Design current in 1.5 GeV ring

Design current in 1.5 GeV ring

MAX IV reached the design current 500 mA in the 1.5 GeV soft X-ray storage ring
during the evening and night between 5 and 6 June.


500 mA beam current was stored and kept in top-up mode over many hours during an accelerator development shift.

This was the culmination of many years of work by the whole MAX IV team and was preceded by several weeks of  preparatory work on all subsystems to work reliably, pushing the current limits during accelerator development shifts, sorting out collective beam instabilities, and improving beam diagnostics as well as our understanding of filling pattern effects on the beam. 

The achievement was not simply the current value, but the fact that the beam was kept free from instabilities in the same way as during delivery at 200 mA. According to the diagnostic tools at hand, these were the beam parameters:

  • Stored current in top-up mode: 500 mA
  • Current*Lifetime: 3 Ah
  • Filling pattern: Small deviations from an even fill
  • Horizontal emittance: < 8 nmrad
  • Vertical emittance: 0.3 nmrad (4 to 5% emittance coupling)
  • Collective instabilities: Suppressed by Harmonic Cavities
RI status Bunch length measurement verifying the effect of the higher harmonic cavitiesBeam size measurements ensuring the transverse stability