
====================================  tc_slit   ==============================

   tc_slit (undulator tuning curves on slit) calculates the flux and power 
   for an ideal undulator while scannling the K value. 

   The calculation is performed by calculationg the flux and spectral density
   for each K point using one of the selected codes (US, URGENT or SRW).
   Therefore, it can be slow for calculations with many points up to higher 
   harmonics.
   Only odd harmonics are considered. 
