The Wide Angular-Range Chopper Spectrometer at SNS

and Doug Abernathy at ARCS

Materials researcher Judy Pang and instrument scientist Doug Abernathy at ARCS.

ARCS is optimized to provide a high neutron flux at the sample and a large solid angle of detector coverage. This spectrometer is capable of selecting incident energies over the full energy spectrum of neutrons, making it useful for studies of excitations from a few to several hundred milli-electron volts. An elliptically shaped supermirror guide in the incident flight path boosts the performance at the lower end of this range. The sample and detector vacuum chambers provide a window-free final flight path and incorporate a large gate valve to allow rapid sample changeout.

A T0 neutron chopper not only blocks the prompt radiation from the source but also eliminates unwanted neutrons from the incident beam line.

Applications

The increased sensitivity of ARCS offers new opportunities for scientific studies in the following areas.

Lattice Dynamics

  • Entropy and the effects of vibrational modes on stability and phase transitions of solids
  • Excitations in disordered materials; effects of nanoscale features on vibrational entropy and thermodynamic stability
  • Equations-of-state from the measured phonon density-of-states versus temperature and pressure
  • Phonons in correlated-electron materials; coupling of lattice and electronic degrees of freedom in high Tc, heavy-fermion and mixed valence materials

Magnetic Dynamics

  • High-temperature superconductivity-spin dynamics in superconductors and precursor compounds and crystal field spectroscopy
  • Low-dimensional systems; one-dimensional quantum magnets and low-dimensional conductors
  • Magnetism in actinide materials; heavy fermion magnetism and superconductivity

Chemical Physics

  • Deep inelastic neutron scattering studies of hydrogen