I approach the monastery of green corrugated steel in a forest of cedar and hemlock. Film badges and radiation dosimeters line the rack by the gate. I clip mine to my belt and enter. It’s a typical Pacific Northwest night. The cool, misty air caresses my face with the clean smell of evergreens. I cross the courtyard and enter the meson hall. The steel door slams behind me. Inside, harsh fluorescent lights illuminate the concrete radiation shielding stacked like a giant’s toy blocks by the overhead crane. Banks of power supplies fill the air with a sixty-cycle hum. My boots sound on the steel stairs as I descend to the counting room. It’s midnight, and I’m here to pull a graveyard shift on experiment 208 at the TRIUMF particle accelerator.
Gordon and Harry tell me that Rudy will be late, and then they leave for their motel rooms. I read the day’s entries in the logbook, record the leakage currents on the high-voltage supplies, and go downstairs to check the flow of magic gas to the wire chambers. Back in the counting room, my fingers dance over the data acquisition computer’s keyboard, and a scatter plot appears on the monitor.
Here’s reality at its most basic level, but it comes at the end of a chain of equipment and abstraction: A beam of protons enters an evacuated aluminum coffin and passes through a hydrogen target, affectionately known as the Hindenburg. Some of these will scatter from the target, and fewer will create a gamma ray when doing so. A fraction of the gammas leave their ghostly traces in sixteen lead-glass detectors, each the size of a cinderblock.
One outgoing proton passes through two wire chambers, an electromagnet, and another two wire chambers. Its bend through the magnet allows us to determine its momentum. Plastic scintillators inside the coffin detect the other proton. Signals pass through two racks of electronics as tall as a man, hundreds of feet of cable, another electronics rack in the counting room, and finally into the computer. By comparing the difference in the reaction rate when incoming protons are spin-up compared to spin-down, we hope to determine which of the competing nuclear forces theorists have proposed is the most accurate.1
A million things can go wrong. Most of them involve cables. Black coaxial cables thick as your middle finger connect all the electronics. They writhe and squirm through the cave and counting room like Medusa’s dreadlocks. I’ve seen physicists waste eight hours of precious beam time tracking down a problem that turned out to be a bad cable. Instead of missile defense, this country should invest in a Cable Connector Initiative, not as sexy but it would pay off in saved money, effort, and frustration.
Are the fundamental building blocks of matter, which can only be observed by a team of Ph.D.s with hundreds of millions of dollars’ worth of equipment, more real than my worries about how I’ll earn a living after completing my postdoc next year? I look through the computer displays. A time-of-flight peak is drifting outside its windows. This could be trouble. Should I wade into the wall of electronics armed only with an oscilloscope and tiny screwdriver (to adjust trim pots), or should I wait for Rudy, who’s better at fixing things. I often find myself facing this dilemma. The clock says 12:45 a.m. It’s so easy to ruin the delicate timing. I decide to wait.
Staying awake until dawn takes a sledgehammer to my circadian rhythms. This jarring of my biological clock saps energy from the mental electric fence that keeps the wolf pack of inadequacy away from my ego. I feel like an imposter posing as a scientist. All those transistors in the mountains of electronics are conspiring to break down, thus revealing my helplessness, unmasking me as the fraud I am.
Someone’s left a Scientific American behind. The cover announces this issue is dedicated to the Standard Model of particle physics. I page through an article on quarks and gluons. The theory has always sounded like something a groggy physicist would dream up at 1 a.m. A colleague told me that in the 1950s he used to work through all the articles in the Physical Review, even those outside his field. You can’t do that anymore. Even for our modest project two theorists took six months developing a computer model to predict the results. I can follow some of the equations, but the details slip through my fingers, like sand does when scooped from the ocean bottom and brought to the surface.
My stomach growls. It’s two o’ clock, and my eyelids begin to droop. Whatever happened to the physics of things you can touch? It went out with the concept of electric fields in the nineteenth century. A professor of mine used to say touch is an illusion, only the electrostatic repulsion between atoms. Even so, I want to crawl into bed and feel my girlfriend’s arms surround me like a warm sweater. Yet I have six hours left, six hours to stay awake and hope nothing goes wrong, six hours to pretend I’m in control of what’s going on.
Footnote, for people who can read those articles:
1. Writing an equation for the nuclear force is not as easy as writing one for gravity or the Coulomb force. For one thing, the nuclear force acts only at short distances. Also, with the exception of the deuteron, nuclei contain more than two particles, so one would need to disentangle multi-particle effects to come up with a force. While the Standard Model of Particle Physics describes the nuclear force, it comes with all the complications of quantum field theory and nucleons that are composed of three quarks. Since reactions in nuclear physics take place at non-relativistic energies, physicists wanted a simpler approximation to use at lower energies. Examples are the Paris Potential and the Bonn Potential. Note that force is the derivative of potential energy.
In quantum mechanics, many particles carry intrinsic angular momentum much like a spinning baseball. This is pretty weird because some of the particles, like the electron, have no size. What is there to spin? The answer falls out of the math when you combine quantum mechanics and special relativity. Anyway, for particles like protons, spins can point in one of two directions, either up or down (more correctly, you can only measure one vector component of the total spin). In our experiment, we bombarded our target with polarized protons (those having their spins aligned instead of in random directions). The normalized difference in the cross section (roughly the reaction rate) is called an analyzing power. We hoped that this would be sensitive to the nuclear potential used in the model, and that this would help choose the best nuclear potential to use when modeling nuclear reactions and nuclear structure.
After all our effort, the experiment wasn’t sensitive enough to tell the difference.