![Beam](https://www.experimental-engineering.co.uk/wp-content/uploads/2022/03/IMG_20220306_200820-scaled.jpg)
![05-LHR-088-097 Tube](https://www.experimental-engineering.co.uk/wp-content/uploads/2022/03/IMG_20220306_200225-300x225.jpg)
Here’s another Helium-Neon to add to the electric glassware collection, a 2mW Melles-Griot 05-LHR-088 which I pulled from the optical assembly from an ancient Spectra-Physics SP910 laser level. This tube is a standard Red 632.8nm with Random beam polarisation. The specifications are in the table below:
Minimum Optical Power | e/2 Beam Diameter | Divergence | c/2L Mode Spacing | Supply Opr/Start Volts | Nominal Current | Diameter/Length |
---|---|---|---|---|---|---|
2mW | 0.63mm | 1.4mR | 641MHz | 1.82/10kV | 4.5mA | 29/241mm |
![Tube Label](https://www.experimental-engineering.co.uk/wp-content/uploads/2022/03/IMG_20220306_200233-300x225.jpg)
The label shows that this tube was manufactured back in 1987. 34 years at the time of writing! There is a slight amount of brown deposit in the main bore, indicating the tube has seen some use, however it’s nowhere near as bad as the Barcode scanner tube I have, which must have spent many years operating. I am assuming the “2.6” hand-written onto the label next to the serial number was the power measured at the factory.
![Anode End](https://www.experimental-engineering.co.uk/wp-content/uploads/2022/03/IMG_20220306_200248-300x225.jpg)
This tube is old enough to have 3-screw locking/adjustment collars on the mirror mounts. This one is at the anode end of the tube, with a cap over the HR mirror for protection.
![OC Mirror](https://www.experimental-engineering.co.uk/wp-content/uploads/2022/03/IMG_20220306_200259-300x225.jpg)
The OC (Cathode) end of the tube has the same locking collar.
![Tube Mounts](https://www.experimental-engineering.co.uk/wp-content/uploads/2022/03/IMG_20220306_200507-300x225.jpg)
The original tube mounts are reattached here, made from Aluminium with silicone rubber pads.
![Tube Running](https://www.experimental-engineering.co.uk/wp-content/uploads/2022/03/IMG_20220306_200645-300x225.jpg)
Here’s the tube running on a LaserDrive 4.5mA PSU. The camera doesn’t quite pick up the colour of the discharge, it’s more salmon-pink.
![Bore Closeup](https://www.experimental-engineering.co.uk/wp-content/uploads/2022/03/IMG_20220306_200748-300x225.jpg)
A closeup of the bore more accurately shows the colour of the glow discharge in the tube.
Finally, the output beam from the tube. This one actually measured at 3.04mW on a Coherent LaserCheck, a bit higher than the assumed factory measurement of 2.6mW!