Limits for an inverse bremsstrahlung origin of the diffuse Galactic soft gamma-ray emission

RXTE, GINGA, and OSSE observations have revealed an intense low-energy gamma-ray continuum emission from the Galactic plane, which is commonly interpreted as evidence for the possible existence of a strong flux of low-energy cosmic ray electrons. In this paper I discuss the scenario of a hadronic origin of the soft Galactic gamma-ray continuum through inverse bremsstrahlung. A flux of low-energy cosmic rays strong enough to produce the observed spectrum of gamma-rays implies substantial gamma-ray emission at a few MeV through nuclear de-excitation. It is shown that the existing limits on excess 3-7 MeV emission from the Galactic plane, in concert with the constraints from pion-decay gamma-ray emission at higher energies, are in serious conflict with an inverse bremsstrahlung origin of the Galactic soft gamma-ray emission for any physically plausible low-energy cosmic ray spectrum. While in case of energetic heavy nuclei the limits are violated by about an order of magnitude, for a large population of low-energy protons the implied gamma-ray line flux and pion-decay continuum intensity are larger than the existing limits by at least a factor of 2.Comment: 4 pages, accepted for publication in A&

AMS tracking in-orbit performance

AMS-02 is a high precision magnetic spectrometer for cosmic rays in the GeV to TeV energy range. Its tracker consists of nine layers of double-sided silicon microstrip sensors. They are used to locate the trajectories of cosmic rays in the 0.14 T field of a cylindrical magnet, thus measuring their rigidity $p/Z$ and charge sign. In addition, they deliver a high resolution measurement of the absolute charge $|Z|$. The detector has been designed to operate in space with a position resolution of about 10 $\mu$m for each hit and charge identification capabilities up to $Z=26$. In this talk I describe the performance in orbit of this detector component and its impact on the overall performance of the spectrometer.Comment: 24th International Workshop on Vertex Detectors, 1-5 June 2015, Santa Fe, New Mexico, US

Experimentation and Physics at a Future Electron-Positron Linear Collider

I summarise the physics opportunities and experimental challenges at future Linear Colliders, using material from the recent ECFA/DESY workshop on the subject as well as contributions to the series of worldwide studies. For reasons of economy, the discussion is restricted to the European Tesla project and to its electron-positron mode only.Comment: 31 pages, 23 figures, 4 tables Invited talk given at the XXVIII International Meeting on Fundamental Physics, Sanl\'ucar de Barrameda, C\'adiz, Spain, 14-18 February 2000 Better figures at http://home.cern.ch/pohl/tesla.htm

Particle detection technology for space-borne astroparticle experiments

I review the transfer of technology from accelerator-based equipment to space-borne astroparticle detectors. Requirements for detection, identification and measurement of ions, electrons and photons in space are recalled. The additional requirements and restrictions imposed by the launch process in manned and unmanned space flight, as well as by the hostile environment in orbit, are analyzed. Technology readiness criteria and risk mitigation strategies are reviewed. Recent examples are given of missions and instruments in orbit, under construction or in the planning phase.Comment: Technology and Instrumentation in Particle Physics 2014 (TIPP 2014), June 2-6, 2014, Amsterdam, The Netherland

A spectral study of gamma-ray emitting AGN

In this paper I investigate the $\gamma$-ray spectra of AGN by summing up the intensity and the power-law fit statistic of Quasars and OVV's and BL Lac's separately. The spectrum of the average AGN is softer than that of the extragalactic $\gamma$-ray background. It may be that BL Lac's, of which the average has a harder spectrum than Quasars, make up the bulk of the extragalactic background. We also find cut-offs both at low and at high energies in the spectra of Quasars and OVV's, however only at the time of $\gamma$-ray outbursts. While the cut-off at high energies may have something to do with opacity, the cut-off at low energies may be taken as indication that the $\gamma$-ray emission of Quasars is not a one component spectrum.Comment: 4 pages, Proceedings of Heidelberg workshop on gamma-ray emitting AG

The average GeV-band Emission from Gamma-Ray Bursts

We analyze the emission in the 0.3-30 GeV energy range of Gamma-Ray Bursts detected with the Fermi Gamma-ray Space Telescope. We concentrate on bursts that were previously only detected with the Gamma-Ray Burst Monitor in the keV energy range. These bursts will then be compared to the bursts that were individually detected with the Large Area Telescope at higher energies. To estimate the emission of faint GRBs we use non-standard analysis methods and sum over many GRBs to find an average signal which is significantly above background level. We use a subsample of 99 GRBs listed in the Burst Catalog from the first two years of observation. Although mostly not individually detectable, the bursts not detected by the Large Area Telescope on average emit a significant flux in the energy range from 0.3 GeV to 30 GeV, but their cumulative energy fluence is only 8% of that of all GRBs. Likewise, the GeV-to-MeV flux ratio is less and the GeV-band spectra are softer. We confirm that the GeV-band emission lasts much longer than the emission found in the keV energy range. The average allsky energy flux from GRBs in the GeV band is 6.4*10^-4 erg cm^-2 yr^-1 or only 4% of the energy flux of cosmic rays above the ankle at 10^18.6 eV.Comment: Astronomy and Astrophysics, version accepted for publicatio