Extending the hydrogen storage limit in fullerene

Li6C60 has been chosen as the most representative system to study the hydrogenation mechanism in alkali-cluster intercalated fullerides. We present here a muon spin relaxation (mu SR) experiment that hints the chance to achieve a higher storage capacity on fullerene with respect to the values suggested in literature. Moreover, a linear relationship between the muonium adduct radical hyperfine frequency and the level of C-60 hydrogenation was found and it can be exploited to probe the C-60 hydrogenation level, giving more credit to this technique in the field of hydrogen storage materials. (C) 2017 Elsevier Ltd. All rights reserved.Peer reviewe

Development of a 3D CZT Spectrometer System with Digital Readout for Hard X/Gamma-Ray Astronomy

We report on the development and of a complete X/γ rays detection system (10-1000 keV) based on CZT spectrometers with spatial resolution in three dimensions (3D) and a digital electronics acquisition chain. The prototype is made by packing four linear modules, each composed of one 3D CZT sensors. Each sensors is realized using a single spectroscopic graded CZT crystal of about 20×20×5 mm3. An electrode structure consisting of 12 collecting anodes with a pitch of 1.6 mm and 3 drift strips between each pair of anodes for 48 strips (0.15 mm wide) on the anodic side was adopted. The cathode is made of 10 strips with a pitch of 2 mm and orthogonal to anode side strips. Since the reading of the drift strips will carried out by putting in parallel all the strips that occupy the same place with respect to a collecting anode, the channels number for each sensors is only 25. The detector readout front-is based on custom designed low noise charge sensitive pre-amplifiers (CSP) implemented in hybrid 16 channels board. The CZT module and its CSP front-end provide the signals to a multichannel Digital Pulse Processing FPGA based system able to digitize and process continuously the signals. The digital system implement an innovative firmware that allow performing fine time-tagging, online pulse shape and height analysis with good energy resolution

Recent advances in the development of high-resolution 3D cadmium zinc telluride drift strip detectors

In the last two decades, great efforts have been made in the development of 3D cadmium-zinc-Telluride (CZT) detectors operating at room temperature for gamma-ray spectroscopic imaging. This work presents the spectroscopic performance of new high-resolution CZT drift strip detectors, recently developed at IMEM-CNR of Parma (Italy) in collaboration with due2lab (Italy). The detectors (19.4 mm × 19.4 mm × 6 mm) are organized into collecting anode strips (pitch of 1.6 mm) and drift strips (pitch of 0.4 mm) which are negatively biased to optimize electron charge collection. The cathode is divided into strips orthogonal to the anode strips with a pitch of 2 mm. Dedicated pulse processing analysis was performed on a wide range of collected and induced charge pulse shapes using custom 32-channel digital readout electronics. Excellent room-Temperature energy resolution (1.3% FWHM at 662 keV) was achieved using the detectors without any spectral corrections. Further improvements (0.8% FWHM at 662 keV) were also obtained through a novel correction technique based on the analysis of collected-induced charge pulses from anode and drift strips. These activities are in the framework of two Italian research projects on the development of spectroscopic gamma-ray imagers (10-1000 keV) for astrophysical and medical applications

Moderately Elliptical Very Low Orbits (MEVLOs) as a Long-Term Solution to Orbital Debris

Long-term orbital debris is a continually growing problem that has proven challenging to overcome. A straightforward solution to the problem is to put the majority of future LEO spacecraft into Moderately Elliptical Very Low Orbits (MEVLOs) with perigees below approximately 300 km, apogees below approximately 500 km, and eccentricities in the range of 0.015 to 0.030. Orbital debris clouds cannot be sustained in this altitude regime and will decay and re-enter in times ranging from a few weeks to at most the time until the next solar maximum. This means that the debris population at this altitude is, and will remain, much lower than at higher altitudes and, of course, any satellites which explode or otherwise die in this region will not be a part of a long-term debris problem. The advantage of the elliptical orbit is that if a temporary failure causes the spacecraft to stop doing orbit maintenance burns for a moderate period of time, apogee will decay, perigee will change very little, and the orbit can be recovered with essentially no loss of total delta V. Of course, if the loss of orbit maintenance delta V is permanent, then the spacecraft will decay and re-enter, as is desirable