Geiger counter

“ See, the Geiger counter shows that the phosphate tracer has already started moving up into the plant. Helps show how important phosphate is to plant growth, and how eagerly the plants absorb it.”
“The plant sure looks healthy enough, all right,” Eddie said.
“Right,” Jim said. “Now let’s see how far up into the plant the tracer has gone.”
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He moved the probe upward over the smaller twigs and leaves. On the lower leaves the Geiger counter kept clicking rapidly. Eddie watched the needle stay forward on the gauge. ”

“ Eddie switched off the Geiger counter. They found some shade under a wind-twisted oak and ate their lunch. Eddie glanced at the sun. “It must be one o’clock,” he said. “Guess we’d better be starting back. The water will be a little choppier than this morning. Won’t be so easy to row. I don’t want to get home late, or my mom will scalp me.”
“Let’s go,” Teena said. “Anyway, we’ve done enough prospecting out here to know there’s no uranium around.”
On the way back to the boat Eddie tried out the Geiger counter in a couple of places they had missed. ”

“ I steadied myself and concentrated on thinking whether I should attach any special significance to her carrying a Geiger counter. Naturally it wasn't the sort of thinking that interfered in any way with my watchfulness—you quickly lose the habit of that kind of thinking in the Deathlands or you lose something else.
It could mean she was some sort of greenhorn. Most of us old-timers can visually judge the heat of a dust drift or crater or rayed area more reliably than any instrument. ”

“ He gave the chronometer, synchronized to start with the take-off, a quick inspection and turned to the meters on the instrument panel. He quickly went over the small control board that would permit him to make deviations and corrections in the ship's course of as much as five degrees and checked the geiger counter apparatus which emitted a faint burp as a stray cosmic ray hit it. The Counter was designed to warn against stray radiation from the engines (but the chances were ten million to one that there would be any, Burger had said) . ”

“ Eddie got the Geiger counter out of the closet. He told his mother how he had been wanting to try it out on Cedar Point. He told her about the dream he had had.
“Well, I guess you never can tell,” Mrs. Taylor said. “According to your father, uranium ore often shows up in most unlikely places.”
“Cedar Point isn’t so unlikely, Mom,” Eddie said. “There are lots of rock formations out there. Uranium ore is usually located where there are plenty of rocks.”
When Teena arrived Eddie was all set to leave. He wore swimming trunks under his blue jeans. ”

“ Nuclear physicists of Chicago University, called in to aid city engineers, have declared that dangerous amounts of escaping gamma-rays in the Atomic Powerplant were first discovered by the Geiger-counter at two a.m. Evacuation of all employees was ordered one hour later as a safety measure. ”

“ But an ordinary man, looking at a Geiger counter, does not understand that a tiny particle at high velocity—so small that it passes through a glass tube and a metal lining without hindrance—makes a Geiger tube temporarily conductive. Murfree stared blankly at Bud Gregory. ”

“ Except for the faint background count, the Geiger counter gave no sign of there being any uranium-bearing ore on Cedar Point.
After a tiring hour and a half of hard climbing over and around the outcroppings, Teena suggested they stop and eat their picnic lunch.
“Might as well,” Eddie said. “Sure doesn’t look like we’re going to find anything out here. Lot of trouble for nothing, huh?”
“Oh, no, Eddie,” Teena disagreed. “We’re having fun aren’t we? After all, you’re supposed to have fun during vacation.” ”

“ Teena asked. Although Eddie had explained it to her, she seemed to feel that, as a pupil, she should ask some questions to help Jim out.
“Stick? Oh, you mean the probe. Actually, it’s called a diode, but probe’s easier to remember. Anyway, the probe is a vacuum tube filled with a special kind of gas. Whenever invisible radioactive particles shoot through the probe and into the gas, the Geiger counter clicks, and the needle on the dial moves forward. The more rays shooting through the probe, the more clicks; the more clicks, the more radioactivity. ”

“ Jim had warmed up to the subject, and wasn’t quite ready to drop it. “Tracers are used in many ways,” he went on. “They are used in medicine to locate diseased tissue which attracts and absorbs certain isotopes. A radiation-sensitive instrument, similar to a super Geiger counter, sniffs out the isotope and locates the damaged tissue. Then the doctor knows what to treat, or where to operate. Radioisotopes are used in various food tests. By watching the tracer with electronic gadgets, they can tell whether the food is a muscle builder, a bone builder, or what.” ”

“ Mr. Taylor glanced up from the notebook. “We’re experimenting with radioactive tracers,” he said. “They’re weak—certainly not dangerous—but there’s no harm in taking a little extra precaution. The gloves are lead-lined and absorb any of the rays which might possibly be picked up from handling the plants.”
“What are tracers, Mr. Taylor?” Teena asked.
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Eddie shot her a quick scowl. He doubted that his father wanted to be bothered with questions at the moment. Then Eddie noticed one of the students holding the wandlike probe—or diode—of a Geiger counter down close to the leaves of one plant. ”

“ Taylor nodded, obviously impressed.
“Eddie explained it to me,” Teena said, smiling, “but he didn’t say anything about tracers.” She turned her attention back to Jim, the student.
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“All right,” Jim said, seeming more at ease, “let’s look at it this way. Any radioisotope keeps shooting out rays. Of course, you can’t see the rays with your eyes. They’re almost too small to think about. But you can follow them with a Geiger counter.” He indicated the black metal instrument which he still held in his hand. ”

“ As our chief here pointed out, the periodicity of gamma ray bombardment is one of the few invariables known to Man. Its constancy matches the monotonous regularity with which uranium transmutes to lead.
"Scientists have traveled all over the world ... east, west, north, south ... but in every latitude and clime their Geiger counters measure the same tempo of cosmic ray bombardment. They have delved into the deepest mine-pits miles below ground, descended in bathyspheres to the ocean's floor, and detected no change. ”

“ The measurement of radioactivity must be accomplished indirectly, so use is made of the physical, chemical, and electrical effects of radiation on materials. One commonly used effect is that of ionization. Alpha and beta particles ionize gases through which they pass, thereby making the gases electrically conductive. A family of counters uses this principle: the ionization chamber, the proportional counter, and the Geiger-Müller counter.
Certain crystals, sodium iodide being an excellent example, emit flashes of visible light when struck by ionizing radiation. ”

“ To avoid ridicule, most pilots and observers now make reports privately; these have been averaging twelve a month, and Project Saucer, in its own words, is making a "serious, scientific evaluation" of the entire picture.
Several of those interviewed by TRUE believe that the project experts do not have the full answer, but are anxiously trying to fit the puzzle together. The project's suspicions, however, are clearly evident. Planes whose pilots report close encounters with "flying saucers" are checked with Geiger counters for radioactivity. ”

“ The “mineral club” deception covered their weekend expeditions because “rock hounds” are notorious for their addiction to scrambling around on mountains in search for specimens.
The equipment that the group had installed in the abandoned building was designed to be self-operating. Geiger tubes were arranged in a pattern so that some idea as to the direction of the radiation source could be obtained. During the original sightings the equipment-malfunction factor could not be definitely established or refuted because certain critical data had not been measured. ”

“ In their passage through air or other gas, the alpha particles produce from the neutral molecules a large number of negatively charged particles called ions. The ionization due to the alpha particles can be readily measured by electrical methods, and it can be shown that the effect to be expected from a single alpha particle is much too small to detect except by very refined methods. In order to overcome this difficulty, Rutherford and Geiger employed a method of magnifying automatically several thousand times the electric effect due to an alpha ”

“ The background-count for standardized Geiger-Miller tubes is a measure of the normal everyday radioactivity of the earth as a whole. When a tube of given dimensions, with given pressure and given voltage applied, indicates that stray subatomic particles have passed through it at the rate of from one to three per minute for each square centimeter of its surface, the cosmos is normal. ”

“ In this manner the range is, in fact, determined. The
dotted curve (Fig. 13) depicts the recent investigation of the
ionisation effected by a sheaf of parallel rays of radium C in
air, as determined by Geiger. The range is laid out horizontally
in centimetres. The numbers of ions are laid out vertically. The
remarkable nature of the results will be at once apparent. We
should have expected that the ray at the beginning of its path,
when its velocity and kinetic energy were greatest, would have
been more effective than towards the end of its range
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when its energy had almost run out. ”

“ It was this fraction of a given number of -particles shot into the foil which Geiger and Marsden found by direct count by the scintillation method to be deflected through the angles included between any assigned limits and . Since and are known, could be at once obtained. It was found to vary with the nature of the atom, being larger for the heavy atoms [Pg 281] than for the lighter ones, and having a value for gold of . This is then an upper limit for the size of the nucleus of the gold atom. ”

“ Here Prestonby kept his hand on his gas-projector, and Yetsko had his rubber hose ready, either to strike or to discard in favor of his pistol. The instructors were similarly on the alert and ready for trouble—he had seen penitentiaries where the guards took it easier. Carpentry and building trades. Machine shop. Welding. 'Copter and TV repair shops—he made a minor and relatively honest graft there, from the sale of rebuilt equipment. Even an atomic-equipment shop, though there was nothing in the place that would excite a Geiger more than the instructor's luminous-dial watch. ”

“ This action discharged the rod, producing 91 an electrical pulse which was amplified and transmitted to the Earth. The rod was then recharged and the fibre returned to its original position.
In order to penetrate the walls of the chamber, protons required an energy of 10 million electron volts (Mev) , electrons needed 0.5 Mev, and alpha particles 40 Mev.
The particle flux detector incorporated three Geiger-Mueller tubes, two of which formed a companion experiment to the ionization chamber; each generated a current pulse whenever a charged particle was detected. ”

“ Commander O'Brine had not exaggerated. The residue of carbon and thorium on the blast tube walls was stubborn, dirty, and penetrating. It was caked on in a solid sheet, but when scraped, it broke up into fine powder.
The Planeteers wore coveralls, gloves, and face masks with respirators, but that didn't prevent the stuff from sifting through onto their bodies. Rip, who directed the work and kept track of the radiation with a gamma-beta ion chamber and an alpha proportional counter, knew they would have to undergo personal decontamination. ”

“ This type of counter also uses a different detection device: a solid, rather than a liquid scintillator. A large crystal, usually of sodium iodide sensitized with thallium, is used to convert gamma rays to light photons.
Let us return to the shielding problem for a moment. Tanks of water, bricks, stone, and lead have been tried by scientists seeking effective, cheap, and convenient shielding. Some early counters were built deep underground in the hope of avoiding cosmic radiation. ”

“ What about the neutrons for the irradiation? Although there isn’t a suitable nuclear reactor [9] in your city, there is one at a university only an hour away by jet. Since it may take a few hours to get the sample to the counter after irradiation, you won’t be able to look for short-lived 22 activation products, i.e., those with half-lives of up to an hour. However, this will exclude only a few elements from detection.
A pulse-height analyzer used for gamma-ray spectrometry. A gamma-ray spectrum is displayed on the television screen. ”

“ After the storage period, the gas is pumped into an array of instruments known as a low-background PROPORTIONAL COUNTER, and its radioactivity is determined. This is an involved process. First there is the matter of the BACKGROUND COUNT.
The background count of an instrument is the number of pulses (counts) it will give per unit time when there is no radioactive sample in it. These counts are caused by cosmic rays, by radioactive contamination always found in the vicinity of the counter, or by any contamination inside the instrument. ”