Vialox Linear Sodium NAV-TS 400W
The concept of a linear double-ended version of the SON lamp was originally introduced by the GEC in 1975, whose SON-L lamps comprised a quartz outer jacket just 20mm diameter. Furthermore the outer was gas-filled instead of the usual vacuum, allowing higher arc tube loading for an increased output, without risk of the alumina tube evaporating and causing lumen depreciation. Owing to the small dimensions the high efficacy source could be precisely located at the focus of compact reflectors to realise improved beam control.

In the early 1980s, Osram GmbH of Germany offered its own double ended high pressure sodium lamps, known as the NAV-TS or SON-TS family. Technologically they are similar to the GEC originals, still making use of a high pressure argon filled outer envelope.

The arc tube in the German lamp is somewhat shorter than in competitive products, and consequently it runs at much higher loading. The outer envelope is also rather shorter than competitive linear HPS products. The Fc2 type of end contacts are used, and the lamp is still produced by Osram in both 250W and 400W ratings. A barium flash-getter is present at one end of the lamp.

The ultra compact size of the German Osram lamp does mean that both lumen depreciation and initial performance suffer a little. Whereas the British SON-L 400W delivers some 51,000 lumens, the German NAV-TS puts out only 48,000 lumens. Also the rate of lumen depreciation is somewhat faster with the German lamp.
Manufacturer: Osram GmbH
Lamp Power: 400 Watts
Lamp Current: 4.4 Amps
Lamp Voltage: 105 Volts (in luminaire) 85 Volts (in free air)
Cap Type: Fc2 Silver plated contacts
Bulb Finish: Clear Quartz
Bulb Type: T-22 T-7 in eighths/inch
Overall Length: 206 mm 8 1/8 inches
Contact Length: 206 mm 8 1/8 inches
Arc Length: 82 mm 3 7/32 inches
Electrodes: Backwound Tungsten Barium Calcium Tungstate
Atmosphere: Na,Hg | Xe Outer: Argon high pressure
Luminous Flux: 48,000 lm @ 100 hours 45,500 lm @ 2,000 hours
Luminous Efficacy: 120.0 lm/W @ 100 hours 114 lm/W @ 2,000 hours
Colour Temperature & CRI: CCT: 2000K CRI: Ra 20
Chromaticity Co-ordinates: CCx: 0.526 CCy: 0.418
Burning Position: Horizontal ± 45°
Rated Lifetime: 10,000 hours to 50% survival
Warm-up & Re-strike Time: 3 minutes 30-60 seconds restrike
Factory: Spandau, Berlin West Germany
Date of Manufacture: January 1989 Date Code qw1
Original & Present Value: £64.33 (1988) £115.55 (2005)
 
References: 1) Osram Vialox Brochure, 1990.
2) Osram Price List, October 1990.