Variable high gradient permanent magnet quadrupole (QUAPEVA)

Abstract

High gradient quadrupoles are necessary for different applications such as laser plasma acceleration, colliders, and diffraction limited light sources. Permanent magnet quadrupoles provide a higher field strength and compactness than conventional electro-magnets. An original design of permanent magnet based quadrupole (so-called "QUAPEVA"), composed of a Halbach ring placed in the center with a bore radius of 6 mm and surrounded by four permanent magnet cylinders capable of providing a gradient of 210 T/m, is presented. The design of the QUAPEVAs, including magnetic simulation modeling, and mechanical issues are reported. Magnetic measurements of seven systems of different lengths are presented and confirmed the theoretical expectations. The variation of the magnetic center while changing the gradient strength is +/- 10 micrometer. A triplet of three QUAPEVA magnets are used to focus a beam with large energy spread and high divergence that is generated by Laser Plasma Acceleration source for a free electron laser demonstration.Comment: 4 pages, 9 figure

Interferometry for full temporal reconstruction of laser-plasma accelerator-based seeded free electron lasers

“…We therefore consider a seed at 160 nm (see table 1) generated in gas [48,49] using a branch of the main laser [49]. The electron beam is transported along a dedicated line allowing for a three steps manipulation [34]: refocusing at the LPA exit using high gradient quadrupoles [50], longitudinal stretching and energy chirping using a chicane and chromatic matching using standard quadrupoles. Locally driving the beam off-axis, the chicane is also used to insert a mirror for the seed injection on-axis.…”

Electron Beam Brightness and Undulator Radiation Brilliance for a Laser Plasma Acceleration Based Free Electron Laser

“…The laser beam is focused by an off-axis parabola into a gas mixture composed of 99% He and 1% N 2 . The first magnetic element is a triplet of tunable high gradient permanent magnet-based quadrupoles (QUAPEVA) [23,45,46], placed 5 cm from the electron source. The triplet strongly focuses the LPA electron beam and permits to handle the large divergence at an early stage of the transport and mitigate the emittance growth.…”

Design and optimization of a laser-PIXE beamline for material science applications

“…We choose for our beamline design a PMQ length of l q = 4.5 cm and a bore radius of r 0 = 1 cm. These parameters can be easily obtained with the existing permanent magnet technology (Halbach and Holsinger, 1976;Eichner et al, 2007;Nirkko et al, 2013;Marteau et al, 2017) and allow us to keep the dimensions of the beamline compact. Using rare-earth materials, these features allow obtaining a value of B 0 in the range of hundreds of mT (Eichner et al, 2007;Nirkko et al, 2013) and a field gradient in the order of several tens of T/m.…”