Intra-beam scattering and minimum achievable emittance in the advanced light source
Intra-beam scattering (IBS) potentially limits the minimum emittance of low-energy storage rings, and this effect strongly influences the choice of energy of damping rings for linear colliders. The Advanced Light Source (ALS) is a third-generation synchrotron light source operating with high-intensity, low-emittance beams at energies up to 2 GeV. It can operate with an emittance coupling of below 1%. We present measurements of the beam growth in three dimensions as a function of current, for normalized natural horizontal emittances of approximately 1 - 10 mm-mrad at energies of 0.7 - 1.5 GeV, values comparable to the parameters in an NLC damping ring. Using a dedicated diagnostic beamline with an x-ray scintillator imaging system, measurements of the transverse beamsize are made, simultaneously with bunch length measurements using an optical streak camera. The bunch volume growth as a function of bunch current is compared with theoretical estimates, for a parameter space of IBS, where very little experimental data exists so far.
