It is a little over a year since I last spoke to Kieran Furlong, the Wexford-born chief executive of Realta Fusion. Back then, Realta had just raised $12 million (€11 million) for his fusion energy start-up from Khosla Ventures, a venture firm set up by Vinod Khosla, the billionaire founding chief executive of Sun Microsystems, and from the United States Department of Energy.  A lot has happened since. Realta Fusion has just completed a nuclear fusion experiment with its partner, the University of Wisconsin-Madison, which set a record for the strongest steady magnetic field in fusion plasma.  The achievement drew…