Lucalox High Pressure Sodium Discharge
Since the introduction of the first 400W High Pressure Sodium product, engineers had striven to satisfy the demand for lower intensity versions of this remarkable light source.  A 250W and 150W version soon followed, but it was more than ten years after the launch of the first lamp until this 50W product was in a state ready for the market - first revealed in 1977.  Early trials had been plagued by short lamp life and numerous developments had to take place before the system could be brought under control in such a small product.

Initially it was believed that this lamp would be used to replace ordinary incandescent lamps in the same kind of luminaires - and consequently it was offered in the A-shape glass bulb envelope pictured here.  In the early days this was made in hard glass to protect it from rain. Within a year though it became obvious that low wattage HPS technology was being embraced at a remarkable rate, and by 1979 the low wattage lamps were given a new ellipsoidal-shaped E23 outer.

Of interest is the fact that the external amalgam reservoir, a familiar design feature of all other high pressure sodium lamps from GE, is absent in this design.  Instead ordinary wire seals are employed.  The reason is that too much heat was conducted away from the small electrodes by the large diameter niobium tube from which the reservoir is constructed, and that had previously led to early arc tube blackening.  The wire seals afforded better insulation and allowed the electrodes to run at a more suitable temperature.  Additionally it was difficult to keep the temperature of the external amalgam reservoir high enough to allow a high sodium vapour pressure to be realised.
Manufacturer: General Electric Company U.S.A.
Lamp Power: 50 Watts
Lamp Current: 1.18 Amps
Lamp Voltage: 52 Volts
Cap Type: E26s/25 Brass + vitrite
Bulb Finish: Clear Lead borosilicate glass
Bulb Type: A-75 A-23½ in eighths/inch
Overall Length: 138 mm 5 7/16 inches
Light Centre Length: 90 mm 3½ inches
Arc Length:
Electrodes: Backwound Tungsten Barium Calcium Tungstate
Atmosphere: Na,Hg | Xe Outer: Hard Vacuum
Luminous Flux: 3,300 lm (@ 100 hrs) 2,970 lm (@ 12,000hrs)
Luminous Efficacy: 66.0 lm/W (@ 100 hrs) 59.4 lm/W (@ 12,000hrs)
Colour Temperature & CRI: CCT: 1900K CRI: Ra 22
Chromaticity Co-ordinates: CCx: CCy:
Burning Position: Universal
Rated Lifetime: 12,000 hours to 50% survival
Warm-up & Re-strike Time: 5 minutes 5 minutes
Factory: Ravenna, OH U.S.A.
Date of Manufacture: 1978
Original & Present Value: Unknown
 
References: 1) General Electric USA Large Lamp Catalogue, Form 9200, 1977.