Helium is the other common choice for a closed Brayton power cycle, and for a very different reason than CO₂'s density trick: it's chemically inert. It won't corrode piping, react with a blanket coolant leak, or become activated the way some other candidate fluids can, which matters a lot when the heat source is a fusion blanket. The tradeoff is that helium behaves like a genuinely ideal gas across the whole cycle, no critical-point density boost to shrink the compressors, so a helium Brayton cycle needs real compression-work management instead.

Intercooling is that management. Compression happens in two stages with an intercooler in between: a main compressor (C1) takes a first pressure bite, the gas is cooled back down close to ambient in an intercooler, and an auxiliary compressor (C2) finishes the job. Splitting the compression and cooling the gas in the middle keeps each stage's compression work down (cooler gas is denser, denser gas is cheaper to compress), the same logic multistage intercooled air compressors use, just applied to a closed helium loop instead.

Regeneration here is a single stage, not split into high-/low-temperature recuperators the way the CO₂ cycle needs. That's a direct consequence of helium being close to an ideal gas: its specific heat barely changes with temperature, so there's no sharp mismatch between the hot and cold streams for one recuperator to struggle with. Downstream of the turbine, it simply preheats the compressor discharge with turbine exhaust heat before the gas heads back to the Secondary HTX.

The turbine inlet here draws from the same solar-salt intermediate loop and Secondary HTX as the other two cycles on this site, 565 °C supply from the same blanket-fed loop, so all three cycles are drawing on a shared, citable heat source rather than three unrelated assumptions.