Abstract
Plasma-wakefield accelerators driven by intense particle beams promise to significantly reduce the size of future high-energy facilities. Such applications require particle beams with a well-controlled energy spectrum, which necessitates detailed tailoring of the plasma wakefield. Precise measurements of the effective wakefield structure are therefore essential for optimising the acceleration process. Here we propose and demonstrate such a measurement technique that enables femtosecond-level (15 fs) sampling of longitudinal electric fields of order gigavolts-per-meter (0.8 GV m−1). This method—based on energy collimation of the incoming bunch—made it possible to investigate the effect of beam and plasma parameters on the beam-loaded longitudinally integrated plasma wakefield, showing good agreement with particle-in-cell simulations. These results open the door to high-quality operation of future plasma accelerators through precise control of the acceleration process.
Highlights
Plasma-wakefield accelerators driven by intense particle beams promise to significantly reduce the size of future high-energy facilities
The resulting energy spectrum of the accelerated particles is determined by the detailed structure of this plasma wakefield, which again depends on the exact distributions of plasma density and beam charge[7]
The method is based on separating the energy and time measurements of the longitudinal phase space of particle beams by energy collimation of chirped bunches, thereby overcoming the practical challenges faced by previous methods of temporally resolving bunches after plasma interaction
Summary
Plasma-wakefield accelerators driven by intense particle beams promise to significantly reduce the size of future high-energy facilities. We propose and demonstrate such a measurement technique that enables femtosecond-level (15 fs) sampling of longitudinal electric fields of order gigavolts-per-meter (0.8 GV m−1) This method—based on energy collimation of the incoming bunch—made it possible to investigate the effect of beam and plasma parameters on the beam-loaded longitudinally integrated plasma wakefield, showing good agreement with particle-in-cell simulations. The energy spectrum is commonly measured close to the plasma module to avoid excessive chromaticity This makes conventional use of a TDS highly impractical: the required ultrahighvacuum conditions cannot be met in the vicinity of a gas load such as a high-density plasma cell; the structure can be damaged by irradiation; and the diverging beams can sample off-axis longitudinal RF fields[22]. The measurement of the longitudinal slice position within the bunch for each collimator step can be entirely
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