AION/Magis

Abstract:

We manipulate a Bose-Einstein condensate using the optical trap created by the diffraction of a laser beam on a fast ferroelectric liquid crystal spatial light modulator. The modulator acts as a phase grating which can generate arbitrary diffraction patterns and be rapidly reconfigured at rates up to 1 kHz to create smooth, time-varying optical potentials. The flexibility of the device is demonstrated with our experimental results for splitting a Bose-Einstein condensate and independently transporting the separate parts of the atomic cloud. © 2006 The American Physical Society.

Abstract:

We investigated the tunnelling dynamics of a zero-temperature Bose-Einstein condensate in configuration of four potential wells arranged in a loop. We found three interesting dynamic regimes: (a) flows of matter with small amplitude, (b) steady flow, and (c) forced flow of matter for large amplitudes. The regime of quantum self-confinement has been studied and a new variant of it has been found for this system. © 2006 The American Physical Society.

Abstract:

We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5x10^{14} Neq/cm^2 to 5.9x10^{14} Neq/cm^2. The model correctly predicts the variation in the profiles as the temperature is changed from -10C to -25C. The measured charge collection profiles are inconsistent with the linearly-varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon. The model is now being used to calibrate pixel hit reconstruction algorithms for CMS.