  In this work, the transport and magnetization properties of
distributed-barrier Rod-in-Tube (RIT) strands and Tube Type strands are
studied. While Tube Type strands had smaller magnetizations and thus better
stabilities in the low field region, their 12 T non-Cu Jcs were somewhat
smaller than those of the RIT strands. Microstructures were investigated in
order to find out the reasons for the difference in non-Cu Jc values. Their
grain size and stoichiometry were found to be comparable, leading to similar
layer Jcs. Accordingly it was determined that the lower A15 area fraction
rather than the quality of A15 layer was the cause of the discrepancy in non-Cu
Jc. Subsequently, the area utilizations of subelements were investigated. While
for a RIT strand the fine grain (FG) A15 area occupies ~60% of a subelement,
for a Tube Type strand it is no more than 40%. Further analysis indicates that
the low FG area fraction in a Tube Type strand is attributed to its much larger
unreacted Nb area fraction. Finally, a simple change in strand architecture is
proposed to reduce the unreacted Nb area fraction.
