X-ray absorption spectra of the Fe/Al2O3/CoAl(111) sample using phase-sensitive current detection of the `on' and `off' cycles of the chopper system. (a) At location `tip A' the spectrum with X-ray illumination (`on') exhibits Fe L3 and Fe L2 absorption edges, indicating the presence of an Fe island. During the photon energy ramp, the tunneling current setpoint, i.e. the feedback signal of 0.1 nA, is maintained as demonstrated by the phase-sensitive detection of the `off' cycle. (b) Similarly, at location `tip B' the chemical fingerprint of the oxide film can be observed, while the tip detector maintains stable tunneling conditions at 0.1 nA.