Physics professor’s team looks for radiation deep underground
When most new users of Alibre Design start on their first project, they usually choose an assembly that is relatively simple and maybe something they can use. Few would be so ambitious to attempt something as exotic as a neutron detector.
But Professor Fredrick Gray at Denver’s Regis University says the mechanics are not as complex as it sounds.
“It was a reasonable for a first learning project because there is a lot of symmetry in it. Not quite everything, but most of it is cylindrically symmetric,” says Gray. “In that respect, the geometry is not difficult.”
And, he says, it is something he needs. Gray is collaborating with a research group at the nearby Colorado School of Mines to collect scientific data from the Sanford Underground Laboratory.
“This is the site of the Homestake Gold Mine in Lead, South Dakota, which we hope will develop into a major facility for experiments,” explains Gray. The 4,850-foot-deep mine was the location of revolutionary discoveries in particle physics in the 1960s and has recently reopened for international scientific use.
The deep silence inside the mine is ideal for experiments that use ultra-sensitive instruments, and the space is relatively free from cosmic rays and other radiation. Surrounding mineral content still contributes some amount of radiation. Measuring the extent of this radiation is one of preliminary tasks that Gray’s team.
“At this point, we’re just gathering information that will be needed in more sophisticated experiments – looking for rare subatomic processes -- that will be placed at the same site eventually. The level of neutrons in the environment can be used to design the fielding around those experiments. Scientists will need to know what background radiation they are going be operating in so they can properly shield their equipment.”
The major components consist of an inner cell that will hold scintillator liquid that will absorb neutrons and gamma rays, and a photomultiplier, which detects very low levels of light produced in response to the ionization of the liquid by radiation.
“You actually can buy a fully assembled neutron detector, but we want one that we would be able to refill ourselves, and one made out of Teflon in particular, which is something you cannot buy. Teflon is chemically resistant; the liquid we need to put inside is a rather strong solvent so it needs to be contained in something that can hold it. Teflon also contains no hydrogen, which means it is not going to shield the neutrons we’re trying to measure.”
The team has obtained a block of Teflon and the final model is ready for fabrication. A machinist at the School of Mines will cut the material with a CNC machine according to the specifications in Gray’s 3D Alibre model.
Gray was impressed that he could pick up the MCAD software and so quickly put it to practical use – whether it’s simple or complex.
“I really only spent a few hours learning the techniques of 3D sketching, extruding, and revolving and I was able to make the parts.”
About Frederick Gray
Frederick Gray is an assistant professor of physics at Regis University in Denver, Colorado, as well as an avid AlibrePowered user.
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