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Atlas SLI/H Linear Low Pressure Sodium |
The most significant change was a diversion from the well established grooved discharge tube of crescent-shaped section to a more efficient design employing a 4-leaf clover section. This incorporated 88 elongated sodium-retention dimples known as 'greenhouses' running along the extremity of each 'leaf'. A further advantage of the new design was that the unobscured 'line of sight' between electrodes lowered the lamp striking voltage considerably. Braided cathodes, formed from seven tungsten wires braided into a tube also enhanced cathode life over coiled designs by captivating a greater quantity of emissive material in the cathode.
A still more efficient 5-leaf clover section was later developed for a new 200W High Output lamp, whose performance was further enhanced by the use of an indium oxide heat reflection film. The gas filling for that lamp was also changed to a more efficient design including Xenon.
These innovations earned Thorn Lighting the top place in the SLI lamps market and the reliability of the Linear design was second to none, suffering from very few early failures. However, the glassworking processes involved in making the lamp were a true nightmare with very high scrap rates, and by the 1970's Thorn re-commenced the production of U-shaped lamps. The SLI market declined until production ceased in 1986.
| Manufacturer: | Thorn Electrical Industries | |
| Lamp Power: | 140 Watts | |
| Lamp Current: | 0.90 Amps | |
| Lamp Voltage: | 175 Volts | |
| Cap Type: | 2x G12 | Aluminium |
| Bulb Finish: | Indium Tin Oxide Film | Soda-lime glass |
| Bulb Type: | Inner: JT-54 Mould | Outer: T-38 |
| Overall Length: | 909 mm | 36 inches |
| Light Centre Length: | N/A | |
| Arc Length: | ||
| Electrodes: | CCC-6 Black Tungsten | BCT emitter |
| Atmosphere: | Na|99%Ne, 0.8%Ar 0.2%Xe | Outer: Hard Vacuum |
| Luminous Flux: | 20,000 lm | Lighting Design Lumens |
| Luminous Efficacy: | 142.9 lm/W | Lighting Design Efficacy |
| Colour Temperature & CRI: | CCT: 1700K | CRI: Ra-44 |
| Chromaticity Co-ordinates: | CCx: 0.574 | CCy: 0.425 |
| Burning Position: | Horizontal ± 5° | |
| Rated Lifetime: | 6,000 hrs (70% survival) | Guaranteed 4,000 hrs |
| Warm-up & Re-strike Time: | 12 minutes | Instantaneous |
| Factory: | Leicester | England |
| Date of Manufacture: | July 1972 | Date Code 67 |
| Original & Present Value: | ||
