نتایج جستجو برای: π electron cloud
تعداد نتایج: 423554 فیلتر نتایج به سال:
The Cornell Electron Storage Ring (CESR) has been reconfigured as a test accelerator (CesrTA) for a program of electron cloud (EC) research at ultra low emittance. The instrumentation in the ring has been upgraded with local diagnostics for measurement of cloud density and with improved beam diagnostics for the characterization of both the low emittance performance and the beam dynamics of high...
Electron cloud density in the Fermilab Main Injector was measured by observing microwave transmission along the vacuum tube. Presence of the electron cloud reduces the velocity of the microwave signal. Both frequency and time domain methods reveal relative cloud density and time evolution. The effect of beam time structure is clearly evident. The accelerator magnetic field effects the distribut...
Electron cloud induces a transverse wake force which makes a correlation between bunch by bunch, namely a transverse displacement of a bunch causes a perturbation of electron cloud, which affects the transverse motion of following bunches. The correlation can be regard as a kind of wake force. We study the coupled bunch instability caused by electron cloud in drift space and in weak solenoid fi...
The transverse instability in a beam and the blow-up in its size caused by an electron cloud become increasingly important in high-intensity accelerators. The electron cloud builds up through beam-induced multipacting. We investigated the energy spectrum of an electron cloud with short bunch using particle simulation. A "stop-band" structure is found and a model is suggested to explain and to d...
The electron cloud induced by the LHC beam in the SPS occurs mainly in the dipoles and it is responsible for strong transverse instabilities. In the horizontal plane a coupled bunch mode instability develops in a few tens of turns at injection. Tune shift measurements, mode number and phase space analyses have been performed at different energies and provide information about the electron cloud...
Incorporation of two biphenylene-bridged 4,4'-bipyridinium extended viologen units into a para-phenylene-based cyclophane results in a synthetic receptor that is ~2 nm long and adopts a box-like geometry. This cyclophane, Ex(2)Box(4+), possesses the ability to form binary and ternary complexes with a myriad of guest molecules ranging from long π-electron-rich polycyclic aromatic hydrocarbons, s...
The interaction of delocalized π-electrons with molecular vibrations is key to charge transport processes in π-conjugated organic materials based on aromatic monomers. Yet the role that specific aromatic motifs play on charge transfer is poorly understood. Here we show that the molecular edge topology in charged catacondensed aromatic hydrocarbons influences the Herzberg-Teller coupling of π-el...
The title mol-ecule, (E)-2,3',4,5-tetra-methoxy-stilbene, C(18)H(20)O(4), is virtually planar. The angle between the two benzene rings is 4.06 (6)°. The inter-molecular inter-actions present in the structure are weak. There are C-H⋯O hydrogen bonds and C-H⋯π-electron ring inter-actions. The mol-ecules are ordered into planes that are parallel to (01). The distance between adjacent planes is abo...
The HADES experiment, installed at GSI, Darmstadt, measures di-electron production in A+A, p/π + N and p/π + A collisions. Here, the π and η Dalitz decays have been reconstructed in the exclusive p + p reaction at 2.2 GeV to form a reference cocktail for long-lived di-electron sources. In the C+C reaction at 1 and 2 GeV/u, these long-lived sources have been subtracted from the measured inclusiv...
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