GEM-MIGAS Electron Multiplier Operation in Argon-Methane Mixtures
A Gas Electron Multiplier with a Micro-Induction Gap Amplifying Structure (GEM-MIGAS) is formed when a conventional GEM is operated with a short induction gap, typically 50 mum. A three-dimensional electric field simulation of a GEM-MIGAS detector was performed in order to evaluate the electric field profile in the different regions of the structure. Different electrostatic conditions were undertaken to forecast the detector performance in gas medium. An experimental study of GEM-MIGAS operating in an Ar/CH4 (90/10%) gas mixture, in pure CH4 and in pure Ar was carried out. Performance characteristics including charge gain and energy resolution for 5.9 keV X-rays are presented.
First results with THGEM followed by submillimetric multiplying gap
This work presents the first results dealing with THGEMs coupled to submillimetric multiplication gaps, operated in an atmospheric pressure of Ne/CF4. The experimental studies done so far with a THGEM coupled to submillimetric multiplication gaps achieved charge-gains of 4 × 104 and 1 × 105 in Ne/CF4 (95:5), for 0.4 mm and 0.8 mm gaps, respectively, values that are one order of magnitude higher than those obtained in single-THGEM configuration and approximately half from those obtained for a cascaded-THGEM configuration. The present studies evaluate the performance operation in terms of the charge-gain characteristics and X-ray energy resolution.
LYAPUNOV-BASED TRANSFER BETWEEN ELLIPTIC KEPLERIAN ORBITS
We present a study of the transfer of satellites between elliptic Keplerian orbits using Lyapunov stability theory specific to this problem. The construction of Lyapunov functions is based on the fact that a non-degenerate Keplerian orbit is uniquely described by its angular momentum and Laplace (- Runge-Lenz) vectors. We suggest a Lyapunov function, which gives a feedback controller such that the target elliptic orbit becomes a locally asymptotically stable periodic orbit in the closed-loop dynamics. We show how to perform a global transfer between two arbitrary elliptic orbits based on the local transfer result. Finally, a second Lyapunov function is presented that works only for circular target orbits.