the range of about 25 mev to about 100 mev e g 35 mev to 55 mev and a beam current in the range of about 30 microamps to about 280 microamps e g 50 microamps to 140 microamps the irradiation of converter plates 16 with the electron beam may result in the production of gamma rays with energies in the range of about 1 mev to about 55 mev e g of about 1 mev to about 40 mev for example in some instances and for medical applications the irradiation may be continued until the conversion to copper 67 yields a copper 67 total activity of at least about 2 u03bcci g target at least about 5 u03bcci g target at least about 10 u03bcci g target or at least about 20 u03bcci g target for example when using a 40 g zinc 68 target such as target 27 fig1 a one may irradiate the metal target with bremsstrahlung produced gamma rays for a time until at least about 80 u03bcci of copper 67 at least about 400 u03bcci of copper 67 or at least until about 800 u03bcci of copper 67 is produced in one instance for example one may.