Image courtesy of Neil Fazel
The inside of the University of Texas, Austin, vacuum chamber where electrons were accelerated to 2 GeV. The laser pulse comes in from the right, ionizes the gas inside the gas cell (center), and sets up the wakefield that creates a huge electric field that pushes the electron bunch along by riding the crest of the waves.
Powerful petawatt laser pulses at University of Texas, Austin, create low density plasmas wakefields that maximize electron acceleration. Energies to 2 gigaelectronvolts (GeV) have been achieved, a breakthrough in plasma wakefield acceleration.
Particle accelerators, a basic tool of physics research--and one that has found widespread use in medicine and security--have been around for more than 70 years. But traditional accelerators have grown ever bigger and more costly to build. The Office of High Energy Physics supports basic research in a technique known as laser wakefield acceleration, a technique that one day may lead to next generation accelerators able to drive table-top coherent light sources such as x-ray free electron lasers at significantly less cost. Achieving two GeV electrons is a step towards making this technique a practical reality.
Laser plasma wakefield is a powerful acceleration technique that may lead to electron and other charged particles having energies far beyond the reach of current accelerators. The potential applications are enormous and may lead to new physics; compact x-ray sources for biological, chemical and materials research; and more cost effective medical centers that rely on charged particle beams for cancer treatment. But accelerating electrons to energies greater than a GeV has been a challenge both in practice and in the theory of understanding the basic physics of laser, electron bunch, and plasma interactions. This is because relatively low power, terawatt laser pulses are able to produce high density plasma wakefields that inherently limit electron energies to approximately 1 GeV due to dephasing between the accelerating electron bunch and the plasma wake and later by the erosion of the plasma itself. Scientists at the University of Texas at Austin have overcome this problem by increasing the power of the laser--no small feat in itself--so that laser-plasma accelerator can be operated in plasmas of lower densities. By doing so they have kept the electron bunch in phase with the wakefields. The result: 2 GeV electrons! This is a major milestone towards next generation particle accelerators.
University of Texas, Austin
Basic research: DOE Office of Science High Energy Physics program
Xiaoming Wang et al., Quasi-monoenergetic laser-plasma acceleration of electrons to 2 GeV, Nature Communications 4, Article number 1988, DOI: 10.1038/ncomms2988
UT Austin laser-based tabletop particle accelerator reaches major milestone
Tabletop Device Accelerates Electrons to 2 GeV