Abstract
The application of quadrupole devices with high field gradients and small apertures requires precise control over higher order multipole field components. We present a new scheme for performance control and tuning, which allows the illumination of most of the quadrupole device aperture because of the reduction of higher order field components. Consequently, the size of the aperture can be minimized to match the beam size achieving field gradients of up to $500\text{ }\text{ }\mathrm{T}\text{ }{\mathrm{m}}^{\ensuremath{-}1}$ at good imaging quality. The characterization method based on a Hall probe measurement and a Fourier analysis was confirmed using the high quality electron beam at the Mainz Microtron MAMI.
Highlights
High field gradient compact quadrupole devices have recently been the subject of an increasing amount of attention, in particular, as a compact element for beam manipulation in laser based particle acceleration
The characterization method based on a Hall probe measurement and a Fourier analysis was confirmed using the high quality electron beam at the Mainz Microtron MAMI
We present a method of tuning Permanent magnet quadrupole devices (PMQs) in order to achieve control over higher order field components; this allows the significant reduction of higher order multipole field components (HOMFC) and allows a large ratio of beam size to aperture
Summary
High field gradient compact quadrupole devices have recently been the subject of an increasing amount of attention, in particular, as a compact element for beam manipulation in laser based particle acceleration. Permanent magnet quadrupole devices (PMQs) with a small aperture can reach high magnetic field gradients because of maintaining high surface magnetization. We present a method of tuning PMQs in order to achieve control over higher order field components; this allows the significant reduction of HOMFC and allows a large ratio of beam size to aperture. We present a method allowing the measurement of all relevant magnetic vector field components relying solely on a miniature Hall probe which can be applied to very small apertures at the precision required. The ability to measure all relevant field components within small apertures allows the introduction of specific HOMFC by changing the position of individual magnet segments. We present measurement results of the tuning of the magnetic field distribution
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