Hi Rohit:
This is the full set of code + definition of variables
Ci = Flatten[Import["Downloads/ctjulien.txt", "table"]]
Cp = Flatten[Import["Downloads/clphiphi.txt", "table"]]
Subscript[C, t] =
Flatten[Import["Downloads/clphiphi.txt", "table"]]
Lp[a_] := 1052*{Cos[a], Sin[a]}
vL[L_] := {L, 0}
l[l1_, \[CapitalPhi]1_] :=
l1*{Cos[\[CapitalPhi]1], Sin[\[CapitalPhi]1]}
f[x_, y_] :=
Ci[[IntegerPart[Norm[x]]]]*Dot[x + y, x] +
Ci[[IntegerPart[Norm[y]]]]*Dot[x + y, y]
F[x_, y_] :=
f[x, y]/(2*Subscript[C, t][[IntegerPart[Norm[x]]]]*
Subscript[C, t][[IntegerPart[Norm[y]]]])
L = 40
NIntegrate[
l1*F[l[l1, \[CapitalPhi]], {L, 0} - l[l1, \[CapitalPhi]]]*
F[Lp[\[CapitalPhi]p], {L, 0} -
Lp[\[CapitalPhi]p]]*(Dot[Lp[\[CapitalPhi]p],
Lp[\[CapitalPhi]p] - l[l1, \[CapitalPhi]]]*
Cp[[Round[Norm[Lp[\[CapitalPhi]p] - l[l1, \[CapitalPhi]]]]]]*
f[-{L, 0} + l[l1, \[CapitalPhi]], {L, 0} - Lp[\[CapitalPhi]p]] +
Dot[Lp[\[CapitalPhi]p],
Lp[\[CapitalPhi]p] -
l[{L, 0} - l[l1, \[CapitalPhi]], \[CapitalPhi]]]*
Cp[[Round[
Norm[Lp[\[CapitalPhi]p] -
l[{L, 0} - l[l1, \[CapitalPhi]], \[CapitalPhi]]]]]]*
f[-l[l1, \[CapitalPhi]], {L, 0} -
Lp[\[CapitalPhi]p]]), {\[CapitalPhi], -Pi,
Pi}, {\[CapitalPhi]p, -Pi, Pi}, {l1, 2, 2900}]
