Founded in 1986 by Lowell’s Cambodian refugees as a way to preserve their culture’s ancient dance traditions, many Valley residents have seen the Angkor Dance Troupe perform. ( they’ve danced at the inauguration of Massachusetts Gov. Charlie Baker.) But few people outside the organization know what happens behind the scenes to make possible the technically challenging, seamless visual wonder that is an Angkor Dance Troupe performance. Photographer Adrien Bisson visited the troupe’s rehearsal space at Lowell’s Patrick J. Mogan Cultural Center to get an inside look at Angkor’s dancers, teachers and the work they do to make it all possible.