In one example, a radiation source comprises a housing and an acceleration chamber within the housing, with a peak acceleration energy greater than the lowest neutron production threshold of tantalum. A source of charged particles is supported by the housing to emit charged particles into the acceleration chamber. A target is supported by the housing downstream of the acceleration chamber. The target consists essentially of at least one isotope having a neutron production threshold greater than the peak acceleration energy. No neutrons are therefore generated. The source may also comprise a collimator, target shielding, and/or housing shielding comprising at least one isotope having a neutron production threshold greater than the peak acceleration energy, reducing or eliminating neutron generation as compared to the prior art, as well. Systems comprising the source, methods of operation of the source, and methods of manufacture of the source are also disclosed.