Progress in the development of low-voltage gyrotron for integration with NMR spectrometer V.L. Bratman, A.E. Fedotov, Yu. K. Kalynov, V.N. Manuilov and I.V. Osharin EPJ Web Conf., 149 (2017) 04039 Published online: 04 August 2017 DOI: 10.1051/epjconf/201714904039