ABSTRACT
The alignment of ultra-high-vacuum sample transfer systems can be problematic when there is no direct line of sight to assist the user. We present the design of a simple and cheap system which greatly simplifies the alignment of sample transfer devices. Our method is based on the adaptation of a commercial digital camera which provides live views from within the vacuum chamber. The images of the camera are further processed using an image recognition and processing code which determines any misalignments and reports them to the user. Installation has proven to be extremely useful in order to align the sample with respect to the transfer mechanism. Furthermore, the alignment software can be easily adapted for other systems.
ABSTRACT
We report measurements of the acoustic and optical phason dispersion curves associated with the lattice of partial dislocations on the reconstructed (111) surface of gold. Our measurements of these low energy (<0.5 meV) weakly dispersive modes have been enabled by the very high resolution of the novel helium spin-echo technique. The results presented here constitute the first measurement of the phason dispersion of misfit dislocations, and possibly of excitations associated with any type of crystalline dislocations.
ABSTRACT
The helium spin echo spectrometer is a powerful apparatus for measuring surface dynamics and can be used in several different modes of operation. In this paper we present the first two-dimensional measurements of the wavelength intensity matrix, offering a new approach for studying surface phonons. The approach that we present is completely independent of the incident beam energy distribution and hence can be used to study inelastic scattering with ultra-high resolution. The additional insights obtained by using this new approach and its technical difficulties are discussed, and a comparison with other existing methods is given.
ABSTRACT
We describe an improved high intensity, recycling, supersonic atomic beam source. Changes address several issues previously limiting performance and reliability of the apparatus, including the use of newly available vacuum pumps and modifications to the recycling system. We achieve a source intensity of 2.5 x 10(19) atoms/s/sr, almost twice that previously achievable during recycling. Current limits on intensity are discussed.
