tuneshift with amplitude

[marlibgin]

I have a general and trivial question
I am trying to activate the calculation of the higher oder thune shifts with amplitude (dnux/daX2, dnuy/dAy2 etc)
using a combination of tune_shift_with_amplitude and twiss_output commands.
However while the linear terms are calculated, there all the higher order elements remain zero

dnux/Ax2 =0.0000 dnux/dAxdAy=0.0000 ...

this is the fragment of my *.ele text. I 'd like to find the flag that activates this calculation:

&tune_shift_with_amplitude
turns = 0,
x0 = 1e-06,
y0 = 1e-06,
x1 = 0.03,
y1 = 0.03,
grid_size = 6
&end

&twiss_output
filename = %s.twi,
radiation_integrals = 1,
matched = 1,
output_at_each_step = 1,
concat_order = 3
higher_order_chromaticity = 1
higher_order_chromaticity_range = 0.0002
chromatic_tune_spread_half_range = 0
compute_driving_terms = 1
leading_order_driving_terms_only = 1
beta_x = 1
beta_y = 1
alpha_x = 0
alpha_y = 0
eta_x = 0
etap_x = 0
&end

[michael_borland]

I've attached a example that may help.

Please note that higher-order coefficients are not always reliable due to the difficulty of identifying and determining tunes when there is motion is both planes at larger amplitudes.

--Michael