Computing the skew components of quadrpoles

[elafmusa]

Hi everyone,

I want to apply this relation to compute the skew component of the quadepoles in a lattices:
skew component = -K1 sin (2.(theta))
Where theta is the tilt angle.

My quistions:

Is there a bult in function in PyAT the returns this value directly?
I tried to implement it as following (looping through all the lattice elements):

while (i < len(elements_indexes)):
if (ring[i].FamName).startswith('q'):
skew_quad_coof = - ring[i].K * sin (2*math.acos(ring[i].R1[0,0]))
else:
skew_quad_coof = 0
k_qs.append(skew_quad_coof)
i += 1

This raised an error: 'Quadrupole' object has no attribute 'R1' For the quadrpoles that was not tilted

My second quistions:
-Is there a better way to calculate the theta angle better than using the R1 matrix: math.acos(ring[i].R1[0,0])
-How can i access the theta angle of value zero for the non-tilted elements in my loop?

@lfarv @simoneliuzzo

[lfarv]

@elafmusa :
I do not clearly see what you want to do:

To tilt an element, you have to use the the functions tilt_elem(elem, angle) for tilting a single element or set_tilt(elem_list, angles) for tilting a sequence of elements. These functions take the tilt angles as arguments and add/modify the R1 and R2 matrices of each element. Then all tracking and optics will respect these tilts. To get back the tilt angle, you can get sin(θ) in R1[0, 1] and cos(θ) in R1[0, 0]. If an element does not have R1 an R2 attributes, it is not tilted.

Alternatively, rather than tilting the element, you could recompute PolynomB and PolynomA according to your formula, but there is no simple way to do that. And don't put both tilt angle and PolynomA: you would get twice the effect!

[lfarv]

How can i access the theta angle of value zero for the non-tilted elements in my loop?

try:
    angle = math.atan2(elem.R1[0, 1], elem.R1[0, 0])
except AttributeError:
    angle = 0.0