Operation of Aladdin at lowered emittance

Abstract

To increase the available photon flux density for users, alternate lattice tunings of the Aladdin synchrotron light source have been developed with horizontal emittances significantly lower than the present value of 127 π nmrad. Reduction of the horizontal emittance by a factor of three has been obtained experimentally. When the fourth harmonic Landau cavity is used to lengthen the bunch, the observed beam lifetime with the new lattice is not significantly changed from that of the existing lattice. The present goal is to achieve a factor of four horizontal and a factor of two vertical emittance reduction routinely. Progress in making this new configuration fully operational is discussed, including the use of quadrupole shunts with correction software for betafunction and dispersion correction, understanding of a mode coupling instability in higher-harmonic RF systems, RF clearing of ions, and fabrication of new optical monitoring stations.

Robinson instabilities with a higher-harmonic cavity

“…Successful operation of the Landau cavity is required to suppress coupled-bunch and microwave instabilities and to obtain a lifetime comparable to the standard Aladdin lattice. In low-emittance mode with the "LF20" lattice, the momentum compaction of 0.0043 is about 1͞8 of its value of 0.0335 in the standard Aladdin lattice, reducing the synchrotron frequency by a factor of ϳ3 [18]. Experimentally, passive operation of the Landau cavity is unstable with optimally lengthened bunches, but stable at ring currents of 80-300 mA when the bunches are lengthened beyond optimal to assume a double-hump shape.…”

Current status of the Synchrotron Radiation Center

“…Recently, experiments have been performed to implement operation with a lower emittance lattice that will increase the available flux density for users. 3 Reduction of the horizontal beam size by a factor of 2-4 has been obtained experimentally and can be seen in Fig. 2.…”