added wavelength wrapper adjustable

qspace.py

@@ -167,6 +167,30 @@ class QSpace1D(Adjustable):
 
 
 
+h = 6.62607015e-34 # J s
+c = 299792458 # m / s
+e = 1.60217663e-19 # C
+f = h * c / e * 1e-3 * 1e9 # E [keV] = f / lambda [nm]
+
+
+class Wavelength(Adjustable):
+
+    def __init__(self, energy):
+        self.energy = energy
+        assert self.energy.units == "keV" # otherwise conversion is wrong
+        super().__init__(energy.ID + "_WL", name=energy.name + " as Wavelength", units="nm")
+
+    def get_current_value(self):
+        E = self.energy.get_current_value()
+        return f / E
+
+    def set_target_value(self, value):
+        E = f / value
+        return self.energy.set_target_value(E)
+
+    def is_moving(self):
+        return self.energy.is_moving()
+
 
 
 # these point to the different motors
@@ -176,7 +200,7 @@ phi = Motor("SATES30-RIXS:MOT_SRX.VAL")
 nu = Motor("SATES30-RIXS:MOT_DRY.VAL")
 
 # and this to the machine wavelength (maybe this needs to be calculated from the energy? then we should add a Wavelength wrapper...)
-wl = PVAdjustable("MACHINE:WAVELENGTH")
+wl = Wavelength(PVAdjustable("MACHINE:ENERGY"))
 
 # put it all together:
 q = QSpace3D("SOMETHING:Q", mu, chi, phi, nu, wl)