Mars/Casim Comparison for Simple Geometries

BooNE Group Meeting - 12/20/98

We have compared the star density predicted by Casim and by Mars for two simple cylindrical geometries. The first is similar to our decay region. The geometry consists of a 1.1 cm radius aluminum target, air out to a radius of 5' 5", then 3' of concrete and finally the soil that is irradiated. The first plot is 50K Mars events and the second is 500K Casim events (the former took 12 hours of Fermilab SUN cpu time; the latter took 4 hours of Cincinnati HP cpu time). As can be seen in these plots, CASIM predicts slightly more and a slightly broader star distribution than MARS does.

The next comparison is with the same geometry as above except iron is inserted in the annulus between 40 and 160 cm. This is a geometry similar to the shielding in the target region of the decay hall. Again, the first plot is 50K Mars events and the second is 500K Casim events. While the statistics are much lower, again CASIM shows more activation.

I propose that we make our initial design decisions using the output from CASIM and that we verify our final design with a MARS calculation. I believe that, based on the above examples, we will find the MARS activation lower than the activation we got from CASIM and therefore or designs will be safe. Furthermore, CASIM runs so much quicker and is so much easier to use that we will be able to check many more variations than we could if we used MARS exclusively.