| Co-Investigator(Kenkyū-buntansha) |
TOJYO Eiki U. of Tokyo, Inst. f. Nucl. Study, Res. Assoc., 原子核研究所, 助手 (10092280)
MORIMOTO Teruhisa U. of Tokyo, Inst. f. Nucl. Study, Res. Assoc., 原子核研究所, 助手 (20174451)
TOKUDA Noboru U. of Tokyo. Inst. f. Nucl. Study, Res. Assoc., 原子核研究所, 助手 (60134649)
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| Research Abstract |
In low-power tests of the 25.5-MHz split coaxial RFQ cavity, we measured field strengths by using the perturbation technique. The azimuthally four-fold symmetry of the electric field, which is essential at the RFQ linac, was examined by setting a perturbator between neighboring vanes. The measured field strengths in the quadrants are same within <plus-minus>0.6% at any longitudinal position of the perturbator. Through another measurement with a perturbator moving along the beam axis, we verified that the intervane voltage is flat over the vane length, and that the actual electric field in the beam aperture is almost same as the ideal one. For fine tuning of the resonant frequency of the cavity, an inductive tuner of the piston type was used and proved that it worked as we expected. We conducted high-power tests by feeding the cavity with rf power from an amplifier, having a maximum output power of 100 kW in peak and a maximum duty factor of 10%. For the power feed, a loop coupler was a
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ttached to the cavity. The impedance matching between the cavity and the amplifier was so well accomplished with the loop coupler as was designed. Trough rf conditioning of 150 minutes effectively (nominal operation time X duty factor), we achieved an intervane voltage of 110 kV, necessary for the acceleration of ions with a charge-to-mass ratio (q/A) of 1/30. For acceleration tests, we constructed a test stand consisting of an ion source, beam transport lines (including vacuum chambers, beam monitors, einzel lenses, a quadruple magnet doublet, a momentum analyzer magnet), and a control system for power supplies, vacuum pumps, and beam monitors. Molecular nitrogen ions (N^+_, q/A = 1/28) were stably extracted at 1 keV/u from a compact 2860-MHz ECR ion source. On January 22, 1991, N^+_ ions were successfully accelerated from 1 through 45.4 keV/u. For detailed tests on the acceleration performance of the RFQ linac, we are now preparing for precise measurements of the energy spectrum of the output beam, the transmission efficiency, etc. Less
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