How does Kronos compare to ITER?

Kronos and ITER are aiming at different things. ITER is a large D–T tokamak built to demonstrate gain at scale; the Kronos breeder is a compact D–T machine built to breed fuel — and it is far smaller.

ITER major radius

6.2 m

HYPERION major radius

1.2 m

ITER plasma current

15 MA

HYPERION plasma current

9.86 MA (≈ ⅔ of ITER)

The clearest contrast is size. ITER is a large conventional tokamak with a 6.2 m major radius; the Kronos HYPERION breeder is a compact spherical tokamak at just 1.2 m. Yet HYPERION carries a plasma current of 9.86 MA — about two-thirds of ITER's 15 MA — in a machine a fraction of the volume. It reaches its gain (Q 3.424) with high field and high power density rather than sheer scale.

The goals differ too. ITER's mission is to demonstrate a large burning D–T plasma. HYPERION's mission is to be a compact, buildable breeder — to make tritium and helium-3 for the second Kronos machine, the D–³He burner. Compactness is the point: it is what makes the breeder-first strategy affordable.

Kronos is careful not to overstate the comparison. HYPERION's compactness raises its heating power density (about 2.2× SPARC) and sets a demanding confinement requirement — both stated in the open record, not hidden behind the size advantage.