  The LBNF Absorber consists of thirteen 6061-T6 aluminum core blocks. The core
blocks are water cooled with de-ionized (DI) water which becomes radioactive
during beam operations. The cooling water flows through gun-drilled channels in
the core blocks. A weld quality optimization was performed to produce National
Aeronautical Standard 1514 Class I quality welds on the aluminum core blocks.
This was not successful in all cases. An existing Gas Tungsten Arc Welding
Procedure Specification was fine tuned to minimize, in most cases, and
eliminate detect-able tungsten inclusions in the welds. All the weld coupons,
however passed welding inspection as per the piping code: ASME B31.3 Normal
Fluid Service. Tungsten electrode diameter, type, and manufacturer were varied.
Some of the samples were pre-heated and others were not. It was observed that
larger diameter electrodes, 5/32 in., with pre-heated joints resulted in welds
with the least number of tungsten inclusions. It is hypothesized that thinner
electrodes breakdown easily and get lodged into the weld pool during the
welding process. This breakdown is further enhanced by the large temperature
differential between the un-preheated sample and the hot electrode.
