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PhD success!

In some more great news to close a disrupted but altogether successful year for the JAI, Oxford DPhil student Eugenio Senes has successfully submitted and defended his thesis. Eugenio joined the JAI in 2017 following a successful period as a technical student at CERN. Since beginning his DPhil Eugenio has worked mostly on the Advanced WAKefield Experiment (AWAKE) at CERN as well as CERN's proton synchrotron.

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AWAKE is a project that aims to study and develop the concept of proton-driven plasma wakefield acceleration. For this purpose, AWAKE uses proton beams from the super proton synchrotron to generate plasma wakefields in a rubidium plasma. The plasma, which is created by shining a laser beam through rubidium vapour, is then used to accelerate an electron beam.

To effectively drive plasma wakefields, the three beams move in close spatial and temporal proximity in a single beamline before entering the plasma. Having three different beams in such close proximity creates a number of challenges for beam instrumentation, that is mostly saturated by the proton beam presence. The goal of Eugenio's DPhil was to study the electron beam position monitor (BPM) system of the AWAKE experiment, and develop a technique to measure the position of the electron beam when the intense proton beam is present in the beam pipe.

In his thesis, Eugenio demonstrated that a measurement of the electron beam position with reduced bias from the proton beam is possible if the BPM system electronics work at a frequency between 20 and 30 GHz. Most conventional BPMs do not, however, work at such high frequencies.

Because of this, a BPM was designed to work on the emission of Cherenkov Diffraction Radiation from dielectric inserts in the beam pipe (pictured right). This innovative design allows the BPM to work at tens of GHz and also be selective on the bunch length. A careful selection of the geometrical dimensions of the dielectric radiators allows the suppression of the sensitivity to the proton beam, whilst leaving the measurement of the electron beam uncompromised. Experimental verification of the design was undertaken at the CERN Linear Electron Accelerator for Research (pictured below).

Eugenio recently defended his thesis via zoom and will continue to work on this system as part of his CERN fellowship, in order to transform this experimental device into an operational instrument for the AWAKE run 2.

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