Low Emittance Beam Transport for e⁻/e⁺ LINAC

Design luminosity of SuperKEKB is 8 x 10³⁵ cm⁻²s⁻¹, which is 40 times higher than that of KEKB achieved. To achieve the design luminosity, the beam have to be transported to the SuperKEKB main ring with the high bunch charge (4 nC) and low emittance: 40/20 um for horizontal/vertical electron beam emittance and 100/15 um for positron beam emittance in Phase 3 final. In the LINAC and the beam transport line, the emittance growth is mainly induced by residual dispersion, beam phase space jitter, wakefield in acceleration structure, and radiation excitation. In the Phase 2 operation, we have evaluated and, if possible, corrected these effects on the emittance. Results of the emittance measurement is described.