Gamma radiation how does it work

For the uranium series, the contribution of uranium and its descendants were taken into account. The bulk of the calculation therefore comes down to a few dozen successive numerical integrations, with about steps each time. It is therefore a much lighter and less demanding procedure in computer time than the Monte-Carlo method for a similar definition.

In fact, formula Eq. For the use of these formulas, it is assumed that there is an electronic equilibrium, that is, the dimensions of the dosimeter are equal to or greater than the secondary electron range of the order of a few mm. Murray [ 9 ] showed that this is verified if the dosimeter mass is greater than mg.

In applying formula Eq. Here one assumes an infinite environment and homogeneous, in which the radioelements are evenly distributed. Let N 0 E be the primary spectrum number of photons per unit time and unit mass of soil. Figure 4 an example of various order spectra for 40 K. The value of absorption or attenuation coefficients was obtained for the Compton effect from the Klein-Nishina formula.

For the photoelectric effect, they were deduced from the data of Hubbell [ 12 ]. Some typical spectra are shown in Figure 5 for 40 K. The low energy cut-off is determined by photoelectric effect and occurs at higher energy for high-Z media. And for Th in pure water Figure 6. Computed energy spectra for 40 K in a dry C soil, b wet S soil, and c pure water [ 5 ].

Computed energy spectra for Th in pure water [ 5 ]. Similar features are also noticed for the more complex case of U and Th series. There is a similarity in the degraded spectrum, even for two very different gamma sources for example, thorium and potassim Our results are in good agreement with those obtained by G.

Valladas [ 7 ] by the Monte-Carlo method for potassium in siliceous medium. The results are given in Table 2. Calculations are performed here with, as a TL dosimeter, CaSO 4 : Dy, but are readily feasible for any combination of known dosimeters and compositions.

This can be explained by the fact that copper absorbs the lower part of the spectrum of energy for which the difference dose between the dosimeter and the soil is significant. This is due to a smaller contribution of low energies to the 40 K spectrum no low energy lines. An important consequence of the foregoing is that, for the experimenter, copper or a close material is well used when the composition especially moisture of the soil is not well known.

In general, it is difficult to determine the respective contribution of the potassium, uranium and thorium series to the total dose rate. The results obtained with our program under the same conditions regarding the dosimeter, the surrounding environment, the capsules and the sources of the gamma rays are slightly superior to the theoretical results of G. Valladas [ 7 ]. The gamma radiation self-absorption coefficient is of great interest in activation analysis.

Since it is difficult to measure this coefficient, various calculation methods have been developed. Measuring the self-absorption coefficient is not a simple thing. The physicists who have faced this problem, for a long time, have always used methods of statistical or non-statistical computation: Parallel beam methods, Monte-Carlo method and many other methods.

In this chapter, we are presenting a method that we have developed, this which allows us control and calibrate the activation analysis experiments [ 13 ]. This method consists of simulating the interaction processes of gamma rays induced by neutron activation of various samples by using the Monte Carlo method adapted to experimental conditions.

Different disk shaped red beet samples and standards were irradiated with 14 MeV neutrons. The induced gamma activities on the sodium, potassium, chlorine and phosphorus elements have been experimentally measured by means of hyper-pure germanium spectrometer.

The analyzed beet samples and standards have a 23 mm diameter and a 6 mm thickness. The different parameters of the nuclear reactions used cross section, isotopic abundance, etc. The produced nuclear reactions by irradiating the samples standards with 14 MeV neutrons.

To take into account the activity measuring time, relation Eq. By combining relations Eq. The calculation of the paths lengths l 1 and 1 2 consists firstly on generating random numbers by using a programme based on a congruentia 1 method. The path length l 1 is given by [ 17 ]:. We have developed the following theory to calculate the path length 1 2 which is given by:.

To complete this study, we have developed another program based on the EGC method [ 18 ]. This program results in determining the energy loss predominant phenomenon that occurs when gamma rays interact with the absorber. Scheme shows changes in gamma-ray direction in the case of multiple interactions.

The measured N m and calculated N c activities of some different irradiated standards containing Na, K, Cl, and P are shown in Table 4. Data obtained for different irradiated standards with a 14 MeV neutron flux by experimental N m and calculation N c methods.

We notice that the results obtained by the two methods experimental and calculation are in good agreement with each other. In the first part of the chapter, a careful study of the correcting factors linked to the environmental and experimental conditions is performed. In the second part, the calculation method was developed. It is very accurate, rapid, adapted to the experimental conditions, it does not necessitate the use of a very expensive detection chain, and can be used to determine the trace element concentrations in materials.

This technique is a good test for neutron activation analysis experiments. It allows these experiments to be calibrated in cases where it is difficult to achieve standards. Gamma-ray astronomy presents unique opportunities to explore these exotic objects. By exploring the universe at these high energies, scientists can search for new physics, testing theories and performing experiments which are not possible in earth-bound laboratories.

If you could see gamma-rays, these two spinning neutron stars or pulsars would be among the brightest objects in the sky. This computer processed image shows the Crab Nebula pulsar below and right of center and the Geminga pulsar above and left of center in the "light" of gamma-rays.

The Crab nebula, shown also in the visible light image, was created by a supernova that brightened the night sky in A. In , astronomers detected the remnant core of that star; a rapidly rotating, magnetic pulsar flashing every 0. Perhaps the most spectacular discovery in gamma-ray astronomy came in the late s and early s. Detectors on board the Vela satellite series, originally military satellites, began to record bursts of gamma-rays -- not from Earth, but from deep space!

Today, these gamma-ray bursts, which happen at least once a day, are seen to last for fractions of a second to minutes, popping off like cosmic flashbulbs from unexpected directions, flickering, and then fading after briefly dominating the gamma-ray sky. Gamma-ray bursts can release more energy in 10 seconds than the Sun will emit in its entire 10 billion-year lifetime!

So far, it appears that all of the bursts we have observed have come from outside the Milky Way Galaxy. Scientists believe that a gamma-ray burst will occur once every few million years here in the Milky Way, and in fact may occur once every several hundred million years within a few thousand light-years of Earth.

Gamma-ray astronomy presents unique opportunities to explore these exotic objects. By exploring the universe at these high energies, scientists can search for new physics, testing theories and performing experiments that are not possible in Earth-bound laboratories.

If we could see gamma rays, the night sky would look strange and unfamiliar. The familiar view of constantly shining constellations would be replaced by ever-changing bursts of high-energy gamma radiation that last fractions of a second to minutes, popping like cosmic flashbulbs, momentarily dominating the gamma-ray sky and then fading.

NASA's Swift satellite recorded the gamma-ray blast caused by a black hole being born This object is among the most distant objects ever detected. Scientists can use gamma rays to determine the elements on other planets. When struck by cosmic rays, chemical elements in soils and rocks emit uniquely identifiable signatures of energy in the form of gamma rays.

These data can help scientists look for geologically important elements such as hydrogen, magnesium, silicon, oxygen, iron, titanium, sodium, and calcium. The gamma-ray spectrometer on NASA's Mars Odyssey Orbiter detects and maps these signatures, such as this map below showing hydrogen concentrations of Martian surface soils. Gamma rays also stream from stars, supernovas, pulsars, and black hole accretion disks to wash our sky with gamma-ray light. These gamma-ray streams were imaged using NASA's Fermi gamma-ray space telescope to map out the Milky Way galaxy by creating a full degree view of the galaxy from our perspective here on Earth.

The composite image below of the Cas A supernova remnant shows the full spectrum in one image. Gamma rays from Fermi are shown in magenta; x-rays from the Chandra Observatory are blue and green. The visible light data captured by the Hubble space telescope are displayed in yellow.

Infrared data from the Spitzer space telescope are shown in red; and radio data from the Very Large Array are displayed in orange.