Method and apparatus for generating high current negative hydrogen ion beam

A method for providing a negative hydrogen ion beam, comprising:

• generating positive molecular hydrogen ions in an ion source;
• providing a charge exchange species in a charge exchange cell, the charge exchange species operative to transform the positive hydrogen ions into negative hydrogen ions;
• and
• extracting the positive hydrogen molecular ions at an extraction voltage effective to maximize negative ion current yield in the charge exchange cell based upon a product of extraction efficiency of the positive molecular hydrogen ions and charge exchange efficiency for converting a species of the positive molecular hydrogen ions to negative hydrogen ions through charge exchange between the extracted hydrogen ions and charge exchange species,
• wherein the extraction voltage lies in a first range between a peak voltage and 30% higher than the peak voltage, the peak voltage corresponding to a peak in charge exchange efficiency for converting H3+ ions to negative hydrogen ions through charge exchange between the molecular hydrogen ions and the charge exchange species when a fraction of H3+ ions to total positive hydrogen ions is above a given threshold.

An ion implantation system to generate a proton beam, comprising:

• an ion source operative to generate a plasma and extract ions from the plasma as positive molecular hydrogen ions;
• a charge exchange cell operative to receive the positive molecular hydrogen ions and convert the extracted positive molecular hydrogen ions to negative hydrogen ions using a charge exchange species;
• an extraction voltage tuner component comprising logic operative to set an adjusted extraction voltage for extraction of the positive molecular hydrogen ions from the ion source, wherein the adjusted extraction voltage lies in a first range between a peak voltage and 30% higher than the peak voltage, the peak voltage corresponding to a peak in charge exchange efficiency for converting H3+ ions to negative hydrogen ions through charge exchange between the molecular hydrogen ions and the charge exchange species when a fraction of H3+ ions to total positive hydrogen ions is above a given threshold;
• and
• a tandem accelerator to convert the negative hydrogen ions into a beam of protons.