Increasing beam currents at the TRIUMF-ISAC Facility; techniques and experiences

The TRIUMF-ISAC radioactive ion beam facility has been in operation since 1998. The facility was designed and constructed to allow irradiation of thick targets with up to 100 muA proton beam intensities. Since beginning operation, beam intensities on targets have progressively increased up to 40 muA for refractory metal target materials and more recently, up to 50 muA for composite metal carbide materials. To achieve the higher irradiation intensities consideration must be given to the beam power deposition, the power dissipation and the limiting temperature criteria of each target material. Increasing irradiation currents have produced both benefits and drawbacks for ISOL operations. With increasing proton beam, radiation enhanced diffusion effects have been observed that lead to increased overall isotope yields. However, radiation damage also increases with increased proton fluxes, limiting the practical target lifetimes.