Abstract: A detector apparatus is disclosed that includes a housing and a multilayer disposed within the housing. The multilayer defining a leading edge and a trailing edge and is adapted to interact with a plurality of high-energy photons, impingent from the leading edge, to permit passage of photons of at least one selected energy. The multilayer is secured to a first securement adjacent to the leading edge. The multilayer is secured to a second securement bracket adjacent to the trailing edge. At least one detector is disposed adjacent to the trailing edge of the multilayer to detect the impingent high-energy photons. An adjustment mechanism operatively connects to the second securement bracket to adjust the position of the second securement bracket, thereby altering an angular position of the multilayer.