The figure “shows the beam tube pulled out of its vacuum tank. The long steel tube at the center contains the C-field region. Thereupon the horizontal part of the cavity is clearly visible. The two shielding boxes for the A and B magnets are mounted at both ends of the steel tube by transition sections made of nonmagnetic material. Holes are provided for adequate pumping. The detector is mounted at the far end of the tube shown in this figure.”