Semiconductor drift detector for detecting radiation, comprising a) a semiconductor substrate in which signal charge carriers are generated during operation, a1) by individual incident photons (h·f), ions or electrons having an energy that is to be determined, in particular in the form of X-ray fluorescence radiation, and/or a2) by a plurality of incident electrons (e), ions or other ionising radiation having a specific signal charge carrier current, in particular in the form of backscattered electrons (e), b) a read-out anode for generating an electrical output signal depending on the signal charge carriers, c) an erase contact for erasing the signal charge carriers that have accumulated in the semiconductor substrate, characterised by a d) long-channel reset transistor which is integrated in the semiconductor substrate and connects the read-out anode to the erase contact in order to discharge the photon-generated signal charge carriers and/or the electron-generated signal charge carriers to the erase contact, which makes it possible to measure the signal charge carrier current and the photon energy, and further characterised in that e) the long-channel reset transistor has a gate, and the channel of the long-channel reset transistor has an electrical resistance, which can be adjusted by applying a gate voltage to the gate of the long-channel reset transistor, f) the semiconductor drift detector can be selectively operated in a first operating mode or in a second operating mode, g) in the first operating mode, the semiconductor drift detector measures the energy of the incident photons (h·f), electrons or other ionising particles, h) in the second operating mode, the semiconductor drift detector measures the signal charge carrier current, and further characterised in that i) the semiconductor drift detector has at least one drift ring (DR1, DR2), which annularly surrounds the read-out anode and generates an electrical drift field in the semiconductor substrate, so that the signal charge carriers drift to the read-out anode, and j) the innermost drift ring is interrupted, at least in part, by a slot extending from inside to outside, and k) the long-channel reset transistor is arranged in the slot in the innermost drift ring, wherein the channel of the long-channel reset transistor extends along the slot. a) a semiconductor substrate in which signal charge carriers are generated during operation, a1) by individual incident photons (h·f), ions or electrons having an energy that is to be determined, in particular in the form of X-ray fluorescence radiation, and/or a2) by a plurality of incident electrons (e), ions or other ionising radiation having a specific signal charge carrier current, in particular in the form of backscattered electrons (e), a1) by individual incident photons (h·f), ions or electrons having an energy that is to be determined, in particular in the form of X-ray fluorescence radiation, and/or a2) by a plurality of incident electrons (e), ions or other ionising radiation having a specific signal charge carrier current, in particular in the form of backscattered electrons (e), b) a read-out anode for generating an electrical output signal depending on the signal charge carriers, c) an erase contact for erasing the signal charge carriers that have accumulated in the semiconductor substrate, characterised by a d) long-channel reset transistor which is integrated in the semiconductor substrate and connects the read-out anode to the erase contact in order to discharge the photon-generated signal charge carriers and/or the electron-generated signal charge carriers to the erase contact, which makes it possible to measure the signal charge carrier current and the photon energy, and further characterised in that e) the long-channel reset transistor has a gate, and the channel of the long-channel reset transistor has an electrical resistance, which can be adjusted by applying a gate voltage to the gate of the long-channel reset transistor, f) the semiconductor drift detector can be selectively operated in a first operating mode or in a second operating mode, g) in the first operating mode, the semiconductor drift detector measures the energy of the incident photons (h·f), electrons or other ionising particles, h) in the second operating mode, the semiconductor drift detector measures the signal charge carrier current, and further characterised in that i) the semiconductor drift detector has at least one drift ring (DR1, DR2), which annularly surrounds the read-out anode and generates an electrical drift field in the semiconductor substrate, so that the signal charge carriers drift to the read-out anode, and j) the innermost drift ring is interrupted, at least in part, by a slot extending from inside to outside, and k) the long-channel reset transistor is arranged in the slot in the innermost drift ring, wherein the channel of the long-channel reset transistor extends along the slot.