Bertram Neville Brockhouse
General Physics, Subatomic Particles, Optics, Biophysics, Theoretical Physics
Won the Nobel Prize in 1994 for designing the Triple-Axis Neutron Spectroscope and his use of it to investigate Condensed Matter
"Your mind is your most valuable survival organ. Learn to tune your mind like a radio, filtering out all the noise and other channels, focusing on one thing."
Brockhouse conducted experiments in the physics of solids such as metals and crystals. This kind of physics is called solid state physics. As his tool he used the neutron spectrometer that he developed at Chalk River, which allowed him to look right inside the crystalline structure of solids to find out how solid things like rocks and gems are held together. Imagine shining a beam of light on an object. Your concept of that object is based on the light reflected from it.
But at the atomic level, the wavelength of the light beam is “too big.” The wavelength (or the “size”) of the light from a flashlight is about 7,000 Angstroms (one Angstrom is roughly the width of a hydrogen atom, or 10-10 metre), while the wavelength of a neutron beam is only around one to four Angstroms. In other words, if you could use a beam of neutron “light” you could see details thousands of times finer than you can see with ordinary light. Incidentally, in the same way, the shorter wavelength of X-rays is what gives them the power to penetrate things and reveal inner details that you cannot see with regular light. According to Brockhouse, “the virtue of neutrons is you can say a great deal about a material by using a neutron beam.” You can work out the distance between atoms, the angle of bonds between atoms, the strength and energy of atomic bonds holding the atoms of a solid together, and much more. All these things are very handy and can be applied to working with metal, rocks, gems and other solid materials. But, fundamentally, Brockhouse was just trying to satisfy his natural human curiosity. He wanted to know what things are made of, what rocks look like inside.
1. The original triple axis spectrometer (1959). (Click image to enlarge.) A spectrometer is a device that measures the angle, wavelength and energy of light or other type of radiation, in this case neutron radiation. The panel of 52 rotary switches in the upper centre of the picture could be preset to go through an energy scan of up to 26 points. A feature of Brockhouse’s spectrometer was the way he could vary three angles: the direction of the neutron beam, the position of the specimen, and the angle of the detector. Add to this the ability to vary the energy of the incoming neutrons and the sensitivity of the detector and he had a Nobel Prize-winning creation. (Photo courtesy of AECL)
2. Monochromating Crystal. “Monochromating” literally means “making one colour.” A special crystal of aluminum was used to separate out neutrons of one particular energy or colour. Knowing the exact colour of the beam going in can tell you more about what is inside the material you are investigating. The beam was then aimed and collimated (straightened out by going through a series of slits) before being sent on to the target.
3. Specimen. The position of the target metal or crystal can be varied on two axes (twirled around sideways or vertically, for instance). The beam of neutrons bounces off the target in different directions that tell something about the atomic structure of the material if they can be detected.
4. Detector. The analyzing crystal, similar to the monochromating crystal, can be tuned to pass only neutrons of particular energies. These neutrons then pass through the analyzing crystal on to the detector, which counts them. By knowing the energy, quantity and angle of the neutrons that go into the specimen and then measuring the energy, quantity and angle of the neutrons that come out, physicists can calculate things about the internal structure of the specimen.
ACTIVITYhas 1 activity for you to try in the Activities section.
Like many retired physicists, Brockhouse liked to explore metaphysical ideas — concepts such as spirit, morality, ethics and beliefs. For the last two decades of his life he worked on what he called “The Grand Atlas,” a sort of rule book for nature incorporating theories both physical and metaphysical. Brockhouse was a religious man, and his belief in physics theory coexisted with his spiritual beliefs. “Science is an act of faith,” he said.
Without faith, how can understanding the existence of a neutron help with the larger moral issues in life?
Brockhouse’s example of a moral problem is “Kantian Doom” — the idea that we are doomed because even though we know that something is bad for us, we do it anyway because everyone else is doing it. Examples might be driving cars, using computers or watching television. Brockhouse believed such problems might require metaphysical solutions, not scientific ones.
Fritjof Capra, The Tao of Physics, fourth edition, Shambhala Books, 2000.
Brockhouse's autobiography on the Nobel website.
Neutron spectroscopy lab in Budapest, Hungary.