Distinguishing Gamma Rays From X-Rays

Article by leading Gamma Radiation expert, Dr. Bruce Banner:

In 1896, just a year after Wilhelm Roentgen had discovered x-rays, the French physicist Henri Becquerel discovered a new kind of ray, quite similar to x-rays, but originating from uranium. He labeled it "metallic phosphorescence", while in actuality what he had observed was gamma radiation (being emitted by radium-226, a part of uranium decay). In 1900 the French chemist and physicist Paul Villard identified gamma radiation while studying the radiation produced by the substance radium. It was not until 1903, however, that Ernest Rutherford named the rays gamma rays, gamma being the third letter in the Greek alphabet, to distinguish it from the alpha and beta rays (thorium* and uranium, respectively) that he [Rutherford] had already discovered. 


The original distinction between x-rays and gamma rays was the wavelength. Radiation producing a wavelength below a number such as 10⁻¹¹ m was labeled as gamma radiation, while radiation producing a wavelength above it was called an x-ray. However, as longer wavelength gamma radiation emitters were found, the distinction begin to overlap. Now they are distinguished primarily by their source; x-rays are emitted by the electron fields outside the nucleus, while gamma rays originate in the nucleus itself. Both gamma rays and x-rays are part of the electromagnetic spectrum.


*Thorium is an element that the Swedish chemist Jons Jakob Berzelius named after Thor, the god of Thunder

Gamma Radiation Shielding

Article by leading Gamma Radiation expert, Dr. Bruce Banner:

I know from experience that exposure to gamma radiation can produce undesirable and unpredictable results. When working with gamma radiation, or any radiation, it's important to maintain secure radiation shielding.

There are three controlling factors of dosage from a radioactive source. These factors are time, distance, and shielding. The time of exposure reduces the dosage proportionally, while the distance from the source reduces it according to the inverse square law. Shielding reduces dosage by absorbing or scattering the radiation, thus reducing the radiation exposure level.  Due to the nature of gamma rays, nearly any material, if used in sufficient amounts, can be used as shielding from gamma rays. However, since greater energy requires greater shielding, which translates as greater thickness, the most practical material so far has been lead, largely due to its density.

Depleted uranium is also used, mainly for transporting gamma ray sources. The primary advantage of depleted uranium over lead is the bulk, since it is 68.4% denser than lead, thus requiring less material to create the shield. On a side note, depleted uranium is also weakly radioactive, albeit 40% less radioactive than uranium and primarily emits alpha particles which can be shielded by paper or skin.

No entirely satisfactory solution has been found yet. For now, those working with radiation, either occupationally or medically, can be safest abiding by the ALARA rule: when working with radiation, use a dosage that's As Low As Reasonably Achievable.

Short-duration GRB's and Hypernovas

Article by leading gamma-ray expert,
Dr. Bruce Banner:

When exceptionally large stars collapse at the end of their lifespan, they produce a massive explosion known as a hypernova.  These explosions emit enormous amounts of high-energy radiation, which is typically referred to as long-duration gamma ray bursts, although the process is dissimilar to the normal process of radioactive decay (the range of the energy being well above 10TeV, an energy range exceeding the output of natural radioactive decay.)  It has been estimated that the emission of these gamma ray bursts (GRB) constitute the only single event with that much raw power thus far discovered in the cosmos. 

Though long-duration GRB's are emitted during hypernovas, it has been questioned whether hypernovas can account for short-duration GRB's, since these bursts seem to have no affiliation with massive stars, not appearing in places where such stars have just been formed. More recent studies have dismissed this link, and the question of the origin of short-duration gamma ray bursts is still open, although leading astronomers hypothesize that the mergers of binary neutron stars is a logical explanation for their appearance.

The giant flairs of soft gamma repeaters in nearby galaxies could also account for the appearance of at least a small portion of short-duration GRB's.