0 0.2 0.4 0.6 0.8 1 0 2 4 6 8 10 12 14 0 0.1 0.2 0.3 (a) (b) anisotropy parameter 2 clust er width y rms  (mm) cluster length x rms  (mm) -1 0 1 2 3 4 5 6 0 2 4 6 8 10 12 14 2 % error,$^{δ}$ r 0 Figure 4: (a) Measured cluster width y$_{rms}$ (open circles), power law fit to data near the zigzag transition (dashed line) and widths computed from the model for κ = 2 . 4 and r 0 = 1 . 25 mm (solid line) vs the measured anisotropy parameter α $^{2}$. (b) Measured cluster length x$_{rms}$ (open circles) and lengths computed from the model (solid line) vs α $^{2}$. (Inset) Comparison of the percentage difference between the x$_{rms}$ data and the model (open circles) with the percentage change in r 0 ∼ ω − 2 / 3 x (broken line) vs α $^{2}$. As shown in Fig. 4(a), the cluster width y$_{rms}$ calculated using the model for κ = 2 . 4 and r 0 = 1 . 25 mm exhibits excellent agreement with the experimental data, including reproduc- ing the transition between the zigzag and elliptical configurations. The agreement between the measured and predicted values of x$_{rms}$ provides a cross check on the model. We find that the predicted values of x$_{rms}$ [Fig. 4(b)] show good agreement for α 2 ≲ 4, but system- atically underestimate the measured cluster length as α 2 increases. For the longest clusters, which are in a straight line configuration, the predicted cluster lengths are about 6% below 9