The He source not only creates He* atoms, but also creates particles that can be measured by the channeltron, but are not useful for the purpose of the setup, which is to create a well defined beam of He* atoms. To find out what percentage of the channeltron signal is caused by He* atoms, we shine a laser beam with a width of a few cm perpendicular to the atomic beam directly behind a diaphragm of 1 mm diameter, placed in the differential pumping section between the two parts of the Zeeman magnet. When we lock the laser on resonance, and make sure that the laser light makes an angle of 90 degrees with the atomic beam, we are able to decrease the channeltron signal with 30 to 60 % by pushing away all the metastable Helium atoms from the centerline of the setup. The percentage of metastable Helium atoms varied from day to day, but most of the time it lies between 40% and 50 % of the total signal.