A 12.5 MHz Heavy Ion Linac for Ion Beam Fusion

Abstract

NOTICE -This report MI prepared at an account or work ipomufed by the United Stilct GawnrnenL Neither the United Sutei not tlie United St«« Deputment of Energy, nor iny of theii employees, not my of their mn tract in v iubconifjctcwi. or then employees, makes any wvraruy, ezpttu of implied, or usunwi any legjl lubiii'v it (cspamibiiity (•< theiccuricy.compkwnetl « inei A i%* ni my infonralipn. > puat-J, ptoduci 01 prikceu diKloKd, ui repfctenu ihli IU at wuuid not ifitringt pnvjtely owned nghti. ;The cavity is now on station in front of the ; ' preaccelerator undergoing low power testing. Shortly it will be put under vacuum and high power testing with beam will commence. The cavity has been tuned 'to the design frequency of 12.500 MHz by adding a 0.409 cm copper ring to the bottom end plate flanqe in order to decrease the end plate capacitance; it had a measured Q of 5500 and a gap impedance of 525 kt?. o Therefore, only 9.52 kW of power will be required to reach the design of 100 kV peak of the gap. Since 25 kW of RF power is available, studies will be undertaken to determine the voltage breakdown limit with beam. ;The next two cavities (shown schematically in '. Fig: 1) The double-stub WiderSe linac is shown schematically in Fig. 1, as the last two tanks on the right. The tanks were designed using a Wideroe linac cods • developed at the Lawrence Berkeley Laboratory' in col--|laboration with GSI. 6The program is interactive and ! j iterative. By varying the position and length of the stubs, the input/output energy, and line loading, we ,find a consistent solution for frequency, drift tube j table, energy gain pe-cell and gap voltages. The ; !program also contains a plotting routine for the vol-j , fcage on the gaps and the current along the linac.In order to control space charge forces and achieve maximum beam transport it is necessary to be ' able to control the voltage tilt along the linac. i A design of a double-stub 5it/ii Wideroe linac using a FODO quadrupole focussing lattice has been completed. This linac increases the ion energy from 2 HeV to 6.4 MeV. The design of the second doublestub HiderSe operating in the 3w/ir mode with FODO focussing has also been completed. It increases the ; ion energy from 6.4 to 11.4 HeV. In order to increase : shunt impedance and reduce cost, a 3n/ir double-stub Wideroe linac for Tank #4 operating with a FOFODODO focussing lattice is currently under study. Acknowledgement

The Status of the Argonne Heavy Ion Fusion Low-Beta Linac

“…The present buncher (lumped inductor cavity) will become the first independently phased accelerating cavity. 5 A new harmonic buncher has been designed^ to replace it.…”

“…IPC #5 will be a 6-gap "drum" type linac cavity. 5 Initially, IPC #4 and #5 will have electrostatic quadrupoles, but are designed so that they can be easily refitted with magnetic quadrupoles. The tank and all other tank parts, except for the quaarupole housing and "short" drift tubes, are made of mild steel and will be electroplated with 250 um of high conductivity, bright copper.…”