Customer Spotlight: Penn State receives Cryomech Cryostat for Cold Neutron Research
Writers
Cryomech cryostats enable a variety of low temperature research opportunities for labs across the globe. One of our most recent deliveries was to the Penn State College of Engineering Radiation Science and Engineering Center, a long-time customer of the Cryomech brand.
After years of development in our Syracuse facility, a custom cryostat has been delivered and is ready to be implemented. The device will be utilized by Dr. Kenan Ünlü, Director, and Daniel Beck, Senior Design Engineer, at the Penn State’s Radiation Science and Engineering Center (RSEC) for cold neutron research.
Dr. Ünlü has a long history with Cryomech products, having previously purchased a similar device back in the early 1990s for his lab at the University of Texas at Austin, in the Nuclear Engineering Teaching Laboratory. The old cryostat was based on a neon thermo-syphon, while the new one that Penn State has procured utilizes our new cold helium circulation system design.
What is Cold Neutron Research?
Beams of neutrons produced by nuclear research reactors are used in condensed matter research to study the arrangement and interactions of atoms in materials. Because neutrons are highly penetrating, it is possible to probe deep within materials.
Neutrons can be used to examine matter at the atomic scale in a way unmatched by other techniques because of their favorable wavelength to energy ratio. In many applications, the structural information provided by neutrons cannot be obtained in any other way.
A neutron beam can also be used for analytical analysis by neutron-capture gamma-ray spectroscopy. Concentrations of different elements in a sample can be determined from the measured emission rates of characteristic prompt gamma rays produced by neutron capture.
While Neutron Activation Analysis is more sensitive for the determination of most elements, it cannot be used for some elements which can only be analyzed by neutron-capture gamma-ray spectroscopy. In addition, basic nuclear physics studies are possible through neutron-capture reaction measurements of gamma rays and internal conversion electrons.
The condensed matter research and analytical analysis applications which utilize a neutron beam can be enhanced using subthermal neutrons — “cold neutrons” — defined as neutrons with energy around 5 meV and below, with a corresponding velocity and wavelength of 980 m/sec and 4 A, respectively.
Obtaining and Guiding Cold Neutrons
Cold neutrons can be obtained by passing a thermal neutron beam through a cooled moderator. To be effective the moderating material should be maintained at a temperature which is significantly below liquid nitrogen temperature. Cold neutrons have longer wavelengths and lower energies on average than thermal neutrons, the majority of the neutrons normally present in neutron beams from nuclear research reactors.
Neutrons with sufficiently long wavelengths can be reflected from some surfaces in the same way light can be reflected from the interface between two transparent media. Cold neutrons, then, can be “guided” down cylinders — neutron guides — without the normal l/r2 attenuation, and can be bent out of the line-of-sight paths followed by other radiation.
Using long wavelength neutrons allows increased size scale for material structure research. Lower energy neutrons give better resolution in the study of molecular motion and interactions.
The usual neutron beams from a research reactor are contaminated by fast neutrons and gamma rays that originate in the reactor core. Filters, collimators, and shielding reduce these undesirable components to some extent. However, cold neutron beams can have a much lower gamma and fast-neutron background. Thus, detectors for capture neutron and basic physics experiments can be placed closer to the sample, increasing sensitivity, and making coincidence techniques feasible in many more situations.
Cold Neutron Capability and Small-Angle Neutron Scattering Research
Small-Angle Neutron Scattering (SANS) allows the Radiation Science & Engineering Center to offer one of the most unique and most broadly used neutron scattering techniques. SANS takes advantage of the similarity of particles of mesoscales (now frequently called nano particles) and the wavelength of the neutron waves used in the experiment.
SANS uses the scattering properties of the neutron that can vary largely between different nuclides, especially between hydrogen and deuterium, to study the samples under investigation. Penn State will be the first and only University research reactor to have SANS capability, which is now only available at National Labs.
Cryomech Cryostats Take Research Further
The delivery of this cryostat enables the Penn State Radiation Science and Engineering Center to develop their research and enhance their ability to further study materials characterized by polymers, magnetic materials, biological materials, and complex structures.
If you’re in need of a custom Cryomech cryostat, be sure to reach out to our Bluefors team in Syracuse!