Oscillators – Molecular or particle resonant type
Patent
1978-03-13
1980-09-23
Davie, James W.
Oscillators
Molecular or particle resonant type
331 945D, 331 945S, H01S 322
Patent
active
042245796
ABSTRACT:
An internal mirror metal vapor laser, and in particular, a helium-cadmium laser discharge tube, which is economical, compact and has a relatively long operating and shelf life, the operating life typically exceeding 10,000 hours. A positive column helium-cadmium laser tube of the consumable type and having optical resonator mirrors integral with the tube ends to hermetically seal the tube is provided which includes a relatively large volume cadmium reservoir capable of containing sufficient cadmium for operating life times exceeding ten thousand hours. A heater is applied to the cadmium reservoir for controlling the cadmium vapor pressure. The helium pressure is actively controlled by releasing helium from a high pressure helium reservoir when the helium pressure is less than a predetermined value. This is accomplished by providing a signal representing the sensed pressure of the helium in the laser discharge tube and comparing electronically this signal with a signal representing the pressure of helium at a desired operating condition (reference pressure). If the sensed pressure is lower than the reference pressure indicating a loss of helium gas, a source of electric current supplies current to a heating element which in turn heats a temperature sensitive permeable membrane. The temperature sensitive membrane, which forms a portion of a reservoir containing high pressure helium, allows the helium in the reservoir to leak into the laser tube when heated until the sensed pressure is substantially equal to the reference pressure. A pair of thermistors mounted within the laser discharge tube are preferably utilized to effectively provide the sensed and reference pressure signals. In particular, the thermistors are utilized to compensate the effects of ambient temperature changes, thereby allowing an accurate measure of the laser discharge pressure. A diffusion confinement section and a cataphoretic confinement section are provided adjacent one end mirror and a diffusion confinement section is provided adjacent the other end mirror to protect the end mirrors from condensing cadmium vapor or other damage. A baffle member is placed adjacent the cathode end of the discharge capillary which separates the cadmium condensate from the discharge at the cathode to inhibit entrappment or gettering of helium gas by the cadmium.
REFERENCES:
patent: 3730606 (1973-05-01), Hernquist et al.
patent: 3822086 (1974-07-01), Paik
patent: 3876957 (1975-04-01), Thatcher
Hug William F.
Johnson Richard C.
Marlett Calvin J.
Reed Edwin A.
Davie James W.
Keschner Irving
Xerox Corporation
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