Small emittance studies at the ALS
Small emittance studies at the ALS
This page is intended to help to keep everybody involved in the small emittance studies at the ALS updated about the current progress of measurements, data analysis and simulation. The page is only accessible from computers at SLAC and LBNL.
The beam emittance at the interaction point of linear colliders is expected to be limited by the emittance of the beams extracted from the damping rings. 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. Theoretical analysis suggests that the NLC damping rings will experience modest emittance growth at 1.98 GeV, however there is little experimental data of IBS effects for very low-emittance machines in the energy regime of interest. The Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory is a third-generation synchrotron light source operating with high-intensity, low-emittance beams at energies of approximately 1 - 2 GeV, and with coupling typically 1% or less. We present measurements of the beam growth in three dimensions as a function of current, for normalized horizontal emittance of approximately 3 - 4 mm-mrad at energies of 1 - 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. Emittance growth as a function of bunch current is determined, and compared with theoretical estimates. By varying coupling and energy, we separate impedance driven effects from the IBS, and derive emittance growth from IBS alone.
Last updated: March 2002,
CSteier@lbl.gov