Improved Method for Determining the $n$-Value of HTS Bulks

The complete penetration magnetic field BP is the main feature of a superconducting pellet submitted to an axial applied magnetic field. The electric E-J characteristics of HTS bulk is generally described by a power law E(J) = E
_C
(J/J
_C
)
ⁿ
. The influence of the n-value and applied magnetic field rise rate V
_b
on the B
_P
of a HTS cylindrical pellet has been presented in a previous paper. The numerical results presented come from a numerical resolution of a nonlinear diffusion problem. With the help of these simulations, a linear relationship between B
_P
, ln V
_b
, and n-value has been deduced. This comparison allows determining the critical current density J
_C
and the n-value of the power law based on direct measurement of B
_P
in the gap between two bulk HTS pellets. In this paper, an improvement of this method is presented. The influence of geometric parameters R and L is studied to give generality to the relationship between B
_P
, V
_b
, and n-value. A previous B
_P
formula is confirmed by these new simulations. To correctly connect simulation and experimental results, the influence of spacing e between bulks is studied and presented. A relationship between B
_P
and measured complete penetration magnetic field B
_PM
is determined.