Conclusions

A model has been developed for predicting the temperature history of PSII targets. The development of this code produced several general conclusions:

• The target surface temperature rise during a single pulse is negligible for most applications.
• Target temperatures can thus be modeled by averaging the input power over the full cycle.
• Temperature gradients in targets are generally negligible, so lumped capacitance thermal models are adequate for target temperature predictions.
• Cooling in a typical PSII chamber geometry is generally dominated by radiation.
• The difference between the target temperature and the base temperature in a typical PSII configuration is generally negligible.
• The steady state temperature distribution in a PSII target is thus determined by the power to the target and base, the ratio of the target and base volumes to their areas, and the emissivities of the target and base materials.

1. If the target or base is actively-cooled, the heat transfer coefficient will be relatively large and the Biot number is likely to be of order 1 (or greater). In this case, the lumped model would be inadequate and a 1-D calculation would be necessary.
2. If one desires high target temperatures, he may choose to insulate the target from the base. In this case modeling the target and base together as a single lumped system would be inadequate and separate, coupled models would be necessary.