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We present a detection system capable of imaging both single photon/positive ion and multiple coincidence photons/positive ions with extremely high spatial resolution. In this detector the photoelectrons excited by the incoming photons are multiplied by microchannel plate(s) (MCP). The process of multiplication is spatially constrained within an MCP pore, which can be as small as 4 μm for commercially available MCPs. An electron cloud originated by a single photoelectron is then encoded by a pixellated custom analog ASIC consisting of 105 K charge sensitive pixels of 50 μm in size arranged on a hexagonal grid. Each pixel registers the charge with an accuracy of

The Gamma-ray Large Area Space telescope (GLAST) is a gamma-ray satellite scheduled for launch in 2008. Before the assembly of the Tracker subsystem of the Large Area Telescope (LAT) science instrument of GLAST, every component (tray) and module (tower) has been subjected to extensive ground testing required to ensure successful launch and on-orbit operation. This paper describes the sequence and results of the environmental tests performed on an engineering model and all the flight hardware of the GLAST LAT Tracker. Environmental tests include vibration testing, thermal cycles and thermal-vacuum cycles of every tray and tower as well as the verification of their electrical performance.

Polarimetry of cosmic X-rays is one of the possible observational approaches, together with spectroscopy, photometry and imaging, to study celestial sources. It can provide a general tool to explore the structure of compact sources and derive information on mass and angular momentum of supermassive objects. Comparing with the other three modalities, the development of X-ray polarimetry is modest, due to the inefficiency of traditional X-ray polarimeters. In this paper a new instrument (the Micropattern Gas Detector) to measure the linear polarization of X-ray sources with high efficiency is presented. It is based on the photoelectric effect. Angle and amount of polarization is computed from the angular distribution of the photoelectron tracks, reconstructed by a finely segmented gas detector. The device has pixel read-out allowing a full 2-D image reconstruction. The improvement in sensitivity is nearly two orders of magnitude with respect to traditional polarimeters. At the focus of a large X-ray telescope, in orbit, it can detect low level of polarization in galactic and extragalactic sources.

Polarimeters flown so far were based on the Thomson scattering and Bragg diffraction with intrinsically limited sensitivity. In the present paper, we review the experiments based on those techniques and discuss possible optimization and implementation for X-ray astronomy.

Gamma-Ray Burst (GRB) emissions are so powerful to strongly influence any surrounding plasma. In this paper, we briefly discuss the possibility that a very intense initial burst of radiation produced by GRBs is the cause of stochastic wakefield particle acceleration in a surrounding plasma of moderate density. The stochastic WakeField Acceleration (WFA) provides an interesting link between GRB engine properties, as emission angle and total energy, and spectral features of the emitted photons.