Beam halo measurements using digital micro mirror device at Diamond Light Source

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Digital micromirror device.

A particular challenge in transverse beam profile monitoring at synchrotron light sources is the detection of beam halo particles. This is due to the high intensity of the synchrotron light coming from the core of the beam overshadowing the much weaker signal coming from halo particles. Changes in beam halo are usually associated with emittance growth, particle losses and even damage to accelerator components. Thus, it is very important to have a method in place which allows non-invasive, high dynamic range measurements of full profile, including the halo.  

Adaptive mask used for the beam halo measurements.

AVA Fellow Milena Vujanovic, who is based at the Cockcroft Institute/University of Liverpool, together with fellow QUASAR Group member, Dr Joseph Wolfenden, designed and developed a monitor based on adaptive optics for high dynamics range measurements of beam halo. The core of this instrument is a digital micromirror device (DMD) to mask the intense beam core light. This allows to measure the halo in more detail as the core signal no longer overshadows the signal. This technique was pioneered in the group and successfully demonstrated in previous proof-of-principle measurements - the study the researchers now conducted targets developing the monitor into an off-the-shelf device that can be used at accelerator facilities around the world. 

In early September 2019, the monitor was installed at Diamond Light Source (DLS), the UK's national synchrotron light source in Oxfordshire. Joseph and Milena performed first beam halo measurements and successfully demonstrated a dynamic range of 10E5, increasing the dynamic range of the camera by two orders of magnitude.

This opens exciting new opportunities to understand the dynamics of the stored beam, as well as the halo particles in much more detail. They are now working on further improvements of the system that shall provide an even higher dynamic range.