Rotor for a Friend
When I began my career in medical engineering, the company I worked for put all their engineers through extensive training. Training included a stint in an X-ray tube reloading facility.
We had the chance to repair x-ray tubes for CT scanners, cath labs and general x-ray rooms. The number one enemy of an X-ray tube is heat. Of all the energy that is pumped into a tube, 99% is converted to heat. The rest is X-radiation. The main problem is that the heat has to be carried away. But after many hours of enduring intense white-hot heat, the glass envelope just says "that's enough." The envelope then generally cracks and the vacuum inside the tube is lost. That's the end of the tube.
The part that cops the most heat, is the rotating anode, or rotor. It spins at very high speed and present a large surface area to the electron beam that produces the x-rays. Lots and lots of heat is generated. To cope with the punishment, the rotor is made of tungsten. It has a high melting point and doesn't stretch or expand too much. Good stuff, eh?
Tungsten is a dense metal. The shape and weight of a rotor feels strangely heavy in your hands. How a heavy rotor spins so freely holds a certain fascination too.
So where's all this leading too? On a previous training trip to the USA, I made friends with an engineer from Washington state. He was very interested in having a rotor for a paper weight on his desk. I transported one from Australia to the USA on a later training trip.
Passing through security at the airports was interesting to say the least. I had the most trouble in San Francisco. Security pulled me aside and asked many probing questions, mostly about who I was, what I was doing in the United States, could I pose a threat to national security? The security blokes were fascinated with the rotor. I'm sure they wondered about the dense object in their X-ray scanner.
My US mate was amazed that I'd remembered the rotor when I presented it to him. He really enjoyed the gift and it makes a nice conversation piece in his office.
Next time, Parking Pains
We had the chance to repair x-ray tubes for CT scanners, cath labs and general x-ray rooms. The number one enemy of an X-ray tube is heat. Of all the energy that is pumped into a tube, 99% is converted to heat. The rest is X-radiation. The main problem is that the heat has to be carried away. But after many hours of enduring intense white-hot heat, the glass envelope just says "that's enough." The envelope then generally cracks and the vacuum inside the tube is lost. That's the end of the tube.
The part that cops the most heat, is the rotating anode, or rotor. It spins at very high speed and present a large surface area to the electron beam that produces the x-rays. Lots and lots of heat is generated. To cope with the punishment, the rotor is made of tungsten. It has a high melting point and doesn't stretch or expand too much. Good stuff, eh?
Tungsten is a dense metal. The shape and weight of a rotor feels strangely heavy in your hands. How a heavy rotor spins so freely holds a certain fascination too.So where's all this leading too? On a previous training trip to the USA, I made friends with an engineer from Washington state. He was very interested in having a rotor for a paper weight on his desk. I transported one from Australia to the USA on a later training trip.
Passing through security at the airports was interesting to say the least. I had the most trouble in San Francisco. Security pulled me aside and asked many probing questions, mostly about who I was, what I was doing in the United States, could I pose a threat to national security? The security blokes were fascinated with the rotor. I'm sure they wondered about the dense object in their X-ray scanner.
My US mate was amazed that I'd remembered the rotor when I presented it to him. He really enjoyed the gift and it makes a nice conversation piece in his office.
Next time, Parking Pains
Labels: rotor x-ray tungsten
posted by Philip at
10:08 pm
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