An Emittance Scanner for Intense Low-Energy Ion Beams

Paul W Allison,Joseph D Sherman,David B Holtkamp

doi:10.1109/tns.1983.4332762

Paul W Allison, Joseph D Sherman + Show 1 more

Open Access

https://doi.org/10.1109/tns.1983.4332762

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Abstract

An emittance scanner has been developed for use with low-energy H- ion beams to satisfy the following requirements: (1) angular resolution of ± 1/2 mrad, (2) small errors from beam space charge, and (3) compact and simple design. The scanner consists of a 10-cm-long analyzer containing two slits and a pair of electric deflection plates driven by a ±500-V linear ramp generator. As the analyzer is mechanically driven across the beam, the front slit passes a thin ribbon of beam through the plates. The ion transit time is short compared with the ramp speed; therefore, the initial angle of the ions that pass through the rear slit is proportional to the instantaneous ramp voltage. The current through the rear slit then is proportional to the phase-space density d2i/dxdx. The data are computer-analyzed to give, for example, rms emittance and phase-space density contours. Comparison of measured data with those calculated from a prepared (collimated) phase space is in good agreement.

Highlights

Described here measures a two-dimensional emittance and was designed to overcome some intensity and angular resolution limitations for low beam energy in the slit and collector type scanner used at many accelerators.'
The ramp voltage changes slowly compared to the ion transit time; for ions passing through the rear slit, there is a simple relationship between the initial angle x' and the instantaneous ramp voltage
Using the paraxial ray approximation, we find for ions passing through the rear slit with deflection voltage V applied across the gap g between the plates that x' = .$I (D - 26)

Summary

Introduction

As beams of increasing intensity and brightness are used in accelerators, the details of the transverse phase-space distribution (the emittance) become more important. Described here measures a two-dimensional emittance and was designed to overcome some intensity and angular resolution limitations for low beam energy in the slit and collector type scanner used at many accelerators.'. Because of the relative simplicity of the ESS, it can be used to produce emittance contours on a storage oscilloscope without a computer;'. A beam of current i impinges on the narrow front slit of the scanner pod. The ramp voltage changes slowly compared to the ion transit time; for ions passing through the rear slit, there is a simple relationship between the initial angle x' and the instantaneous ramp voltage

Methods

Discussion

Conclusion