GEC SLI/H 'Golden Linear' Low Pressure Sodium
Following on from AEI's innovative development of the Linear Sodium lamp, it didn't take long before competitors GEC also commenced production of an equivalent range.  GEC technology offered a further enhancement to the luminous efficacy of this lamp design by replacing the glass heat insulation sleeves with an advanced 50 nanometre thick film of pure gold, sputtered onto the inside of the outer jacket.

Although costly, this raised lamp efficacy by almost 10% because a thin film of gold reflects infrared radiation back onto the discharge tube far more effectively than a glass sleeve.  Absorption of the yellow sodium light is greater than for glass, but the gain in efficacy offsets this loss.  Film thickness had to be critically controlled to give the optimum compromise between thermal insulation and light loss.

The GEC Golden Linear lamps were offered in two wattages.  The company entered the SLI market with a new small lamp, the 60-watt size shown here.  A 160-watt model soon followed which had an advantage over AEI's 200W model in that it was compatible with existing 180W SOX ballasts.

Launched in 1961, the "Golden Linear" enjoyed great success until 1966, when it was superseded by still more efficient lamps employing heat reflection films of semiconductor materials and a further advance in the discharge tube design was made.  This particular lamp here makes use of an experimental discharge tube having very short indents.  Although made by GEC, the discharge tube was based on the German Osram design.  That company was active in SLI lamp production for only a very brief period.
Manufacturer: The General Electric Company of England PLC
Lamp Power: 60 Watts
Lamp Current: 0.83 Amps
Lamp Voltage: 80 Volts
Cap Type: 2x G13 Brass
Bulb Finish: Striped Gold Film 50nm Soda-lime glass
Bulb Type: Inner: TD-20 Outer: T-38
Overall Length: 419.1 mm 16½ inches
Light Centre Length: N/A
Arc Length:
Electrodes: CCC-6 Black Tungsten BCT emitter
Atmosphere: Na|98.5%Ne, 1.5%Ar Outer: Hard Vacuum
Luminous Flux: 5,700 lm (100 hrs)
Luminous Efficacy: 95.0 lm/W (100 hrs)
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 hours to 70% survival
Warm-up & Re-strike Time: 12 minutes Instantaneous
Factory: Shaw, Oldham England
Date of Manufacture: Circa 1961-1966
Original & Present Value: Unknown