Search results for "stopp"
showing 10 items of 75 documents
Nonlinear stopping power of an electron gas for slow ions
1986
Theoretical calculations of the stopping power of the electron gas for slow ions, v${v}_{F}$, are reviewed. New results are presented for stopping power and effective charge based on nonlinear density-functional calculations. Extensive comparisons with available experimental data show that these new theoretical results are clearly superior to earlier calculations based on linear theory.
New experimental stopping power data of 4He, 16O, 40Ar, 48Ca and 84Kr projectiles in different solid materials
2018
Abstract New experimental data on energy loss of 4 He, 16 O, 40 Ar, 48 Ca and 84 Kr ions in thin, self-supporting foils of C, Al, Ni, Ag, Lu, Au, Pb and Th are presented. The measurements, using the TOF-E method, were done in a very broad energy range around the stopping power maximum; typically from 0.1 to 11 MeV/u. When available, the extracted stopping power values are compared with the previously published data. The overall agreement is good although a fair comparison is difficult as the covered energy range is much larger than in previous measurements. The small error bars and a broad coverage allowed us to test the predictions of theoretical codes: PASS, CasP, and semi-empirical progr…
A novel method for obtaining continuous stopping power curves
2001
Abstract A new method has been developed for obtaining continuous stopping power curves in transmission geometry. In the method both the incident energy of the particle and its energy after passing through the sample foil are extracted directly from the semiconductor detector. Full range of energies is measured simultaneously eliminating step-by-step measurements and providing continuous data. A time-of-flight (TOF) spectrometer provides unambiguous matching of relevant particle groups from the run with and without absorber. Suitable energy distribution of incident particles was achieved by choosing the right thickness and tilting angle of a scattering foil. The method is very fast and reli…
Probe prototypes based on TlBr detectors
2009
Abstract Detectors based on TlBr crystals are ideally suited for the probes, where small size and rapid stopping power are highly desirable attributes. The development results of TlBr probes for medical and nuclear industry applications are presented here. Probes for both applications include TlBr detectors with dimensions of 5×5×2 mm 3 and a microelectronics preamplifier. The different construction and technological aspects of probes designed for both application types are discussed. The probes were tested over a wide energy range. We obtained energy resolutions of 3.6, 4.9 and 14.5 keV at energies of 59.6, 122 and 662 keV, respectively, for the developed probe prototypes at room temperatu…
Barkas effect with use of antiprotons and protons.
1989
The difference in the range of protons and antiprotons in matter, an example of the Barkas effect, is observed in a simple time-of-flight apparatus. The ranges of 5.9-MeV antiprotons and protons differ by about 6% in a degrader made predominantly of aluminum.
Energy loss measurement of protons in liquid water
2011
The proton stopping power of liquid water was, for the first time, measured in the energy range 4.7-15.2 MeV. The proton energies were determined by the time-of-flight transmission technique with the microchannel plate detectors, which were especially developed for timing applications. The results are compared to the literature values (from ICRU Report 49 (1993) and Janni's tabulation (1982 At. Data Nucl. Data Tables 27 147-339)) which are based on Bethe's formula and an agreement is found within the experimental uncertainty of 4.6%. Thus, earlier reported discrepancy between the experimental and literature stopping power values at lower energies was not observed at the energies considered …
Optional Sampling Theorems
2020
In Chapter 9 we saw that martingales are transformed into martingales if we apply certain admissible gambling strategies. In this chapter, we establish a similar stability property for martingales that are stopped at a random time (optional sampling and optional stopping). In order also to obtain these results for submartingales and supermartingales, in the first section, we start with a decomposition theorem for adapted processes. We show the optional sampling and optional stopping theorems in the second section. The chapter finishes with the investigation of random stopping times with an infinite time horizon.
Optimal selection of thek best of a sequence withk stops
1997
We first consider the situation in which the decision-maker is allowed to have five choices with purpose to choose exactly the five absolute best candidates fromN applicants. The optimal stopping rule and the maximum probability of making the right five-choice are given for largeN eN, the maximum asymptotic value of the probability of the best choice being limN→∝P (win) ≈ 0.104305. Then, we study the general problem of selecting thek best of a sequence withk stops, constructing first a rough solution for this problem. Using this suboptimal solution, we find an approximation for the optimal probability valuesPk of the form $$P_k \approx \frac{1}{{(e - 1)k + 1}}$$ for any k eN.
Appaesamenti alpini. Dal caos percettivo al contrafactum geografico.
2016
Un'analisi della costruzione del paesaggio alpino nell'opera "Il Bel paese" di Antonio Stoppani. Le relazioni con Von Humboldt e de Saussure.
Determination of molecular stopping cross section of 12C, 16O, 28Si, 35Cl, 58Ni, 79Br, and 127I in silicon nitride
2015
Abstract Silicon nitride is a technologically important material in a range of applications due to a combination of important properties. Ion beam analysis techniques, and in particular, heavy ion elastic recoil detection analysis can be used to determine the stoichiometry of silicon nitride films, which often deviates from the ideal Si3N4, as well as the content of impurities such as hydrogen, even in the presence of other materials or in a matrix containing heavier elements. Accurate quantification of IBA results depends on the basic data used in the data analysis. Quantitative depth profiling relies on the knowledge of the stopping power cross sections of the materials studied for the io…