The U.S. Senate on Thursday unanimously confirmed John R. Lausch Jr. to be Chicago’s top federal prosecutor.Lausch, a partner at Kirkland & Ellis LLP, will be returning to his old stomping grounds when he is sworn in as the U.S. attorney for the Northern District of Illinois.He worked as an unpaid intern in the office during the 1995-96 school year and served as an assistant U.S. attorney from 1999 to 2010.Lausch will head an office that has about 170 slots for prosecutors in Chicago and Rockford.The office&rsquo …