1. Department of Physics, Indiana University 1 , Bloomington, Indiana 47408, USA
2. Quantum Science and Engineering Center, Indiana University 2 , Bloomington, Indiana 47408, USA
3. Neutron Sciences Directorate, Oak Ridge National Laboratory 3 , Oak Ridge, Tennessee 37830, USA
4. ISIS, Rutherford Appleton Laboratory 4 , Chilton, Oxfordshire, United Kingdom