On December 10, 2016, members of the Advanced Wakefield Experiment (AWAKE) at CERN announced a major milestone in the pursuit of a novel particle acceleration method, proton-driven wakefield-based acceleration. For the first time ever, researchers confirmed the generation of strong electromagnetic fields in plasmas by high-energy proton bunches. The AWAKE research team, including a delegation of NSERC-funded TRIUMF scientists, is investigating proton-driven plasma wakefields and their capacity to accelerate electrons.
For a full description of this achievement and the background of the AWAKE project, please see the below words from AWAKE spokesperson Alan Caldwell:
"The AWAKE Collaboration observed the strong modulation of high-energy proton bunches in plasma during the final week of CERN accelerator running this year, signalling the generation of very strong electromagnetic fields. This is a major milestone towards the goal of using the proton-driven plasma wakefield technique to accelerate electrons. This exciting development, the culmination of three years of an intense preparation phase, opens a new era of particle accelerator development at CERN and worldwide.
It has long been known that plasmas are capable of supporting very strong electric fields. The challenge for researchers is to understand the best way to take advantage of this capability to build high energy but much smaller scale accelerators than is possible today. Several groups worldwide have observed the acceleration of electrons either in the wake of a laser pulse or an electron bunch. The results from AWAKE are the first ever demonstration of strong wakefields driven by a proton bunch. This result is of particular interest because of the huge energy carried by the proton bunches. Achieving the acceleration of electrons using this large stored energy via proton-driven plasma wakefield acceleration would be a great step in accelerator science. The plans of the AWAKE Collaboration are to study the proton bunch modulation in detail in 2017, and then start on a program of demonstrating the acceleration of electrons in the wake of the proton bunch. Demonstration of GV/m scale accelerating gradients for electrons is planned until Long Shutdown 2 of the LHC at the end of 2018. The results achieved last week are the first step in this ambitious and exciting project."
With responses from Victor Verzilov, TRIUMF scientist and Group Leader of Diagnostics & Probes:
1) What is the AWAKE project? What has been involved in the 3-year preparation phase?
AWAKE is a proof-of-concept Plasma Wakefield Acceleration (PWFA) R&D experiment at CERN, and it is unique in that wakefield generation and electron acceleration are driven by proton bunches carrying a large stored energy. The experimental phase was preceded by extensive simulations to prove the feasibility and optimize parameters of the experiment, and lead to a discovery of a new phenomenon, Self-Modulated Instability (SMI) of a long proton bunch in plasmas. After overcoming a number of technological challenges, the AWAKE team observed SMI for the first time on December 10, 2016.
2) What is TRIUMF’s involvement in AWAKE? As members since September 2015, what are the roles that TRIUMF’s researchers have taken within the project?
TRIUMF joined the AWAKE collaboration in September 2015, and is mainly contributing to the beam instrumentation for the electron and common proton-electron beam lines. For successful wakefield acceleration, the proton, electron, and laser beam have to satisfy strict space and time relations which are impossible to achieve without high precision instrumentation. The TRIUMF developed beam position monitor system was tested at the CERN CALIFES facility in November 2016, confirming all required parameters have been achieved. TRIUMF is also participating in other aspects of the experiment when corresponding opportunities arise, e.g., plasma cell temperature measurements (together with the University of Victoria).
3) What are the next steps in the AWAKE timeline?
Studies of the physics of the SMI effect will continue in 2017 in parallel with the installation and commissioning of the source of the “witness” electron beam and beamlines (including equipment provided by TRIUMF). The first acceleration experiment is planned for the end of 2017, and followed by 3-4 years of physics programs. Speaking about opportunities, it is well understood in the community that the future of accelerator based high-energy physics is limited unless new accelerator technologies arise to achieve presently unthinkable beam energies. In addition to providing tools to high-energy physics, very high acceleration rates available with PWFA technologies, especially those driven by high power lasers, will open an era of low-cost, compact “table-top” linear accelerators for various applications in research, industry and medicine.
Congratulations to Victor, the TRIUMF team and everyone involved the AWAKE collaboration!