New world record vertical emittance in the SLS Storage Ring

Sabrina El Yacoubi — Wed, 17 Sep 2014 13:58:28 +0000

New world record vertical emittance in the SLS Storage Ring
by Yannis Papaphilippou (CERN); Andreas Streun (PSI); Marica Biagini (INFN)

Cross section of the SLS beam (in green) is superimposed on an electron microscope picture of a human hair (click image to enlarge). Image credit: Andreas Streun (PSI).

At the end of 2011, the Swiss Light Source (SLS) team reduced the vertical emittance to 0.9±0.4 picometer-radian, a new world record, only five times larger than its limit.

This accomplishment was based on careful magnet re-alignment, application of different steering methods and extending the emittance monitor performance. The blade-shaped electron beam is only 4 micrometers thick (see picture), proving that emittance levels required by future linear collider projects (e.g. CLIC) could indeed be reached.

Emittance, the product of particle beam size and divergence, represents the extent to which beams can be concentrated and defines the performance of light sources, colliders and particle factories. In electron storage rings, emittance is determined by synchrotron radiation. Horizontal emittance is largely specified by beam energy and ring circumference. Vertical emittance however has ideally a very small natural limit although positioning errors of the ring magnetic elements can lead to much larger values.

The SLS Vertical Emittance Tuning (SVET) Work Package within TIARA preparatory phase is a collaboration between PSI, CERN and INFN on instruments and methods for establishing an R&D infrastructure on vertical emittance reduction at the SLS storage ring of PSI.

The TIARA-SVET collaborators are now working on the application of further emittance reduction methods and on a new emittance monitor with higher resolution.

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Vertical emittance

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New world record vertical emittance in the SLS Storage Ring