gamma radiation experiment

Geiger-Müller Tube

The virtual Geiger-Müller Tube provides a remarkably realistic simulation of the real equipment without the expense. Identify a random alpha, beta or gamma source, or even use a simulated Ba-137m source for half-life experiments. You can also add cardboard, plastic, and lead barriers to your experiments. The activity guides below are free to reproduce for classroom use.

• Half-Life of Ba-137m Lab Guide
• Identifying Unknown Radiation Lab Guide

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• Radioactivity and Half-Life SwiftStudy
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Nuclear Science for Teaching Teens

Inspiring curiosity and wonder through nuclear science.

Lesson 5: Observing Radiation with Cloud Chambers

Photo: .

Description

Now that students have learned what the different forms of radiation are, how they interact with matter, and how they are measured (lessons 3 and 4), they'll be able to see these principles with their own eyes.

Using a cloud chamber, students will be able to directly observe radioactive decay and how radiation interacts with matter They will also be able to distinguish between different types of radiation.

Why it Matters

One of the things that makes radiation a source of fear is that it's very difficult to see it as anything other than an abstract concept. With a cloud chamber, you can see radiation with your own eyes, and gain an intuitive understanding of its behavior. Furthermore, cloud chambers have been important tools in the history of nuclear science, and this simple experiment can show students that real scientific research is within their grasp.

There are four types of ionizing radiation that are usually taught in nuclear science and produced from nuclear interactions. Each interacts with matter in different ways, which produce different visible results in a cloud chamber.

A cloud chamber contains alcohol vapor at the edge of precipitation. Ionizing radiation can trigger condensation and produce visible tracks.

Ionizing radiation produces enough energy to ionize atoms in matter and break chemical bonds.

Alpha particles are helium nuclei, ionized with a +2 charge. Their charge allows them to strongly interact with matter. The charge pulls on the electrons in atoms, slowing the alpha particle and ionizing atoms. This means they deposit a lot of energy and are stopped quickly. Their large mass means they have high inertia, so these interactions slow them, and don't change their direction as much, resulting in the short thick tracks seen in the cloud chamber.

Beta particles are electrons, with a -1 charge. They interact less strongly, so travel farther, but change direction more easily. They interact similarly to alpha particles, but with less intensity. They have long, thin tracks because the range of interaction around the path is smaller.

Gamma rays are high energy photons. They increase the energy levels of electrons in their path enough that some electrons are kicked out of their atoms. They travel far and ionize around their path. Their direct interaction is not visible in a cloud chamber, but the paths of the electrons kicked out are visible.

Cloud Chamber Video

This video shows a cloud chamber in operation with radiation tracks visible.

Student Objectives

• The student will observe radioactive decay and the interaction of radiation and matter using a cloud chamber.

Learning Objectives

• Radiation is usually invisible, but we can see its path in a cloud chamber.
• Each of the four types of radiation leaves a different path. 

Material names are linked to example supplies.

• clear plastic container with metal lid
• thorium mantle source
• 99.9 % isopropyl alcohol
• furniture pads
• insulating Styrofoam tray
• acquired locally
• Cooler for dry ice
• Hand Warmer

Cloud Chamber Setup

• Stick furniture pads on the sides of the cloud chamber.
• Carefully spread dry ice onto the Styrofoam tray to form a bed for cloud chamber.
• Soak the furniture pads with isopropyl alcohol.
• Place thorium mantle in the cloud chamber, and close the box.
• Place the box onto dry ice. Wait 5 minutes for vapor layer to form.
• Observe radiation tracks.

Lecture Video

Lesson Plan

Before beginning the lesson, set up the cloud chamber, and have it running.

• Now that students have learned about the interaction of radiation and matter, ask them what it would look like for radiation to go into a solid, liquid, or gas. Would it be damaged?
• Ask students to think about how you could make it easy to see radiation with their own eyes.

Exploration

• Have students gather around the cloud chamber.
• Point out the individual components: the chamber itself, the dry ice, the alcohol soaked felt pad, and the thorium mantle.
• Point out the faint cloud of vapor at the bottom.
• Answer: Alcohol vaporizes easily, and the dry ice makes it condense, so together it makes it easy to get the cloud seen at the bottom.
• Realize that the streaks are radiation which is released during the radioactive decay of the thorium.

Explanation

• Cloud chambers work by having a layer of alcohol vapor on the bottom of the chamber.
• Just like water vapor in the air, this alcohol is not visible unless something causes it to condense into a cloud.
• The dry ice brings the alcohol vapor to the brink of condensing, and it only needs a slight push to do so.
• Alpha particles are heavy and have a +2 charge. This means they interact with their surroundings a lot, but also slow down quickly as a result. They have short, thick, straight tracks.
• Beta particles have a -1 charge and have very little mass. Their lower charge means they don't interact with their surroundings as much as alpha particles do, so they can travel further. But since they are lighter, each interaction can change their direction. Beta particles have long, thin, squiggly tracks.
• Gamma rays don't have a charge, so they don't directly produce a track. Instead, they produce secondary electrons in the air, producing faint, squiggly tracks.
• Long, straight, thin lines are produced by cosmic ray particles like muons. These particles have a -1 charge like an electron, so interact lightly in the same way and travel far. However, they are much heavier, so their tracks are straight.

• Ask the students to identify the radiation they see on the video and in the cloud chamber in person.

Suggested Evaluations

• Ask students to identify types of radiation based on the tracks seen in the video and in the cloud chamber.
• Ask students how radiation would behave similarly or differently in a human body instead of a cloud chamber? What about the metal of a reactor? Have them think about the effects of the density of the material, and the size of the its atoms.

Supplemental Resources

• https://www.ans.org/webinars/view-edvr2023/
• https://www.nuclear-power.com/nuclear-engineering/radiation-detection/cloud-chamber/
• https://indico.cern.ch/event/335863/contributions/785342/attachments/1168798/1686802/cloudchamber_salt_ice_mix.pdf
• https://iopscience.iop.org/article/10.1088/0031-9120/47/4/429/pdf

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Basic Physics of Nuclear Medicine/Attenuation of Gamma-Rays

We covered the interaction of gamma-rays with matter from a descriptive viewpoint in the previous chapter and we saw that the Compton and Photoelectric Effects were the major mechanisms. We will consider the subject again here but this time from an analytical perspective. This will allow us to develop a more general understanding of the phenomenon.

Note that the treatment here also refers to the attenuation of X-rays since, as we noted before gamma-rays and X-rays are essentially the same physical entities.

Our treatment begins with a description of a simple radiation experiment which can be performed easily in the laboratory and which many of the early pioneers in this field did. We will then build on the information obtained from such an experiment to develop a simple equation and some simple concepts which will allow us generalise the situation to any attenuation situation.

Attenuation Experiment

The experiment is quite simple. It involves firing a narrow beam of gamma-rays at a material and measuring how much of the radiation gets through. We can vary the energy of the gamma-rays we use and the type of absorbing material as well as its thickness and density.

The experimental set-up is illustrated in the figure below. We refer to the intensity of the radiation which strikes the absorber as the incident intensity , I 0 , and the intensity of the radiation which gets through the absorber as the transmitted intensity , I x . Notice also that the thickness of the absorber is denoted by x .

From what we covered in the previous chapter we can appreciate that some of the gamma-rays will be subjected to interactions such as the Photoelectric Effect and the Compton Effect as they pass through the absorber. The transmitted gamma-rays will in the main be those which pass through without any interactions at all.

We can therefore expect to find that the transmitted intensity will be less than the incident intensity, that is

But by how much you might ask. Before we consider this let us denote the difference between I x and I 0 as ∆ I , that is

Effect of Atomic Number

Effect of Density

Effect of thickness, effect of gamma-ray energy, mathematical model.

We will consider a mathematical model here which will help us to express our experimental observations in more general terms. You will find that the mathematical approach adopted and the result obtained is quite similar to what we encountered earlier with Radioactive Decay . So you will not have to plod your way through any new maths below, just a different application of the same form of mathematical analysis!

Let us start quite simply and assume that we vary only the thickness of the absorber. In other words we use an absorber of the same material (i.e. same atomic number) and the same density and use gamma-rays of the same energy for the experiment. Only the thickness of the absorber is changed.

From our reasoning above it is easy to appreciate that the magnitude of ∆ I should be dependent on the radiation intensity as well as the thickness of the absorber, that is for an infinitesimally small change in absorber thickness:

the minus sign indicating that the intensity is reduced by the absorber.

Turning the proportionality in this equation into an equality, we can write:

where the constant of proportionality, μ, is called the Linear Attenuation Coefficient .

Dividing across by I we can rewrite this equation as:

So this equation describes the situation for any tiny change in absorber thickness, dx . To find out what happens for the complete thickness of an absorber we simply add up what happens in each small thickness. In other words we integrate the above equation. Expressing this more formally we can say that for thicknesses from x = 0 to any other thickness x , the radiation intensity will decrease from I 0 to I x , so that:

This final expression tells us that the radiation intensity will decrease in an exponential fashion with the thickness of the absorber with the rate of decrease being controlled by the Linear Attenuation Coefficient. The expression is shown in graphical form below. The graph plots the intensity against thickness, x . We can see that the intensity decreases from I 0 , that is the number at x = 0, in a rapid fashion initially and then more slowly in the classic exponential manner.

The influence of the Linear Attenuation Coefficient can be seen in the next figure. All three curves here are exponential in nature, only the Linear Attenuation Coefficient is different. Notice that when the Linear Attenuation Coefficient has a low value the curve decreases relatively slowly and when the Linear Attenuation Coefficient is large the curve decreases very quickly.

The Linear Attenuation Coefficient is characteristic of individual absorbing materials. Some like carbon have a small value and are easily penetrated by gamma-rays. Other materials such as lead have a relatively large Linear Attenuation Coefficient and are relatively good absorbers of radiation:

The materials listed in the table above are air, water and a range of elements from carbon ( Z =6) through to lead ( Z =82) and their Linear Attenuation Coefficients are given for three gamma-ray energies. The first point to note is that the Linear Attenuation Coefficient increases as the atomic number of the absorber increases. For example it increases from a very small value of 0.000195 cm -1 for air at 100 keV to almost 60 cm -1 for lead. The second point to note is that the Linear Attenuation Coefficient for all materials decreases with the energy of the gamma-rays. For example the value for copper decreases from about 3.8 cm -1 at 100 keV to 0.73 cm -1 at 500 keV. The third point to note is that the trends in the table are consistent with the analysis presented earlier.

Finally it is important to appreciate that our analysis above is only strictly true when we are dealing with narrow radiation beams. Other factors need to be taken into account when broad radiation beams are involved.

Half Value Layer

As with using the Half Life to describe the Radioactive Decay Law an indicator is usually derived from the exponential attenuation equation above which helps us think more clearly about what is going on. This indicator is called the Half Value Layer and it expresses the thickness of absorbing material which is needed to reduce the incident radiation intensity by a factor of two. From a graphical point of view we can say that when:

the thickness of absorber is the Half Value Layer:

The Half Value Layer for a range of absorbers is listed in the following table for three gamma-ray energies:

The first point to note is that the Half Value Layer decreases as the atomic number increases. For example the value for air at 100 keV is about 35 meters and it decreases to just 0.12 mm for lead at this energy. In other words 35 m of air is needed to reduce the intensity of a 100 keV gamma-ray beam by a factor of two whereas just 0.12 mm of lead can do the same thing. The second thing to note is that the Half Value Layer increases with increasing gamma-ray energy. For example from 0.18 cm for copper at 100 keV to about 1 cm at 500 keV. Thirdly note that relative to the data in the previous table there is a reciprocal relationship between the Half Value Layer and the Linear Attenuation Coefficient, which we will now investigate.

Relationship between μ and the HVL

As was the case with the Radioactive Decay Law, where we explored the relationship between the Half Life and the Decay Constant, a relationship can be derived between the Half Value Layer and the Linear Attenuation Coefficient. We can do this by using the definition of the Half Value Layer:

and inserting it in the exponential attenuation equation, that is:

These last two equations express the relationship between the Linear Attenuation Coefficient and the Half Value Layer. They are very useful as you will see when solving numerical questions relating to attenuation and frequently form the first step in solving a numerical problem.

Mass Attenuation Coefficient

We implied above that the Linear Attenuation Coefficient was useful when we were considering an absorbing material of the same density but of different thicknesses. A related coefficient can be of value when we wish to include the density, ρ, of the absorber in our analysis. This is the Mass Attenuation Coefficient which is defined as the:

The measurement unit used for the Linear Attenuation Coefficient in the table above is cm -1 , and a common unit of density is the g cm -3 . You might like to derive for yourself on this basis that the cm 2 g -1 is the equivalent unit of the Mass Attenuation Coefficient.

Two questions are given below to help you develop your understanding of the material presented in this chapter. The first one is relatively straight-forward and will exercise your application of the exponential attenuation equation. The second question is a lot more challenging and will help you relate exponential attenuation to radioactivity and radiation exposure.

How much aluminium is required to reduce the intensity of a 200 keV gamma-ray beam to 10% of its incident intensity? Assume that the Half Value Layer for 200 keV gamma-rays in Al is 2.14 cm.

A 10 5 MBq source of 137 Cs is to be contained in a Pb box so that the exposure rate 1 m away from the source is less than 0.5 mR/hour. If the Half Value Layer for 137 Cs gamma-rays in Pb is 0.6 cm, what thickness of Pb is required? The Specific Gamma Ray Constant for 137 Cs is 3.3 R hr -1 mCi -1 at 1 cm.

External Links

• Mucal on the Web - an online program which calculates x-ray absorption coefficients - by Pathikrit Bandyopadhyay, The Center for Synchrotron Radiation Research and Instrumentation at the Illinois Institute of Technology.
• Tables of X-Ray Mass Attenuation Coefficients - a vast amount of data for all elements from National Institute of Science & Technology, USA.

• Book:Basic Physics of Nuclear Medicine

EXPERIMENT #3: STOP THAT GAMMA

Introduction.

     The purpose of this experiment is to find the range of gamma rays and determine if the inverse square law applies.

Going Further

Geiger Counter Experiment #3

Detecting alpha, beta and gamma radiation.

Nuclear radiation is ionizing radiation. Ionizing radiation is radiation that can strip electrons from atoms and molecules. We classify this ionizing radiation into three major categories; gamma rays, beta and alpha particles. Gamma (and x-rays) are ultrashort electromagnetic radiation. They have great penetrating power and can easily pass through the body and are attenuated by dense materials such as lead. Beta particles are electrons. Beta particles have a net negative charge. They have low penetrating power. Most beta radiation can be blocked by 1/8” (4mm) of aluminum.

What conclusions can you draw about the penetrating power of radiation?

If you were supplied with a radioactive sample, could you determine the percentages of alpha, beta and gamma radiation being emitted from the source?

Test Results

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Experiment 4. GAMMA-RAY ABSORPTION

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Gamma-ray Astronomy

Long before experiments could detect gamma rays emitted by cosmic sources, scientists had known that the Universe should be producing such high energy photons . Hard work by several brilliant scientists had shown us that a number of different processes which were occurring in the Universe would result in gamma-ray emission. These processes included cosmic ray interactions with interstellar gas, supernova explosions, and interactions of energetic electrons with magnetic fields . In the 1960s, we finally developed the ability to detect these emissions, and we have been looking at them ever since.

Artist's concept of Explorer 11 in orbit. (Credit: NASA)

Gamma-rays coming from space are mostly absorbed by the Earth's atmosphere . So gamma-ray astronomy could not develop until it was possible to get our detectors above all or most of the atmosphere, using balloons or spacecraft. The first gamma-ray telescope carried into orbit , on the Explorer 11 satellite in 1961, picked up fewer than 100 cosmic gamma-ray photons. These appeared to come from all directions in the Universe, implying some sort of uniform "gamma-ray background". Such a background would be expected from the interaction of cosmic rays (very energetic charged particles in space) with gas found between the stars .

The first detection of significant gamma-ray emission from our galaxy was made in 1967 by the the gamma-ray detector aboard the OSO-3 satellite. In fact, OSO-3 also detected the first gamma-rays from outside our galaxy! All told, it detected 621 cosmic gamma rays. However, the field of gamma-ray astronomy took great leaps forward with the SAS-2 (1972) and the COS-B (1975-1982) satellites. These two satellites provided an exciting view into the high-energy universe, sometimes called the "violent" universe, because the type of events in space that produce gamma rays tend to be explosions and high-speed collisions. The data from the satellites confirmed the earlier findings of the gamma-ray background, produced the first detailed map of the sky at gamma-ray wavelengths , and detected a number of point sources, where the sources of radiation were very concentrated and emanated from a small area. However, the poor resolution of the instruments made it impossible to identify most of these point sources with individual stars or stellar systems.

The Vela 5B satellite in low-Earth orbit. (Credit: LANL)

Perhaps the most spectacular discovery in gamma-ray astronomy came in the late 1960s and early 1970s from a collection of defense satellites that were put into orbit for a reason completely unrelated to astronomy research. Detectors on board the Vela satellite series were designed to detect flashes of gamma rays from nuclear bomb blasts. They began to record bursts of gamma rays, not from the vicinity of Earth, but from deep space. These gamma-ray bursts (GRBs) can 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. Studied for over 25 years with instruments on board a variety of satellites and space probes, including Soviet Venera spacecraft and the Pioneer Venus Orbiter , the sources of these enigmatic high-energy flashes for a while remained a mystery. In one of the most intense debates in modern astrophysics, some scientists claimed that the bursts originate in a halo of neutron stars which surround our Galaxy while others argued that their origins are far beyond the Galaxy, at cosmological distances . This was settled in 1996 when the BeppoSax satellite and the Hubble Space Telescope pinpointed the location of a gamma-ray burst in a distant galaxy.

In 1977, NASA announced plans to build a "great observatory" for gamma-ray astronomy. The Compton Gamma-Ray Observatory (CGRO) was designed to take advantage of the major advances in detector technology during the 1980s, and was launched in 1991. The satellite carried four major experiments which greatly improved the spatial and temporal resolution of gamma-ray observations. The CGRO provided large amounts of data which have been used to improve our understanding of the high-energy processes in our Universe. CGRO was de-orbited in June 2000 as a result of the failure of one of its stabilizing gyroscopes.

Artist's rendering of the Swift satellite. (Credit: Spectrum Astro)

In November 2004, NASA launched the Swift satellite. Its primary mission is to detect and locate GRBs as quickly as possible, report the position of the burst, then follow up with other observations of that location in the X-ray, UV and visual spectra. On April 13, 2010, NASA's Swift satellite recorded its 500th GRB.

To continue the study of the universe in the gamma-ray spectrum, Swift currently operates in conjunction with the Fermi Gamma-Ray Space Telescope , launched in 2008. Fermi, originally called GLAST (Gamma-ray Large Area Space Telescope), also studies GRBs, as well as blazars, neutron stars, gamma-ray background radiation, supernova remnants, dark matter and more.

What can gamma rays tell us about the cosmos? Gamma-rays are the most energetic form of electromagnetic radiation , with over 10,000 times more energy than visible light photons . If you could see gamma-rays, the night sky would look strange and unfamiliar. The familiar sights of constantly shining stars and galaxies would be replaced by something ever-changing. Your gamma-ray vision would peer into the hearts of solar flares , supernovae , neutron stars , black holes , and active galaxies . 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. Watch the video below to see a few of the highlights of Fermi's first five years in orbit for an idea of the types of objects gamma-ray astronomers study.

Fermi at five years, a compilation video summarizing the wide range of science from the first five years of the Fermi Gamma-ray Telescope. (Credit: NASA)

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Multiwavelength Astronomy

Gamma Ray Science, Dieter Hartmann

Early experiments.

Ernest Rutherford in the lab: Ernest Rutherford sitting in his lab (right) with his assistant, Hans Geiger. Circa 1913. Credit: Reference number  PAColl-0091-1-011,  Sir Ernest Marsden Collection, Alexander Turnbull Library,  Wellington, New Zealand.

Before we knew about cosmic gamma radiation we discovered it through experiments carried out by Paul Villard and Ernest Rutherford . Villard was doing radioactivity research in Paris at the same time as Marie and Pierre Curie . Villard and Rutherford collaborated on separating radiation into alpha , beta , and gamma components, based on their ability to penetrate objects and cause ionization . Radium experiments showed that alpha-rays are stopped by paper, beta-rays are stopped by glass or aluminum, but gamma-rays pass through all substances except lead, concrete, steel, and the atmosphere of Earth. Villard also noticed that gamma rays traveled in a straight line and were unaffected by magnetism. This is because gamma rays are photons – particles with no mass and no charge – so they can’t be affected by a magnetic field .

Of course these experiments were done in extremely short distances compared to the vastness of space. Cosmic gamma rays travel billions of light years . As they approach Earth they are absorbed in the atmosphere. Gamma rays don’t reach the surface of Earth, thus we have to fly balloons or satellites to collect data on them – this is also true for X-rays. If you want to study higher energy phenomena, you have to go above the atmosphere because this type of radiation does not make it to the ground – directly. But more about that later.

Gamma-ray penetration of materials: Our atmosphere is too thick to be penetrated by gamma radiation. On the other hand, gamma rays can easily penetrate considerable distances in materials such as paper and aluminum. Only heavy metals (such as lead) and other materials like concrete can prevent deep penetration by gamma rays. Credit: Courtesy of Ehamberg and Stannered on Wikimedia Commons, available under Creative Commons Attribution 2.5 Generic license.

Gamma Ray  >  Science, Dieter Hartmann

This material is based upon work supported by NASA under Grant Nos. NNX09AD33G and NNX10AE80G issued through the SMD ROSES 2009 Program.

Any opinions, findings, and conclusions or recommendations expressed in this website are those of the author(s) and do not necessarily reflect the views of the National Aeronautics and Space Administration.

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Rutherford's Experiment to Understand β-Rays

Nikolas martelaro february 20, 2017, submitted as coursework for ph241 , stanford university, winter 2017, introduction.

Scientific experiments are the foundation for building our understanding of the physical world. While experiments may seem complex to the non-scientist, in reality, many influential scientific discoveries have been made with beautifully simple experiments. One such example is Earnest Rutherford's experiment on the nature of uranium radiation and its ability to pass through various materials. [1] Using the fact that the radiation from Uranium ionizes a gas, thus creating charges particles, Rutherford was able to measure the current produced by a sample of uranium placed between two charged metal plates. By placing metal foils on top of the uranium, Rutherford showed that part of the ionizing radiation was stopped while another part appeared to pass through the foils. This helped to confirm the work of Becquerel, showing that there were two components of the ionizing radiation. [2] These two rays were given the names α-rays and β-rays. While Becquerel's works suggested the existence of the two types of rays, there was still little understanding of their nature. Specifically, through how much and what types of material did these rays pass through? Rutherford aimed to explore this using his simple and beautiful experiment and was able to show the differences between α and β radiation absorption. This experiment would later lead to him advising Geiger and Mardsen's famous gold foil experiment, whereupon α particles moving through gold foil were shown to sometimes deflect, suggesting the positive nuclear core model of the atom that we know today. [3] This report gives an overview of the design and results of Rutherford's experiment, which is described in detail in his 1899 paper. [1] It should be noted that Rutherford details a number of experiments in his paper, only the experiment that confirmed the existence of α and β rays will be discussed here.

Known Theory of Uranium Radiation

At the time of Rutherford's experiment, uranium was know to emit an ionizing radiation similar to x-rays. When subjected to a gas, this radiation would create positively and negatively charged particles. This allows the gas to be a temporary conductor of electricity and would allow an electric potential and current to be measured. From Becquerel's work, it was known that the radiation would penetrate solid material, but it was not known through how much material. It was also known that the rays emitted from uranium had varying powers.

From this theory, Rutherford hypothesized that the rays emitting from uranium would be complex, composed of different types of rays. He proposed that testing how well the rays penetrated metal foils may help to show what the characteristics of the rays were.

Experiment Setup

Rutherford's experimental setup was quite simple. A diagram of it is shown in Fig. 1. A sample of uranium is placed between two plates A and B. Plate A is charged by a battery to 50 V, while plate B is connected to the sensing element of an electrometer. This creates an electrical potential between the plates. Due to the ionizing radiation coming from the uranium, the gas in between the plates will become electrically charged. Positive ions will move away from plate A while negative ion will move toward it. This will induce a small current between the plates. As this current flows in the gas, it will create a charge on the sensing element of the electrometer.

The electrometer works by having four separated quadrants. The quadrants are hollow inside, much like a bicycle tire without a tube. The diagonally opposing quadrants are connected together electrically. One set of quadrants is connected to earth ground while the other acts as the sensing quadrant and is connected to Plate B. A metal vane (or needle) is placed inside this hollow area of the quadrants. The vane hangs from a thread, allowing it to spin inside of the quadrants. The vane is then charged. When a charge is induced on Plate B and the sensing quadrant of the electrometer, it begins to spin the vane due to the opposing electrical forces, similar to how magnets with the north poles facing each other will repel each other. The degree that the vane turns is associated with the voltage, while the rate that the vane turns is associated with the current.

To explore the nature of the radiation, Rutherford covered the uranium with a thin sheet of metal foil. He then measured the "rate of leak" given by the electrometer vane when in constant motion (indicating a specific amount of current, and thus an amount of charge induced by the ionizing radiation). By placing successive sheets of foil, Rutherford was able to see how much the rate of leak diminished, indicating how much of the radiation was blocked.

Number of Layers Leak/min in scale divisions Ratio for each layer 0 91 1 77 0.85 2 60 0.78 3 49 0.82 4 42 0.86 5 33 0.79 6 24.7 0.75 8 15.4 0.79 10 9.1 0.77 13 5.8 0.86 Adding Layers of Dutch Metal (Brass) Rutherford first began by adding sheets of Dutch metal (brass foil), on top of the uranium and measured the leak rate per minute in the electrometer scale divisions. The second column of the table in Fig. w shows the leak rate as each layer of foil was added. The third column shows the ratio that the leak rate had decreased from the previous layer, helping to show the effect of each layer on blocking the radiation. The exponential nature of the attenuation with increating thickness is evident in Fig. 2. Adding Layers of Aluminum Foil Rutherford then used thicker aluminum foil (0.0005 cm thick) to block the radiation from the uranium. Adding four layers of the aluminum foil blocked much of the radiation, as shown in Fig. 3. However, after the fourth layer, it took another eight layers of aluminum to decrease the leak rate from 9.4 to 7. This simple test shows that there appear to be two components of ionizing radiation from the uranium, one that is blocked very easily (corresponding to the radiation that is blocked with the first four layers of aluminum) and one that is barely blocked by the aluminum (corresponding to the leak rate even after 12 layers are added). Number of Layers Leak/min in scale divisions Ratio for each layer 0 182 1 77 0.42 2 33 0.43 3 14.6 0.44 4 9.4 0.65 12 7 Rutherford described these two components of the radiation as α-rays and β-rays. Exploring β-Rays After understanding that the radiation from uranium was composed of α- and β-rays, Rutherford then extended his experiment to explore the penetration of β-rays. From the earlier results, he knew that he could block all of the α-rays with a few sheets of material. He found that this could be done with aluminum, tin, and even paper. With the α- rays blocked by 0.005 cm of aluminum, Rutherford added aluminum sheets to explore the penetration of β-rays. Thickness of Aluminum Leak rate 0.005 1 0.028 0.68 0.051 0.48 0.09 0.25 The results of this experiment, reproduced in Fig. 4, show that β-rays appear to only have one component and a fairly constant penetrating power. This shows why the decrease in detected leak rate was fairly linear only when the β-rays were tested without α-rays. Rutherford does note though that there may be another component to the radiation from uranium, but that it must be so small or so penetrating that it was undetectable with his experimental setup. In 1903, Rutherford would later go on to discover γ-rays (gamma-rays), a third ionizing radiation with very high penetration. Rutherford's beautiful experiment is one example of how we can understand nature without needing complex and expensive equipment. Though some of the measurement equipment used in Rutherford's day, such as the electroscope, was an intricate mechanical measurement tool, it still relies upon simple principles of nature. By understanding that ionizing radiation could create a current in a gas between charged plates and by testing how that current was changed when trying to block the radiation, Rutherford was able to understand and characterize two fundamental components of nuclear radiation. What is even more impressive is that Rutherford's brilliant experiment can easily be recreated today with more modern radiation detectors, such as the Geiger counter and naturally occurring uranium ore. [4,5] Both Geiger counters and small samples of uranium ore can readily be purchased online for less than $200. One could then recreate Rutherford's analysis using grocery store aluminum foil. Overall, Rutherford's experiment shows how with just enough understanding of the world as we know it, simple tools, and a bit of creativity, we can create simple ways to explore nature and better our understanding. © Nikolas Martelaro. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author. [1] E. Rutherford, "Uranium Radiation and the Electrical Conduction Produced by It," Philos. Mag. 47 , 109 (1899). [2] H. Alaeian, " An Introduction to β-Ray Spectroscopy ," Physics 241, Stanford University, Winter 2014. [3] E. Rutherford, "The Scattering of α and β Particles by Matter and the Structure of the Atom," Philos. Mag. Ser. 6 21 , 669 (1911). [4] T. English, " Radiation Detectors ," Physics 241, Stanford University, Winter 2015. [5] A. Lange, " Nature's Radioactive Material ," Physics 241, Stanford University, Winter 2011. Investors External Lab Experiment 9: Gamma-Ray Coincidence Counting Techniques Share to Facebook Share to Twitter Share to Linkedin To use the technique of coincidence detection and demonstrate the basic principles of coincidence measurements. Equipment Required: Theoretical Overview: Coincidence measurements are an important tool in the detection of ionizing radiation for a wide range of applications. Many nuclear processes produce two photons simultaneously, while other processes produce two or more photons in quick succession. In such cases, it is possible to study the temporal and angular correlations between the two photons by setting up a coincidence detector system. These emissions can occur simultaneously or within a time period that is very short compared to the time resolution of the detection system. For example, decay by beta emission to a daughter nucleus, which in turn decays by gamma emission, produces the beta particle and the gamma ray at essentially the same time. Similarly, one nucleus may emit several gamma rays in cascade, which are effectively simultaneous because the delay between the events is short. Delays of 10 -9 seconds are common. In nuclear physics applications, coincidence systems are used to detect and identify weak detection signals or to distinguish a physics signal from background signals, as is done in Compton suppression or cosmic veto systems. In high-energy or particle physics, detection systems consisting of thousands of detectors and electronics channels are all operated in coincidence when two accelerated beams collide to search for newly formed particles or new decay pathways. Time-coincidence measurements In addition to radiation detector characteristics such as efficiency or energy resolution, time resolution is important to measure. This is required to determine the time dependence of nuclear decays as discussed previously. It reflects the ability to measure the arrival time of the incident particle or the time of a specific interaction and its associated signal. The time resolution of a specific detector depends on several parameters such as signal shape called “walk time” and signal noise called “jitter time”. In some cases the actual time difference between the two events can be measured, but in many cases it is only necessary to determine that the events are correlated in time. The determination that two nuclear events occur at the same time is made electronically with a coincidence system. This unit operates on standardized pulses and determines whether events occur within a certain time interval, called the resolving time. The standard pulses from any single channel analyzer are used as input, with one input from each detector. The number of coincidences that are real, not random, is determined by the physics of the decay and the solid angles and efficiencies of the detectors. These are the true coincidences. In some experiments, the number of coincidences is the only information needed. Often, however, the coincidence signal is used to open the linear gate in a multichannel analyzer so that a spectrum is acquired under coincidence conditions. This experiment has three separate parts which use the coincidence technique in different ways. γγ Angular correlations The angular correlation of two gamma rays, γ 1 and γ 2 may be defined as the probability of γ 2 being emitted at an angle relative to the direction of γ 1 . The emission of gamma rays from excited nuclei can be treated mathematically as the classical radiation of electromagnetic energy from a charged system. The electric field can be expanded in vector spherical harmonics, corresponding to the various multipoles of the charge distribution. The shape of the angular distribution of the radiation with respect to the radiating system is uniquely determined by the order of the multipole. In nuclear systems, the order of the multipole depends upon the angular momentum numbers and the parities of the initial and final states involved in the transition. Thus, if all nuclei in a radioactive sample could be oriented so that their nuclear angular momenta were aligned, the shape of the angular distribution of gamma rays could be used to determine the multipolarity of the transition. However, nuclei are randomly oriented. Very strong magnetic fields at low temperature could be used to provide orientation, but a simpler method is to use coincidence technique for cases in which two or more gamma rays are emitted in cascade. The first gamma ray establishes the direction of the spin axis of the nucleus; hence the second gamma ray will have a definite distribution with respect to this axis. One needs only to measure the angular correlation for the two gamma rays and compare it with the tabulated values for various multipolarities. In nuclear physics experiments the angular correlation is measured between two gamma rays, which are emitted almost simultaneously in the cascade from the decay of a radioactive nucleus. The gamma rays are detected using two NaI scintillation counters in which the height of the electronic output pulses is proportional to the incident gamma ray energies. By pulse height selection, in “single channel analyzer mode”, one counter will be used to record γ 1 and the other γ 2 . The counting rate of each counter, R i , for detecting its selected gamma ray is given by: N 0 is the number of decays per second in the radioactive source. e i is the efficiency of the detector. O i is the geometrical solid angle subtended by the detector. I n the absence of the angular correlations, the true rate of detected gamma-ray coincidences is: The random coincidence rate between a gamma ray detected in Detector 1 and a gamma ray detected in Detector 2 is: where Δt is the resolving time of the coincidence counting system between the two detectors. If both detectors are set to respond to both gamma rays, the counting rate in each detector is the sum of counting rates for different gamma rays. Experiment 9 Guide: Time-coincidence measurements using TLIST acquisition mode NaI-NaI coincidences Energy calibration 1. Use two NaI Detectors (one connected via an Osprey unit and the other with the 2007P Preamp and Lynx II DSA) connected to the measurement PC either directly or via your local network. 2. Open the ProSpect Gamma Spectroscopy Software and connect to both MCAs. 3. Configure both MCAs as recommended in Experiment 1 for configuration to a NaI detector. 4. Select the High Voltage Settings on the Detector tab on the ProSpect software to apply the recommended high voltage on both detectors. 5. Place the 22 Na source between the two detectors in a close geometry. 6. Set the Conversion gain on the MCA tab of the ProSpect software to 2048 channels for both MCAs. 7. Adjust the coarse and fine gain settings on the MCA tab of the ProSpect software on both MCAs such that the 1275 keV full-energy peak is in the upper part each spectrum. 8. Click on Start (on the top of each Spectral Display) to start accumulating the two spectra. Use a count time such that there is at least 10 000 counts in the full-energy peak. 9. Perform an energy calibration using the 511.0 and 1274.5 keV peaks of 22 Na, referring to Experiment 1 if necessary. Decay spectra 10. On the acquisition tab set the acquisition mode to TLIST mode. The TLIST mode allows acquisition of event data which provide the energy and time for each event. 11. Set the two devices up according to Table 9-1. Note that the external sync setting needs to be applied first. Connect the Sync BNC connector on the Lynx II DSA rear panel to the GPIO input channel 1 of the Osprey unit. See Figure 9-1. (If necessary, utilize a 50 ohm terminator to reduce reflections.) 12. Press Control-Start to begin acquisition simultaneously on both devices. Figure 9-1: Cable configuration for synchronization of Lynx II and Osprey DSAs. 13. Ensure that both detectors go into waiting mode (blue backgrounds on the datasource thumbnails). Rapidly (before the 20 second timeout is reached), switch the Lynx II DSA External Synchronization from Slave to Master B. 14. Ensure that both detectors begin acquiring data (PHA data appears in the display and both backgrounds turn green in the datasource thumbnail view). 15. Acquire data for around 5 minutes, press Control-Stop to stop both MCAs from acquiring data and save the PHA data. The TLIST data is saved automatically during the acquisition. Table 9-1: Settings of synchronized TLIST mode acquisition with an Osprey and Lynx II DSA 16. To analyze the TLIST mode data and see the results of the coincidence measurement use the application called ProSpect Data Scanner (downloadable from Mirion website www.mirion.com). Follow the steps below to run the ProSpect Data Scanner. 17. Select the folder of interest, where the data are stored. 18. Select the Pre-Scan option to sort the events by the time stamp. Note that for each file the elapsed and the live time is displayed. Additionally, the total number of events in PHA and TLIST mode data and the elapsed real and live times for the TLIST mode data file are displayed. 19. Enter the energy calibration equations for both detectors, found on the energy calibration tab. Select Energy-Scan to reconstruct the energy spectra for both devices from the TLIST events. 20. To ensure the time correlations between the events can be observed, set a gate around the 511 keV full-energy peak. 21. Select the Time-Scan to generate the time coincidence spectrum. The display spectrum will show the time correlation between the events recorded in both detectors. 22. Comment on the time-correlated spectrum. NaI-HPGe coincidences 1. Connect the Lynx II DSA (with the HPGe detector connected) to the measurement PC or via your local network using the Ethernet connection. 2. Connect the Osprey unit (with the NaI(Tl) detector connected) to the measurement PC either directly or via your local network. 3. Open the ProSpect Gamma Spectroscopy Software and connect to the Lynx II and Osprey units. 4. Configure the NaI detector as recommended in Experiment 1, and the HPGe detector as recommended in Experiment 7. 5. Select the High Voltage Settings on the Detector tab on the ProSpect software to apply the recommended high voltage on both detectors. 6. For each detector perform an energy calibration using the 511.0 and 1274.5 keV peaks of 22 Na, referring to Experiment 1 if necessary. 7. Save both spectra. Once you have set the gain and the energy calibration coefficients, do not change it, otherwise you will have to redo the calibration. 8. On the ProSpect software set the data acquisition to TLIST mode. The TLIST mode allows simultaneous acquisition of event data which provide the energy and time for each event. 9. To acquire data in TLIST mode set both detectors as shown in Table 9-1. 10. After the two devices are setup as described in Table 9-1, make sure to connect the Sync BNC connector on the Lynx II DSA rear panel (add a 50 ohm terminator to prevent reflections) to the GPIO input channel 1 of the Osprey unit. 11. Select Control-Start to begin acquisition simultaneously on both devices. 12. Ensure that both detectors go into waiting mode (blue backgrounds on the datasource thumbnails). Rapidly (before the 20 second timeout is reached) switch the Lynx II DSA External Synchronization from Slave to Master B. 13. Ensure that both detectors begin acquiring data (PHA data appears in the display and both backgrounds turn green in the datasource thumbnail view). 14. Acquire data for around 5 minutes and save the data. 15. To analyze the TLIST mode data and see the results of the coincidence measurement use the application called the ProSpect TLIST Data Scanner (downloadable from the Mirion website). Follow the steps below to run the ProSpect TLIST Data Scanner. 16. In the Search Directories tab, identify the directory with the acquired TLIST data. Press the start button to begin analyzing. 17. In the Scan Results tab, select the appropriate acquisitions and set the beginning time Range to -6000 ns, maximum time range to 6000 ns, and the Time Bins to 1000. 18. On the Analysis tab, select the two acquisitions using the Device and Acq Start tabs. Plot Energy on the X-axis and Time on the Y-axis to observe the coincident counts. Comment on the graph that is observed. Note: You can copy the graph to your clipboard for further analysis. 19. Comment on the time coincidence spectrum and compare with the spectrum acquired for the two Osprey units above. Time-coincidence measurements using lynx II hardware gating This section requires the following: ProSpect Version 1.1 1. Make sure the high-purity germanium (HPGe) and NaI detectors are energy calibrated. 2. Place 137 Cs and 22 Na sources between the two counter detectors in a closed geometry. 3. Connect the GPIO 1 unit of the Osprey digital MCA to the gate input of the Lynx II DSA. 4. For the NaI detector, open the GPIO dialog on the MCA tab of the ProSpect software and set the GPIO to the single-channel analyzer, SCA 1. 5. For the NaI detector, go to the Single-Channel Analyzer under the MCA tab of the Prospect software and Enable the SCA. 6. Go to the Acquisition tab of the Prospect software for the Lynx II unit and set the coincidence gate parameters as follows: Table 9-2: ProSpect Settings for Step 6. 7. Launch the Digital Oscilloscope and look at the Lynx II traces. Set the trigger on the Store pulse and make sure the external gate is overlapping with the peak detect pulse. Increase the Gate Delay Ext such that the edge of the peak detected will overlap with the edge of the external gate. 8. Acquire an energy-gated spectrum in the HPGe detector. Use a count time such that there are at least 10 000 counts in each photopeak. 9. Save the spectrum. 10. Set the coincidence gate settings as follows: Table 9-3: ProSpect Settings for Step 10. 11. Acquire an energy-gated spectrum in the HPGe detector. Use a count time such that there are at least 10 000 counts in each photopeak. 12. Save the spectrum. 13. Set the coincidence gate settings as follows: Table 9-4: ProSpect Settings for Step 13. 14. Acquire an energy-gated spectrum in the HPGe detector. Use a count time such that there are at least 10 000 counts in each photopeak. 15. Save the spectrum. 16. Plot the energy spectra acquired with different coincidence-gating conditions and compare the number of counts in the photopeaks for the different gating conditions. Related Articles Genie™ 4.0 and apex ® products operating system and database qualifications. Software Options for GR1™, Sigma™, and TN-15™ Family Devices ProSpect TLIST Data Scanner Badge Processing: Mail-in Information Looking for Services or Support? We're here to help. Welcome to Physics 122 Advanced Lab Physics 122 Experiments You are here, gamma ray spectroscopy. 1.   2.   3.   4.   1. Knoll, G,  Chapters 2 and 10. (Optional). 2.  γ Ray Spectrum Catalog 3.   4.   5.   6.   1.   2.   3.   4.   5.     This experiment gives you the opportunity to study high energy photons from radioactive nuclear decays. These photons have energies that are characteristic of the specific initial- and final- state nuclear energy levels and thus provide a means of studying the energy levels, nuclear reactions, and also provide a way to identify radioactive nuclear species in test samples. You will explore several different nuclear "fingerprints." You will also learn about scintillators, photomultiplier tubes, and pulse height analysis. [This experiment uses the same electronics as the gamma ray coincidence experiment, so they cannot be done by different teams at the same time.] Your report should show results for and discuss ALL the experiments in the Pre-lab, Guide and Other Required Experiments files. SCINTILLATION COUNTER is coupled to a photo sensor such as a photomultiplier tube which absorbs the light emitted by the scintillator and generates electrons via the photo-electric effect. Multiplication of those photo-electron results in an electrical pulse whose amplitude is related to the energy of the particle producing the scintillation. Mandatory Data Analysis Nuclear Decay Electronics Elective Fundamental Noise Pulse NMR Zeeman Effect Resistivity & Hall Effect Ferro Electricity Superconductivity Balmer Series Gamma Ray Spectroscopy Muon Lifetime Rutherford Scattering Optical Pumping Cosmic Microwave Background 227 IMAGES a) Graphical illustration of the gamma radiation (γ-ray) experiment 14 questions with answers in GAMMA-RAY SPECTROMETER Absorption of γ radiation Physicists find ways to control gamma radiation Edexcel A Level Physics:复习笔记11.8 Core Practical 15: Investigating Gamma Practical: Inverse-Square Law for Gamma Radiation COMMENTS Geiger-Müller Tube (Virtual Lab) Identify a random alpha, beta or gamma source, or even use a simulated Ba-137m source for half-life experiments. You can also add cardboard, plastic, and lead barriers to your experiments. The activity guides below are free to reproduce for classroom use. Half-Life of Ba-137m Lab Guide; Identifying Unknown Radiation Lab Guide Gamma ray A gamma ray, also known as gamma radiation (symbol γ), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei.It consists of the shortest wavelength electromagnetic waves, typically shorter than those of X-rays.With frequencies above 30 exahertz (3 × 10 19 Hz) and wavelengths less than 10 picometers (1 × 10 −11 m), gamma ray photons have the ... Required Practical: Inverse Square-Law for Gamma Radiation Spanish. Past Papers. CIE. Spanish Language & Literature. Past Papers. Other Subjects. Revision notes on 8.1.7 Required Practical: Inverse Square-Law for Gamma Radiation for the AQA A Level Physics syllabus, written by the Physics experts at Save My Exams. Lab Experiment 3: Gamma-Ray Absorption in Matter (Basic) In the Compton effect, the gamma ray scatters from an electron, transferring an amount of energy that depends upon the angle of scatter. where: E' is the scattered energy of the gamma ray. E is the incident gamma-ray energy. θ is the angle of scatter. The term m 0 c 2 is the rest mass of the electron, equal to 511 keV. The energy given to the ... Experiment #4: Penetrating Power Gamma rays have the most penetrating powers of all three radiation sources. Objective. The purpose of this experiment is to demonstrate the interactions of alpha, beta, and gamma radiation with matter. Absorber/Shielding Set; Materials. radiation sources: Po-210 (alpha source) Sr-90 (beta source) ... Lab Experiment 1: Gamma-Ray Detection with Scintillators How gamma rays are produced Radioactive nuclei decay by emitting beta or alpha particles. Often the decay is to an excited state in the daughter nucleus, which usually decays by emission of a gamma ray. The energy level sequence and therefore the gamma-ray energy spectrum for every nucleus is unique and can be used to identify the nucleus. Lesson 5: Observing Radiation with Cloud Chambers Stick furniture pads on the sides of the cloud chamber. Carefully spread dry ice onto the Styrofoam tray to form a bed for cloud chamber. Soak the furniture pads with isopropyl alcohol. Place thorium mantle in the cloud chamber, and close the box. Place the box onto dry ice. Wait 5 minutes for vapor layer to form. Observe radiation tracks. Basic Physics of Nuclear Medicine/Attenuation of Gamma-Rays The experiment is quite simple. It involves firing a narrow beam of gamma-rays at a material and measuring how much of the radiation gets through. We can vary the energy of the gamma-rays we use and the type of absorbing material as well as its thickness and density. The experimental set-up is illustrated in the figure below. PDF Experiment 10: Absorption of β and γ Rays Interaction of gamma rays with matter is governed by three processes: 1. Compton scattering (photon-electron collision): 1. Photoelectric effect: photon hits an atom and kicks one of the electrons out. Minimum energy required (because atomic levels are quantized) 2. Pair production: The photon converts into a electron-positron pair. Experiment #3: Stop That Gamma The source of gamma radiation for the experiment is Cobalt-60 (Co-60). In this experiment, the distances are 8 cm, 16 cm, and 24 cm from the source. 8 cm equal one data point, 16 cm equals two data points and so on. Objective. The purpose of this experiment is to find the range of gamma rays and determine if the inverse square law applies ... Gamma radiation: inverse square law Cobalt-60 is the best pure gamma source. However, you may have a sealed radium source in your school. This gives out alpha, beta and gamma radiation. You can use it for this experiment by putting a thick aluminium shield in front of it. This will cut out the alpha and beta radiations. An alternative is to try using a Geiger-Muller tube sideways. Geiger Counter Experiment 3 Ionizing radiation is radiation that can strip electrons from atoms and molecules. We classify this ionizing radiation into three major categories; gamma rays, beta and alpha particles. Gamma (and x-rays) are ultrashort electromagnetic radiation. They have great penetrating power and can easily pass through the body and are attenuated by dense ... How Gamma-rays are Generated In physics, this process produces neutral pions that quickly decay into gamma rays. The results from electron-positron annihilations were seen by the OSSE experiment aboard the CGRO satellite. The colors in this map represent the intensity of gamma-ray emission from positron-electron annihilation in the plane of our galaxy near the galactic center. Experiment 4. GAMMA-RAY ABSORPTION Experiment 4. GAMMA-RAY ABSORPTION. In this experiment you will measure the transmission of gamma rays through different absorbers. Theoretically, there should be an exponential decrease of the transmitted counts with thickness of absorber, determined by a mass absorption coefficient. You will determine mass absorption coefficients and evaluate ... Gamma-ray Astronomy Advanced; Basic; The History of Gamma-ray Astronomy Long before experiments could detect gamma-rays emitted by cosmic sources, scientists had known that the Universe should be producing such high energy photons.Hard work by several brilliant scientists had shown us that a number of different processes which were occurring in the Universe would result in gamma-ray emission. Gamma-ray Astronomy Gamma-ray Astronomy. Long before experiments could detect gamma rays emitted by cosmic sources, scientists had known that the Universe should be producing such high energy photons.Hard work by several brilliant scientists had shown us that a number of different processes which were occurring in the Universe would result in gamma-ray emission. Pound-Rebka experiment Jefferson laboratory at Harvard University. The experiment occurred in the left "tower". The attic was later extended in 2004. The Pound-Rebka experiment monitored frequency shifts in gamma rays as they rose and fell in the gravitational field of the Earth. The experiment tested Albert Einstein's 1907 and 1911 predictions, based on the equivalence principle, that photons would gain energy ... Early Experiments Before we knew about cosmic gamma radiation we discovered it through experiments carried out by Paul Villard and Ernest Rutherford.Villard was doing radioactivity research in Paris at the same time as Marie and Pierre Curie.Villard and Rutherford collaborated on separating radiation into alpha, beta, and gamma components, based on their ability to penetrate objects and cause ionization. Physics revision Gamma radiation from a point source spreads out radialy as it travels away from the source. Within the lab you can ignore absorption by the air in the room. ... The experiment will show the inverse square relationship for gamma rays if you have obtained a straight line. The closer your points are to that line the better your experiment will ... Rutherford's Experiment to Understand β-Rays Exploring β-Rays. After understanding that the radiation from uranium was composed of α- and β-rays, Rutherford then extended his experiment to explore the penetration of β-rays. From the earlier results, he knew that he could block all of the α-rays with a few sheets of material. He found that this could be done with aluminum, tin, and ... Lab Experiment 9: Gamma-Ray Coincidence Counting Techniques In nuclear physics experiments the angular correlation is measured between two gamma rays, which are emitted almost simultaneously in the cascade from the decay of a radioactive nucleus. The gamma rays are detected using two NaI scintillation counters in which the height of the electronic output pulses is proportional to the incident gamma ray ... Gamma Ray Spectroscopy Overview. This experiment gives you the opportunity to study high energy photons from radioactive nuclear decays. These photons have energies that are characteristic of the specific initial- and final- state nuclear energy levels and thus provide a means of studying the energy levels, nuclear reactions, and also provide a way to identify ... essay homework paper phd project resume review study thesis