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Sources of errors in radioactive decay analogue experiment

Sources of errors in radioactive decay analogue experiment

Caution: This experiment should be done under the supervision of a science teacher at a High School Physics laboratory.

Handle the radioactive materials with tweezers, tongs, or gloves. You should not consume any food, drink or make-up during this experiment. You should wash your hands with soap and water after doing the experiment. Space Settlement Relevance To distinguish between alpha, beta, and gamma radiation by comparing the ability of these radioactive sources to penetrate different materials Concepts Alpha, beta or gamma radiation is released when changes take place in the nucleus of an atom.

Alpha particle is a helium nucleus composed of two neutrons and two protons. Beta particle is a high energy electron, and gamma ray is a high-energy photon.

The mechanics of radiation absorption vary with the type of radioactive source, the initial energy of the radioactive particle or ray, and type of absorbing material.

Using M & M's to model Radioactive Decay Rates

There is a close relationship between the initial energy of the alpha particle and its penetration of a particular absorbing material. However, because the alpha particle is a helium nucleus with a relative heaviness, an alpha particle is quickly absorbed.

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Since beta particles have the same mass as the electrons in the absorber, the beta particle is deflected in collisions with other electrons; it does not follow a well-defined path through the material.

For beta particles, penetration is inversely proportional to the density of the absorbing material. While charged particles gradually lose their energy in many collisions, photons lose all their energy in a single collision. Therefore, absorption of gamma rays is defined in terms of the absorption photons in a beam by a certain percentage.

Thus, the intensity of a gamma ray is reduced exponentially as it penetrates a given material. In this experiment, you will measure and compare the penetrating ability of alpha, beta, gamma radiation through cardboard, aluminum, and lead absorbers.In this laboratory you will determine radioactive the half-life of Bariumm, a metastable state of Barium.

You will measure the activity of the Bam as a function of time by detecting the gamma rays with a Geiger-Mueller GM tube.

Half-Life Coins

From the data you will determine the decay constant and the half-life of the sample. The number of radioactive decays must be measured over a series of short time intervals. The number of particles detected with a GM tube is a fraction of the total number of decays since the radiation is emitted from the source in all directions and the detector only intercepts a small portion of these directions.

Detectors cannot accurately count particles that enter nearly simultaneously. The detected number of particles per unit time interval is then proportional to the activity of the sample and has the same decay constant.

Background radiation is a common source of error when measuring radioactive decay. This error can lead to inaccuracies in the determination of the half-life. The background radiation comes from many naturally occurring sources and from cosmic rays entering our upper atmosphere from space.

Background radiation is a constant addition to the activity from the sample. It does not exponentially decay and cannot be fitted with an exponential function. To account for the background we must fit our results with an exponential function plus a constant offset. The source of the Bam is an isotope generator consisting of an exempt quantity of Cs An exempt quantity is a quantity small enough so that no license is required to purchase the material. It is deemed to be a minimal health hazard.

The Cesium atoms are in molecules of a Cesium salt, CsCl, that have been adsorbed by small beads of a resin material.

As the Cs nuclei decay to the Bam nuclei, the Bam atoms remain adsorbed on the surface of the resin. But because Barium has a different chemistry than Cesium, it is more loosely bound to the resin and can be de-adsorbed with a weakly acidic salt solution containing HCI and NaCI.

Small amounts of the short lived Bam isotope can be extracted from the resin by this eluting solution. The Bam is said to be selectively "milked" from the generator that is sometimes called a "cow. Equilibrium is again reached in less than an hour.Whereas SPECT data are commonly interpreted qualitatively in a clinical setting, the ability to accurately quantify measurements will increase the utility of the SPECT data for laboratory measurements involving small animals.

In this work, we assess the effect of photon attenuation, scatter and partial volume errors on the quantitative accuracy of small animal SPECT measurements, first with Monte Carlo simulation and then confirmed with experimental measurements.

sources of errors in radioactive decay analogue experiment

We simulated the imaging of a radioactive source within a cylinder of water, and reconstructed the projection data using iterative reconstruction algorithms. The size of the source and the size of the surrounding cylinder were varied to evaluate the effects of photon attenuation and scatter on quantitative accuracy. We varied the size of the source to evaluate partial volume errors, which we found to be a strong function of the size of the volume of interest and the spatial resolution.

The simulation results were compared with and found to agree with experimental measurements. The inclusion of attenuation correction in the reconstruction algorithm improved quantitative accuracy. We also found that an improvement of the spatial resolution through the use of resolution recovery techniques i. Small animal SPECT imaging has many applications for the in vivo assessment of a physiological function in basic biological research and drug development Booij et alBennink et alMeikle et alZhou et al However, the scientific utility of these data is increased when they are analyzed and recorded quantitatively.

In fact, various approaches have been developed to analyze nuclear medicine data in a quantitative manner. For example, the regional uptake of radiopharmaceuticals such as 99m Tc-sestamibi is often compared with a database to quantify the severity of myocardial perfusion defects in patients with coronary artery disease. In this paper, radionuclide quantification is used to describe absolute physical quantification, the measurement of the absolute concentration of a radiotracer within a volume of interest VOI.

Quantitative measurement of the radioactivity uptake using SPECT is hampered by a number of physical perturbations, namely photon attenuation, photon scatter and partial volume errors. Photon attenuation is caused by interactions between the emitted photons and the surrounding tissues, which reduce the number of photons incident upon the detector and result in a reduction in the measured radioactivity.

The magnitude of this effect is related to the energy of the emitted photon, and the amount and type of overlying tissue. Likewise, scatter results from the interactions of emitted photons with the surrounding tissue, resulting in a change in the photon's energy and trajectory. This changes the apparent source of the photon and affects the image contrast, although some scattered photons can be rejected by energy discrimination.

These phenomena occur in all forms of radionuclide imaging, but have different magnitudes in small animal imaging in comparison to clinical imaging.

sources of errors in radioactive decay analogue experiment

The objective of this work is to estimate the magnitude of the above-discussed perturbations in small animal SPECT, errors that may be expected in the quantification of radiotracers. We also show that iterative image reconstruction algorithms can be used to improve quantitative accuracy by compensating for these errors.

In order to assess the quantitative accuracy of small animal SPECT imaging, we performed Monte Carlo simulations and experimental measurements to estimate the effect of various perturbations on the quantitative accuracy of SPECT imaging. We used Monte Carlo simulations to generate projection data for a spherical source of radioactivity to assess the effects of photon attenuation, scatter and partial volume errors. The data were then reconstructed using iterative reconstruction algorithms designed to compensate for various effects, including photon attenuation correction and collimator response modeling.

The concentration of radioactivity in the VOI was then measured. The SPECT imaging component of this system is based on a gamma camera using a segmented NaI Tl scintillator coupled to position-sensitive photomultiplier tubes. For this study, imaging was performed with a pinhole collimator having a focal length of 9 cm and pinhole apertures of 1 mm or 2 mm diameter. The spatial resolution was assessed for planar imaging using a line source filled with technetiumm placed 4 cm from the pinhole and was determined to be 1.

However, the methods and results of this study are generally applicable to SPECT systems with multiple heads. Monte Carlo methods are powerful tools for simulating a variety of physical processes and are often used to model radionuclide imaging systems. Monte Carlo simulations are particularly useful for studying quantitative measurements in SPECT because it becomes possible to simulate the imaging of a well-defined radionuclide source while modeling complex physical phenomena such as photon scatter.

The simulations in this work modeled physical effects including Compton scatter, coherent Rayleigh scatter and photoelectric absorption, and were performed using GATE Geant4 Application for Tomographic Emissionwhich is based on the Geant4 Monte Carlo package Agostinelli et alSantin et alStrul et alAllison et al The simulation geometry assumed a simplified model of the X-SPECT scanner figure 1 having a simplified pinhole collimator created by simulating a round sheet of tungsten with a keel edge pinhole aperture in the center.

The radius of rotation was 4 cm for all simulations. The simulated detector energy resolution and energy windows are shown in table 1. The energy resolution was based on published information about the detector McElroy et aland the energy windows were based on the settings that we use experimentally.A radioactive source is a known quantity of a radionuclide which emits ionizing radiation ; typically one or more of the radiation types gamma raysalpha particlesbeta particlesand neutron radiation.

Sources can be used for irradiationwhere the radiation performs a significant ionising function on a target material, or as a radiation metrology source, which is used for the calibration of radiometric process and radiation protection instrumentation. They are also used for industrial process measurements, such as thickness gauging in the paper and steel industries. Sources can be sealed in a container highly penetrating radiation or deposited on a surface weakly penetrating radiationor they can be in a fluid.

As an irradiation source they are used in medicine for radiation therapy and in industry for such as industrial radiographyfood irradiationsterilizationvermin disinfestation, and irradiation crosslinking of PVC. Radionuclides are chosen according to the type and character of the radiation they emit, intensity of emission, and the half-life of their decay. Common source radionuclides include cobalt[1] iridium[2] and strontium An irradiation source typically lasts for between 5 and 15 years before its activity drops below useful levels.

Many radioactive sources are sealed, meaning they are permanently either completely contained in a capsule or firmly bonded solid to a surface. Capsules are usually made of stainless steeltitaniumplatinum or another inert metal. Sealed sources are categorised by the IAEA according to their activity in relation to a minimum dangerous source where a dangerous source is one that could cause significant injury to humans.

Note that sources with sufficiently low radioactive output such as those used in Smoke detectors as to not cause harm to humans are not categorised.

Calibration sources are used primarily for the calibration of radiometric instrumentation, which is used on process monitoring or in radiological protection. Capsule sources, where the radiation effectively emits from a point, are used for beta, gamma and X-ray instrument calibration.

High level sources are normally used in a calibration cell: a room with thick walls to protect the operator and the provision of remote operation of the source exposure. The plate source is in common use for the calibration of radioactive contamination instruments. Such measurements are typically counts per unit time received by the detector, such as counts per minute or counts per second.

Unlike the capsule source, the plate source emitting material must be on the surface to prevent attenuation by a container or self-shielding due to the material itself. This is particularly important with alpha particles which are easily stopped by a small mass. The Bragg curve shows the attenuation effect in free air. Unsealed sources are sources that are not in a permanently sealed container, and are used extensively for medical purposes. Unsealed sources are also used in industry in a similar manner for leak detection as a Radioactive tracer.

Disposal of expired radioactive sources presents similar challenges to the disposal of other nuclear wastealthough to a lesser degree. Spent low level sources will sometimes be sufficiently inactive that they are suitable for disposal via normal waste disposal methods — usually landfill.

Other disposal methods are similar to those for higher-level radioactive waste, using various depths of borehole depending on the activity of the waste. From Wikipedia, the free encyclopedia.

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General Physics Experiment 13

Retrieved 22 March International Atomic Energy Agency. Vienna: International Atomic Energy Agency. Radiation physics and health. Earth's energy budget Electromagnetic radiation Synchrotron radiation Thermal radiation Black-body radiation Particle radiation Gravitational Radiation Cosmic background radiation Cherenkov radiation Askaryan radiation Bremsstrahlung Unruh radiation Dark radiation. Radiation syndrome acute chronic Health physics Dosimetry Electromagnetic radiation and health Laser safety Lasers and aviation safety Medical radiography Mobile phone radiation and health Radiation protection Radiation therapy Radioactivity in the life sciences Radioactive contamination Radiobiology Biological dose units and quantities Wireless electronic devices and health Radiation Heat-transfer.Using sealed sources, you can demonstrate most of the properties of alpha, beta and gamma radiation.

The experiments in this collection allow students to see their ranges, penetrating powers and, in the case of beta radiation, how it is deflected in a magnetic field. They can link these properties to the nature of each type of radiation, and start to form a picture of why these types of radiation behave in the way they do. The first experiment introduces the idea that radioactive atoms give out three distinct types of radiation, known as alpha, beta and gamma.

The next four experiments allow you to investigate their properties in more detail. Each of these experiments is built around one type of radiation and all its properties.

However, you could equally choose to reshuffle these experiments and focus on each property in turn — i. Practical Activity for Measuring the half-life of a radioactive isotope brings some of the wonder of radioactive decay into the school laboratory. Students can witness one element turning into another and hear or see the decrease in the radiation it gives out as it transmutes.

This demonstration uses a protactinium generator to show the exponential decay of protactinium, a grand-daughter of uranium.

sources of errors in radioactive decay analogue experiment

It has a half-life of just over a minute, which gives students the chance to measure and analyze the decay in a single lesson. Managing radioactive materials in schools. To limit the risk of radioactive liquids being spilt, there should be special instructions in the local rules for handling and preparing this source.

It is now possible to purchase the chemicals already made up in a sealed bottle. Tel: However, you can make your own if you prefer. These quantities make a total volume of 20 cm3. You can scale them up if you have a larger bottle. A '30 ml' bottle has a capacity of about 35 ml, so there is still room to shake the solution when the total volume is 30 ml.

Once you have made the protactinium generator, you can store it with other radioactive materials, taking care to follow your school code of practice and local rules: see the Managing radioactive materials in schools guidance note:.

A polypropylene bottle is preferable to polythene because it is somewhat more resistant to attack by the acid and ketone. Nevertheless, polythene bottles can be used, provided no attempt is made to store the liquid in them for more than a few weeks.

The organic layer which separates out contains the protactinium This decays with a half-life of about 70 seconds. This uses fabric gas mantles designed for camping lights. Each mantle contains a small quantity of radioactive thorium. More details are available on the Cooknell Electronics website:. Table of count rate: Get the students to make a table of count rate against time, and correct it for background count. The first second reading should be allocated to a time of zero. Plot a graph: Get the students to plot a graph of count rate against time.

They should draw a smooth curve through the points. How Science Works extension This experiment provides an opportunity to assess the accuracy of the measured half-life value and how the random nature of decay affects the answer.Many nuclear species are unstable and make transitions to other species by absorbing or emitting particles and photons of high energy, gamma rays.

Nuclear detectors such as the GM tube give a measure of the number of particles emitted per second by a piece of radioactive matter. Neutrons that have low kinetic energies are readily absorbed by many nuclei thus transmuting them to an isotope with a mass number that is one unit larger.

Neutrons are provided by a plutonium beryllium source that is located in a cylindrical tank filled with water. Energetic neutrons are slowed by collisions with the hydrogen nuclei in the water.

Indium nuclei mass number ofatomic number 49 each absorb a neutron to become radioactive indium mass number While you are waiting for the 60 minutes of data collection to be completed, proceed to part B or C. User Tools Login. Site Tools. Table of Contents General Physics Experiment Determination of the Half-life of Indium To test the exponential law of decay of a radioactive source, and to measure the half-lives and the decay constants of neutron activated indium.

Plug the GM tube into the signal interface Channel 1. This is VERY important, make sure not to set the sample rate to 1 hz or data studio will take 1 readings of data per second. We want to take one reading every minute. With no source nearby, take a background count for 1 minute and record this as the back ground count, BC. Set the stop time to 60 minutes and ask the lab instructor to bring your indium sample and place it on the tray in the top slot.

Click Start to begin collecting data, once you begin counting do not disturb the apparatus. When the hour of counting is completed, copy and Paste the data into Graphical Analysis. Add a new calculated column defining the column to be the counts minus the background count, title this column as: count - BC.

Add a new calculated column column for error bars, defined as the square root of the counts minus the background column. Perform a half life fit following Eq.

Radioactive source

Perform a natural exponential curve fit, following Eq 2. In the box next to A, enter the value where you estimate the data crosses the y axis. In the box next to B, enter 5e Begin with pennies and place them in a bucket.

Compare the measured half-life with the theoretical value by finding the percent difference.

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Combine Equation 3 and 4 to show how you can get Equation 2. Begin with dice, roll all of them and remove all that come up with a single dot. Remove the ones that come up with a single dot and again record the number remaining.

After all the groups have written their data on the board, add the all the first trial data together, add all the second trial data together, etc.Key concepts Energy Radioactivity Exponential decay Odds. Introduction One way of creating energy is with nuclear reactors. These plants are generally safe, but occasionally there are accidents in which dangerous radioactive material escapes.

You might have read about nuclear disasters, such as those at Chernobyl, Three Mile Island and Fukushima, in the news or in a history lesson. Disasters like these can take years or even decades to clean up, and make it unsafe for humans to live nearby for even longer.

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Why does the contamination last so long? In this perfectly safe! Background All matter is made of atoms.

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Certain types of atoms are "radioactive," meaning that they will eventually decay, or "break down" into a different type of atom. When this breakdown process occurs, the atom emits radiation. Some types of radiation surround us every day and are perfectly safe, such as radio waves and visible light; other types, such as x-rays and gamma rays, can be dangerous to humans.

The types of atoms used as fuel in nuclear reactors can produce such dangerous radiation, which is why it is very important to keep the fuels safely contained. Thus it can be very dangerous when there is an explosion—or in the case of Fukushima, an earthquake—at a nuclear plant, and some of the radioactive atoms escape into the surrounding air, water or soil, causing contamination. The decay of radioactive materials is a random process, kind of like flipping a coin or rolling a die.

At any given moment in time, there is a chance that an atom will decay, but there is also a chance it will remain the same. The rate at which radioactive materials decay is measured with something called the "half-life.

The half-lives of different atoms can vary widely—some are less than a second, and others are thousands or even millions of years. In this activity, you will simulate radioactive decay by flipping coins. Coins that land tails-up "decay," and coins that land heads-up remain the same.

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This will allow you to learn more about the process of radioactive decay—without using any radioactive materials! Observations and results You should have seen that the number of coins in the bag decreases by roughly, but not exactly, half each time you count heads and tails.

General Physics Experiment 13

For example, even if you always start out with coins, that does not mean you will have exactly 50 heads and 50 tails the first time you shake the bag. You might get 56 heads and 44 or tails, or 49 heads and 51 tails. You will lose about half the coins each time, and it will probably take you about 6 turns until there are no coins left when you start out with remember that flipping a coin is a random process—so your results will not be exactly the same each time.

The resulting graph does not form a straight line. Instead, it forms an exponential curve that starts off very steep, but then gradually tapers off towards zero. If you start out with more or fewer coins, the number of turns it takes you to reach zero coins will change, but the shape of the curve will remain the same.

This is why radioactive contamination is dangerous in the environment and hard to remove. Even though large amounts of the material may decay very quickly at first, smaller amounts can linger for a long time. For example, some of the contaminants in the Chernobyl disaster have half-lives of about 30 years.

Imagine that you could re-do this experiment and wait 30 years until you repeated each turn. There would probably still be some coins left after more than years!

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That is why, even though the Chernobyl disaster occurred inthe area is still unsafe for humans to inhabit. You have free article s left. Already a subscriber? Sign in. See Subscription Options. Key concepts Energy Radioactivity Exponential decay Odds Introduction One way of creating energy is with nuclear reactors.

Materials About coins this can be a mix of pennies, nickels, dimes and others Resealable plastic bag Flat table top for counting coins Paper or notepad Pencil Preparation Assemble all of your materials at your workspace.