helium flight tube for x-rays to pass through

[vono]

We are trying to design a low cost expandable flight tube that can cut down the air scatter of x-rays. This flight tube need to expand like a bellows from 100mm collapsed to about 800mm fully extended. It needs to have a inside dimension of 300mm x 300mm square ( it could also be round). I was thinking of mounting a few guide rods on top and have the ends fixed . The material I was thinking of using is aluminized Mylar and Kapton film on the ends. There will also need to be a dump chamber piped into the system to store the Helium when collapsed. Has anyone ever used Aluminized Mylar as a bellows? Could there be a company that might be able to make such a bellows?

THANKS,
Jay

 

[3DDave]

Seems like you need two bellows that share a volume of helium. This will allow the helium to remain at ambient pressure and not require pressure resistance from the bellows. As as one bellows is extended the other will naturally collapse and vice versa. You may need to add some weights and perhaps some carbon fiber hoops to offset the buoyancy of the helium to keep it from floating up and distorting while trying to do so.

It's not that difficult to make such a thing - material availability being the top obstacle. Normally aluminized mylar can be heat-welded, but a bellows may require alternating layers; aluminum to aluminum won't bond so well. There are transfer tapes - basically a releasable adhesive that can bond face-to-face. 3M has a selection of them. They skip the need for working out the parameters to manage a heat-weld.

I'd look to the basic construction for camera bellows to get the geometry of the cut pieces.

 

[EdStainless]

Why use metallized film for the bellows?
I do like the idea of using tape for building them.
And building two balancing bellows would make life a lot easier.
I presume that you will keep them at a pressure just a couple of mm above ambient.

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P.E. Metallurgy, consulting work welcomed

 

[vono]

Yes a balanced bellows system would be the best idea. I could make the bellows out of any material as long as it can hold a slight positive pressure of helium for a while ...and is flexible enough.
thanks for the input! I have

J