A measurement of the tagging efficiency should be performed about once a day and before and after a beam optimization. To measure tagging efficiency, do the following things:

1) Make sure that you know which tagger trigger configuration is currently active, so you can restore it after the tagging efficiency measurement. Look in the run logbook to find out.

2) Make sure the present current in the Faraday cup is noted in the runlog book so that you can restore it after the tagging effciency measurement.

3) Stop the current run.

4) Call the operator and tell him, you're going to make a measurement of the tagging efficiency. Therefore you need the beam to be turned off for a few minutes.

5) Move the radiator out of the beamline (ELECTRON BEAM MUST BE OFF! ).

6) Move the leadglas detector into the photon beam. (see below). (The electron beam should be turned off!)