Philips SDW-R95 White SON Reflector

In 1986 Philips launched the SDW-T White Sodium lamps, having very high sodium vapour pressure around 95 kPa to realise a warm white light of 2500K with excellent colour rendering. The increased pressure required a hotter arc tube, and to avoid short life the seals were redesigned to the 'protruding plug' concept. The hot sodium reservoir and relatively cool seals to thin niobium-zirconium wires are separated from each other by long and thick-walled ceramic extension pieces. The arc tube is filled to high xenon pressure to maximise efficacy. Ignition is facilitated with a coiled tungsten antenna, supported on a moving bi-metal strip to prevent sodium loss while hot.

It was originally envisaged that White SON would replace incandescent lamps for high-end accent and display lighting applications, consuming about a third of the power. As such the early samples were prototyped in similar glass bulbs as incandescent lamps - such as this blown reflector type and a crown silver version. These were extensively trialled in shop lighting environments, but were never launched for sale.

This lamp is one of the engineering samples produced at Philips' Eindhoven laboratories during the early 1980s. It has been observed that the effects of heat reflection onto the arc tube are significant, and considerable variation can be expected depending on the exact positioning of the arc tube within the reflector. This is not well controlled with ordinary GLS lampmaking techniques, and since arc tube temperature is critical for SDW lamps is maybe one reason why reflector types were never launched for sale. The final production tubular versions were equipped with a precision-focussed cap to reduce this problem with luminaire reflectors.
Manufacturer: Philips
Lamp Power: 50 Watts
Lamp Current: 0.76 Amps
Lamp Voltage: 92 Volts
Cap Type: E27/27 Ni plated brass + Porcelain
Bulb Type: R-95 R-30 in eighths/inch
Bulb Finish: Aluminised, inside frosted Soda-lime glass
Electrodes: Tungsten-rhenium rod No emitter
Atmosphere: Inner: Na,Hg | Xe Outer: Hard Vacuum
Luminous Flux: Approx. 1600 ℓm
Luminous Efficacy: Approx. 32 ℓm/W
Luminous Intensity: Approx. 5000 cd
Beam Distribution: Approx. 25°
Colour Temperature & CRI: CCT: 2500K CRI: Ra 80
Chromaticity Co-ordinates: CCx: 0.479 CCy: 0.417
Rated Lifetime: N/A
Warm-up & Re-strike Time: 5 minutes 30 minutes max.
Burning Position: Universal
Overall Length: 150 mm 6 inches
Factory: Eindhoven The Netherlands
Date of Manufacture: Approx. 1985
Original Value: N/A
References: 1) Photoelectric Measurement
2) Philips SDW-AR 35W lamp of Maxime Gendre at
3) The High Pressure Sodium Lamp, J.J de Groot & J.A.J.M. van Vliet, publ. Philips Technical Library 1985, p.256