Scientists Use Nanoscale Diamonds to Generate More Efficient Accelerator Beams
Electron beamlets as observed on YAG screens at varying distances from a cathode source.
Credit: Argonne National Laboratory
Beam-driven wakefield acceleration approaches are promising candidates for future large-scale machines, including X-ray free electron lasers and linear colliders, as they have the potential to improve efficiency and reduce operation cost.
One of the key factors that drives this efficiency improvement involves manipulating the temporal distribution of beams of electrons. Over the past few decades, researchers have investigated a number of different mechanisms that successfully produce temporally shaped electron beams of varied quality with different limitations.
“It’s as if by applying these fields we can change a brick wall into drywall — it’s much easier to go through it.” — Argonne accelerator physicist Jiahang Shao
In a new study from the U.S. Department of Energy’s (DOE) Argonne and Los Alamos national laboratories, scientists used a phenomenon called field emission to explore the use of arrays of tiny diamond tips to produce what they hoped would be a transversely shaped electron beam. The beam will then be sent into an emittance exchange beamline to convert the transverse distribution into the temporal one.
Field emission works by decreasing the quantum barriers that electrons can, according to the laws of probability, occasionally tunnel through. “It’s as if by applying these fields we can change a brick wall into drywall — it’s much easier to go through it,” said Argonne accelerator physicist Jiahang Shao, an author of the study.
Other methods to generate electrons had involved either thermionic cathodes, which use hot filaments — analogous to those used in incandescent light bulbs — to expel electrons from a solid, or photoelectric cathodes, which use ultrashort laser pulses to spring electrons loose.
The advantage of field emission cathodes, according to Shao, is that they require neither a heat source nor an expensive laser setup. “We’re using electric fields regardless when it comes time to accelerate the electrons,” Shao said. “It’s not much more inconvenient to use them to generate them in the first place.”