Alpha and beta radiation

Alpha and beta radiation, on the other hand, are particles that possess mass and charge. If we set the weight of a hydrogen atom as 1 and the charge on its ion as +1, then the table below gives the corresponding properties of the radioactive emissions known in the early twentieth century. 

The resistance to gamma radiation is excellent without significant degradation after more than 1000 Mrad, exceeding even the behaviour of polystyrene. With alpha and beta radiations, resistance would be higher than 10 000 Mrad. 

If the number of neutrons and protons in a nucleus gets too large, the nucleus can become unstable (radioactive) and break apart, forming a new element and emitting small particles called alpha and beta radiation. 

Corpuscular emissions, such as alpha- and beta-radiation or rays of mixed or unknown type. 

There also are many applications for alpha and beta radiation sources, including ... 

The isotopes typically emit only gamma rays because alpha and beta radiation are more likely to harm the patient. Technetium-99m is a commonly used isotope for diagnostic radiology. Many radioisotopes are used in diagnostic medicine outside the body for blood tests. 

Gamma radiation is detected and measured by the methods described in. Scclions 12B-4 and I2B-5 for X-radiation. Interference from alpha and beta radiation is easily avoided by filtering the radiation with a thin piece of aluminum or plastic. 

In 1898, in Cambridge, England, a New Zealander, Ernest Rutherford, demonstrated that there were at least two different types of radiation with different penetrating power. He called these alpha and beta radiation. He subsequentiy worked at McGill University in Montreal, Canada, and found more radioactive elements different types of radium and thorium, and actinium. He proposed that these were links in chains of radioactive materials, called the transformation theory. Rutherford and his colleague, Frederic Soddy, described that the rate of decay of radioactive elements were characteristic of the element, and came to be known as half-life. Decay follows the law of probability. Over a given period of time, each atom has a certain probability of decaying, a process that results from the random movements of the subatomic components of the radioactive atoms. This was the first instance in physics of a truly unpredictable phenomenon. The decay of a radioactive atom was probabilistic. 

Hahn found the university s physicists more congenial than its chemists and regularly attended the physics colloquia. At one colloquium at the begiiming of the autumn term in 1907 he met an Austrian woman, Lise Meitner, who had just arrived from Vienna. Meitner was twenty-nine, one year older than Hahn. She had earned her Ph.D. at the University of Vieima and had already published two papers on alpha and beta radiation. Max Planck s lectures in theoretical physics had drawn her to Berlin for postgraduate study. 

Lord Ernest Rutherford was born in New Zealand in 1871, but went to Cambridge University in England to pursue his Ph.D. in physics in 1895. His original interest was in a phenomenon that we now call radio waves, and he apparendy hoped to make his fortune in the field, largely so he could marry his fiancee back in New Zealand. However, his professor at Cambridge, J.J. Thomson, convinced him to work on the newly discovered phenomenon of radioactivity. Rutherford discovered alpha and beta radiation while at Cambridge. In 1899, he moved to McGill University in Canada where he did further experiments to prove that alpha radiation is actually composed of helium nuclei and that beta radiation consists of electrons. For this work he received the Nobel Prize in chemistry in 1908. 

Liquid scintillation counting developed around the need to count radionucleotides emitting low-level alpha and beta radiation. The common constituents of a liquid scintillator are a solvent, usually an alkyl benzene, and one or more fluors. The purpose of the solvent is to absorb energy from radioactive disintegrations and transfer that energy to the fluor. The fluor converts the energy to light, which is measured by the scintillation counter. 

In other cases where the radioactive material is released, it can he deposited upon environmental surfaces or skin. It could also he inhaled or ingested. The radioactive material on skin and environmental surfaces can usually he washed away, but the close contact with skin may give high doses of radiation to the skin from those isotopes that emit alpha and beta radiation. When radioactive material is inhaled or ingested, it continues to emit radiation and gives the internal areas of the body exposure. If the radioactive material has a chemical affinity for a particular organ of the body, it may accumulate there and selectively irradiate that particular organ. Examples are radioactive iodine (accumulates in tlie thyroid), radioactive cesium (accumulates in the liver), or radioactive strontium (accumulates in bone). 

Increasing their distance from the source—the rate of exposure is proportional to the inverse square of the distance from the source for a point source emitting gamma radiation (see Table 9.3) for alpha and beta radiation, which only travels a few centimeters (for alpha) or a few meters (for beta) in air, the dose rate falls much more rapidly with... 

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