Arrangement provided with a low-pressure vapour discharge lamp

Claim 1

A lighting arrangement comprising a low-pressure mercury vapour discharge lamp having an oblong discharge vessel of circular cross-section and including at least one rare gas, two input terminals adapted for connection to a source of power for the lamp, a controlled switching element, means connecting the lamp and the switching element in series circuit across said input terminals, means connecting said switching element to a control device with alternately controls said switching element in a manner such that an intermittent current flows through the lamp during a time interval of W seconds followed by a substantially currentless time interval of R seconds, means for reversing the direction of the current flowing through the lamp from time to time, the maximum pressure of the rare gas being 6 Torr and the diameter of the discharge vessel being chosen to satisfy the condition that Tau E< Tau D , and wherein the ratio W/W+R is limited to the range of values between 0.35 and 0.65 and the duration of a period (W+R) of the lamp supply is limited between the values 2 pi . Tau E and 2 pi . Tau D in which: Tau E is the energy relaxation period (in seconds) of the electrons in the discharge vessel, and Tau D is the diffusion period (in seconds) of the electrons in the discharge vessel.