Standing-wave excitation for fluorescence microscopy

The method consists in fitting the end portions of the tubes one inside the other with a predetermined clearance, the steel tube being placed on the outside and provided at its extremity with an external machined annular flange forming a reservoir, in filling the reservoir with a suitable brazing compound, in placing the assembly in a vacuum and heating it to a temperature of 1,020 DEG to 1,030 DEG C and in removing the reservoir after the brazing operation.