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Carbon Dioxide Gas Lasers

Carbon Dioxide Gas Lasers. Fredrick Brown Spring 2004. Overview. Questions Introduction of CO2 Gas lasers Gas Flow CO2 Laser Sealed Tube CO2 Laser (T.E.A.) CO2 Laser Power Supplies for CO2 Gas Laser Applications Answers to questions. Questions.

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Carbon Dioxide Gas Lasers

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  1. Carbon Dioxide Gas Lasers Fredrick Brown Spring 2004

  2. Overview • Questions • Introduction of CO2 Gas lasers • Gas Flow CO2 Laser • Sealed Tube CO2 Laser • (T.E.A.) CO2 Laser • Power Supplies for CO2 Gas Laser • Applications • Answers to questions

  3. Questions • How do you control the voltage and gas flow rate in a Flowing Gas CO2 Laser? • What is the operating voltage and current for a typical Sealed CO2 Gas Laser?

  4. Introduction • CO2 laser emits an invisible infrared beam of a single wavelength in the form of a small, intense beam. Specifically, CO2 emits photons at 10.6 and 9.6um. • The laser gases for CO2 lasers normally contain a mixture of helium, nitrogen, and carbon dioxide. Some laser types also require small amounts of CO, H2 or Xe in the laser gas mixture because of dissociation of gas molecules. Fig. 1 Laser warning tag 60 W max for the CO2 beam. http://www.repairfaq.org/sam/laserpic/laserpic.htm

  5. Types of CO2 Gas Laser • Flowing Gas Laser • Sealed Tube Gas Laser • T.E.A. Gas Laser

  6. Flowing Gas Laser • Gas Mixtures are pumped from one end of the tube and out other to provide fresh gas to replace the CO2 depleted mix due to the seperation of gas molecules. • He and N2 are added to the mixtures to boost efficiency the laser. Fig. 2 Flowing Gas Laser. Fig. 3 CO2 mix bottle and primary regulator plovdiv.techno-link.com/ClientsSites/ladec/default.htm

  7. Flowing Gas Cont. • Power output is typically 40 to 80 watts/meter of the tube length. • A device called the Variac (Variable Transformer)can be used for voltage control. A control valve is used to adjust the rate of gas flow. • In commercial lasers, the Variac and the control valve is coupled together so that when the voltage is increased the flow valve is opened in proportion to the power setting. Fig.4 Output voltage Variac. http://www.elect-spec.com/variacy.htm

  8. Sealed Gas Laser • The typical Sealed CO2 Laser tube has an operating voltage between 3 to 12KV and a operating current of 2 to 15mA DC. • A high starting voltage usually 2-5 times the operating voltage is needed to initiate the discharge. Fig.5 Low voltage sealed CO2 laser Fig.6 Gas discharge tube for Sealed CO2 Laser http://www.repairfaq.org/sam/laserpic/laserpic.htm

  9. Sealed Tube Cont. • There are separate control loops for the voltage and currents. - Voltage:An auxiliary winding on the transformer feeds a bridge rectifier and filter capacitor which provides a feedback voltage proportional to the output of the power supply. - Current: The current control returns the current through a sensing resistor (with a filter capacitor) providing a voltage proportional to the tube current. Fig.7 Sealed CO2 Laser connected to power supply. http://www.repairfaq.org/sam/laserpic/laserpic.htm

  10. T.E.A. Gas Laser Most high power CO2 lasers are constructed using TEA (Transverse Excited Atmospheric) designs. Rather than having a long tube with a electrical discharge along its length and the CO2 gas mixture flowing from one end to the other, a series of electrodes and gas inlets are spaced along the tube. • Chamber with CO2 laser gas in it. • Two electrodes run down the length of the chamber. • The pulse excites the CO2 laser gas, which then begins spontaneous emission. • A reflector and an output coupler outside the chamber form the resonating cavity. • The "TE" in "TEA" comes from the fact that the excitation is performed transverse to the direction of the laser output, as opposed to down the length of the tube like in the Flowing CO2 laser. Fig. 8 TEA Diagram Fig. 13 View of a TEA CO2 Laser in operation

  11. T.E.A. Continued • Specifications - pulse duration: 15 ns - 20 µs - peak power: 100 kW - 500 MW - wave length: 9.12 µm - 11.22 µm - average power: 5 mW - 150 W Fig. 10 TEA CO2 Laser cutting metal sheet Fig. 11 Using TEA laser on a uncooperative computer monitor http://www.repairfaq.org/sam/laserpic/laserpic.htm

  12. Power Supplies For CO2 Gas Laser Fig. 12 View of the power supply and a Variac (autotransformer) for the primary voltage adjustment. Fig. 13 View of the power supply powering up a CO2 laser http://www.repairfaq.org/sam/laserpic/laserpic.htm

  13. Applications • The beam for a CO2 Gas Laser produces a very high temperature that may be used for engraving, cutting, drilling, marking, welding and in various medical applications such as dermatology and as a medical tool for producing clean cuts with little bleeding. Fig. 14 Laser cuts/breaks and or inscribes based upon power settings Fig. 15 Laser cutting thin piece of wood http://www.repairfaq.org/sam/laserpic/laserpic.htm

  14. Answers to Questions 1.) How do you control the voltage and gas flow rate in a Flowing Gas CO2 Laser? • A device called the Variac can be used for voltage control. A control valve is used to adjust the rate of gas flow. 2.) What is the operating voltage and current for a typical Sealed CO2 Gas Laser? - The typical Sealed CO2 Laser tube has an operating voltage between 3 to 12KV and a operating current of 2 to 15mA DC.

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