Patent ID: 8044591

Claim:
A fluorescent lamp comprising: a tube configured in a tubular shape having a first end, a second end, and an inner surface, the inner surface of the tube including a phosphor layer, and the tube defining a tubular space therein; a first stem and a second stem each including a tubular shaped exhaust pipe, a gateway, and an emitter electrode, the first stem and second stem being located opposite to each other and at the first end and second end, respectively, of the tube, and each exhaust pipe extending outside of the tube and defining a tubular space therein, the tubular space of each of the exhaust pipes being connected to the tubular space of the tube via a respective gateway, and the emitter electrode of the first stem facing and opposed to the emitter electrode of the second stem in the tube; a damping material connected to an open end of the exhaust pipe of the first stem, the damping material configured in a tubular shape and having a first open end and a second open end; a coolest portion configured in a tubular shape having both a closed end and an open end, and the open end of the coolest portion connected to the first open end of the damping material; a filler gas including a mercury vapor located in and sealed in an air proof state within the tube, wherein the coolest portion includes a first material that has a higher thermal conductivity than both a thermal conductivity of the tube and a thermal conductivity of the first stem, and the damping material includes both the first material and a second material that has a lower thermal conductivity than the thermal conductivity of the first material, the damping material being connected to the first stem via the exhaust pipe of the first stem, and the content ratio of the first material with respect to the second material of the damping material changes along a distance between the first open end of the damping material located adjacent the coolest portion and the second open end of the damping material located adjacent the exhaust pipe such that the content ratio becomes relatively higher towards the first open end and becomes relatively lower towards the second open end of the damping material.