Folded acoustic phonons in InAs-AlAs strained-layer superlattices
Raman spectroscopy is used to characterize highly mismatched (7%) InAs‐AlAs superlattices grown by atomic layer molecular beam epitaxy. In particular, folded acoustic modes are presented and compared with two different theoretical models (Rytov and linear chain). We find good agreement between theory and experiments. We estimate, with a simple model, the magnitude of the effect of the strain on the phonon frequency shifts.
Higher order zone‐folded modes in ZnSe‐ZnS strained‐layer superlattices
Higher order (up to the 5th order) zone‐folded acoustic modes in ZnSe‐ZnS strained‐layer superlattices (SLSs) were observed by means of Raman scattering. Structural characterization of both periodicity of superlattices and roughness of the interface was done by means of transmission electron microscopy (TEM). The Raman spectrum of zone‐folded modes was well explained by the theoretical calculation which takes account of two observed structural characteristics of the sample, the periodicity of the superlattices, and the roughness of the interface. This clearly shows the strain does not matter to the observation of the zone‐folded modes.
A slowly rotating coil system for AC field measurements of Fermilab Booster correctors
A method for measurement of rapidly changing magnetic fields has been developed and applied to the testing of new room temperature corrector packages designed for the Fermilab Booster Synchrotron. The method is based on fast digitization of a slowly rotating tangential coil probe, with analysis combining the measured coil voltages across a set of successive magnet current cycles. This paper presents results on the field quality measured for the normal and skew dipole, quadrupole, and sextupole elements in several of these corrector packages.