# impact cutoff 50 microns
ion_x, ion_y, ion_z = np.random.uniform(-50e-6,50e-6), np.random.uniform(-50e-6,50e-6), z
while(np.sqrt(ion_x**2+ion_y**2) > 50e-6):
    ion_x, ion_y, ion_z = np.random.uniform(-50e-6,50e-6), np.random.uniform(-50e-6,50e-6), z

# new r based off randomnly placed ion (assuming electron or ion starts at origin, if ion at origin, then below is electron position)
r = [ion_x,ion_y,ion_z, 0, 0, vz]