Mazda 60W SO/H Linear Low Pressure Sodium

The Linear Sodium concept was first introduced in 1959 by Associated Electrical Industries (formerly the British Thomson-Houston company, a division of General Electric of USA). It was the first artificial light source to break the 100 lm/W barrier. The first model was rated 200 Watts, and it was joined in 1961 by this smaller 60W equivalent.

The range was characterised by a novel grooved discharge tube having an alternating crescent shaped cross-section, based on GE's PowerGroove Fluorescent products. Because hot sodium vapour absorbs its own radiation, narrow diameter tubes are desirable to allow escape of light created below the surface. However efficacy also rises as the current density in the discharge falls, thereby favouring a large diameter tube. In traditional sodium lamps, a compromise must be found to determine the optimum tube diameter.

The novel shape of AEI's linear sodium lamps achieved both efficient light extraction and low current density, and thereby delivered a notable increase in efficacy. Although other cross-sections were still more efficient, the crescent-shape was chosen because of its ease of manufacture. The tips of the crescents are made sufficiently sharp that they also serve as sodium reservoirs, holding the liquid metal in place by capillary action. The reason for the alternate side of grooving is to prevent the sodium running along the length of the tube, while also increasing discharge path length. Thermal insulation of the original 200W lamp was effected by enclosing the discharge tube in a heat-reflecting glass sleeve and a secondary outer envelope, but this smaller 60W model maintains the impressive 100lm/W efficacy by employing two glass sleeves within the outer jacket.
Manufacturer: Associated Electrical Industries
Lamp Power: 60 Watts
Lamp Current: 0.83 Amps
Lamp Voltage: 80 Volts
Cap Type: 2x G13 Aluminium + Paxolin insulator
Bulb Type: T-38 T-12 in eighths/inch
Bulb Finish: Clear Soda-lime glass
Electrodes: CC-6 Black W + BCT emitter
Arc Length: 290 mm 117/16 inches
Atmosphere: Na | 99%Ne 1%Ar Outer: Hard Vacuum
Luminous Flux: 6,000 lm (@ 100 hrs) 5,700 lm (average)
Luminous Efficacy: 95 lm/W (@ 100 hrs)
Colour Temperature & CRI: CCT: 1700K CRI: Ra -44
Chromaticity Co-ordinates: CCx: 0.574 CCy: 0.425
Rated Lifetime: 6,000 hours 70% survival, 100% flux
Warm-up & Re-strike time: Approx. 15 minutes Instantaneous
Burning Position: Horizontal ± 20°
Overall Length: 426.2 mm 16¾ inches
Insertion Length: 419.1 mm max 16½ inches
Factory: Leicester England
Date of Manufacture: July 1965 Date Code 2591
Original & Present Value: £3 15s 0d (1963) £52.57 (2005)
 
References: 1) High Output Linear Sodium Lamps, WESTON R.F., Electrical Times (135) 1959, pp.719-722.
2) Patent GB 923,961, Improvements Relating to Discharge Lamps, AEI Lamp & Lighting Co. Ltd., Filed May 1958.
3) AEI Mazda Lamp Data Sheet 96-201, September 1961.
4) AEI Mazda Lamp Catalogue, 1963.