Abstract
The laser plasma accelerator has shown a great promise where it uses plasma wakefields achieving gradients as high as GeV/cm. With such properties, one would be able to build much more compact accelerators, compared to the conventional RF ones, that could be used for a wide range of fundamental research and applied applications. However, the electron beam properties are quite different, in particular, the high divergence, leading to a significant growth of the emittance along the transport line. It is, thus, essential to mitigate it via a strong focusing of the electron beam to enable beam transport. High-gradient quadrupoles achieving a gradient greater than 100 T/m are key components for handling laser plasma accelerator beams. Permanent magnet technology can be used to build very compact quadrupoles capable of providing a very large gradient up to 500 T/m. We present different designs, modeled with a 3D magnetostatic code, of fixed and variable systems. We also review different quadrupoles that have already been built and one design is compared to measurements.
Highlights
Ever since the discovery of the electron using a cathode-ray tube at the end of the 19th century, particle accelerators have seen tremendous progress where they became widely used tools for basic research, industry, medicine, material science etc
Regarding plasma wakefield accelerators, where the electron beam is generated with initial large divergence, quadrupoles of gradient 100–500 T/m and above are required with low multipole contents to ensure a good handling of the beam transport
We present here solutions offered by permanent magnet quadrupoles and compare the performance of different designs of fixed and variable gradient with numerical simulations using Radia code [36]
Summary
Ever since the discovery of the electron using a cathode-ray tube at the end of the 19th century, particle accelerators have seen tremendous progress where they became widely used tools for basic research, industry, medicine, material science etc. A FODO high gradient quadrupoles lattice placed very close to the plasma-vacuum interface allows for handling and controling the LPA beam divergence. Their focusing is not symmetric, unlike APL, and at least three systems are required to provide a round beam. High energy accelerators require larger gradient quadrupoles to transport the beam, where the electro-magnet technology reaches a limit it cannot surpass. Regarding plasma wakefield accelerators, where the electron beam is generated with initial large divergence, quadrupoles of gradient 100–500 T/m and above are required with low multipole contents to ensure a good handling of the beam transport. Measurements using a stretched wire conducted for one design are compared to simulations
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