I think biggest downfall of ITER is also why we must do it. The downfall is thus - ITER is huge and that generally implies lots construction delays and cost ove

I think biggest downfall of ITER is also why we must do it. The downfall is thus - ITER is huge and that generally implies lots construction delays and cost overruns. But, being huge also means it will be able to study sustaining high volume of plasma for long durations. ITERs plasma density will be comparatively low, and that is where SPARC with stronger magnets comes in. SPARC will produce data on lower volume and limited burn time, but significantly higher plasma density.