  We investigate the limiting factors in the standard implementation of the Ca
magneto-optical trap. We find that intercombination transitions from the 4s5p
1P1 state used to repump electronic population from the 3d4s 1D2 state severely
reduce the trap lifetime. We explore seven alternative repumping schemes
theoretically and investigate five of them experimentally. We find all five of
these schemes yield a significant increase in trap lifetime and consequently
improve the number of atoms and peak atom density by as much as ~20x and ~6x,
respectively. One of these transitions, at 453 nm, is shown to approach the
fundamental limit for a Ca magneto-optical trap with repumping only from the
3d4s 1D2 state, yielding a trap lifetime of ~5 s.
