General Electric XP1-4 and XP2-4.5 Tubes (ca. 1930s, 1940s)
The General Electric XP1-4 (top photo) and XP2-4.5 (second photo) x-ray tubes are dual focus diagnostic tubes that were probably manufactured in the 1930s or 1940s. These dates are purely speculative since I have no specific information about this model tube.
"XP" refers to "X-ray Protected." The first number in the designations (i.e., "1" or "2") indicates that one of the tube's two filaments produces a very fine (1) or fine to medium focus (2) while the second number, "4" or "4.5", indicates that the other filament produces a broad focus. More specifically, this number indicates the approximate diameter of the projected focal spot in mm.
The XP series tubes were said to be of a "unit construction" that consisted of the vacuum unit (the tube proper), a protective cover (not present) and an air-cooling or water-cooling radiator (not present).
Size: ca. 18" long, 2 1/4" diameter
The XP1-4 tube was kindly donated by Margie Wheaton in memory of her father Dr. Julius E. Marfy. The XP2-4.5 tube was donated by the University of Kansas courtesy of Michael Lemon. Thanks also go to John Gabbitas for his insights and for providing the advertisement.