Mini-β insertion and luminosity for the RHIC lattice

The requirement and implication of the mini-β insertion where a pair of common quadrupoles are inserted between the interaction point and the first beam crossing dipole, in the RHIC (Relativistic Heavy Ion Collider) lattice are studied. For heavy ion operation, it is found that β*=1 m can be achieved with a ±5 m free space for the experimental setup used and β=500 m. The beam size limitation is located at the second beam crossing dipole, BC2, where an 8 cm coil i.d. is considered. When the machine is operating in the proton-heavy-ion collision mode, these common quadrupoles should be removed physically in order to let both beams cross the center line at 3.4 mrad. This mini-β insertion can increase the luminosity by a factor of 2~3. For the proton-proton collision mode, it is found that β*=0.5 m is also operable with the mini-β quadrupoles due to smaller emittance for the proton beam