is aimed at a point located between two of the slits so that the reconstructed beam profile can be determined with the proper orientation a detailed description of such an arrangement can be found in pending u s application ser no 11 158481 entitled u201c a trigger probe for determining the orientation of an electron beam u201d by elmer et al also herein incorporated by reference in its entirety in the method of the present invention the strength of the magnetic lens provided by focus coil 57 is often first manually adjusted by the operator thus arbitrarily raising or lowering the sharp focus position in the weld chamber in order to determine an arbitrary machine u201c sharp focus u201d current setting the operator in manually making such an adjustment directs the beam onto a high melting point target material such as tungsten and adjusts the focus coil 57 current setting while observing the intensity of the light emitted from the target when the emitted light reaches a maximum intensity the beam is considered to be substantially close to the desired machine sharp focus and computer 65 is utilized to generate the signals actuating the electron beam sweep to acquire beam profile data from for example an mfc 20 specifically electron gun 50 is turned on and computer 65 is arranged to activate deflection coil 58.