HeNe Beam Diameter

I just got my first HeNe laser and the beam diameter is approximately 10mm or 3/8'' at the aperture.

Is this normal? I baught it off of Ebay and the seller didn't have any specs in the description. I just assumed it would be around 1mm.

Don`t get me wrong. It's a great laser. I even think that it's brand new.

Also, I turned it on for about an hour, and it seemed to really heat up. I expected to get warm, but it got pretty hot.
It wasn't too hot to touch or anything but I don't want a fire hazard.

Any answers would be appreciated.

It looks to me like the head had a beam expander on it (that nub sticking out the front) so the 1cm beam is probably to be expected (and you will have super low divergence).

As to the heating, it might be designed for a little forced air cooling, but as long as you can still hold it in your hand (most people start to feel pain at abotu 140f, which is within spec for most hene's) you should be fine. If not just put a little fan on it

Those HeNe's are usually packed full of silicone and are not meant to be actively cooled in any way... some of them just get warm.

As far as 10mm at the aperture, there are definitely some optics in there (which might turn out to be useful someway!!). Pull them out and you will get the 1mm beam you should have.

If it were 10mm straight out of the tube, you would have a 10mm bore which would just be nuts!! ;D

Yeah, the current would have to be about 100 times that of a 1mm bore.