Manchester University researchers create miniture particle accelerator
Efficient in predicting ultra-short electron beams with laser light at more than 99.99% of the speed of light, the innovation works by decreasing light to match the speed of the electrons using a specifically developed metal structure lined with quartz layers thinner than a human hair.
Described as a substantial leap forward, this simultaneously uses the ability to determine and manipulate particle bunches on time scales of less than 10 femtoseconds (0.000 000 000 000 01 seconds, or the time is takes light to travel 1/100th of a millimetre). This will enable them to create strobe photos of atomic motion.
The group's work, utilized lasers to produce pulses of light in the terahertz (THz) frequency, a region of the electromagnetic spectrum between infrared and microwave.
Laser-generated THz radiation exists in the ideal millimetre-scale wavelength program, making structure fabrication simpler however, most importantly, offering the half-cycle lengths that are well suited for acceleration of whole electron lots with high levels of charge.
The paper's lead author, Dr Morgan Hibberd from Manchester University said: "The main challenge was matching the velocity of the accelerating THz field to the almost speed-of-light electron beam velocity, while also preventing the inherently lower velocity of the THz pulse envelope propagating through our accelerating structure from significantly degrading the length over which the driving field and electrons interact.
" We overcame this problem by developing a unique THz source which produced longer pulses containing only a narrow range of frequencies, significantly enhancing the interaction. Our next milestone is to demonstrate even higher energy gains while maintaining beam quality. We anticipate this will be realised through refinements to increase our THz source energy, which are already underway."
Teacher Steven Jamison of Lancaster University, who collectively leads the programme, explained: "The controlled acceleration of relativistic beams with terahertz frequency laser-like pulses is a milestone in development of a new approach to particle accelerators. In using electromagnetic frequencies over one hundred times higher than in conventional particle accelerators, a revolutionary advance in the control of the particle beams at femtosecond time scales becomes possible.
" With our demonstration of terahertz acceleration of particles travelling at 99.99% of the speed of light, we have confirmed a route to scaling terahertz acceleration to highly relativistic energies."
As well as short-term impacts in fields such as radio-therapy and materials characterisation, the group claims that the technology might even ultimately replace huge multi-kilometre scale research accelerators such as Hamburg's 3 km long XFEL instrument (European X-ray Free Electron Laser).