Report on the activities in Electricity and Magnetism within the LNE between 2007 and 2009

The "Lampard" structure of the standard has been significantly modified. The two plates supporting the electrodes have been redesigned to implement a new prepositioning stage. In order to allow an optimum assembly of the different mechanical parts, position locking devices have been added. This will guarantee a better position of the electrodes after mounting, more favorable to realize the final adjustment of the cavity. The pre-positioning step makes it possible to align the electrodes on the reference shape. This operation consists first of all in centering the measuring machine on the reference shape. Then the top and the bottom of the electrodes are directly aligned with the reference shape without taking into account the machine defects. The pre-positioning settings are then locked. The first tests showed that the prepositioning of the electrodes is achievable within 5 μm from their final positions; this point is consistent with the objective.