Neutron scattering experiments on liquid droplets using electrostatic levitation

Abstract

We present a compact electrostatic levitator as a new sample environment for high quality neutron scattering experiments on melts. By this containerless approach we are able to investigate chemically highly reactive melts in a broad temperature range from high temperatures down to very low temperatures in the metastable liquid. The sample volume typical for former electrostatic levitation facilities was increased by one order of magnitude to a sample diameter of 6 mm. A minimized amount of scattering material in the vicinity of the neutron beam results in a low background of the device and thus in a significantly improved signal-to-noise ratio. Even in these large samples the temperature gradient induced by laser heating is less than 20 K. As a first result the Ni self-diffusion coefficient in Zr$_{64}$Ni$_{36}$ was measured by quasielastic neutron scattering at the time-of-flight spectrometer TOFTOF at the {FRM II} as a function of temperature. At an undercooling of 167K below the melting point deviations from an Arrhenius-type temperature dependence as observed in bulk metallic glass forming alloys become evident. Neutron diffraction experiments were performed at the high flux diffractometer D20 at the ILL. With a neutron wavelength of 0.94 AA a high quality total structure factor of Zr_64Ni_36 was measured in a broad temperature range at wave numbers between 0.6 AA-1 and 12 AA-1.