A southwest Iowa farmer is one of the brains behind the Irish touring show “Riverdance” which opened last night in Des Moines. Backstage, Don Adcock is the “Chief of Sound” for the international dance sensation. The 40-year-old Shenandoah native runs what’s called the Radar Machine — a 24-track recorder and computer, the show’s nerve center for lights, music, vocals and sound effects. He also monitors a multitude of mini-microphones, including those in dancers’ shoes. Riverdance usually goes through a couple of those every week.Adcock spent four years doing theatre production in Des Moines before joining the “Riverdance” touring crew a year ago. He says he’s looking forward to being back in Iowa this week but he won’t have time to get in any hunting or fishing. Adcock enjoys his fast-paced job — most of the time, he says he missing being on his farm.Still, Adcock says he wouldn’t trade this tour of North America with the troupe of talented Irish tappers. “Riverdance” opened last night at the Civic Center of Greater Des Moines. There will be eight shows through Sunday.