Ion beam energy is calculated using Beamcalc (https://web-docs.gsi.de/~lestinsk/beamcalc/electron.php)

Electron current is set to 4.3 mA and can be taken from Grafana

Alpha factor is 50

Ion energy is then adjusted using the cooler voltage

The cooler voltage inserted into BeamCalc is taken from the FC20 voltage divider. However an offset from the space charge correction is required!

This correction is determined experimentally by changing the electron current and finding the cooler voltage which maintains the optimum cooling of the beam.

Attachment 1 shows this plot for 15N1+ at  ~0.426 MeV/u

Attachment 2 shows this same plot in comparison with BeamCalc

To obtain the correct energy we need to subtract 2V from the voltage used in BeamCalc

An example is shown in attachment 3

Here to obtain an ion energy of 426.6 keV/u requires a cooler voltage of 246.7 V. But, due to the space charge correction this value should be 244.7 V.

The cooler voltage setpoint should therefore be chosen so that the FC20 voltage divider reads 244.7 V.

The setpoint needs to be ~0.55 V higher than the desired value i.e setpoint of 245.25 V to obtain the required 244.7 V (at least this beamtime it does)