A Beginners’ Guide to Plasma Accelerator Technology By: Cockcroft Institute More Information: sCIence

Accelerator science has seen major breakthroughs over recent years, which is driving an increase in demand for state-of-the-art particle accelerators with applications across many different fields of science. Accelerator technology is a billion dollar industry – with more than 30,000 particle accelerators currently in operation worldwide serving medicine, industry, energy and discovery science. Accelerators are used for medical diagnostics, cancer treatment, semiconductor research, materials development and particle physics. X-ray technology is made possible by accelerators such as the MRI machine (right) and portable X-ray for non-destructive testing (left) Large Hadron Collider at CERN is at the forefront of particle physics research (CERN). Accelerator Science CERN, European Organization for Accelerator Research,

Current accelerators use radiofrequency (RF) cavities to accelerate charged particles to the speed of light. These cavities are metallic chambers that contain an alternating electric field which “kicks” the incoming particles to accelerate them. The electric field within these cavities is limited to <1000 MV/m, and their metal walls tend to break down if higher electric fields are attempted. To overcome this issue, RF cavities must be built in sequence. This increases the length of the accelerator and it can be many kilometers long. For accelerators to be more accessible for use in industry and medicine we need to reduce their size and cost. RF cavities within the Large Hadron Collider - used to accelerate particles & keep them in controlled bunches Large Hadron Collider in Geneva, Switzerland 27km long particle accelerator underground Current Particle Accelerators CERN, European Organization for Accelerator Research, Maximilien Brice (CERN) – CERN Document Server

Plasma cells (left) are gaining much attention in physics research. Plasma medium has heavy ions and free electrons (middle). Our sun is a plasma star (right). When the plasma is subjected to a laser, particles become charged and a strong electric field is formed. This principle can then be applied to plasma accelerators. Plasma is the fourth state of matter. It is an electrically conducting medium with positively and negatively charged particles, created by applying high energy to a gas. Solution: Plasma Accelerators DESY, - Heiner Müller-Elsner Bringing Light Into Research Laser Plasma Accelerators: The Revolution, Victor Malka, Lasers for Science and Society Symposium,

Plasma is the most effective known transformer of an electromagnetic wave. By directing a laser through a plasma medium, a wave is created which forces the electrons to create a strong electric field. Plasma can sustain a very large electric field with values that are up to 10,000 times stronger than those seen in the RF cavities of the particle accelerator. Diagram of laser pulse travelling through a plasma and creating a plasma wave Comparison of electric field from RF cavity (left) versus plasma medium (right). Over a shorter distance (1mm), plasma medium can obtain electric fields greater than 100 GV/m Solution: Plasma Accelerators Bringing Light Into Research Laser Plasma Accelerators: The Revolution, Victor Malka, Lasers for Science and Society Symposium

Imagine wakeboarders on a lake eager to experience the waves created by a boat’s wake. Behind the boat, wakeboarders gain energy from the wave, and they will be able to travel at high speeds. Laser wakefield technique is best compared to wakeboarders enjoying a ride on the wake of a boat. In the laser wakefield technique, the lake is the plasma and the boat is the laser driven beam. The laser wakefield are the waves within the plasma created by the laser. Particles are injected/trapped between the waves so they can be accelerated to the speed of light. Laser driven beam Laser wakefield Plasma medium Technique: Laser wakefield Bringing Light Into Research Laser Plasma Accelerators: The Revolution, Victor Malka, Lasers for Science and Society Symposium

Laser Plasma Accelerator Demo Video

By oscillating between the transverse field (perpendicular to laser) of an electromagnetic wave and the longitudinal field (same direction as the laser) of a plasma wave the electrons are accelerated creating a high quality beam. Higher energy gained through particle acceleration has many industrial and research applications. It can allow us to understand the origin of the universe and to view the smallest building blocks of nature. Technique: Laser Wakefield

Plasma accelerators produce a high energy beam capable of improving medical imaging. Phase contrasting can reveal many cellular structures that remain hidden with simple bright-field microscopes. Very tiny details can be observed in a single shot that disappear in multiple shots because of the loss of resolution. Applications include early cancer detection in dense breast tissue; an improved beam would visualise a cancer tumour even with a very small resolution. a) Single shot – all details present b) Multiple shots – tiny details lost a) X ray absorption imaging, b) X ray contrast phase imaging Industry applications: Medical Imaging S. Fourmaux et. al., Opt. Lett. 36, 2426 (2011) M. Bech et. al., Scientific Reports (2013)

NDT radiography can show changes in thickness, defects, assembly and material details in most dense objects without damaging the item. With a plasma accelerator, more sophisticated, compact and portable NDT equipment is achievable. Applications Art and artifact fraud Nuclear inspection Cargo scanning Aircraft maintenance Pipeline damage Applications in Industry: Non-destructive testing (NDT) LABEC, INFN’s Laboratory for Cultural Heritage and Environment, Italy

Incoming accelerated electrons from plasma accelerator Magnetic undulator End product – high quality light beams Free electron lasers (FELs) are high energy, high brightness lasers. Electrons are first brought to high energies in a plasma accelerator. They then fly through a special arrangement of magnets (undulator) in which they emit laser-like flashes of radiation. FELs are made possible with plasma accelerators. ` Discovery Science Applications: Free Electron Laser Horst Frank, Wikipedia

Powerful tool for applications that benefit from bright pulses of light in specific wavelengths: Biomolecules: Give insight into the progress of infections at a molecular level to inform the development of new medicines. Nanomaterials: Can discover the form and behaviour of different materials on the nanoscale – eg. quantum dots. And more, including magnetisation, filming chemical reactions and investigating extreme states of matter. Complex folded proteins can be better understood using FELs with targeted wavelengths Miniaturisation of high-tech materials requires even better understanding of nanoworld Quantum dots irradiated with UV light – applications in LED Applications of Free Electron Lasers Image courtesy PlasmaChem, DESY,

The Cockcroft Institute carries out a broad research program into laser and beam-driven plasma accelerators, often in collaboration with international partners. Plasma Accelerators at CI awake.web.cern.chwww.scapa.ac.uk sCIence