Sylvania Very High Ouptut F48T12-CW-VHO
Since the origins of the fluorescent lamp, engineers have striven to increase its power density but faced the challenge that higher loading leads to increased mercury vapour pressures and higher electron densities in the plasma - both of which cause a major decrease in luminous efficacy.

The first problem was overcome with GE's High Output 'HO' lamps of 1954, having a longer gap behind the electrodes to realise a cold spot and limit mercury vapour pressure. That also marked the first use of RDC recessed-double-contact bases for electrical safety. The second challenge of reducing electron density was overcome with GE's PowerGroove lamp of 1958. Its special shape decreases the diffusion distance of mercury ions to the wall, thereby increasing the ambipolar ion loss rate, which in turn increases electron temperatures. This leads to reduced electron density, hence improved lamp efficacy. But it was a very complex and expensive design.

A more elegant solution was invented by John Waymouth of Sylvania, which introduced this Very High Output 'VHO' lamp in 1959. It was originally known as the 'Powertube' and distinguished by its golden end caps. The fundamental difference is a change of the gas filling from argon to neon or helium at lower pressure than normal, which Waymouth's impressive mathematical modelling of the plasma during a five-year period proved would lead to a decrease of electron density, and hence avoid the efficacy drop. To further limit the mercury pressure, a nickel heat radiation shield is present behind the deeply-mounted electrodes. A pair of anode wires having an anti-emission coating are also applied around the cathode coil, in order to limit the decrease of lamp life when driven at such high current levels.
Manufacturer: Sylvania Electric Products Inc.
Lamp Power: 110 Watts
Lamp Current: 1.500 Amps
Lamp Voltage: 85 Volts 320 Volts ignition
Cap Type: R17d Anodised aluminium
Bulb Type: T-38 T-12 in eighths/inch
Bulb Finish: Cool White, silicone coat 3Ca3(PO4)2.Ca(F,Cl)2:Sb,Mn
Electrodes: Coiled-Coil + Anode Wires (Ba,Sr,Ca)CO3 + ZrO2 emitter
Discharge Length: mm inches
Atmosphere: Hg | He-Ar 1 torr pressure
Luminous Flux: 6,900 lm (@ 100h)
Luminous Efficacy: 62.7 lm/W (@ 100h)
Colour Temperature & CRI: CCT: 4150K CRI: Ra62
Chromaticity Co-ordinates: CCx: CCy: 0
Rated Lifetime: 7500 hours
Warm-up & Re-strike Time: 2 minutes Instant
Burning Position: Universal
Nominal Length: 1219 mm 48 inches
Lighted Length: mm inches
Factory: Danvers, MA U.S.A.
Date of Manufacture: January 1963 Date Code: _....../...
Original Value:
 
References: 1) "Allis in Wonderland - Physics for Profit and Fun", by J.F. Waymouth, Physics Today, Vol.54 No.2, June 2000, pp.38-42
2) US Patent 3,013,169, Very High Output Fluorescent Lamp having Ne Fill & radiation shields, W.C.Gungle, J.F.Waymouth & F.Bitter, Filed 27-Jun-1956
3) US Patent 3,052,813, Very High Output Fluorescent Lamp having HeAr Fill, W.C.Gungle & J.F.Waymouth, Filed 30-Jun-1959
4) Sylvania VHO Powertube Brochure, 1959.
5) Sylvania VHO Powertube Brochure, 1962.
6) Sylvania Lamp Catalogue, 1966 France