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StelloxHigh Pressure Sodium |
The arc tube is made of "Stellox", a polycrystalline alumina doped with magnesia and yttria to produce the unique bi-phase grain structure invented at the Leicester works of AEI Lamp & Lighting Co. The properties of the arc tube are similar to GE's Lucalox, the first translucent polycrystalline alumina, but the differing structure of Stellox was of crucial importance in circumventing the GE patent. The greater thickness of this arc tube coupled with its rough crystalline surface makes it appear far more opaque than modern tube.
Seals to the arc tube ends are made with pressed cups of niobium. These are brazed to the Stellox tube using a reactive alloy of titanium, zirconium and vanadium. Titanium is the element forming the reactive seal to the alumina, however its melting point is inconveniently high at around 1800-1850C. The addition of the other metals forms an alloy having a lower melting temperature around 1400C which is much more desirable for seal fabrication. Typically, the seal of this type was made by sandwiching three thin washers of each metal over the end of the arc tube and capping them with the niobium cup, before heating in a vacuum furnace. The titanium washer is always the one in contact with the alumina to form the most reactive seal. One end is blind, while the other is extended into a niobium exhaust tube. This has been pinched-off by cold fusion to contain the sodium and xenon gas within the arc tube.
| Manufacturer: | British Lighting Industries Ltd. | |
| Lamp Power: | 250 Watts | |
| Lamp Current: | 3.0 Amps | |
| Lamp Voltage: | 100 Volts | |
| Cap Type: | E40s/45 | Nickel plated, vitrite |
| Bulb Finish: | Clear | Hard glass |
| Bulb Type: | TD-51 | TD-16 in eighths/inch |
| Overall Length: | 257 mm | 10 1/8 inches |
| Light Centre Length: | 160 mm | 6¼ inches |
| Arc Length: | ||
| Electrodes: | Backwound Tungsten | BCT emitter |
| Atmosphere: | Na,Hg | Xe | Outer: Hard Vacuum |
| Luminous Flux: | 25,000 lm | (@ 100 hrs) |
| Luminous Efficacy: | 100.0 lm/W | (@ 100 hrs) |
| Colour Temperature & CRI: | CCT: 1800K | CRI: Ra 12 |
| Chromaticity Co-ordinates: | CCx: | CCy: |
| Burning Position: | Universal | |
| Rated Lifetime: | 10,000 hours | to 50% survival |
| Warm-up & Re-strike Time: | 4 minutes | 7 minutes |
| Factory: | Leicester | England |
| Date of Manufacture: | November 1970 | Date Code 3904 |
| Original & Present Value: | Engineering Sample - No Commercial Value | |
