Radiation Interactions with Matters PDF

Interactions of radiation with matters Radiation Physics and Instrumentation. II Course Code: AMRR222 Dr. Huda M. Almabadi Introduction Alpha, beta, gamma and X radiations are all ionizing radiation with the ability to produce ions in living tissue. It is most important to understand the way radia...

Interactions of radiation with matters Radiation Physics and Instrumentation. II Course Code: AMRR222 Dr. Huda M. Almabadi Introduction Alpha, beta, gamma and X radiations are all ionizing radiation with the ability to produce ions in living tissue. It is most important to understand the way radiation interacts with matter and transfers its energy. Energy from radiation is transferred to matter in two ways: Ionization and Excitation. .‫ ﻛﻠﮭﺎ إﺷﻌﺎﻋﺎت ﻣﺆﯾﻨﺔ ﻣﻊ اﻟﻘﺪرة ﻋﻠﻰ إﻧﺘﺎج أﯾﻮﻧﺎت ﻓﻲ اﻷﻧﺴﺠﺔ اﻟﺤﯿﺔ‬X‫إﺷﻌﺎﻋﺎت أﻟﻔﺎ وﺑﯿﺘﺎ وﻏﺎﻣﺎ و‬ .‫ﻣﻦ اﻟﻤﮭﻢ ﻟﻠﻐﺎﯾﺔ ﻓﮭﻢ اﻟﻄﺮﯾﻘﺔ اﻟﺘﻲ ﯾﺘﻔﺎﻋﻞ ﺑﮭﺎ اﻹﺷﻌﺎع ﻣﻊ اﻟﻤﺎدة وﯾﻨﻘﻞ طﺎﻗﺘﮭﺎ‬ .‫ اﻟﺘﺄﯾﻦ واﻹﺛﺎرة‬:‫ﯾﺘﻢ ﻧﻘﻞ اﻟﻄﺎﻗﺔ اﻟﻨﺎﺗﺠﺔ ﻋﻦ اﻹﺷﻌﺎع إﻟﻰ اﻟﻤﺎدة ﺑﻄﺮﯾﻘﺘﯿﻦ‬ • Ionization is the process of removal of an electron from an atom leaving the atom with a net positive charge. • In excitation, the energy of incoming radiation raises an outer electron to a higher energy state from which it returns very rapidly (10-8s) to its original state emitting a photon of light in the process. • The mechanisms involved in the transfer of energy are dependent on the nature of the ionizing radiations involved. • Alpha and beta radiations are made up of charged particles and these interact with matter via electrostatic forces. • Gamma and X radiations are a type of electromagnetic wave and interact with matter via the Compton Effect and the Photoelectric Effect described below. .‫• اﻟﺘﺄﯾﻦ ھﻮ ﻋﻤﻠﯿﺔ إزاﻟﺔ اﻹﻟﻜﺘﺮون ﻣﻦ ذرة ﺗﺎرﻛﺔ اﻟﺬرة ﺑﺸﺤﻨﺔ ﻣﻮﺟﺒﺔ ﺻﺎﻓﯿﺔ‬ .‫ ﺛﺎﻧﯿﺔ( إﻟﻰ ﺣﺎﻟﺘﮫ اﻷﺻﻠﯿﺔ اﻟﺘﻲ ﺗﻨﺒﻌﺚ ﻣﻨﮭﺎ ﻓﻮﺗﻮن ﻣﻦ اﻟﻀﻮء ﻓﻲ ھﺬه اﻟﻌﻤﻠﯿﺔ‬8-10) ‫ ﺗﺮﻓﻊ طﺎﻗﺔ اﻹﺷﻌﺎع اﻟﻮارد اﻹﻟﻜﺘﺮون اﻟﺨﺎرﺟﻲ إﻟﻰ ﺣﺎﻟﺔ طﺎﻗﺔ أﻋﻠﻰ ﯾﻌﻮد ﻣﻨﮭﺎ ﺑﺴﺮﻋﺔ ﻛﺒﯿﺮة‬،‫• ﻓﻲ اﻹﺛﺎرة‬ .‫• ﺗﻌﺘﻤﺪ اﻵﻟﯿﺎت اﻟﻤﺸﺎرﻛﺔ ﻓﻲ ﻧﻘﻞ اﻟﻄﺎﻗﺔ ﻋﻠﻰ طﺒﯿﻌﺔ اﻹﺷﻌﺎﻋﺎت اﻟﻤﺆﯾﻨﺔ اﻟﻤﻌﻨﯿﺔ‬ .‫• ﺗﺘﻜﻮن إﺷﻌﺎﻋﺎت أﻟﻔﺎ وﺑﯿﺘﺎ ﻣﻦ ﺟﺰﯾﺌﺎت ﻣﺸﺤﻮﻧﺔ وﺗﺘﻔﺎﻋﻞ ھﺬه ﻣﻊ اﻟﻤﺎدة ﻋﺒﺮ اﻟﻘﻮى اﻟﻜﮭﺮوﺳﺘﺎﺗﯿﻜﯿﺔ‬ .‫ ھﻲ ﻧﻮع ﻣﻦ اﻟﻤﻮﺟﺎت اﻟﻜﮭﺮوﻣﻐﻨﺎطﯿﺴﯿﺔ وﺗﺘﻔﺎﻋﻞ ﻣﻊ اﻟﻤﺎدة ﻋﺒﺮ ﺗﺄﺛﯿﺮ ﻛﻮﻣﺒﺘﻮن واﻟﺘﺄﺛﯿﺮ اﻟﻜﮭﺮوﺿﻮﺋﻲ اﻟﻤﻮﺿﺢ أدﻧﺎه‬X‫• إﺷﻌﺎﻋﺎت ﻏﺎﻣﺎ و‬ Charged Particles • The charged particles After each interaction the interact with matter via electrostatic forces leaving behind an ionized atom or molecule. loses energy and with sufficient interactions will eventually be ‘stopped’. .‫ ﺳﯿﻔﻘﺪ اﻟﻄﺎﻗﺔ وﻣﻊ اﻟﺘﻔﺎﻋﻼت اﻟﻜﺎﻓﯿﺔ ﺳﯿﺘﻢ "إﯾﻘﺎﻓﮭﺎ" ﻓﻲ ﻧﮭﺎﯾﺔ اﻟﻤﻄﺎف‬،‫ ﺑﻌﺪ ﻛﻞ ﺗﻔﺎﻋﻞ‬.‫• ﺗﺘﻔﺎﻋﻞ اﻟﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ ﻣﻊ اﻟﻤﺎدة ﻋﺒﺮ ﻗﻮى ﻛﮭﺮوﺳﺘﺎﺗﯿﻜﯿﺔ ﺗﺘﺮك وراءھﺎ ذرة أو ﺟﺰيء ﻣﺘﺄﯾﻦ‬ Alpha Particles particles are relatively large, doubly charged and travel at about 1/20 of the speed of light. Because of its slow speed and high charge the a particle will ionise virtually every molecule it encounters, consequently they lose their energy in a short distance and have a short range. ‫جسيمات ألفا كبيرة نسبيا ومشحونة بشكل مضاعف وتسافر بسرعة‬ ‫ من سرعة الضوء‬1/20 ‫حوالي‬. ‫ سيؤين الجسيم تقريبا كل جزيء‬،‫بسبب سرعته البطيئة وشحنته العالية‬ ‫ وبالتالي يفقد طاقته على مسافة قصيرة ولديهم مدى قصير‬،‫يواجهه‬. Beta Particles B- and B+ particles are much lighter than alphas, are singly charged and travel at about the speed of light. Consequently they interact less strongly than alphas and will produce an ion pair once every thousand molecules encountered (air or water). When B particles pass close to an atom they can lose some of their energy by a radiative process1 and emit bremsstrahlung radiation ('breaking radiation') in the form of X-rays. Most of the B energy is lost by ionisation and only a small amount is lost to bremsstrahlung. .‫ وهي مشحونة منفردة وتسافر بسرعة الضوء تقريبا‬،‫ و §* أخف بكثير من ألفا‬-B ‫الجسيمات‬ ‫وبالتالي فإنها تتفاعل بقوة أقل من ألفا وستنتج زوجا أيونيا مرة واحدة كل ألف جزيء مواجهتها‬ .(‫)الهواء أو املاء‬ ‫ يمكن أن تفقد بعض طاقتها عن طريق عملية‬،‫عندما تمر الجسيمات البائية بالقرب من الذرة‬ ‫ يتم‬.‫ وتنبعث منها إشعاع بريمستراهلونغ )"اإلشعاع املكسير"( في شكل أشعة سينية‬1‫إشعاعية‬ ‫ عن طريق التأين وال يتم فقدان سوى كمية صغيرة بسبب‬B ‫فقدان معظم الطاقة‬ .bremsstrahlung Introduction ❑ When radiation strikes matter, both the nature of the radiation and the composition of the matter affect what happens. ❑ The process begins with the transfer of radiation energy to the atoms, heating the matter or even modifying its structure. ❑ If all the energy of a bombarding particle or photon is transferred, the radiation will appear to have been stopped within the irradiated matter. .‫ ﺗﺆﺛﺮ طﺒﯿﻌﺔ اﻹﺷﻌﺎع وﺗﻜﻮﯾﻦ اﻟﻤﺎدة ﻋﻠﻰ ﻣﺎ ﯾﺤﺪث‬،‫❑ ﻋﻨﺪﻣﺎ ﯾﻜﻮن اﻹﺷﻌﺎع ﻣﮭﻤﺎ‬ .‫❑ ﺗﺒﺪأ اﻟﻌﻤﻠﯿﺔ ﺑﻨﻘﻞ اﻟﻄﺎﻗﺔ اﻹﺷﻌﺎﻋﯿﺔ إﻟﻰ اﻟﺬرات أو ﺗﺴﺨﯿﻦ اﻟﻤﺎدة أو ﺣﺘﻰ ﺗﻌﺪﯾﻞ ھﯿﻜﻠﮭﺎ‬ .‫ ﻓﺴﯿﺒﺪو أن اﻹﺷﻌﺎع ﻗﺪ ﺗﻮﻗﻒ داﺧﻞ اﻟﻤﺎدة اﻟﻤﺸﻌﻌﺔ‬،‫❑ إذا ﺗﻢ ﻧﻘﻞ ﻛﻞ طﺎﻗﺔ ﺟﺴﯿﻢ أو ﻓﻮﺗﻮن ﻗﺼﻒ‬ ❑A charged particle is surrounded by its Coulomb electric force field that interacts with orbital electrons (collision loss) and the nucleus (radiative loss) of all atoms it encounters as it penetrates into matter. ❑The energy transfer from the charged particle to matter in each individual atomic interaction is generally small, so that the particle undergoes a large number of interactions before its kinetic energy is spent. .‫❑ﯾﺤﯿﻂ ﺑﺎﻟﺠﺴﯿﻢ اﻟﻤﺸﺤﻮن ﺣﻘﻞ اﻟﻘﻮة اﻟﻜﮭﺮﺑﺎﺋﯿﺔ ﻛﻮﻟﻮم اﻟﺬي ﯾﺘﻔﺎﻋﻞ ﻣﻊ اﻹﻟﻜﺘﺮوﻧﺎت اﻟﻤﺪارﯾﺔ )ﻓﻘﺪان اﻻﺻﻄﺪام( واﻟﻨﻮاة )اﻟﺨﺴﺎرة اﻹﺷﻌﺎﻋﯿﺔ( ﻟﺠﻤﯿﻊ اﻟﺬرات اﻟﺘﻲ ﯾﻮاﺟﮭﮭﺎ أﺛﻨﺎء اﺧﺘﺮاق اﻟﻤﺎدة‬ .‫ ﺑﺤﯿﺚ ﯾﺨﻀﻊ اﻟﺠﺴﯿﻢ ﻟﻌﺪد ﻛﺒﯿﺮ ﻣﻦ اﻟﺘﻔﺎﻋﻼت ﻗﺒﻞ إﻧﻔﺎق طﺎﻗﺘﮫ اﻟﺤﺮﻛﯿﺔ‬،‫❑ﻧﻘﻞ اﻟﻄﺎﻗﺔ ﻣﻦ اﻟﺠﺴﯿﻢ اﻟﻤﺸﺤﻮن إﻟﻰ اﻟﻤﺎدة ﻓﻲ ﻛﻞ ﺗﻔﺎﻋﻞ ذري ﻓﺮدي ﺻﻐﯿﺮ ﺑﺸﻜﻞ ﻋﺎم‬ Nonpenetrating Radiation ❑Because of the strong electrical force between a charged particle and the atoms of an absorber, charged particles can be stopped by matter with relative ease. ❑Compared with photons, charged particles transfer a greater amount of energy in a shorter distance and come to rest more rapidly. ❑ For this reason, they are referred to as nonpenetrating radiation. Stopping power is the parameter used to describe the gradual loss of energy of the charged particle, as it penetrates into an absorbing medium. ‫ﻗﻮة اﻟﺘﻮﻗﻒ ھﻲ اﻟﻤﻌﻠﻤﺔ‬ ‫اﻟﻤﺴﺘﺨﺪﻣﺔ ﻟﻮﺻﻒ اﻟﺨﺴﺎرة‬ ‫اﻟﺘﺪرﯾﺠﯿﺔ ﻟﻠﻄﺎﻗﺔ ﻟﻠﺠﺴﯿﻢ‬ ‫ ﻷﻧﮭﺎ ﺗﺨﺘﺮق وﺳﻄﺎ‬،‫اﻟﻤﺸﺤﻮن‬ .‫ﻣﻤﺘﺼﺎ‬ ‫ ﯾﻤﻜﻦ إﯾﻘﺎف اﻟﺠﺴﯿﻤﺎت‬،‫❑ﺑﺴﺒﺐ اﻟﻘﻮة اﻟﻜﮭﺮﺑﺎﺋﯿﺔ اﻟﻘﻮﯾﺔ ﺑﯿﻦ اﻟﺠﺴﯿﻢ اﻟﻤﺸﺤﻮن وذرات اﻟﻤﻤﺘﺺ‬ .‫اﻟﻤﺸﺤﻮﻧﺔ ﺑﻮاﺳﻄﺔ اﻟﻤﺎدة ﺑﺴﮭﻮﻟﺔ ﻧﺴﺒﯿﺔ‬ ‫ ﺗﻨﻘﻞ اﻟﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ ﻛﻤﯿﺔ أﻛﺒﺮ ﻣﻦ اﻟﻄﺎﻗﺔ ﻋﻠﻰ ﻣﺴﺎﻓﺔ أﻗﺼﺮ‬،‫❑ﺑﺎﻟﻤﻘﺎرﻧﺔ ﻣﻊ اﻟﻔﻮﺗﻮﻧﺎت‬ .‫وﺗﺴﺘﺮﯾﺢ ﺑﺴﺮﻋﺔ أﻛﺒﺮ‬ .‫ ﯾﺸﺎر إﻟﯿﮭﺎ ﺑﺎﺳﻢ اﻹﺷﻌﺎع ﻏﯿﺮ اﻟﻤﺨﺘﺮق‬،‫❑ﻟﮭﺬا اﻟﺴﺒﺐ‬ Two classes of stopping power are known: collision stopping power that results from charged particle interaction with orbital electrons of the absorber and radiation stopping power that results from charged particle interaction with nuclei of the absorber. :‫ھﻨﺎك ﻓﺌﺘﺎن ﻣﻌﺮوﻓﺘﺎن ﻣﻦ ﻗﻮة اﻟﺘﻮﻗﻒ‬ ‫ﻗﻮة إﯾﻘﺎف اﻻﺻﻄﺪام اﻟﻨﺎﺗﺠﺔ ﻋﻦ ﺗﻔﺎﻋﻞ اﻟﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ ﻣﻊ اﻹﻟﻜﺘﺮوﻧﺎت اﻟﻤﺪارﯾﺔ ﻟﻠﻤﻤﺘﺺ و‬ .‫ﻗﻮة إﯾﻘﺎف اﻹﺷﻌﺎع اﻟﻨﺎﺗﺠﺔ ﻋﻦ ﺗﻔﺎﻋﻞ اﻟﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ ﻣﻊ ﻧﻮى اﻟﻤﻤﺘﺺ‬ Stopping powers. depend on the properties of the charged particle such as its mass, charge, velocity and energy as well as on the properties of the absorbing medium such as its density and atomic number. .‫إﯾﻘﺎف اﻟﻘﻮى‬ .‫ﯾﻌﺘﻤﺪ ﻋﻠﻰ ﺧﺼﺎﺋﺺ اﻟﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ ﻣﺜﻞ ﻛﺘﻠﺘﮫ وﺷﺤﻨﺘﮫ وﺳﺮﻋﺘﮫ وطﺎﻗﺘﮫ وﻛﺬﻟﻚ ﻋﻠﻰ ﺧﺼﺎﺋﺺ اﻟﻮﺳﻂ اﻟﻤﻤﺘﺺ ﻣﺜﻞ ﻛﺜﺎﻓﺘﮫ وﻋﺪده اﻟﺬري‬ General Aspects of Energy Transfer from Charged Particle to Medium As a charged particle travels through an absorber, it experiences Coulomb interactions with the nuclei and orbital electrons of absorber atoms. These interactions can be divided into two categories. 1. Coulomb force interaction of the charged particle with the external nuclear field of the absorber atom (bremsstrahlung production). 2. Coulomb force interaction of the charged particle with orbital electron of the absorber atom (collision). ‫ ﻓﺈﻧﮫ ﯾﺨﺘﺒﺮ‬،‫ﻋﻨﺪﻣﺎ ﯾﻨﺘﻘﻞ اﻟﺠﺴﯿﻢ اﻟﻤﺸﺤﻮن ﻋﺒﺮ ﻣﻤﺘﺺ‬ ‫ﺗﻔﺎﻋﻼت ﻛﻮﻟﻮم ﻣﻊ اﻟﻨﻮى واﻹﻟﻜﺘﺮوﻧﺎت اﻟﻤﺪارﯾﺔ ﻟﺬرات‬ .‫اﻟﻤﻤﺘﺺ‬ .‫ﯾﻤﻜﻦ ﺗﻘﺴﯿﻢ ھﺬه اﻟﺘﻔﺎﻋﻼت إﻟﻰ ﻓﺌﺘﯿﻦ‬ ‫ ﺗﻔﺎﻋﻞ ﻗﻮة ﻛﻮﻟﻮم ﻟﻠﺠﺴﯿﻢ اﻟﻤﺸﺤﻮن ﻣﻊ اﻟﻤﺠﺎل‬.1 ‫اﻟﻨﻮوي اﻟﺨﺎرﺟﻲ ﻟﺬرة اﻟﻤﻤﺘﺺ‬ .(bremsstrahlung‫)إﻧﺘﺎج‬ ‫ ﺗﻔﺎﻋﻞ ﻗﻮة ﻛﻮﻟﻮم ﻟﻠﺠﺴﯿﻢ اﻟﻤﺸﺤﻮن ﻣﻊ اﻹﻟﻜﺘﺮون‬.3 .(‫اﻟﻤﺪاري ﻟﺬرة اﻟﻤﻤﺘﺺ )اﻟﺘﺼﺎدم‬ Excitation ❑Charged particles (alphas, betas, and positrons) interact with the electrons surrounding the atom’s nucleus by transferring some of their kinetic energy to the electrons. ❑ The energy transferred from a low- energy particle is often only sufficient to bump an electron from an inner to an outer shell of the atom. This process is called excitation. ‫❑ ﺗﺘﻔﺎﻋﻞ اﻟﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ )أﻟﻔﺎس واﻟﺒﯿﺘﺎ واﻟﺒﻮزﯾﺘﺮوﻧﺎت( ﻣﻊ‬ ‫اﻹﻟﻜﺘﺮوﻧﺎت اﻟﻤﺤﯿﻄﺔ ﺑﻨﻮاة اﻟﺬرة ﻋﻦ طﺮﯾﻖ ﻧﻘﻞ ﺑﻌﺾ طﺎﻗﺘﮭﺎ‬ .‫اﻟﺤﺮﻛﯿﺔ إﻟﻰ اﻹﻟﻜﺘﺮوﻧﺎت‬ ‫❑ ﻏﺎﻟﺒﺎ ﻣﺎ ﺗﻜﻮن اﻟﻄﺎﻗﺔ اﻟﻤﻨﻘﻮﻟﺔ ﻣﻦ ﺟﺴﯿﻢ ﻣﻨﺨﻔﺾ اﻟﻄﺎﻗﺔ ﻛﺎﻓﯿﺔ ﻓﻘﻂ‬ .‫ﻟﺼﺪم اﻹﻟﻜﺘﺮون ﻣﻦ ﻏﻼف داﺧﻠﻲ إﻟﻰ ﻏﻼف ﺧﺎرﺟﻲ ﻟﻠﺬرة‬ .‫❑ ﺗﺴﻤﻰ ھﺬه اﻟﻌﻤﻠﯿﺔ اﻹﺛﺎرة‬ ❑ Following excitation, the displaced electron promptly returns to the lowerenergy shell, releasing its recently acquired energy as an X-ray in a process called de-excitation ❑ Because the acquired energy is equal to the difference in the binding energies of the electron shells, and the binding energies of the electron shells are determined by the atomic structure of the element, the X-ray is referred to as a characteristic X-ray. ‫ ﯾﻌﻮد اﻹﻟﻜﺘﺮون اﻟﻤﺸﺮد ﻋﻠﻰ اﻟﻔﻮر إﻟﻰ‬،‫❑ ﺑﻌﺪ اﻹﺛﺎرة‬ ‫ وﯾﻄﻠﻖ طﺎﻗﺘﮫ اﻟﻤﻜﺘﺴﺒﺔ‬،‫اﻟﻐﻼف ﻣﻨﺨﻔﺾ اﻟﻄﺎﻗﺔ‬ ‫ﻣﺆﺧﺮا ﻛﺄﺷﻌﺔ ﺳﯿﻨﯿﺔ ﻓﻲ ﻋﻤﻠﯿﺔ ﺗﺴﻤﻰ إﻟﻐﺎء اﻹﺛﺎرة‬ ‫❑ ﻧﻈﺮا ﻷن اﻟﻄﺎﻗﺔ اﻟﻤﻜﺘﺴﺒﺔ ﺗﺴﺎوي اﻟﻔﺮق ﻓﻲ‬ ‫ وﯾﺘﻢ ﺗﺤﺪﯾﺪ‬،‫اﻟﻄﺎﻗﺎت اﻟﻤﻠﺰﻣﺔ ﻷﺻﺪاف اﻹﻟﻜﺘﺮون‬ ‫اﻟﻄﺎﻗﺎت اﻟﻤﻠﺰﻣﺔ ﻟﻘﺬاﺋﻒ اﻹﻟﻜﺘﺮوﻧﯿﺔ ﻣﻦ ﺧﻼل‬ ‫ ﯾﺸﺎر إﻟﻰ اﻷﺷﻌﺔ اﻟﺴﯿﻨﯿﺔ‬،‫اﻟﺘﺮﻛﯿﺐ اﻟﺬري ﻟﻠﻌﻨﺼﺮ‬ .‫ﻋﻠﻰ أﻧﮭﺎ أﺷﻌﺔ ﺳﯿﻨﯿﺔ ﻣﻤﯿﺰة‬ Ionization ❑ Charged particles of sufficient energy may also transfer enough energy to an electron (generally one in an outer shell) to eject the electron from the atom. ❑ This process is called ionization. ❑ The hole in the outer shell is rapidly filled with an unbound electron. ❑ If an inner-shell electron is ionized (a much less frequent occurrence), an outer-shell electron will “drop” into the inner-shell hole and a characteristic X-ray will be emitted. .‫❑ ﻗﺪ ﺗﻨﻘﻞ اﻟﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ ذات اﻟﻄﺎﻗﺔ اﻟﻜﺎﻓﯿﺔ أﯾﻀﺎ طﺎﻗﺔ ﻛﺎﻓﯿﺔ إﻟﻰ إﻟﻜﺘﺮون )ﻋﺎدة واﺣﺪ ﻓﻲ ﻏﻼف ﺧﺎرﺟﻲ( ﻹﺧﺮاج اﻹﻟﻜﺘﺮون ﻣﻦ اﻟﺬرة‬ .‫❑ ﺗﺴﻤﻰ ھﺬه اﻟﻌﻤﻠﯿﺔ اﻟﺘﺄﯾﻦ‬ .‫❑ ﯾﺘﻢ ﻣﻞء اﻟﺜﻘﺐ ﻓﻲ اﻟﻐﻼف اﻟﺨﺎرﺟﻲ ﺑﺴﺮﻋﺔ ﺑﺈﻟﻜﺘﺮون ﻏﯿﺮ ﻣﻘﯿﺪ‬ ‫ ﻓﺈن إﻟﻜﺘﺮون اﻟﻐﻼف اﻟﺨﺎرﺟﻲ "ﺳﯿﺴﻘﻂ" ﻓﻲ ﺛﻘﺐ اﻟﻐﻼف اﻟﺪاﺧﻠﻲ و‬،(‫❑ إذا ﺗﻢ ﺗﺄﯾﻦ إﻟﻜﺘﺮون اﻟﻐﻼف اﻟﺪاﺧﻠﻲ )ﺣﺪوث أﻗﻞ ﺗﻮاﺗﺮا ﺑﻜﺜﯿﺮ‬ .‫❑ ﺳﯿﺘﻢ إﺻﺪار أﺷﻌﺔ ﺳﯿﻨﯿﺔ ﻣﻤﯿﺰة‬ Annihilation ❑ This interaction involves a positron (positive electron) and an electron (negatron). ❑ After a positron has transferred most of its kinetic energy by ionization and excitation, it combines with a free or loosely bound negative electron. ❑ Remember that electrons and positrons have equal mass but opposite electric charge. ❑ This interaction is explosive, as the combined mass of the two particles is instantly converted to energy in the form of two oppositely directed photons, each of energy 511keV. • Positron & electron disappear • Replaced by 2 oppositely directed annihilation quanta (photons) • Each has energy = 0.511 MeV ،‫❑ بعد أن ينقل البوزيترون معظم طاقته الحركية عن طريق التأين واإلثارة‬ .‫فإنه يتحد مع إلكترون سالب حر أو مرتبط بشكل فضفاض‬ ‫❑ تذكر أن اإللكترونات والبوزيترونات لها كتلة متساوية ولكن معاكسة‬ .‫للشحنة الكهربائية‬ ‫ حيث يتم تحويل الكتلة المركبة للجسيمين على‬،‫❑ هذا التفاعل متفجر‬ ‫ كل منهما طاقة‬،‫الفور إلى طاقة في شكل فوتونين موجهين عكسيا‬ .511keV .‫❑ يشار إلى هذا باسم رد فعل اإلبادة‬ ❑ This is referred to as an annihilation reaction . • During annihilation .(‫❑ يتضمن هذا التفاعل بوزيترون )إلكترون موجب( وإلكترون )نيغاترون‬ .‫ﺎدة‬F‫• أﺛﻨﺎء اﻹ‬ ‫ﺘﺮون‬Q‫ﺘﺮون واﻹﻟ‬S‫ﺨﺘﻔﻲ اﻟﺒﻮز‬Z • ‫ﺎدة‬F‫ﺎﺛﻨﻴﻦ ﻣﻦ ^ﻤ\ﺎت اﻹ‬F ‫ﺪاﻟﻪ‬de‫• ﺗﻢ اﺳ‬ (‫اﻟﻤﻮﺟﻬﺔ ﻋﻜﺴ\ﺎ )اﻟﻔﻮﺗﻮﻧﺎت‬ Positron kinetic energy (EK) loss in absorber medium by Coulomb interactions: MeV 0.511 = ‫ﻪ ﻃﺎﻗﺔ‬Z‫• ^ﻞ ﻣﻨﻬﺎ ﻟﺪ‬ Collisional loss when interaction is with orbital electron Radiation loss (bremsstrahlung) when interaction is with the nucleus Final collision (after all EK lost) with orbital electron (due to Coulomb attraction) called (positron annihilation) ❑ Annihilation Reaction . is another example of the interchangeability of mass and energy described in Einstein’s equation: energy equals mass times the speed of light squared, or E=mc2. . .‫❑ رد ﻓﻌﻞ اﻹﺑﺎدة‬ :‫❑ ھﻮ ﻣﺜﺎل آﺧﺮ ﻋﻠﻰ ﻗﺎﺑﻠﯿﺔ ﺗﺒﺎدل اﻟﻜﺘﻠﺔ واﻟﻄﺎﻗﺔ اﻟﻤﻮﺻﻮﻓﺔ ﻓﻲ ﻣﻌﺎدﻟﺔ أﯾﻨﺸﺘﺎﯾﻦ‬ .mc2=E ‫ أو‬،‫❑ اﻟﻄﺎﻗﺔ ﺗﺴﺎوي اﻟﻜﺘﻠﺔ أﺿﻌﺎف ﺳﺮﻋﺔ اﻟﻀﻮء اﻟﻤﺮﺑﻊ‬ :‫( ﻓﻲ وﺳﻂ اﻟﻤﻤﺘﺺ ﻋﻦ طﺮﯾﻖ ﺗﻔﺎﻋﻼت ﻛﻮﻟﻮم‬EK) ‫ﻓﻘﺪان اﻟﻄﺎﻗﺔ اﻟﺤﺮﻛﯿﺔ اﻟﺒﻮزﯾﺘﺮوﻧﯿﺔ‬ ‫اﻟﺨﺴﺎرة اﻟﺘﺼﺎدﻣﯿﺔ ﻋﻨﺪﻣﺎ ﯾﻜﻮن اﻟﺘﻔﺎﻋﻞ ﻣﻊ اﻹﻟﻜﺘﺮون اﻟﻤﺪاري‬ ‫( ﻋﻨﺪﻣﺎ ﯾﻜﻮن اﻟﺘﻔﺎﻋﻞ ﻣﻊ اﻟﻨﻮاة‬bremsstrahlung) ‫ﻓﻘﺪان اﻹﺷﻌﺎع‬ ‫( ﻣﻊ اﻹﻟﻜﺘﺮون اﻟﻤﺪاري )ﺑﺴﺒﺐ ﺟﺎذﺑﯿﺔ ﻛﻮﻟﻮم( ﯾﺴﻤﻰ )إﺑﺎدة‬EK ‫اﻻﺻﻄﺪام اﻟﻨﮭﺎﺋﻲ )ﺑﻌﺪ ﻛﻞ ﺷﻲء ﻓﻘﺪت‬ (‫اﻟﺒﻮزﯾﺘﺮون‬ Bremsstrahlung ❑Small charged particles such as electrons or positrons may be deflected by nuclei as they pass through matter, which may be attributed to the positive charge of the atomic nuclei. ❑ This type of interaction generates X-radiation known as bremsstrahlung which in German means “braking radiation.” ❑ Translated from German as 'breaking radiation' ❑ Light charged particles (β− & β+) slowed down by interactions with other charged particles in matter (e.g. atomic nuclei) ❑ Kinetic energy loss converted to electromagnetic radiation. ❑ Bremsstrahlung energy spectrum Non-discrete (i.e. continuous) Ranges: zero - kinetic energy of initial charged particle. ‫❑ﻗﺪ ﺗﻨﺤﺮف اﻟﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ اﻟﺼﻐﯿﺮة ﻣﺜﻞ اﻹﻟﻜﺘﺮوﻧﺎت أو‬ ‫ واﻟﺘﻲ ﻗﺪ‬،‫اﻟﺒﻮزﯾﺘﺮوﻧﺎت ﺑﻮاﺳﻄﺔ اﻟﻨﻮى أﺛﻨﺎء ﻣﺮورھﺎ ﻋﺒﺮ اﻟﻤﺎدة‬ .‫ﺗﻌﺰى إﻟﻰ اﻟﺸﺤﻨﺔ اﻟﻤﻮﺟﺒﺔ ﻟﻠﻨﻮى اﻟﺬرﯾﺔ‬ ‫ اﻟﻤﻌﺮوف ﺑﺎﺳﻢ‬X ‫❑ﯾﻮﻟﺪ ھﺬا اﻟﻨﻮع ﻣﻦ اﻟﺘﻔﺎﻋﻞ إﺷﻌﺎع‬ ."‫ واﻟﺬي ﯾﻌﻨﻲ ﺑﺎﻟﻠﻐﺔ اﻷﻟﻤﺎﻧﯿﺔ "إﺷﻌﺎع اﻟﻜﺒﺢ‬bremsstrahlung "‫ﺗﺮﺟﻤﺖ ﻣﻦ اﻷﻟﻤﺎﻧﯿﺔ ﺑﺎﺳﻢ "اﻹﺷﻌﺎع اﻟﻤﻜﺴﯿﺮ‬ ‫( ﺑﺴﺒﺐ اﻟﺘﻔﺎﻋﻼت ﻣﻊ اﻟﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ اﻷﺧﺮى ﻓﻲ اﻟﻤﺎدة‬+β & −β) ‫ﺗﺒﺎطﺄت اﻟﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ ﺑﺎﻟﻀﻮء‬ (‫)ﻋﻠﻰ ﺳﺒﯿﻞ اﻟﻤﺜﺎل اﻟﻨﻮى اﻟﺬرﯾﺔ‬ .‫ﺗﻢ ﺗﺤﻮﯾﻞ ﻓﻘﺪان اﻟﻄﺎﻗﺔ اﻟﺤﺮﻛﯿﺔ إﻟﻰ إﺷﻌﺎع ﻛﮭﺮوﻣﻐﻨﺎطﯿﺴﻲ‬ Bremsstrahlung ‫طﯿﻒ طﺎﻗﺔ‬ ((‫ﻏﯿﺮ ﻣﻨﻔﺼﻞ )أي ﻣﺴﺘﻤﺮ‬ .‫ اﻟﻄﺎﻗﺔ اﻟﺤﺮﻛﯿﺔ ﻟﻠﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ اﻷوﻟﯿﺔ‬- ‫ ﺻﻔﺮ‬:‫اﻟﻨﻄﺎﻗﺎت‬ ❑ ❑ ❑ ❑ ❑ ❑ ❑ Range RANGE The initial energy of an a or 3 particle is nite. We nd that in traversing matter it continuously loses energy producing ionisations and is nally stopped, thus charged particle radiations have a nite range. The range of an a or B particle is dependent on the number of atoms the particle encounters when it travels through a medium. The best way to estimate the number of atoms in a medium is using the concept of mass per unit area. If the density of a material is given by p gcm-3, then the mass per unit area of a sheet of thickness t is pt gcm-2 fi fi fi fi fi If we express the range in this form then we nd that the formula for the range of a and B particles can be given in terms of the energies of the particles only. Symbolically: ‫ الطاقة األولية لجسيم‬a ‫ نجد أنه عند عبور املادة‬.‫ محدودة‬3 ‫أو‬ ‫ وبالتالي‬،‫يفقد باستمرار الطاقة املنتجة للتأين ويتم إيقافه أخيرا‬ ‫فإن إشعاعات الجسيمات املشحونة لها نطاق محدود‬. ‫ يعتمد نطاق الجسيم‬a ‫ أو‬B ‫على عدد الذرات التي يواجهها‬ ‫ أفضل طريقة لتقدير عدد‬.‫الجسيم عندما يسافر عبر وسيط‬ .‫الذرات في الوسط هي استخدام مفهوم الكتلة لكل وحدة مساحة‬ ‫ إذا تم إعطاء كثافة املادة بواسطة‬p gcm-3، ‫فإن الكتلة لكل‬ ‫ وحدة مساحة من ورقة سمك‬t ‫ هي‬pt gcm-2 ‫ فسنجد أنه يمكن إعطاء صيغة‬،‫إذا عبرنا عن النطاق بهذا الشكل‬ ‫ نطاق الجسيمات‬a ‫و‬B ‫ رمزيا‬.‫من حيث طاقات الجسيمات فقط‬: .‫❑ اﻟﻨﻄﺎق ھﻮ اﻟﻤﺴﺎﻓﺔ اﻟﺘﻲ ﯾﻨﺘﻘﻞ ﺑﮭﺎ اﻹﺷﻌﺎع ﻋﺒﺮ اﻟﻤﻤﺘﺺ‬ ،(‫ وﻟﮭﺎ ﺷﺤﻨﺔ أﻗﻞ )ﻣﺜﻞ ﺟﺴﯿﻤﺎت ﺑﯿﺘﺎ‬،‫❑ اﻟﺠﺴﯿﻤﺎت اﻷﺧﻒ وزﻧﺎ‬ ‫ وﻟﮭﺎ‬،‫أو ﻟﺪﯾﮭﺎ طﺎﻗﺔ أﻛﺒﺮ ﺗﻨﺘﻘﻞ أﺑﻌﺪ ﻣﻦ اﻟﺠﺴﯿﻤﺎت اﻷﺛﻘﻞ‬/‫و‬ .‫أو ﻟﺪﯾﮭﺎ طﺎﻗﺔ أﻗﻞ‬/‫ و‬،(‫ﺷﺤﻨﺔ أﻛﺒﺮ )ﻣﺜﻞ ﺟﺴﯿﻤﺎت أﻟﻔﺎ‬ ❑ The range is the distance radiation travels through an absorber. ❑ Particles that are lighter, have less charge (such as beta particles), and/ or have greater energy travel farther than particles that are heavier, have a greater charge (such as alpha particles), and/or have less energy. Summary Charge particle kinetic energy (EK) loss in absorber medium by Coulomb interactions: Collisional loss when interaction is with orbital electron (Exaction and Ionization ) Radiation loss (bremsstrahlung) when interaction is with the nucleus Final collision (after all EK lost) with orbital electron (due to Coulomb attraction) called (positron annihilation) :‫( ﻓﻲ وﺳﻂ اﻟﻤﻤﺘﺺ ﺑﻮاﺳﻄﺔ ﺗﻔﺎﻋﻼت ﻛﻮﻟﻮم‬EK) ‫ﻓﻘﺪان اﻟﻄﺎﻗﺔ اﻟﺤﺮﻛﯿﺔ ﻟﻠﺠﺴﯿﻤﺎت اﻟﻤﺸﺤﻮﻧﺔ‬ (‫اﻟﺨﺴﺎرة اﻟﺘﺼﺎدﻣﯿﺔ ﻋﻨﺪﻣﺎ ﯾﻜﻮن اﻟﺘﻔﺎﻋﻞ ﻣﻊ اﻹﻟﻜﺘﺮون اﻟﻤﺪاري )اﻟﺘﻤﺪﯾﺪ واﻟﺘﺄﯾﻦ‬ ‫( ﻋﻨﺪﻣﺎ ﯾﻜﻮن اﻟﺘﻔﺎﻋﻞ ﻣﻊ اﻟﻨﻮاة‬bremsstrahlung) ‫ﻓﻘﺪان اﻹﺷﻌﺎع‬ (‫( ﻣﻊ اﻹﻟﻜﺘﺮون اﻟﻤﺪاري )ﺑﺴﺒﺐ ﺟﺎذﺑﯿﺔ ﻛﻮﻟﻮم( ﯾﺴﻤﻰ )إﺑﺎدة اﻟﺒﻮزﯾﺘﺮون‬EK ‫اﻻﺻﻄﺪام اﻟﻨﮭﺎﺋﻲ )ﺑﻌﺪ ﻛﻞ ﺷﻲء ﻓﻘﺪت‬