Undulator phase tuning with mechanical shimming

A tunable undulator device comprising:

• a first magnet array disposed along a central axis of the undulator device;
• a first structural keeper physically coupled to the first magnet array to support and maintain a position of the first magnet array;
• a second magnet array disposed along the central axis, the second magnet array disposed on an opposite side of the central axis from the first magnet array with a gap distance separating the second magnet array from the first magnet array;
• a second structural keeper physically coupled to the second magnet array to support and maintain a position of the second magnet array;
• at least one strongback structure physically coupled to the first structural keeper and second structural keeper, the strongback structure configured to support and maintain a position of the first structural keeper and the second structural keeper;
• and
• a plurality of tuning elements (i) disposed along the central axis, (ii) physically coupled to at least one of the first magnet array or the second magnet array, and (iii) configured to tune the magnetic field profile along the central axis between the first magnet array and the second magnet array.