Time-domain terahertz compressive imaging

We present an implementation of the single-pixel imaging approach into a terahertz (THz) time-domain spectroscopy (TDS) system. We demonstrate the indirect coherent reconstruction of THz temporal waveforms at each spatial position of an object, without the need of mechanical raster-scanning. First, we exploit such temporal information to realize (far-field) time-of-flight images. In addition, as a proof of concept, we apply a typical compressive sensing algorithm to demonstrate image reconstruction with less than 50% of the total required measurements. Finally, the access to frequency domain is also demonstrated by reconstructing spectral images of an object featuring an absorption line in the THz range. The combination of single-pixel imaging with compressive sensing algorithms allows to reduce both complexity and acquisition time of current THz-TDS imaging systems.

Absorbed dose rate estimation for protons, leptons and helium observed with AMS01 experiment in low earth orbit during STS-91 mission

The Alpha Magnetic Spectrometer (AMS01), a high-sensitivity particle spectrometer, was successfully flown for 10 d in June 1998 (STS91) in the orbit of the International Space Station (51.7 degrees, -380 km). A high-statistics dataset of galactic cosmic rays were measured as a function of geomagnetic latitude, including the primary protons, leptons and helium as well as the trapped and quasi-trapped proton and lepton components. In this paper, the absorbed dose rate owing to the protons, leptons and helium are presented and compared with measurements made by other instruments flown on the same mission.