ALPHA DECAY.pptx

7/30/2019 ALPHA DECAY.pptx

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ALPHA DECAY

MEANING AND APPLICATION IN PHYSICS


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ALPHA DECAY

Alpha decay is a type ofradioactive decay in which anatomic nucleus emits an alpha particle (two protons andtwo neutrons) and thereby transforms (or 'decays') into anatom with a mass number 4 less and atomic number 2 less.

For example: 238U234Th +

Because an alpha particle is the same as a helium-4nucleus, which has mass number 4 and atomic number 2,this can also be written as:

238

92 U

23490Th + 42He

Unlike beta decay, alpha decay is governed by the interplaybetween the nuclear force and the electromagnetic force.
http://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Radioactivityhttp://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Mass_numberhttp://en.wikipedia.org/wiki/Atomic_numberhttp://en.wikipedia.org/wiki/Uranium-238http://en.wikipedia.org/wiki/Thorium-234http://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Mass_numberhttp://en.wikipedia.org/wiki/Mass_numberhttp://en.wikipedia.org/wiki/Atomic_numberhttp://en.wikipedia.org/wiki/Atomic_numberhttp://en.wikipedia.org/wiki/Atomic_numberhttp://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Mass_numberhttp://en.wikipedia.org/wiki/Atomic_numberhttp://en.wikipedia.org/wiki/Uranium-238http://en.wikipedia.org/wiki/Uranium-238http://en.wikipedia.org/wiki/Thorium-234http://en.wikipedia.org/wiki/Helium-4http://en.wikipedia.org/wiki/Thorium-234http://en.wikipedia.org/wiki/Helium-4http://en.wikipedia.org/wiki/Helium-4http://en.wikipedia.org/wiki/Beta_decayhttp://en.wikipedia.org/wiki/Nuclear_forcehttp://en.wikipedia.org/wiki/Electromagnetic_forcehttp://en.wikipedia.org/wiki/Electromagnetic_forcehttp://en.wikipedia.org/wiki/Nuclear_forcehttp://en.wikipedia.org/wiki/Beta_decayhttp://en.wikipedia.org/wiki/Helium-4http://en.wikipedia.org/wiki/Helium-4http://en.wikipedia.org/wiki/Helium-4http://en.wikipedia.org/wiki/Thorium-234http://en.wikipedia.org/wiki/Thorium-234http://en.wikipedia.org/wiki/Thorium-234http://en.wikipedia.org/wiki/Thorium-234http://en.wikipedia.org/wiki/Uranium-238http://en.wikipedia.org/wiki/Uranium-238http://en.wikipedia.org/wiki/Uranium-238http://en.wikipedia.org/wiki/Atomic_numberhttp://en.wikipedia.org/wiki/Mass_numberhttp://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Helium-4http://en.wikipedia.org/wiki/Helium-4http://en.wikipedia.org/wiki/Helium-4http://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Thorium-234http://en.wikipedia.org/wiki/Uranium-238http://en.wikipedia.org/wiki/Atomic_numberhttp://en.wikipedia.org/wiki/Mass_numberhttp://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Radioactivity


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ALPHA DECAY

Alpha particles are commonly emitted by all of the

larger radioactive nuclei such as uranium, thorium,

actinium, and radium, as well as the transuranic

elements

Alpha particles have a typical kinetic energy of 5 MeV

and a speed of 15,000 km/s

The smallest nuclei that have to date been found to be

capable of alpha emission are the lightest nuclides of

tellurium (element 52)
http://en.wikipedia.org/wiki/Alpha_particleshttp://en.wikipedia.org/wiki/Alpha_particles


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APHA DECAY-MCHANISM OF

PRODUCTION Alpha decay results from the Coulomb repulsion between the

alpha particle and the rest of the nucleus, which both have apositive electric charge, but which is kept in check by the nuclearforce. In classical physics, alpha particles do not have enough

energy to escape the potential well from the strong force insidethe nucleus (this well involves escaping the strong force to go upone side of the well, which is followed by the electromagneticforce causing a repulsive push-off down the other side).

However, the quantum tunnelling effect allows alphas to escapeeven though they do not have enough energy to overcome the

nuclear force. This is allowed by the wave nature of matter, whichallows the alpha particle to spend some of its time in a region sofar from the nucleus that the potential from the repulsiveelectromagnetic force has fully compensated for the attraction ofthe nuclear force. From this point, alpha particles can escape, andin quantum mechanics, after a certain time, they do so.


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DAMAGE


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SMOKE DETECTOR


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HISTORY

In the years 1899 and 1900, physicists Ernest Rutherford

(working in Manchester) and Paul Villard (working in

Paris) separated radiation into three types: eventually

named alpha, beta, and gamma by Rutherford, basedon penetration of objects and deflection by a magnetic

field.

Alpha rays were defined by Rutherford as those having

the lowest penetration of ordinary objects.

Rutherford's work also included measurements of theratio of an alpha particle's mass to its charge,

Alpha particles are doubly charged helium( proved in

1907 by Rutherford & Thomas Royd)


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HISTORY

To do this they allowed alpha particles to penetrate a

very thin glass wall of an evacuated tube, thus

capturing a large number of the hypothesized helium

ions inside the tube. They then caused an electric sparkinside the tube, which provided a shower of electrons

that were taken up by the ions to form neutral atoms of

a gas. Subsequent study of the spectra of the resulting

gas showed that it was helium and that the alpha

particles were indeed the hypothesized helium ions.


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PROBLEMS

If substances emitting alpha particles are ingested, inhaled,

injected or introduced through the skin, then it could

result in a measurable dose causing cellular damage.

alpha radiation is the most destructive form of ionizingradiation

It is the most strongly ionizing, and with large enough doses

can cause any or all of the symptoms of radiation

poisoning. It is estimated that chromosome damage from

alpha particles is anywhere from 10 to 1000 times greater

than that caused by an equivalent amount of gamma orbeta radiation. The powerful alpha emitter polonium-210

is suspected of playing a role in lung cancer and bladder

cancer related to tobacco smoking.


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APPLICATION

Most smoke detectors contain a small amount of the alphaemitter americium-241. The alpha particles ionize airbetween a small gap. A small current is passed through thationized air. Smoke particles from fire that enter the air gap

reduce the current flow, sounding the alarm.

Alpha decay can provide a safe power source forradioisotope thermoelectric generators used for spaceprobes and artificial heart pacemakers.

Researchers are currently trying to use the damagingnature of alpha emitting radionuclides inside the body bydirecting small amounts towards a tumor. The alphasdamage the tumor and stop its growth while their smallpenetration depth prevents radiation damage of thesurrounding healthy tissue. This type of cancer therapy iscalled unsealed source radiotherapy.


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SMOKE DETECTOR


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CHALLENGES

PRTECTING PEOPLE FROM EXPOSURE OF ALPHA

PARTICLES.

You must have specialized equipment to detect alpha

radiation. Generally, this equipment is expensive andrequires an expert to operate it.

Documents

ALPHA DECAY.pptx