Alpha-particle heating

It is important to understand that ITER (O Fig. 60.10) will not be a fusion reactor, but a combined plasma confinement and fusion technology experiment. From the plasma physics point of view, it should demonstrate plasma operation under reactor conditions with Q = 10 in 500 s pulses. The plasma current would be driven inductively. Long pulse operations are planned with noninductive current drive at about Q = 3 fusion performance. ITER should demonstrate plasma operation with dominant alpha particle heating and should be capable of exploring diagnostics and plasma control schemes toward a reactor. 

Astatine can be produced by bombarding bismuth with energetic alpha particles to obtain the relatively long-lived 209-211At, which can be distilled from the target by heating in air. 

Once a fusion reaction has begun in a confined plasma, it is planned to sustain it by using the hot, charged-particle reaction products, eg, alpha particles in the case of D—T fusion, to heat other, colder fuel particles to the reaction temperature. If no additional external heat input is required to sustain the reaction, the plasma is said to have reached the ignition condition. Achieving ignition is another primary goal of fusion research. 

Alpha carbon atoms, 348 Alpha decay, 417, 443 Alpha particle, 417 scattering, 245 Aluminum boiling point, 365 compounds, 102 heat of vaporization, 365 hydration energy, 368 hydroxide, 371 ionization energies, 269, 374 metallic solid, 365 occurrence, 373 properties, 101 preparation, 238. 373 reducing agent, 367 Alums, 403 Americium... 

A is the manufacturer s rated activity based on calorimetric measurement of the heat evolved by the source. Since one 3-m.e.v. alpha particle produces 3 X 104 ion pairs in air of 1 mg. sq. cm. 1 density we calculate 7, the number of ion pairs produced per second above the leak in 1 cc. air at p torr pressure as ... 

Sample preparation is rather involved. A sample of urine or fecal matter is obtained and treated with calcium phosphate to precipitate the plutonium from solution. This mixture is then centrifuged, and the solids that separate are dissolved in 8 M nitric acid and heated to convert the plutonium to the +4 oxidation state. This nitric acid solution is passed through an anion exchange column, and the plutonium is eluted from the column with a hydrochloric-hydroiodic acid solution. The solution is evaporated to dryness, and the sample is redissolved in a sodium sulfate solution and electroplated onto a stainless steel planchette. The alpha particles emitted from this electroplated material are measured by the alpha spectroscopy system, and the quantity of radioactive plutonium ingested is calculated. Approximately 2000 samples per year are prepared for alpha spectroscopy analysis. The work is performed in a clean room environment like that described in Workplace Scene 1.2. 

Natural zircons heated at 800 °C during one hour when natural yellow broadband luminescence nearly totally disappears and irradiated by different doses of alpha particles. 

Self-heating, due to the stoppage of the alpha particles within the solid, is a well known phenomenon and calculation shows that the energy release from one gram of polonium metal would be about 140 watts. This high energy output affords a useful and absolute method for the rapid determination of polonium in large sources by calorimetry. 

Commercial uses of Se, Te, and Po are limited, though selenium is used to make red colored glass and in photocopiers (see the Interlude at the end of this chapter). Tellurium is used in alloys to improve their machinability, and polonium (2i0po) has been used as a heat source in space equipment and as a source of alpha particles in scientific research. 

Step 5. Pipette 100 X of the uranium solution each onto the centers of two planchets and dry under a heat lamp. Count one with the proportional counter and then with the alpha-particle spectrometer. Save the second planchet for Part 1C, Step 8. 

The deposition of polonium on metal wires gives rise to a useful a-source. Tips of metal wires having a length 10 mm and a diameter of 0.2 mm were utilized. They were made of Al, Ni, Pd, Pt or An. Each was immersed in 100 pi of a solution containing °Po (300 Bqml ) for 15 h at 27°. Alpha particle emission was measured using a liquid scintillation system. There was an observed diminution in the a-pulse spectra for all of the wires except Al. This was attributed to the mutual diffusion between the wire metal and °Po. The °Po deposited on the Al wire had a tendency to be eluted with the liquid scintillator. This was attributed to physical absorption on the porous metal oxide layer on the Al wire and °Po. The °Po deposited by the Al wire had a tendency to be eluted with the liquid scintillator. It was possible to prepare a °Po -Al wire as a useful a-source by heating at 120° for 30 minutes. 

The long-lived isotope of radium, Ra, decays hy alpha particle emission to its daughter radon, Rn, with a half-life of 1622 years. The energy of the alpha particle is 4.79 MeV. Suppose 1.00 g of Ra, freed of all its radioactive progeny, were placed in a calorimeter that contained 10.0 g of water, initially at 25°C. Neglecting the heat capacity of the calorimeter and heat loss to the surroundings, calculate the temperature the water would reach after 1.00 hour. Take the specific heat of water to be 4.18 J g. ... 

At the end of the neon burning the core is left with a mixture of alpha particle nuclei ieO and 24Mg. After this another core contraction phase ensues and the core heats up, until at Tg 2, ieO begins to react with itself ... 

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