Helium-Neon Laser Tube: Siemens LGR7641S, 1 mW

This is a Siemens model LGR7641S helium-neon laser tube removed from a supermarket barcode scanner. It is in excellent condition and has been tested, producing at least 1 mW after a 10 minute warmup. The tube requires a ballast resistance of 75K ohms, and power supply capable of 1,300 V at 3.7 to 4 mA with an 8 kV start (not included). (Output power may increase by 10 to 20 percent if run at 5 to 6 mA - I don't know if this will adversely affect life expectancy.) It is 243 mm (9.6 inches) long by 30 mm (1.25 inches) in diameter. Beam diameter: .75 mm, divergence: 2.6 mR (can be improved with a positive lens), random polarization, output from anode-end of tube. I'll also toss in a set of four (4) 27.4K resistors to use for the ballast resistance (3 should be sufficient but some power supplies may be happier with 4) and a pair of plastic HeNe tube mounting brackets.