30 Years Of High Intensity Negative Ion Sources For Accelerators

Download or read book 30 Years of High-intensity Negative Ion Sources for Accelerators written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Thirty years ago, July 1, 1971, significant enhancement of negative ion emission from a gas discharge following an admixture of cesium was observed for the first time. This observation became the basis for the development of Surface Plasma Sources (SPS) for efficient production of negative ions from the interaction of plasma particles with electrodes on which adsorbed cesium reduced the surface work-function. The emission current density of negative ions increased rapidly from j (approximately) 10 mA/cm2 to 3.7 A/cm2 with a flat cathode and up to 8 A/cm2 with an optimized geometrical focusing in the long pulse SPS, and to 0.3 A/cm2 for DC SPS, recently increased up to 0.7 A/cm2. Discovery of charge-exchange cooling helped decrease the negative ion temperature T below 1 eV, and increase brightness by many orders to a level compatible with the best proton sources, B = j/T> 1 A/cm2 eV. The combination of the SPS with charge-exchange injection improved large accelerators operation and has permitted beam accumulation up to space-charge limit and overcome this limit several times. The early SPS for accelerators have been in operation without modification for (approximately) 25 years. Advanced version of the SPS for accelerators is described. Features of negative ion beam formation, transportation, space-charge neutralization-overneutralization, and instability damping is considered. Practical aspects of SPS operation and high brightness beam production is discussed.