A close‐wound helix of 0.010‐in.‐diam tungsten wire has been successfully bonded into the bore of a 24‐in.‐long, 0.625‐in.‐diam glass tube by shrinking the glass over the mandrel‐supported helix. The additional problem of furnishing a nonmagnetic glass‐to‐metal seal on one end of the glass cylinder has been answered by adapting a new seal combination of molybdenum and alumino‐silicate glass in cylindrical form.