Temporal response of number density in loading region after heating laser turn-on, with and without feedforward to optical power. Operating at constant heating power, the oven takes ∼3 min to reach 80% of its steady state output; with a simple two-level turn-on profile, this response time can be reduced to ∼15 s, shown in more detail in the inset. The number density drops rapidly after turn-off, reaching 20% of its steady state value in 11 s.