The tube holder accommodates all tubes of the series D and their accessories, such as the Helmholtz Coils D (100644) and Auxiliary Coil (100645).
 

(1000656). The tube holder consists of a robust base plate with an upright stanchion and a fork-shaped holder for hot cathode tubes that can be rotated by 360° and is made of heat-resistant, highly insulating plastic. The tubes are secured into sprung clamps with retaining sliders. Two holes are bored in the base plate to accommodate a pair of Helmholtz coils at the “Helmholtz separation distance” for generating a uniform magnetic field. The tube holder rests on three non-slip rubber feet.