PRODUCTION OF MULTIPLY CHARGE-STATE IONS IN A MULTICUSP ION-SOURCE

High charge state ion beams are commonly used in atomic and nuclear ph ysics experiments. Multiply charged ions are normally produced in an E CR or in an EBIS. Multicusp generators can confine primary electrons v ery efficiently. Therefore, the electrical and gas efficiencies of the se devices are high. Since the magnetic cusp fields are localized near the chamber wall, large volumes of uniform and high density plasmas c an be obtained at low pressure, conditions favorable for the formation of multiply charged state ions. Attempts have been made at LBNL to ge nerate multiply charged ion beams by employing a 25-cm diam by 25-cm l ong multicusp source. Experimental results demonstrated that charge st ates as high as 7+ can be obtained with argon or xenon plasmas. Multip ly charged metallic ions such as tungsten and titanium have also been successfully formed in the multicusp source by evaporation and sputter ing processes. In order to extend the charge state to higher values, a novel technique of injecting high energy electrons into the source pl asma is proposed. If this is successful, the multicusp source will bec ome very useful for radioactive beam accelerators, ion implantation, a nd nuclear physics applications. (C) 1996 American Institute of Physic s.