Measurement of the Cosmic Ray e(+)+e(-) Spectrum from 20 GeV to 1 TeV with the Fermi Large Area Telescope

Designed as a high-sensitivity gamma-ray observatory, the Fermi Large Area Telescope is also an electron detector with a large acceptance exceeding 2 m2 sr at 300 GeV. Building on the gamma-ray analysis, we have developed an efficient electron detection strategy which provides sufficient background rejection for measurement of the steeply falling electron spectrum up to 1 TeV. Our high precision data show that the electron spectrum falls with energy as E-3.0 and does not exhibit prominent spectral features. Interpretations in terms of a conventional diffusive model as well as a potential local extra component are briefly discussed

Fermi establishes classical novae as a distinct class of gamma-ray sources

A classical nova results from runaway thermonuclear explosions on the surface of a white dwarf that accretes matter from a low-mass main-sequence stellar companion. In 2012 and 2013, three novae were detected in γ rays and stood in contrast to the first γ-ray-detected nova V407 Cygni 2010, which belongs to a rare class of symbiotic binary systems. Despite likely differences in the compositions and masses of their white dwarf progenitors, the three classical novae are similarly characterized as soft-spectrum transient γ-ray sources detected over 2- to 3-week durations. The γ-ray detections point to unexpected high-energy particle acceleration processes linked to the mass ejection from thermonuclear explosions in an unanticipated class of Galactic γ-ray sources

X-Ray Computed Tomography for Dimensional Metrology

X-ray computed tomography (CT) has emerged over the last years as an innovative dimensional measuring technique and has been increasingly applied in industry. This chapter describes the state of the art, the main technical characteristics, and examples of applications of CT in industrial dimensional metrology. Although still in its youth, metrological CT offers unique solutions and provides several advantages in comparison to other coordinate measuring systems such as tactile coordinate measuring machines. In particular, CT systems allow reconstructing holistic three-dimensional models of the scanned workpieces, which are then used to obtain nondestructive and noncontact measurements of outer as well as inner features. However, important drawbacks still limit a wider acceptance of CT in industrial metrology. One of the most critical aspects is the establishment of metrological traceability, which is often challenging due to many and complex error sources that affect CT measurements and complicate the evaluation of metrological performances and of task-specific uncertainties