For mechanical applications, beam-driven wakefield acceleration techniques are promising for future large-scale machines. This includes electron lasers free of X-ray and linear colliders, as they feature the potential to reduce operation cost and improve efficiency.
To drive the improvement in efficiency, one of the key factors is manipulating temporal distribution of beams of electrons. To attain this, for the past few decades, researchers have examined a number of different mechanisms that successfully generate temporally shaped electron beams. In addition, these electron beams are of varied quality with varying limitations.
Meanwhile, a new study carried out at the Argonne and Los Alamos national laboratories, U.S. Department of Energy, scientists employed a phenomenon called field emission. This is to explore how the use of arrays of tiny diamond tips work to produce what scientists hoped would be transversely shaped electron beam. In the next step, the beam is sent into an emittance exchange beamline to transform the transverse distribution into the temporal one.
“Theoretically, by the law of probability, field emission functions by decreasing the quantum barriers that electrons can occasionally pass through. This means, if these fields are applied, a brick wall can be changed into a drywall – the latter being much easier to pass,” said one of the authors of the study.
Earlier, other methods to produce electrons involved either thermionic cathodes or photoelectric cathodes. The former uses hot filaments comparable to the ones used in incandescent light bulbs to eject electrons from a solid. On the other hand, photoelectric cathodes use ultrashort laser pulses for electrons to jump out loose.
In fact, serving as an advantage, field emission cathodes neither require heat source nor expensive laser setup.