Refactor

- Change PenningTrap so that perturbation is its own field
- Add Calcium mass and charge to constants

include/constants.hpp

@@ -18,4 +18,8 @@
 
 #define V 9.64852558*1e7 ///< 1 Volt. unit: \f$ \frac{u (\mu m)^2}{(\mu s)^2 e} \f$
 
+#define CA_MASS 40.078 ///< Mass of a single calcium ion. unit: amu
+
+#define CA_CHARGE 1. ///< Charge of a singly charged calcium ion. unit: e
+
 #endif