Chris Tulk

Chris Tulk

Position: Lead Instrument Scientist

Instrument: Spallation Neutrons and Pressure Diffractometer

Group: Advanced Diffraction

Division: Chemical and Engineering Materials Division

Facility: Spallation Neutron Source

Contact: tulkca@ornl.gov or (865) 574-5764

I have been studying the physics and chemistry of water, ice and related compounds for over 25 years. My current interests include the structural and dynamical properties of water ice phases up to extremely high pressures and at both low and high temperatures. Using both neutron scattering and Raman laser spectroscopic techniques I continue to study water ices at conditions we often see throughout the universe. Most recently we have begun to study the structure of the postulated ‘non-molecular’ phase of ice, the so called symmetric ice, thought to occur at room temperature under mega-bar pressure conditions.

Education

Ph.D. (condensed matter physics) from Memorial University in Canada, Determination the elastic constant tensor elements of high pressure single crystal phases of ice III, V and VI using Brillouin Laser Spectroscopy.

Research

National Science and Engineering Research Council of Canada, NSERC, post-doctoral fellow at the National Research Council of Canada Steacie Institute for Molecular Sciences in Ottawa Canada. I studied water clathrate hydrate systems, including methane + water, CO2 + water, and how anthropogenic green-house gasses interact with water in both the liquid and glassy forms (this area of study is ongoing).

Resident associate at the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory. I’ve used neutron scattering techniques (both diffraction and INS), in addition to high energy x-ray total scattering at the APS, to study the structural properties of various glassy water phases, this includes the formation of high pressure glassy and crystalline phases of clathrate hydrates.

Senior Research and Development Staff Member, Chemical and Engineering Materials Division (CEMD), Oak Ridge National Laboratory. I’ve designed and constructed the High Pressure Neutron Diffraction Instrument (SNAP) at the Spallation Neutron Source. Subsequently neutron diffraction patterns have been measured from samples held under Mbar pressure conditions (1 Mbar  ~ 100 GPa, nearly the pressure at the Earth’s core-mantle boundary). This is at least a factor of 4 higher than has been measured before. The SNAP team has achieved this by implementing diamond anvil cell pressure technology onto ‘purpose built’ neutron instrumentation. Previous pressures available at ORNL measured in the 5-6 kbar range, and at the most advanced neutron sources world-wide routine pressures accessible were in the 100 - 200 kbar (~ 0.1 – 0.2 Mbar) range.