Measurement of ionization loss of 50 GeV protons in silicon with smoothly tunable up to 1 cm thickness using a single flat detector

Research of the ionization loss of 50 GeV protons, the path of which in the depleted layer of the silicon detector was smoothly regulated in the range from 0.3 to 10 mm, is presented. In the experiment, we used a flat silicon detector with a fixed thickness of the depleted layer of 300 μm. The smooth regulation of the path was realized due to the variation of the angle between the surface of the detector and the incident proton beam. The comparison of experimental data and theoretical calculations of the ionization loss demonstrates agreement in all range of thicknesses. Results of the research can be used in order to control the angle between the surface of the detector and the incident beam of relativistic particles. Besides, the results can be used in the analysis of data from astrophysical silicon detectors of charged particles if high-energy particles crossed flat detectors at arbitrary angle.

Cosmic-ray-related Signals from Detectors in Space: The Spitzer/IRAC Si:As IBC Devices

We evaluate the hit rate of cosmic rays and their daughter particles on the Si:As IBC detectors in the IRAC instrument on the Spitzer Space Telescope. The hit rate follows the ambient proton flux closely, but the hits occur at more than twice the rate expected just from this flux. Toward large amplitudes, the size distribution of hits by single-charge particles (muons) follows the Landau Distribution. The amplitudes of the hits are distributed to well below the energy loss of a traditional “average minimum-ionizing proton” as a result of statistical fluctuations in the ionization loss within the detectors. Nonetheless, hits with amplitudes less than a few hundred electrons are rare; this places nearly all hits in an amplitude range that is readily identified given the read noises of modern solid-state detectors. The spread of individual hits over multiple pixels is dominated by geometric effects, i.e., the range of incident angles, but shows a modest excess probably due to: (1) showering and scattering of particles; (2) the energy imparted on the ionization products by the energetic protons; and (3) interpixel capacitance. Although this study is focused on a specific detector type, it should have general application to operation of modern solid-state detectors in space.

On the ionization loss spectra of high-energy channeled negatively charged particles

The ionization loss spectra of high-energy negatively charged particles which move in the planar channeling mode in a silicon crystal are studied with the use of numerical simulation. The case when the crystal thickness is on the order of the dechanneling length $$l_d$$ld is considered. It is shown that in this case the shape of the spectrum noticeably depends on $$l_d$$ld. The evolution of various characteristic parameters of the spectrum with the change of $$l_d$$ld is investigated. A method of the experimental determination of $$l_d$$ld on the basis of the measurement of the ionization loss spectrum is proposed.

Earth's radiation belts' ions: patterns of the spatial-energy structure and its solar-cyclic variations

Spatial-energy distributions of the stationary fluxes of protons, helium, and ions of the carbon–nitrogen–oxygen (CNO) group, with energy from E ∼100 keV to 200 MeV, in the Earth's radiation belts (ERBs), at L∼1–8, are considered here using data from satellites during the period from 1961 to 2017. It has been found that the results of these measurements line up in the {E,L} space, following some regular patterns. The ion ERB shows a single intensity peak that moves toward Earth with increasing energy and decreasing ion mass. Solar-cyclic (11-year) variations in the distributions of protons, helium, and the CNO group ion fluxes in the ERB are studied. In the inner regions of the ERB, it has been observed that fluxes decrease with increasing solar activity and that the solar-cyclic variations of fluxes of Z≥2 ions are much greater than those for protons; moreover, it seems that they increase with increasing atomic number Z. It is suggested that heavier ion intensities peak further from the Earth and vary more over the solar cycle, as they have more strong ionization losses. These results also indicate that the coefficient DLL of the radial diffusion of the ERB ions changes much less than the ionization loss rates of ions with Z≥2 due to variations in the level of solar activity.

Structural features of monohydrated 2-(4-fluorophenyl)ethylamine: a combined spectroscopic and computational study

A jet-cooled singly hydrated 2-(4-fluorophenyl)ethylamine (4-FPEA–H2O) cluster has been studied by ionization-loss stimulated Raman spectroscopy of the 4-FPEA photofragment and density functional calculations of the parent.