Characterization Of Electron Bunches Research Articles

Анализ фазовых равновесий в тройной системе Ge–P–Sn

На основании анализа характера фазовых равновесий в двойных системах, ограняющих диаграмму состояний тройной системы Ge – P – Sn, предложены теоретически возможные схемы ее фазового субсолидусного разграничения. Исследование методом рентгенофазового анализа образцов, принадлежащих политермическим сечениям Sn4P3-Ge, Sn4P3-GeP, показало, что разделение трехкомпонентной диаграммы состояния ниже солидуса осуществляется с помощью сечений Sn4P3-Ge, Sn4P3 -GeP и SnP3-GeP. Построенная по данным дифференциального термического анализа фазовая диаграмма сечения Sn4P3-Ge представляет диаграмму эвтектического типа с координатами эвтектической точки 800 К, 15 mol % Ge.
 
 
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Optical gating and streaking of free electrons with sub-optical cycle precision

The temporal resolution of ultrafast electron diffraction and microscopy experiments is currently limited by the available experimental techniques for the generation and characterization of electron bunches with single femtosecond or attosecond durations. Here, we present proof of principle experiments of an optical gating concept for free electrons via direct time-domain visualization of the sub-optical cycle energy and transverse momentum structure imprinted on the electron beam. We demonstrate a temporal resolution of 1.2±0.3 fs. The scheme is based on the synchronous interaction between electrons and the near-field mode of a dielectric nano-grating excited by a femtosecond laser pulse with an optical period duration of 6.5 fs. The sub-optical cycle resolution demonstrated here is promising for use in laser-driven streak cameras for attosecond temporal characterization of bunched particle beams as well as time-resolved experiments with free-electron beams.

Erratum: Generation and Characterization of Electron Bunches with Ramped Current Profiles in a Dual-Frequency Superconducting Linear Accelerator [Phys. Rev. Lett.108, 034801 (2012)

Erratum: Generation and Characterization of Electron Bunches with Ramped Current Profiles in a Dual-Frequency Superconducting Linear Accelerator [Phys. Rev. Lett.<b>108</b>, 034801 (2012)

Generation and Characterization of Electron Bunches with Ramped Current Profiles in a Dual-Frequency Superconducting Linear Accelerator

We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radio frequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced ~700-MeV bunches have peak currents of the order of a kilo-Ampère. Data taken for various accelerator settings demonstrate the versatility of the method and, in particular, its ability to produce current profiles that have a quasilinear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak accelerating electric fields with transformer ratios larger than 2 in dielectric-lined waveguides.

Single-shot terahertz pulse characterization via two-dimensional electro-optic imaging with dual echelons

A single-shot measurement of terahertz electromagnetic pulses is implemented using two-dimensional electro-optic imaging with dual echelon optics. The reported embodiment produces sequentially delayed multiprobe beamlets, routinely providing a time window of >10 ps with ~25 fs temporal step sizes. Because of its simplicity and robustness, the technique is ideally suited for real-time ultrashort relativistic electron bunch characterization.

Terahertz radiation as a bunch diagnostic for laser-wakefield-accelerated electron bunches

Experimental results are reported from two measurement techniques (semiconductor switching and electro-optic sampling) that allow temporal characterization of electron bunches produced by a laser-driven plasma-based accelerator. As femtosecond electron bunches exit the plasma-vacuum interface, coherent transition radiation (at THz frequencies) is emitted. Measuring the properties of this radiation allows characterization of the electron bunches. Theoretical work on the emission mechanism is presented, including a model that calculates the THz wave form from a given bunch profile. It is found that the spectrum of the THz pulse is coherent up to the 200 μm thick crystal (ZnTe) detection limit of 4THz, which corresponds to the production of sub-50fs (rms) electron bunch structure. The measurements demonstrate both the shot-to-shot stability of bunch parameters that are critical to THz emission (such as total charge and bunch length), as well as femtosecond synchronization among bunch, THz pulse, and laser beam.