We have been using the 3d PIC code WARP6 to model the behavior of beams in a heavy ion induction accelerator; such linacs are candidates for an ICF driver. Improvements have been added to the code to model an axially confined beam using comoving axial electric fields to simulate the confining ears'' applied to the accelerating pulses in a real system. We have also added a facility for modeling a beam in a round pipe, applying a capacity matrix to each axial Fourier mode in turn. These additions are described along with results, such as the effect of pipe shape on the beam quality degradation from quadrupole misalignments. 5 refs., 6 figs., 1 tab.

The argon storage dewar at the D0 Assembly Hall was filled with approximately 3100 gallons of high purity liquid argon for the first time on December 3,1990. The oxygen analyzer and high voltage test cell both indicated an oxygen impurity level between 0.4 and 0.5 ppm which is acceptable. The condenser and insulated piping sizing appears to be correct for a fill rate of a couple of hours. Insulation is required around the inlet to this piping in order to reduce the amount of filling time significantly. The graph of the level indication vs. volume of the dewar should be changed to reflect the apparent 5.2-5.4 in. offset. Another data point may be required to narrow this number down further. A majority of the time spent to fill the vessel was associated with the testing of the liquid-this time will shorten as we gain experience. Subsequent deliveries should be ordered to initiate as early in the morning as possible, this appears to be nearly an all day effort. The argon checked prior to delivery by us indicated that it was acceptable. The analysis of the argon purity that Linde provides us is merely a check that the liquid meets our …

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