Abstract
Knowledge of the transverse four-dimensional beam rms-parameters is essential for applications that involve lattice elements that couple the two transverse degrees of freedom (planes). Of special interest is the removal of inter-plane correlations to reduce the projected emittances. A dedicated ROtating System for Emittance measurements (ROSE) has been proposed, developed, and successfully commissioned to fully determine the four-dimensional beam matrix. This device has been used at the High Charge injector (HLI) at GSI using a beam line which is composed of a skew quadrupole triplet, a normal quadrupole doublet, and ROSE. Mathematical algorithms, measurements, and results for ion beams of 83Kr13+ at 1.4 MeV/u are reported in this paper.
Highlights
Emittance is an important figure of merit for propagation of charged particle beams. It is defined as the amount of phase space being occupied by the particle distribution to quantify the beam quality and to match the following optics
We summarize that in order to obtain reliable evaluation results a four-dimensional emittance measurement needs: (i) one reference emittance measurement with 100% transmission efficiency between location i and location f to obtain projected beam parameters at location i. (ii) all quadrupoles varied numerically in a brute-force method in order to check each setting for full transmission efficiency from location i to location f, and for reasonable beam sizes on slit and grid (2 mm < σrms < 5 mm in our case)
During rotating system for emittance measurements (ROSE) commissioning it was found that three of the parameters extracted from the four-dimensional beam matrix are quite sensitive even to very small errors in the measurements, especially for notably correlated beams t > 1
Summary
Emittance is an important figure of merit for propagation of charged particle beams. It is defined as the amount of phase space being occupied by the particle distribution to quantify the beam quality and to match the following optics. Precise knowledge from measurements of particle distribution parameters is important for accelerator design and for phase-space manipulation. Correlations between the two planes, i.e. x − y, x − y0, x0 − y, and x0 − y0 are often assumed as zero Such interplane correlations may be produced by interplane coupling fields such as dipole fringes, solenoids, and titled magnets [4] or just by beam losses
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