The R Type was from the beginning a hard vacuum valve. Hard pumping with the vacuum pumps of the day was a long process and to remove adsorbed gasses from the metal parts heat was applied. This was successful but not complete. Over time, and when hot in use, gases would be released and bombard the electrodes. The use of gettering both shortened the pumping time and, after the valve was sealed, the getter would continue to take in gas molecules that evolved from other electrodes. Here we have a beautiful red/gold colour that is the result of using phosphorus as the getter. Only later bright emitters were gettered and this example is probably from 1923 or 1924.
The Marconi Osram Valve logo is etched into the envelope but is hard to see. The nickel plated brass base shell was used up to 1924 and then replaced with the cheaper Bakelite. SeeR Type for the later version.
Rotating shows the gettering covers the whole of the glass interior.
Not easy to see any internal details.
taken with the microscope, the loops of the helix look to be spot welded to the support rod.
The other end of the filament shows the spring like loops to aid maintaining tension when the filament was hot. The tungsten wire is held in a fold of the support.
The balloon envelope is 45 mm in diameter, and excluding the B4 base pins is 99 mm tall.
References: Private communication, 1005 & 1003. Type R Type was first introduced in 1916. See also1916 adverts.
