Continuous energy measurement of the electron beam in the storage ring of Diamond Light Source with resonant spin depolarization

Niki Vitoratou,Guenther Rehm,Pavel Karataev

doi:10.1103/physrevaccelbeams.22.122801

Niki Vitoratou, Guenther Rehm + Show 1 more

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https://doi.org/10.1103/physrevaccelbeams.22.122801

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Abstract

Electron spin polarization occurs naturally in an electron storage ring due to spin-flip synchrotron radiation. The equilibrium polarization level that is achieved in Diamond Light Source was studied theoretically and experimentally. A novel approach that enables measurements during user operation is presented, compatible with beams of small vertical emittance in the range of pm rad. An array of four custom-made scintillation detectors has been installed around the beam pipe downstream from the collimators to capture a significant fraction of the lost particles and witness the depolarization process in the presence of a background loss rate. A new concept for detecting the depolarization resonance even when it coincides with higher-order betatron resonances was introduced. The momentum compaction factor was measured to be in very good agreement with the storage ring numerical model. In the end, we measured a good long-term stability of the beam energy during user operation time.

Highlights

Resonant spin depolarization (RSD) is a wellestablished technique to measure the electron beam energy in synchrotrons [1,2,3,4,5]
The key aim of this project is to make the energy measurements compatible with the user operation using a beam with a small vertical emittance
Diamond Light Source operates with a small vertical emittance in the range of 8 pm rad, and the main challenge is not to affect this quantity when the beam is excited during the depolarization scans

Summary

Introduction

Resonant spin depolarization (RSD) is a wellestablished technique to measure the electron beam energy in synchrotrons [1,2,3,4,5]. Energy measurements with RSD have been achieved [6] but so far have not been compatible with operational user time and required long time periods during the dedicated machine development. This resulted in rare readings of the electron beam energy. The implementation of a technique that makes RSD compatible with user time would give information about the energy stability of the electron beam

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