Hi Sveinn,
This is not so fancy, digital oscilloscope saving current traces is all is needed, no spectrometer except if you can call lifetime measurement a spectrometer. Digital oscilloscope has very nice time accuracy.
My question is about calibration -- do you know how Leif Holmlid is doing it? To calibrate in such a scenario, you would normally measure a source of known decay energy. I do not see how he can with his particular setup, as it records the time from the start of a laser pulse to when a signal is registered by his oscilloscope. But a radioactive source is not normally triggered in this way -- you typically just wait for it to emit. That means you cannot accurately record the travel time of an alpha particle from a radioactive standard, because you didn't trigger its decay. I do not see any mention of blank runs or calibrations in his two recent draft papers on arXiv. Calibrations of this kind are so basic in the field of spectroscopy that no researcher, even especially one who has built his own time-of-flight spectrometer, would think to omit such a step.
When you use a weighing scale, you tare it to zero before you conclude anything about your weight. When you report a current of charged particles of such-and-such MeV u-1, you compare it to a current that you already know something about so that you know that your numbers are right.
If Holmlid is not calibrating against a decay source of known decay energy, can you confirm that he is simply reasoning from first principles about the pulse delay without the benefit of a calibration?