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It is important to optimize the crystal-photodetector coupling for gamma detection since it improves the light extraction and is directly linked to the achieved time resolution. In this paper we present our work on altering the geometry of the crystal coupling face to enhance the light output. Simulations compare the light output of alternative geometries of the crystal extraction face with respect to that of the regular cuboid geometry. We machined two different crystal shapes from 2 × 2 × 15 mm3 LSO crystals and measured the light output for different wrapping and coupling conditions. We also measured the coincidence time resolution (CTR) of the shaped crystals to compare the effect of timing on shaped crystals with respect to the reference samples. Simulations predicted an increase of up to 35% in light transfer efficiency for certain geometries of the exit face with respect to that of a regular cuboid geometry. Experimental measurements performed on shaped LSO crystals (2 × 2 × 15 mm3) show that an increase in light output of up to 40% and a systematic improvement in CTR of at least 5% is possible for one of the tested geometries. This opens new windows for preparing crystals used in TOF-PET scanners and high energy physics experiments.

Laser-cooled atoms are central to modern precision measurements. They are also increasingly important as an enabling technology for experimental cavity quantum electrodynamics, quantum information processing and matter-wave interferometry. Although significant progress has been made in miniaturizing atomic metrological devices, these are limited in accuracy by their use of hot atomic ensembles and buffer gases. Advances have also been made in producing portable apparatus that benefits from the advantages of atoms in the microkelvin regime. However, simplifying atomic cooling and loading using microfabrication technology has proved difficult. In this Letter we address this problem, realizing an atom chip that enables the integration of laser cooling and trapping into a compact apparatus. Our source delivers ten thousand times more atoms than previous magneto-optical traps with microfabricated optics and, for the first time, can reach sub-Doppler temperatures. Moreover, the same chip design offers a simple way to form stable optical lattices. These features, combined with simplicity of fabrication and ease of operation, make these new traps a key advance in the development of cold-atom technology for high-accuracy, portable measurement devices. © 2013 Macmillan Publishers Limited. All rights reserved.

We have made magneto-optical traps (MOTs) on a chip which is able to cool and trap ~108 atoms directly from a ~1cm3 thermal background of 87Rb. Diffraction gratings are used to manipulate the light from a single input beam to create the beams required for a MOT [1,2]. The gratings are etched into the surface of a silicon or GaAs wafer by either electron beam, or photo-lithography making them simple to fabricate and integrate into other atom chip architectures. We have developed a variety of gratings for utilisation both inside and outside a vacuum chamber - facilitating their incorporation into both new and existing devices. Unlike previously integrated cold atom sources on a chip [3,4] the atoms now sit above the surface where they can be easily imaged, manipulated and transferred into other on-chip potentials.