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Proton

About: Proton is a research topic. Over the lifetime, 31263 publications have been published within this topic receiving 573472 citations. The topic is also known as: p & ¹H⁺.


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Journal ArticleDOI
TL;DR: In this paper, the authors measured the time integrated transverse profile of the proton bunch at two locations downstream of the AWAKE plasma and inferred the occurrence of self-modulation instability (SMI) by measuring defocused protons with an angle of 1 mrad.
Abstract: AWAKE, the Advanced Proton-Driven Plasma Wakefield Acceleration Experiment, is a proof-of-principle R&D experiment at CERN using a 400 GeV / c proton beam from the CERN SPS (longitudinal beam size σ z = 12 cm ) which will be sent into a 10 m long plasma section with a nominal density of ≈ 7 × 10 14 atoms / cm 3 (plasma wavelength λ p = 1.2 mm ). In this paper we show that by measuring the time integrated transverse profile of the proton bunch at two locations downstream of the AWAKE plasma, information about the occurrence of the self-modulation instability (SMI) can be inferred. In particular we show that measuring defocused protons with an angle of 1 mrad corresponds to having electric fields in the order of GV/m and fully developed self-modulation of the proton bunch. Additionally, by measuring the defocused beam edge of the self-modulated bunch, information about the growth rate of the instability can be extracted. If hosing instability occurs, it could be detected by measuring a non-uniform defocused beam shape with changing radius. Using a 1 mm thick Chromox scintillation screen for imaging of the self-modulated proton bunch, an edge resolution of 0.6 mm and hence an SMI saturation point resolution of 1.2 m can be achieved.

14 citations

Journal ArticleDOI
TL;DR: In this article, a self-contained time-of-flight spectrometer for neutrons from 1 to about 500 MeV was developed, which consists of two scintillation counters.

14 citations

Journal ArticleDOI
TL;DR: A kinetic PT model derived from all-atom molecular dynamics simulations is used and it is demonstrated that the 2DIR spectrum of the isotope-labeled channel contain information on the PT rate, which may be extracted by analyzing the antidiagonal linewidth of the spectral feature related to the labeled site.
Abstract: We propose a new method to determine the proton transfer (PT) rate in channel proteins by two-dimensional infrared (2DIR) spectroscopy. Proton transport processes in biological systems, such as proton channels, trigger numerous fundamental biochemical reactions. Due to the limitation in both spatial and time resolution of the traditional experimental approaches, describing the whole proton transport process and identifying the rate limiting steps at the molecular level is challenging. In the present paper, we focus on proton transport through the Gramicidin A channel. Using a kinetic PT model derived from all-atom molecular dynamics simulations, we model the amide I region of the 2DIR spectrum of the channel protein to examine its sensitivity to the proton transport process. We demonstrate that the 2DIR spectrum of the isotope-labeled channel contain information on the PT rate, which may be extracted by analyzing the antidiagonal linewidth of the spectral feature related to the labeled site. Such experiments in combination with detailed numerical simulations should allow the extraction of site dependent PT rates, providing a method for identifying possible rate limiting steps for proton channel transfer.

14 citations

Journal ArticleDOI
TL;DR: In this paper, the low-lying structure of 55Sc has been investigated using in-beam \gamma-ray spectroscopy with the 9Be(56Ti,55Sc+\gamma)X one-proton removal and inelastic-scattering reactions at the RIKEN Radioactive Isotope Beam Factory.
Abstract: The low-lying structure of 55Sc has been investigated using in-beam \gamma-ray spectroscopy with the 9Be(56Ti,55Sc+\gamma)X one-proton removal and 9Be(55Sc,55Sc+\gamma)X inelastic-scattering reactions at the RIKEN Radioactive Isotope Beam Factory. Transitions with energies of 572(4), 695(5), 1539(10), 1730(20), 1854(27), 2091(19), 2452(26), and 3241(39) keV are reported, and a level scheme has been constructed using \gamma\gamma coincidence relationships and \gamma-ray relative intensities. The results are compared to large-scale shell-model calculations in the sd-pf model space, which account for positive-parity states from proton-hole cross-shell excitations, and to {\it ab initio} shell-model calculations from the in-medium similarity renormalization group that includes three-nucleon forces explicitly. The results of proton-removal reaction theory with the eikonal model approach were adopted to aid identification of positive-parity states in the level scheme; experimental counterparts of theoretical 1/2+1 and 3/2+1 states are suggested from measured decay patterns. The energy of the first 3/2- state, which is sensitive to the neutron shell gap at the Fermi surface, was determined. The result indicates a rapid weakening of the N=34 subshell closure in pf-shell nuclei at Z>20, even when only a single proton occupies the \pi f7/2 orbital.

14 citations

Journal ArticleDOI
TL;DR: It was found that fluorination leads to an ordered hydrogen bonding structure of the hydrated protons near the channel surface, and confinement weakens the formation of the bifurcated hydrogen bonds in the radial direction.
Abstract: The relationship between the proton conductive channel and the hydrated proton structure is of significant importance for understanding the deformed hydrogen bonding network of the confined protons which matches the nanochannel. In general, the structure of hydrated protons in the nanochannel of the proton exchange membrane is affected by several factors. To investigate the independent effect of each factor, it is necessary to eliminate the interference of other factors. In this paper, a one-dimensional carbon nanotube decorated with fluorine was built to investigate the independent effects of nanoscale confinement and fluorination on the structural properties of hydrated protons in the nanochannel using classical molecular dynamics simulation. In order to characterize the structure of hydrated protons confined in the channel, the hydrogen bonding interaction between water and the hydrated protons has been studied according to suitable hydrogen bond criteria. The hydrogen bond criteria were proposed based on the radial distribution function, angle distribution and pair-potential energy distribution. It was found that fluorination leads to an ordered hydrogen bonding structure of the hydrated protons near the channel surface, and confinement weakens the formation of the bifurcated hydrogen bonds in the radial direction. Besides, fluorination lowers the free energy barrier of hydronium along the nanochannel, but slightly increases the barrier for water. This leads to disintegration of the sequential hydrogen bond network in the fluorinated CNTs with small size. In the fluorinated CNTs with large diameter, the lower degree of confinement produces a spiral-like sequential hydrogen bond network with few bifurcated hydrogen bonds in the central region. This structure might promote unidirectional proton transfer along the channel without random movement. This study provides the cooperative effect of confinement dimension and fluorination on the structure and hydrogen bonding of the slightly acidic water in the nanoscale channel.

14 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,468
20222,886
2021714
2020722
2019758
2018750