Abstract: A metal halide lamp has, when the lamp is operated in a vertical orientation, a coldest spot that is close to the top of the discharge chamber. Means are provided enabling more heat to be supplied to the bottom part than to the upper part of the lamp. In a lamp assembly, comprising the lamp arranged inside a bulb, the additional heat generating means may include a radiation coil.

Abstract: A method is described for driving a gas discharge lamp (1), specifically a HID lamp, more specifically a metal halide lamp, most specifically a metal halide lamp with an aspect ratio larger than 3 or even 4. The lamp is supplied with a commutating DC current having a duty cycle (D) and an average current intensity (IAV) at a certain electrical output power. The method comprises the step of varying the average current intensity (IAV) and the electrical output power in order to vary the color temperature of the lamp. Preferably, the average current intensity (IAV) is changed by changing the duty cycle (D), and the electrical output power is varied in relation to the average current intensity (IAV).

Abstract: A method for driving a metal halide lamp (1) is described, the method comprising the step of generating a light controlling DC electric field E with a desired direction and a desired strength inside the lamp such as to obtain a desirable ion distribution inside the lamp. The lamp is supplied with a commutating current with a DC component, preferably having a constant current intensity and a duty cycle differing from 50%. By setting the duty cycle, it is possible to set a certain average value of the lamp current, allowing the efficacy and/or color temperature of the lamp to be influenced.

Abstract: A metal halide lamp (101) is described, the lamp being designed such that, when the lamp is operative in a vertical orientation, the location of the salt pool is close to the top of the discharge chamber (5). In an embodiment, the coldest spot is close to the top of the discharge chamber. Means are provided enabling more heat to be supplied to the bottom part than to the upper part. In a lamp assembly (10), comprising a lamp (101) arranged inside a bulb (11), additional heat generating means (90) may comprise a radiation coil (91).

Abstract: Metal halide lamp includes a discharge vessel having a ceramic wall with an internal diameter Di and enclosing two electrodes whose tips are a distance EA apart, wherein EA/Di>5. The vessel has a filling comprising Hg, CeI, and LiI.

Abstract: Metal halide lamp includes a discharge vessel having a ceramic wall with an internal diameter Di and enclosing two electrodes whose tips are a distance EA apart, wherein EA/Di>5. The vessel has a filling comprising Hg, CeI, and LiI.