SELA Abadie 6002 DC Blacklight Glow
This unusual lamp is believed to have been developed to provide a small source of UV-A energy for the illumination of aircraft cockpits, whose instruments & panels were often labelled with fluorescent paints. That principle was developed during WW2 to reduce light levels within the cockpit, so as to maintain improved night vision of the pilots while also making aircraft less visible to the enemy.

The earliest applications employed small tubular fluorescent lamps, but those were not efficient owing to the relatively high electode losses, and complex control gear to convert the low voltage DC electrical supply of the aircraft to high voltage AC for running the lamps. Developments therefore focussed on miniature DC fluorescent lamps, the first of which is believed to have been the GE F5000 around 1941. Some years later the design was simplified with the Russian УФО-4 (UFO-4) lamps.

Whereas those earlier lamps employ separate cathode and anode structures optimised for DC operation, this modern lamp made by the small French manufacturer SELA (Société d'Exploitation du Laboratoire Abadie) has a construction similar to AC mercury glow devices like the G4S11 Ozone lamps, illustrated in the X-Ray shadowgraphs. Nevertheless, the technical datasheet indicates that it is intended for DC operation. The reason for the change from the reflector-shape bulbs of the original developments to a tubular shape was perhaps to facilitate use with a large external reflector for producing a narrower beam distribution. It is intended for use on 28.5V DC via a 33Ω variable rheostat and fixed 21Ω resistor, this arrangement ensuring that a minimum 19V is available across the lamp to ensure reliable ignition.
Manufacturer: SELA
Lamp Power: 4 Watts 9 Watts Max
Lamp Voltage: 12 Volts Min. 19V for ignition
Lamp Current: 0.25 Ampere 0.75 Ampere Max
Cap Type: BA15s Negative to cap shell
Bulb Type: T-20 T-6 in eighths/inch
Bulb Finish: Blacklight phosphor Soda-lime glass
Electrodes: Tungsten Coil CC-2U
Electrode Gap: Approx. 5mm 0.2 inches
Atmosphere: Hg | Ar
Luminous Flux: 22 lumens @ 750mA
Luminous Efficacy: 2.4 lm/W @ 750mA
Blacklight Flux: 265 mW/m² @ 10cm @ 750mA
Colour Temperature & CRI: CCT: 12000K CRI: Ra 10
Chromaticity Co-ordinates: CCx: 0.250 CCy: 0.305
Rated Lifetime: 200 hours
Warm-up & Re-strike Time: 5 minutes Approx 5 seconds
Burning Position: Universal
Overall Length: 63 mm 21/2 inches
Factory: Vic-en-Bigorre France
Date of Manufacture: 1992 January Date Code: 0292
Original Value: Unknown
References: 1) Private Communication, Bertrand Abadie, August 2011.
2) Instruction sheet supplied with lamp.
3) SELA Abadie Technical Datasheet FT6002/6008/6010, April 1994.
4) French Patent FR 1,109,052 - Lampes Fluorescentes pour Courant Continu Basse Tension, J.B.J.M. Abadie, Filed 1st June 1954.
5) French Patent FR 1,164,884 - Perfectionnements Apportés aux Lampes Fluorescentes Courant Continu BT, L.F.S. Abadie, Filed 19th January 1957.
6) French Patent FR 1,241,129 - Lampes à Décharge Luminescentes, L.F.S. Abadie, Filed 15th October 1958.
7) Photoelectric and Spectroradiometric Measurements @ 750mA.