Complex sentence: In order to emit x-rays, the metal must be heated to very high temperatures, which uses up a considerable amount of the laser energy, so while the compression is more efficient, the overall energy delivered to the target is nevertheless much smaller.
Split into simpler sentences: In order to emit x-rays, the metal must be heated to very high temperatures, which uses up a considerable amount of the laser energy. So while the compression is more efficient, the overall energy delivered to the target is nevertheless much smaller.