Development of a vacuum arc ion source for injection of high current uranium ion beam into the unilac at GSI

Abstract

To fill up the GSI heavy ion synchrotron (US) to its space charge limit wjith uranium ions, a new vacuum arc ion ,source (VARIS). based on the MEVVA IV ion source ha.s been developed and implemented into operation. The ion source ha.s proven its ctlpahility in several long period beam rimes at the high current injector at GSI. With the new ion source it was possible to e.rceed the space charge limit of I S mA ri" ions at the entrance of the linear accelerator (UN1LAC)for the veyfirst time.The reliability as well as the noise behaviour has heen imprnved to such a degvec, that thi.s ion .source can be used f o r injection info an accelerator without uhjection. I n this article we present the improvements of the ion s o n~c e with the most important operational data. The emission current density of the new ion source has heen increasedfrom 60 mA/cmz for the common used GSI-M E W A to 170 mA/cni2. Thi.s results in a full beam ion current of IS6 mA at 35 kV with a fraction of /bur fold charged uranium ions of 67 54. The analysed v" ion heam after dc post occeleration amounts tu 25 mA at 131 kV which is 1.7 times higher than the requested ion heam current at the entrance of the RFQ. The reduced power density of the vactnini arc resu1t.v in a higher eflciency and longer life time. So1enoid.Y which are creating magneticfields to enhance the charge state of the ions are no more placed inside the vacuum system. This ion source design results in a higher availability after ion source replacement at the injector, and longer life time.