Implement scattering of an irregular linear array of spheres

[ronandrevon]

adapt base class HardSphereArrayBase and class QdotSphereArray in case kd is a list(or np.array)

• Validate by checking continuity of the wave function and radial derivatives at interfaces
• optional convergence test using HardSphereArrayBase.test_convergence()
• Example case N=5,10,20; ka=1; kd=2.5ka+epsnp.random.rand(N); nref=1.1 where esp varies in 0-0.5.
• Show far field with show_ff for each values of eps
• Show sigma(eps) for N=5,10 et 20 using HardSphereArrayBase.get_s()

[kitine]

Continuity check :

[kitine]

Convergence test :

for nmax=3, ok

[kitine]

Far field for each value of eps : N=5

N=10

N=20

[kitine]

Sigma(eps) for N=5,10 et 20 :

Red : N=5 Green : N=10 Blue : N=20