We describe a reproducible method of fabricating adiabatic tapers with 3 -4 m diameter. The method is based on a heat-and-pull rig, whereby a CO 2 laser is continuously scanned across a length of fiber that is being pulled synchronously. Our system relies on a CO 2 mirror mounted on a geared stepper motor in order to scan the laser beam across the taper region. We show that this system offers a reliable alternative to more traditional rigs incorporating galvanometer scanners. We have routinely obtained transmission losses between 0.1 and 0.3 dB indicating the satisfactory production of adiabatic tapers. The operation of the rig is described in detail and an analysis on the produced tapers is provided. The flexibility of the rig is demonstrated by fabricating prolate dielectric microresonators using a microtapering technique. Such a rig is of interest to a range of fields that require tapered fiber fabrication such as microcavity-taper coupling, atom guiding along a tapered fiber, optical fiber sensing, and the fabrication of fused biconical tapered couplers.

On page 38, line 20, units of is printed as (rad)15 1, it should have been printed as (rad s 1. On page 39, line 51, the text was incorrectly printed as follows: 'This leads to an avoidable acceleration of the electron beam, and to a different ionisation impact cross-section (and branching fractions) than encountered for the case of the NIST tabulation at the standard 70 eV ionisation energy' The text should have been printed as: 'This leads to an unavoidable acceleration of the electron beam, and to a different ionisation impact cross-section (and branching fractions) than encountered for the case of the NIST tabulation at the standard 70 eV ionisation energy'. The publishers apologize for these errors.

Localisation of gamma-ray interaction points in monolithic scintillator crystals can simplify the design and improve the performance of a future Compton telescope for gamma-ray astronomy. In this paper we compare the position resolution of three monolithic scintillators: a 28 × 28 × 20 mm 3 (length × breadth × thickness) LaBr 3 :Ce crystal, a 25 × 25 × 20 mm 3 CeBr 3 crystal and a 25 × 25 × 10 mm 3 CeBr 3 crystal. Each crystal was encapsulated and coupled to an array of 4 × 4 silicon photomultipliers through an optical window. The measurements were conducted using 81 keV and 356 keV gamma-rays from a collimated 133 Ba source. The 3D position reconstruction of interaction points was performed using artificial neural networks trained with experimental data. Although the position resolution was significantly better for the thinner crystal, the 20 mm thick CeBr 3 crystal showed an acceptable resolution of about 5.4 mm FWHM for the x and y coordinates, and 7.8 mm FWHM for the z-coordinate (crystal depth) at 356 keV. These values were obtained from the full position scans of the crystal sides. The position resolution of the LaBr 3 :Ce crystal was found to be considerably worse, presumably due to the highly diffusive optical interface between the crystal and the optical window of the enclosure. The energy resolution (FWHM) measured for 662 keV gamma-rays was 4.0% for LaBr 3 :Ce and 5.5% for CeBr 3 . The same crystals equipped with a PMT (Hamamatsu R6322-100) gave an energy resolution of 3.0% and 4.7%, respectively.

Carbon dioxide has been produced from the impact of a monoenergetic O( 3 P) beam upon a surface cooled to 4.8 K and covered with a CO ice. Using temperature-programmed desorption and mass spectrometer detection, we have detected increasing amounts of CO 2 formation with O( 3 P) energies of 2, 5, 10, and 14 eV. This is the first measurement of polyatomic molecule formation on a surface with superthermal atoms. The goal of this work is to detect other polyatomic species, such as CH 3 OH, which can be formed under conditions that simulate the grain temperature, surface coverage, and superthermal atoms present in shock-heated circumstellar and interstellar regions.