2003 Radium HRI-TS 2000W/N/L

In 2001 Radium released a long-arc version of their (and Osram’s) popular 2 kW compact rare-earth filled double-ended metal halide lamp, the HRI-TS 2000W/N/L intended for general lighting applications where flux output and durability are more important than color quality and source luminance. The linear lamp is essentially the burner used in the company’s standard single-ended HRI-T 2000W/N, with the end seals modified for a reliable operation in free air. The seal’s molybdenum foils are wider and longer, with their extremities cooled by cemented ceramic end caps which act as heat sinks and radiators. The same K12s-36 connectors as those found on the company’s short-arc variant of the lamp are used here, which enables the precise positioning of the light source, close to the reflector due to the absence of an outer bulb. Such design ensures a superior optical control of the emitted light, in a compact luminaire format. In such system the luminaire plays an integral role in ensuring that the lamp operates at its optimum temperature. Burner end losses are limited by the conical electrode chambers and the narrow end seals, which are connected via a narrow junction. This not only ensures a sufficiently high cold-spot temperature, such burner design also limits the amount of heat transferred to the end seals and prevents the condensation of sodium iodide behind the electrodes, a cause of seal failure.

Like its jacketed variant, the HRI-TS 2000W/N/L is designed for an operation on 380-415 V mains with a series-connected 2-kW mercury lamp ballast (plus an ignitor for the linear lamp). It is also filled with a standard Na-Tl-In iodide mix which combines a relatively high lumen efficacy, due to its discontinuous emission spectrum, with a good chemical stability (no corrosion of the quartz envelope). The latter, combined with a low wall loading, results in an 8000 h mean service life, corresponding to a 2-year maintenance cycle under regular service, suitable for most outdoor lighting installations. Interestingly, the linear lamp has a reduced mercury dosage which results in a lower operating voltage of 225 V. The discharge current is raised to 10.3 A while the dissipated power is increased to 2150 W. This, combined with a 120-mm electrode gap, results in a discharge power load of 160 W/cm that translates into a plasma condition yielding a source efficacy of 107 lm/W. Overall, this ensures an enhanced light output of 230 klm, 15 % higher than that of the standard 2 kW HRI-T. Another contributing factor to the lamp’s performances is its operating position which is limited to horizontal ±15° (the tolerance is 30° in the jacketed variant). This enabled a tighter optimization of its salt dosage.

The HRI-TS 2000W/N/L has the highest efficacy and output of all linear double-ended metal halide lamps in the 2-kW class. Such characteristics prompted Philips to develop a modified variant of its MHN-LA since none of its rare-earth long-arc lamps came near Radium’s new lamp in terms of performances. The resulting MHN-FC 2000W was released in 2008, and although it did not achieve the same high efficacy and flux output, Philips managed to increase the mean service life to 14 kh thanks to their unique double-seal end construction. It is only in 2016 that the Dutch finally released a 2.2 kW version of their MHN-FC with a matching 230 klm initial output.