 −7  eV ) - also called ultra-cold neutrons (UCN). Such neutrons show total reflection on surfaces at flat angles of incidence, and they can also be stored for a sufficiently long time in magnetic traps; Sufficient here means a duration in the range of the half-life of the neutrons. As a free particle, the neutron decays into a proton, an electron and a neutrino with a half-life of 611 seconds.

The resolution of a light microscope is limited by the wavelength of the electromagnetic radiation used. As with electrons , neutrons can also be assigned a so-called matter wavelength . Due to the significantly higher mass, the wavelength of such a matter wave is significantly shorter for neutrons than for electrons. While with optical microscopes (max. 200 nm) the resolution actually almost reaches the physical limit set by the light wavelength, with neutron microscopes the imaging errors of the components worsen the usable resolution (theoretically 1 nm); the enlargement of current test facilities is still very small (22.5 times).

literature

  • P. Herrmann, K.-A. Steinhauser, R. Gähler, A. Steyerl, W. Mampe: Neutron Microscope . In: Physical Review Letters . tape 54 , no. 18 , 1985, pp. 1969–1972 , doi : 10.1103 / PhysRevLett . 54.1969 .
  • MR Eskildsen, PL Gammel, ED Isaacs, C. Detlefs, K. Mortensen, DJ Bishop: Compound refractive optics for the imaging and focusing of low-energy neutrons . In: Nature . tape 391 , no. 6667 , 1998, pp. 563-566 , doi : 10.1038 / 35333 .

Web links

  • "Seeing" with neutrons. Max Planck Society, 2009, accessed on April 29, 2016 (description of the neutron microscopy process, with animation).

Individual evidence

  1. ↑ Neutronenmikoskop , elektormagazine.de, December 10, 2013; Accessed December 9, 2018
  2. ^ What shall we do with a neutron microscope? , newatlas.com dated October 21, 2013; Accessed December 9, 2018
  3. ^ New kind of microscope uses neutrons , MIT of October 4, 2013; Accessed December 9, 2018
  4. ^ PR Huffman, CR Brome, JS Butterworth, K. J Coakley, M. S Dewey, S. N Dzhosyuk, R. Golub, GL Greene, K. Habicht, SK Lamoreaux, CEH Mattoni, DN McKinsey, FE Wietfeldt, JM Doyle : Magnetic Trapping of Neutrons . In: nucl-ex / 0001003 . 2000, arxiv : nucl-ex / 0001003 .
  5. ↑ JT Cremer, MA Piestrup, H. Park, CK Gary, RH Pantell, CJ Glinka, JG Barker: Imaging hydrogenous material with a neutron microscope . In: Applied Physics Letters . tape 87 , no. 16 , 2005, pp. 161913 , doi : 10.1063 / 1.2089172 .