Eph1 = 2.525  # actual photon energy in keV. Don't forget .0 at the end!!
Eph2 = 2.425  # desired photon energy in keV. Don't forget .0 at the end!!

do_elog = True

undlist = ("SARUN03","SARUN04","SARUN05","SARUN06","SARUN07","SARUN08","SARUN09",
           "SARUN10","SARUN11","SARUN12","SARUN13","SARUN14","SARUN15")

K1, K2 = {}, {}
for und in undlist:
  K = caget(und + "-UIND030:K_SET")
  K1[und] = K
  K2[und] = ((Eph1 / Eph2 * (K**2 + 2) - 2))**0.5
print K1,K2
for und in undlist: caput(und + "-UIND030:K_SET",  K2[und])

#Elog entry
if do_elog:
  title = "Wavelength change"
  log_msg =           "Old photon energy:  %0.2f"   % Eph1            + " kev\n"
  log_msg = log_msg + "New photon energy:  %0.2f"   % Eph2            + " keV\n"
  elog(title, log_msg)
  
set_return("Success")