An implicit factorization method has been developed for solving numerically the complete two-dimensional Navier-Stokes and continuity equations for pressure transients in a slightly compressible viscous liquid contained in a rigid pipe. Two problems have been analyzed: (1) The stopping of a steady Poiseuille flow by closure of a valve, and (2), the initiation of a nearly rectangular pressure pulse at the end of the pipe. In problem (1), radial as well as axial pressure variations were found; nearly periodic damped waves exist at the centerline and at the wall, and are approximately 180 deg out of phase. Essentially plane waves are found for problem (2), regardless of whether the fluid is flowing or not, provided that the initial pulse magnitude is not too large; the results show that the viscous effects are concentrated in a thin boundary layer.

A separated function, variable energy, drift tube linac (DTL) operating in cw mode at 105 MHz is being built for the ISAC radioactive beam facility at TRIUMF. Included in the design are three buncher cavities installed in the first, second and third drift spaces between the five IH tanks. The main requirements of the bunchers are: cw mode, high effective voltage (up to 0.32 MV), large velocity acceptance (1.8-4.1%). The first DTL buncher has been developed at INR and is being tested at TRIUMF. It is a triple gap split-ring rf structure operating at 105 MHz. Signal level measurements give a Q-value of 4300 which is 74% of MAFIA simulation predictions and a resonant frequency within 0.6% of the calculated value. With cooling water flow of 20 l/min the mechanical vibrations were measured to be of the order of 1 µm. Although the design parameters are 56 kV gap voltage and 8 kW nominal power, we demonstrated 85 kV and 16 kW respectively with stable operation.

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Five rf systems, each operating in cw mode, have so far been specified for the ISAC accelerator system; a prebuncher, an RFQ, a MEBT re-buncher, five DTL cavities and three DTL bunchers. The pre-buncher was designed and built to operate at a frequency of 11.66 MHz plus three harmonics. So far it has operated successfully at full nominal voltage with fundamental plus the addition of two harmonics. Both the 8-meter long, 4-rod, split-ring type RFQ and the spiral two gap MEBT re-buncher were designed to operate at 35 MHz. The initial 2.8 meters of the RFQ (7 out of 19 rings) were installed in the 8 m long tank and have been successfully operated at full power with beam. Dark currents associated with field emission initially accounted for 40% extra power consumption at full voltage but could be eliminated with high power pulse conditioning. The remaining 12 rings are being installed to enable us to accelerate cw radioactive ion beams to 150 keV/u. A full scale model of the MEBT re-buncher was built and tested and the final structure is in the design stage. The DTL accelerator system consists of a series of multi-gap interdigital H-mode tanks and three gap splitring buncher cavities both operating at 105 MHz. The first DTL cavity has been fabricated and is undergoing rf tests.The first DTL buncher was tested to twice the nominal operating power. All amplifiers for the above were designed and built in house. This paper will report on the performance achieved for these systems.