Electrodeless fluorescent lamps operable in and out of fixture with little change in performance
An electrodeless fluorescent lamp is configured such that the lamp operates at frequencies less than 500 kHz both in and out of a fixture with little change in performance. The lamp employs relatively high rare gas pressure, relatively small reentrant cavity diameter and a relatively short magnetic core to achieve good performance in the fixture.
1 . An electrodeless lamp comprising:
a bulbous, light-transmissive lamp envelope having a reentrant cavity, the lamp envelope being filled with a metal vapor and a rare gas, and having a phosphor coating on an interior surface for generation of visible light, the rare gas having a pressure greater than 25 torr/D, where D is the diameter of the lamp envelope in millimeters; and
an excitation coil located in the reentrant cavity and disposed around a magnetic core, the excitation coil configured for operation at a frequency of less than 500 kHz.
2 . An electrodeless lamp as defined in claim 1 , wherein the rare gas comprises krypton at a pressure greater than 25 torr/D.
3 . An electrodeless lamp as defined in claim 2 , wherein the diameter of the lamp envelope is less than 100 millimeters.
4 . An electrodeless lamp as defined in claim 2 , wherein the krypton pressure is greater than 0.25 torr.
5 . An electrodeless lamp as defined in claim 1 , wherein the rare gas comprises argon at a pressure greater than 50 torr/D.
6 . An electrodeless lamp as defined in claim 1 , wherein the rare gas comprises a mixture of krypton and argon and wherein the sum of the krypton pressure and one half the argon pressure is greater than 25 torr/D.
7 . An electrodeless lamp comprising:
A bulbous, light-transmissive lamp envelope having a reentrant cavity, the lamp envelope being filled with a metal vapor and a rare gas, and having a phosphor coating on an interior surface for generation of visible light, the reentrant cavity having a diameter less than 0.3 times the diameter of the lamp envelope; and
an excitation coil located in the reentrant cavity and disposed around a magnetic core, the excitation coil configured for operation at a frequency of less than 500 kHz.
8 . An electrodeless lamp as defined in claim 7 , wherein the reentrant cavity has a diameter less than 25 mm.
9 . An electrodeless lamp comprising:
a bulbous, light-transmissive lamp envelope having a reentrant cavity, the lamp envelope being filled with a metal vapor and a rare gas, and having a phosphor coating on an interior surface for generation of visible light; and
an excitation coil located in the reentrant cavity and disposed around a magnetic core, the excitation coil configured for operation at a frequency of less than 500 kHz, the magnetic core having a length less than 0.65 times the diameter of the lamp envelope.
10 . An electrodeless lamp as defined in claim 9 , wherein the magnetic core comprises a ferrite material.
11 . An electrodeless lamp as defined in claim 9 , wherein the magnetic core has a length less than 65 millimeters.
12 . An electrodeless lamp as defined in claim 9 , wherein the excitation coil has a length of at least two thirds the length of the magnetic core.
13 . An electrodeless lamp as defined in claim 12 , wherein the excitation coil comprises Litz wire having 7 to 120 strands.
14 . An electrodeless lamp as defined in claim 9 , wherein the rare gas comprises krypton having a pressure greater than 25 torr/D, where D is the diameter of the lamp envelope in millimeters.
15 . An electrodeless lamp as defined in claim 14 , wherein the reentrant cavity has a diameter less than 0.3 times the diameter of the lamp envelope.
16 . An electrodeless lamp as defined in claim 14 , wherein the rare gas comprises krypton having a pressure greater than 0.25 torr.
17 . An electrodeless lamp as defined in claim 14 , wherein the diameter of the lamp envelope is less than 100 millimeters.
18 . A lamp assembly comprising:
an electrodeless lamp comprising a bulbous, light-transmissive lamp envelope having a reentrant cavity, the lamp envelope being filled with a metal vapor and a rare gas, and having a phosphor coating on an interior surface for generation of light, and an excitation coil located in the reentrant cavity and disposed around a magnetic core, the excitation coil configured for operation at a frequency of less than 500 kHz; and
a conducting fixture configured for mounting of the electrodeless lamp, the conducting fixture having a diameter at an axial location of maximum lamp envelope diameter that is in a range of about 1.25 to 2.0 times the maximum lamp envelope diameter.
19 . A lamp assembly as defined in claim 18 , wherein the rare gas has a pressure greater than 25 torr/D, where D is the diameter of the lamp envelope in millimeters.
20 . A lamp assembly as defined in claim 18 , wherein the lamp envelope has a diameter less than 100 millimeters, wherein the rare gas comprises krypton having a pressure greater than 0.25 torr, wherein the reentrant cavity has a diameter less than 25 millimeters and wherein the magnetic core has a length less than 65 millimeters.
21 . A lamp assembly comprising:
an electrodeless lamp comprising a bulbous, light-transmissive lamp envelope having a reentrant cavity, the lamp envelope being filled with a metal vapor and a rare gas, and having a phosphor coating on an interior surface for generation of light, the rare gas having a pressure greater than 25 torr/D, where D is the diameter of the lamp envelope in millimeters, and an excitation coil located in the reentrant cavity and disposed around a magnetic core, the excitation coil configured for operation at a frequency of less than 500 kHz; and
a conducting fixture configured for mounting of the electrodeless lamp, the conducting fixture having a diameter at an axial location of maximum lamp envelope diameter that is in a range of about 1.25 to 2.0 times the maximum lamp envelope diameter.
22 . A lamp assembly as defined in claim 21 , wherein the rare gas comprises krypton at a pressure greater than 25 torr/D.
23 . A lamp assembly as defined in claim 21 , wherein the rare gas comprises argon at a pressure greater than 50 torr/D.
24 . A lamp assembly as defined in claim 21 , wherein the rare gas comprises a mixture of krypton and argon and wherein the sum of the krypton pressure and one half the argon pressure is greater than 25 torr/D.
25 . A lamp assembly comprising:
an electrodeless lamp comprising a bulbous, light-transmissive lamp envelope having a reentrant cavity, the lamp envelope being filled with a metal vapor and a rare gas, and having a phosphor coating on an interior surface for generation of light, the reentrant cavity having a diameter less than 0.3 times the diameter of the lamp envelope, and an excitation coil located in the reentrant cavity and disposed around a magnetic core, the excitation coil configured for operation at a frequency of less than 500 kHz; and
a conducting fixture configured for mounting of the electrodeless lamp, the conducting fixture having a diameter at an axial location of maximum lamp envelope diameter that is in a range of about 1.25 to 2.0 times the maximum lamp envelope diameter.
26 . A lamp assembly as defined in claim 25 , wherein the reentrant cavity has a diameter less than 25 millimeters.
27 . A lamp assembly comprising:
an electrodeless lamp comprising a bulbous, light-transmissive lamp envelope having a reentrant cavity, the lamp envelope being filled with a metal vapor and a rare gas, and having a phosphor coating on an interior surface for generation of light, and an excitation coil located in the reentrant cavity and disposed around a magnetic core, the excitation coil configured for operation at a frequency of less than 500 kHz, the magnetic core having a length less than 0.65 times the diameter of the lamp envelope; and
a conducting fixture configured for mounting of the electrodeless lamp, the conducting fixture having a diameter at an axial location of maximum lamp envelope diameter that is in a range of about 1.25 to 2.0 times the maximum lamp envelope diameter.
28 . A lamp assembly as defined in claim 27 , wherein the magnetic core comprises a ferrite material.
29 . A lamp assembly as defined in claim 27 , wherein the magnetic core has a length less than 65 millimeters.
30 . A lamp assembly as defined in claim 27 , wherein the excitation coil has a length of at least two thirds the length of the magnetic core.