A monthly column of technology rambling, rumination and reality

By: Jud Early, Corporate Vice President, Research, [TC]²

Neutrinos and Other Small Stuff

How big is a nano? Like most questions asked in that way, the answer is, “it depends”. A lot of ink is given today to newspaper and magazine articles, and rarely does a week go by that my fax machine fails to spit out some hot stock tip by a paid hustler to invest in the next wave, nanotechnology. Before we get to neutrinos, let's put nano in perspective. If we don’t, we’ll have no frame of reference for something really small. Simply put, a nano is one billionth of something. A nanomile is equivalent to 0.000634 inches. That still seems too small to form a mental picture. In visualizing area, we can use two dimensions. An acre contains 43,560 square feet. Each square foot contains 2,304 patches of one-quarter inch to each side, with an acre containing 100,362,240 of these patches. Divide by one billion and the result is one tenth of one quarter inch by quarter inch patch, or, about 6/1000 of a square inch.

One nanoacre ! (the dot)

Nanotechnology, to which most current information refers, is properly framed in nanometers, or one billionth of a meter. Since a meter is substantially smaller than a mile, relating a nanometer to anything in our daily life will be difficult. The wavelength of light can be measured in nanometers. An angstrom, another measure of electromagnetic radiation is 0.1nanometer. Nanotechnologists routinely manipulate molecules and atoms. Nanotechnology is being developed to improve dye sites for hard to dye fibers. Nanotech is also believed to be useful in medical applications: picture a surgical device that can be injected into the bloodstream, and which can operate from within the body, by remote control.

The atoms that are manipulated by technologists sometimes aren’t easy to move to the exact location where they are needed. NIST reports that they have built an atom trap that allows a single atom to be produced in an “atoms on demand” basis. The method relies on six intersecting laser beams and a magnetic field to trap neutral atoms in a vacuum chamber. The system sends a stream of atoms past a laser tuned to a frequency that the atom can easily absorb. As soon as one atom absorbs the laser energy, it enters a lower energy state, and drops into the trap. The atom in the trap fluoresces, and when the fluorescence stops, (this occurs when the atom escapes the trap), another atom takes its place, which then fluoresces. Sensors can measure the amount of light produced by one atom, and if two atoms attempt to enter the trap at the same time, the additional light is sensed, and both are dumped and the next single atom enters. Lesson: grab the atom while it is glowing or it will soon be gone! NIST scientists claim 99% accuracy in catching single atoms this way.

You may be wondering what all this has to do with anything. We’ll be discussing ink jet printing in an upcoming article. The nozzle size from which ink is expelled is stated in microns. Microns are huge in size when contrasted with atoms and nanometers. Now let’s move on to something really small…

Neutrino is not a term that many ordinary folks use in daily conversation. They are certainly an interesting physical entity. How big is a neutrino? We don’t know, and that is what makes the story of neutrinos interesting to propeller heads, and maybe to you, too.

Researching neutrinos, you will find that there are differing opinions of how it should be defined. Some works state that it has no mass, while other references proclaim it to be very small, having little, or no mass. All agree that it has no electrical charge, thus the name Neutrino. It was first postulated in 1930 by Wolfgang Pauli, but was not observed until 1956. Must have been really small.

Another thing upon which scientists in quantum mechanics seem to agree is that these little particles, produced by cosmic rays from exploding stars and supernovas, are ubiquitous, streaming through space, and not stopping for anything as they penetrate our planet, our homes and our bodies. Ouch!

In 1957 a physicist, Bruno Pontecorvo hypothesized that neutrinos might come in more than one flavor. By 1960, Brookhaven Laboratory and Columbia University had conducted experiments that proved there were three different types of neutrino. It is believed that the neutrino can oscillate between types, and will have mass in one state and will exhibit no mass in an alternate state. Today, researchers from Fermilab are planning to trap some of these small particles to see if the theory can be proven. That brings us to the fascinating part of this story.

To create the neutrinos to study, a stream of 120 gigaelectron volt protons will be accelerated in a particle accelerator and will slam into a graphite target to create a stream of pions and kaons. These particles must be generated to provide a source from which the neutrinos can decay, and which prior to decaying into neutrinos, will be collimated with huge magnets, which can act on the pions and kaons, but to which the neutrinos are oblivious because they have no charge, and therefore cannot be steered by magnets. They must be pointed accurately at the target from the start. It is hoped that a few of these tiny particles, from among the billions/trillions released, will reach the detector target. So now that we have some neutrinos, what do we do to detect them?

Oh, did I mention that this stream of energy will be located deep underground? The target that will trap the neutrinos will be located 735 kilometers away at Soudan, Minnesota, in an iron mine 800 meters below ground level. The stream of particles will travel from Fermilab, located about forty miles west of Chicago to Soudan, passing through rock, dirt, sewer pipes, and anything else in the path of this highly directed column. Remember, these critters don’t stop for anything! After traveling more than 450 miles underground, detectors that have been built underground (because there is no entry to the mine large enough to pass the finished collection plates), will detect the arrival of the neutrinos. Sensitive monitoring equipment will measure the energy as it arrives and scientists hope to prove that neutrinos do indeed oscillate between states, and can both possess mass and can oscillate to a massless state. Incidentally, the detector plates are eight meters (26 feet) in diameter and are 1.25 centimeters (about ½”) thick. There are 450 of these plates, all assembled in a line, like so many file folders hanging in a file drawer. In this case, the drawer is the length of a football field, and the combined weight is about 4,000,000 kilograms of steel, and 405,000 kilos of plastic that separates the steel plates. It’s ironic that such huge structures are required to determine if such a small, subatomic particle can have any mass at all.

After four years of work in a former iron mine a half-mile underground, the Main Injector Neutrino Oscillation Search (MINOS) collaboration celebrated a milestone for the ambitious MINOS particle physics experiment. On June 5, technicians erected the last of 485 house-high detector planes of steel and plastic in the Soudan Underground Laboratory in Soudan, Minnesota

Science of this scale is hard for the everyday person to grasp. I wanted to bring you this story because it will likely be seen by very few people, and although the scientific value and increased human knowledge will enjoy many pages in the journals of science, the person in the street has no way of knowing what is taking place literally under their feet.

Next month: Fractals, fabrics , and coherent light

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