Later studies have shown that there are actually two kinds of mesons, heavier ones called п-mesons or pions, and lighter ones known as u-mesons. Both pions and muons can carry either a positive or negative electric charge (п+, л-, u.+, u.), and in addition there also exist neutral pions (n°). All of these new particles, as well as the positive and negative cosmic ray electrons (e+, e) are genetically related to each other and form a sequence somewhat similar to the sequence of the radioactive elements. It is now established that the primary high-energy protons entering the outer fringes of the atmosphere give rise to neutral and charged pions. Neutral pions possess a very short lifetime (about 10"" sec) and, in spite of their high velocity, break up into two y-quanta:
n°-* y + y1
before reaching the surface ofthe earth. The charged pions (both positive and negative) live somewhat longer (108 sec) but still most of them break up high in the atmosphere according to the equation:
я*-* u* + neutrino
Accordingly, for the study of pions and their decay into muons photographic equipment attached to large balloons must be sent high into the stratosphere.
The mean lifetime of muons is comparatively long (106 sec), and many of them reach the surface of the earth and permit themselves to be photographed in ordinary cloud chambers. Since cloud chamber equipment is too bulky and heavy to be sent up in balloons, cosmic ray researchers have developed a new method for photographing the tracks of cosmic particles at high altitudes. Instead of using the ionizing properties of fast charged particles passing through humid air, the new method is based on the fact that these particles affect the grains through which they pass when they travel through a finegrained photographic emulsion. When the photographic plate is developed it shows dark streaks that correspond to the trajectories followed by particles. A very rare photograph of this kind showing the formation of a pion resulting from the collision of a primary cosmic ray particle with a composite nucleus and the subsequent decay of this pion into a muon and an electron is shown in the figure below.
Apart from mesons, which have a mass intermediate between those of an electron and a proton recent studies of cosmic rays have discovered particles that are heavier than protons and are known under the collective name hyperons. The study of these particles and of their interrelation with each other was, for a time, the most interesting and most important field of exploration in physics.
• Find equivalents for the following phrases.
ядерные силы, вероятно, обуславливаются наличием; в соответствии с теоретическими предположениями; протоны чрезвычайно высоких энергий; межзвездное пространство; энергии колеблются от сравнительно низких величин до; проникающее излучение; и положительно и отрицательно заряженные; приблизительно в 100 раз тяжелее; в соответствии с теоретическим предположением; либо положительный, либо отрицательный электрический заряд; кроме того, существуют нейтральные пионы; а также электроны; ряд, несколько похожий на; несмотря на их высокую скорость; среднее время жизни; слишком громоздкое; набольших высотах; вместо использования; воздействует на зерна; когда фотопластинку проявляют; помимо мезонов, соответствующих траекториям, по которым следуют частицы; пион, образующийся в результате столкновения
• Re-read the passage and supply answers to the questions.
1. What problem does the passage deal with?
2. What assumption did a Japanese physicist, Hidekei Yukawa, make in 1932?
3. What did Yukawa try to explain?
4. What did he assume concerning the mass of these hypothetical particles?
5. Who observed these particles experimentally?
6. Where did Carl Andersen observe mesons?
7. What instruments did physicists use then for observing primary cosmic ray particles?
8. Why were mesons first called "heavy electrons"?
9. How many kinds of mesons were discovered later?
10. What is the difference between n- and u.-mesons?
11. How many types of я-mesons are there?
12. What two particles does n° break up into before reaching the surface of the earth?
13. What is the lifetime of a neutral pion?
14. What particles does the breakup of л° give rise to?
15. Why does if practically never reach the surface of the earth while many ofthe muons reach the surface of the earth?
16. Why is cloud chamber equipment difficult to be sent up in balloons?
17. What new method has been developed by physicists for detecting tracks of cosmic particles at high altitudes?
18. What fact is the photographic emulsion method based on?
• Match the synonyms from both columns.
II
mean, altitude, to affect, to estimate, usual, to result in, regardless of,
to range, actually, in addition, similar, to give rise to, in spite of, ordinary, to result from
alike, to arise from, height, besides, in fact, average, to evaluate, to influence, to vary
to cause, to result in, to give rise to, to bring about — привести к... to be caused, to result from, to be due to, to arise from — являться результатом...
• Translate into Russian paying attention to the words in bold type.
1. The errors may have resulted from lack of accuracy in the measurements.
2. Neutron absorption frequently results in the emission of secondary gamma rays.
3. The disintegration ofthe radiative elements gives rise to three types of radiation.
4. The black spots on the surface might be due to long exposure.
5. The compound nucleus formation will bring about elastic scattering.
6. The mistake has been caused by lack of operator knowledge.
Remember!
определительное существительное (какой?) <— (какой?) «- (что?) сущ. + сущ. + сущ.
При переводе такой группы слов следует прежде всего начинать перевод с последнего существительного (определяемого). Все остальные существительные, стоящие перед ним, его определяют.
gam ma-ray sensitivity — чувствительность по гамма лучам
energy-charge relation - зависимость заряда от энергии
• Translate the following word combinations.
electron rest-mass, phase shift analysis, electron velocity distribution, pulse series generator
• Translate into English using both... and, either... or, neither... nor.
1. И теория, и практика показывают, что новый метод лучше.
2. Ни он, ни другие ученые не сумели установить это соотношение.
3. Эту книгу можно найти или в библиотеке, или в читальном зале.
4. Отклонение рентгеновских лучей наблюдалось как в магнитном, так и в электрическом поле.
5. Ни я, ни мой друг не смогли решить это уравнение.
CLASSWORK
READING (1 IB)
• Skim the passage rapidly and explain (he title.
THE MYSTERIOUS NEUTRINO
The early studies of radioactive (3-decay (the emission of an electron by an unstable atomic nucleus) led to the conclusion that there is something wrong with the energy balance involved. While the (x-particles emitted by a given radioactive element always carry a well-defined amount of energy characteristic of that particular clement, (3-particles show a wide energy spread (разброс) ranging from almost zero to rather high energy values. Since the total energy liberation in the transformation of one atomic nucleus into another is expected to be the same for all nuclei of a given kind, it was suspected that there would be another particle coming out ofthe nucleus along with the electron that carries the missing (недостающий) balance of energy. This hypothetical particle, which must be electrically neutral and must have a mass that is much smaller than even the mass of an electron, received the name neutrino which means "little neutral" in Italian.
The absence of electric charge and the extremely small mass allow neutrinos to penetrate thick material layers with the greatest of ease; a thick concrete (бетонная) wall is just as ineffective in stopping a beam of neutrinos as a chicken wire fence (проволочная изгородь) is in stopping a swarm (рой) of mosquitos. The neutrinos that are produced in great quantities near the center of the sun in the process of nuclear energy production pierce its entire body and fly away as if there were nothing there at all. It has been estimated theoretically that in order to stop effectively a beam of neutrinos we would need a shield several light-years thick.
In spite of the almost incredible ability of neutrinos to make their "getaway" (выход) physicists managed in 1955 to stop a few of them, thus finding unquestionable proof of their existence. F. Reines and C. Cowen of the Los Alamos Scientific Laboratory used forthis purpose the collision process between neutrinos and the nuclei of hydrogen atoms (protons) in which the neutrino was expected to produce a positron and to transform the proton into a neutron:
я + neutrino^ n + e+
These two scientists built a giant particle counter that registered neutrinos as well as positrons and placed it near one of the nuclear piles. The nuclear reactions taking place in the operating pile produce a tremendous number of neutrinos that stream out through a heavy shielding which holds back all other nuclear radiations. Although the chance of a neutrino hitting a proton and producing the above-mentioned reaction is only 1 out of 103u, some of these reactions do actually take place, resulting in the simultaneous appearance of a neutron and the accompanying positron. Thus, the uncatchable neutrino was finally caught and joined the company of well-established elementary particles.
• Re-read the passage and give answers to the following questions.
1. What made scientists search for a hypothetical particle neutrino?
2. Why do physicists say of a neutrino that it is next to nothing?
3. What experimental procedure did scientists stage to detect neutrinos?
4. Why docs a heavy shielding of a reactor hold back all other nuclear particles but neutrinos?
• Give a free translation of the following passage.
Интерес к космическим лучам сверхвысоких энергий объединяет представителей двух наук — астрофизики и физики элементарных частиц. Дело втом, что, с одной стороны, источниками этого излучения могут быть такие пока недостаточно познанные астрономические объекты, как пульсары, оболочки сверхновых звезд, черные дыры, активные ядра галактики и квазары, и потому информация, приносимая космическим излучением, очень важна для физики космоса. С другой стороны, это излучение состоит из частиц самых больших из известных нам энергий, в тысячи и миллионы раз превосходящих те, которые достигнуты на созданных человеком ускорителях. Вот почему изучение таких частиц имеет важнейшее значение и для физики высоких энергий. В целом же можно сказать, что исследование космических лучей — это своего рода глубокая разведка (reconnaissance) в «горячих точках» науки.
HOMEWORK
(to be done in writing)
1. Translate into Russian.
1. The substance under investigation should be examined both by chemical and physical means.
2. They should have used some other metal for the conductor, for this one offers too high resistance to current.
3. You should have used a specially designed computer.
4. An operator of a computing machine should have an engineering background.
5. The density of the medium would change with temperature no matter what measures they took.
6. There were electron tube devices in our laboratories but now they are replaced by semiconductor ones.
7. It would be desirable that all necessary calculations be made before the experiment starts.
2. Translate into English.
1. Огромное количество энергии высвобождалось бы в этом случае.
2. Вам следовало бы провести всесторонний анализ этого процесса.
3. Мы хотели определить это отношение, но никак не могли.
4. Мы узнали, что нейтроны не будут испытывать отталкивания при приближении к ядрам атомов.
5. Падающий нейтрон был бы захвачен ядром.
6. Вам следует знать, что растепление ядра урана на две почти равные части открыло новые перспективы в области ядерной физики.
UNIT TWELVE GRAMMAR: GERUND
Adverbial Modifier
in | In measuring the current they used that device. Измеряя (при измерении) силу(ы) тока, они использовали этот прибор. |
on, upon, after | On measuring the current they put down the results. Измерив (после измерения) силу(ы) тока, они записали результаты. |
by | They achieved good results by experimenting. Они получили хорошие результаты путем экспериментирования (экспериментируя). |
without | Не left the room without saying a word. Он ушел из комнаты, не сказав ни слова. |
• Phrases to be completed.
1. In solving the problem...
2. On comparing those phenomena...
3. In processing the data...
4. Upon calculating the mass...
5. By diluting the solution...
6. Without increasing the speed...
WORD AND PHRASE STUDY
• Study the meanings of due, be due to and due to.
due (to) adj. — соответствующий, надлежащий, вызванный,
обусловленный be due to — бытьобусловленным, являться следствием;
быть разработанным, предложенным due to prep. — благодаря, из-за, вследствии
(syn. because of, on account of, owing to, in view of, thanks to, by/in virtue of, consequent on)
• Now translate these sentences.
1,. Due consideration must be given to missile performance requirements.
2. No difference due to n-p scattering in the target was found.
3. Coincidences arise due to second-order effects.
4. A due explanation ofthe phenomenon of radioactivity was first given by the Curies.
5. This phenomenon was found to be due to the lowering of the temperature down to -200 °C.
6. An up-to-date apparatus, due to Frankenburg, isshown in Fig. 10.
READING (12A)
• Study the schematic representation of the passage given below, then read the passage and be prepared to summarize the problem using this diagram.
inactive (\Jm) T
critical size (10 cm) |
I chai |
i active (U235) i |
|
fission —» neutrons |
(carbon/graphite) |
fissile —> materials
demonstration of scientific ideas
efficiency production of
heavier isotopes I
 |
FERMI-PILE AND PLUTONIUM
I n the Fe rmi-pile, the fission chain reaction could be maintained in natural uranium, buTThe naturajuranium was so highly diluted by carbon thiaTRigh efficiency in energy production could not be achieved. Owing to the presence of inactive U238, the chain reaction in the pile could not possibly develop into an efficient explosion, nor could it be very useful as a power source. So what good was the Fermi-pile, except for demonstrating the purely scientific principle of the possibility of a self-maintaining nuclear reaction? Of course, the demonstration of a purely scientific principle is always of very great importance, but the Fermi-pile was built at great expense in the midst of a perilous war when all expenditures were supposed to be judged on the basis of their military usefulness. The Fermi-pile stood this acid test. Although the energy released in the fission of U235 nuclei could not be utilized and was literally sent down the drain by means of the water-cooling system, a new fissionable element was produced inside the pile during operation. The neutrons that were not used in the maintenance ofthe chain reaction in U235 nuclei were captured by U238 nuclei, producing the heavier isotope: 92U238 + on'->,2U23' + Y Having an excess of neutrons, the nuclei of92U239 underwent two successive P- transformations, giving rise to elements with atomic numbers 93 and 94. These two elements, which do not exist in nature but have been produced artificially by human genius, were given the names neptunium andplutonium. The reactions following the neutron capture by U238 can be written: |
A good tourist is supposed to be able to build a campfire even ifthe wood is soaking wet. This role of a good hiking tourist in the nuclear energy project was played by the Italian-American physicist, Enrico Fermi, who actually made the "wet" uranium logs "burn'VHe was able to do so by utilizing the fact mentioned above, that the effectiveness of fission ne utron s in producing t he fission of U235 nuclei increases quite considerably wjicjalhcy are slowed down. llsucfTilowing~fTown of fission neutrons could be achieved, the presence of inactive U 238 would not make much difference.t To slow down the original fission neutro ns it was necessary to mix natural uranium with a large amountof car bon in the form of graphite. A large "pile" of graphite bricks with small pieces of natural uranium included in the structure was constructed in great secrecy under the grandstand ofthe University of Chicago Stadium, and on December 2, 1941, Professor A. Compton wired to Dr. Vannevar Bush in Washington, D.C.: "The Italian navigator has landed. The natives are friendly." In the secret language ofthe Manhattan Project this meant: "The Fermi-pile works successfully. Nuclear chain reaction is achieved."
92U»8^0,Np2-w + c-
Being chemically different from uranium, the plutonium produced in the Fermi-pile can be separated and purified with much less effort than it takes to separate a light uranium isotope from the heavy one, and this element turned out to be even more fissionable than U235. In fact, whereas U2'5 gives rise to 2.5 fission neutrons, the corresponding figure for Pu239 is 2.9 fission neutrons.
Critical Size
When a single fission process occurs inside a given sample of pure U235 or Pu239, several fission neutrons are ejected from the point where the nuclear breakup took place. The average distance a fission neutron must travel through the material in order to run into another nucleus is about 10 cm so that if the size ofthe sample in question is less than that, most of the fission neutrons will cross the surface of the sample and fly away before they have a chance to cause another fission and produce more neutrons. Thus, no progressive chain reaction can develop if the sample of fissionable material is too small. Going to larger and larger samples, we find that more fission neutrons produced in the interior have a chance to produce another fission by colliding with a nucleus before they escape through the surface, and for samples of a very large size only a small fraction of the neutrons produced in them has a chance to reach the surface before collidi ng with one of the nuclei. The size ofthe sample of a given fissionable material for which the percentage of neutrons giving rise to subsequent fission processes is high enough to secure a progressive reaction is known as the critical size for that particular material. Since the number of neutrons per fission is larger in the case of plutonium than in the case of uranium-235, the critical size of plutonium samples is smaller than that of uranium-235 samples because the former can afford larger losses of neutrons through its surface.
• Find English equivalents for the following Russian phrases.
не имело бы большого значения; зажечь костер, даже если дерево насквозь пропиталось водой; самоподдерживающаяся цепная реакция; выдержал суровое испытание; из-за наличия неактивного U23S; за исключением демонстрации чисто научного принципа; претерпели последовательные преобразования; приводя к образованию элементов; заставил гореть ценой огромных расходов; буквально была спущена в дренажную трубу; ценой гораздо меньших усилий, чем требуется для...; может позволить большие потери
• Read the passage carefully again and supply answers to the following questions.
1. What scientific discoveries led to the idea ofthe first chain reaction?
2. When and where was the first atomic pile constructed?
3. What fissile material was used in it?
4. What conditions should be met for the chain reaction to be achieved?
5. Could the Fermi-pile be useful as a power source? Why not?
6. What two scientific ideas did the Fermi-pile demonstrate?
• Give a summary of the passage using the scheme on p. 94.
• Choose the correct form to fit into each sentence.
(collisions, collide, colliding)
1. Quite frequently the two types of atom will.... The energy given up by the electron injumpingtoa lower state goes into creating an additional photon with the same characteristics as the... photon. For samples of a very large size only a small fraction of the neutrons produced in them has a chance to reach the surface before... with one of the nuclei. There are two kinds of... between the electrons and the atoms.
(the question, in question, question)
2. The substance... contains traces of this element. One might... these results. Ifthe size of the sample... is less than 10 cm, most ofthe fission neutrons will cross the surface and flyaway.... arises of how accurately these data present the results obtained.
• Translate the following word combinations.
original fission neutrons, nuclear chain reaction, single fission process, vertical cloud chamber, cosmic ray particle, wide energy spread, total energy liberation, thick material layer, critical size level, nuclear power production, ordinary steam turbine
• Translate into Russian, observe the use of "theformer, the latter".
1. There are two different methods to count scintillations: in the former the microscope is used, in the latter, the Geiger-counter.
2. There are two ways to detect and measure radioactivity. The former is the gold-leaf electroscope, the latter, the Wilson cloud chamber.
3. Only two types of rays are deflected in the magnetic field: the former to the left, the latter to the right.
CLASSWORK
READING (12B)
• Skim the passage as fast as possible and find answers to the following questions.
1. What is the main problem in maintaininga steady chain reaction?
2. What are "control rods" used for?
3. What is the design of a "swimming pool" reactor?
4. For what purposes are nuclear power reactors used?
NUCLEAR REACTORS
A sample of fissionable material smaller than the "critical size" is unable to carry on a nuclear chain reaction. If the size of the sample is exactly critical, the number of neutrons produced in each generation is the same as that produced in the previous one, resulting in steady nuclear energy liberation. The original Fermi-pile and its later modifications maintain nuclear reactions at the critical size level. *It must be mentioned in this connection that the conditions of "criticality" are extremely unstable: a small deviation (отклонение) in one direction will result in the rapid extinction (уменьшение количества нейтронов) of fission neutrons and the cut-off of the nuclear chain reaction, whereas a deviation in another direction will lead to a rapid multiplication ofthe fission neutrons and the melting (плавление) of the entire structure. Thus, the important problem in maintaining a steady chain reaction is that of regulating the rate of neutron production and of keeping the chain reaction from "dying out" or "running away". *This is achieved by using "controlrods" made from neutron-absording materials (such as boron) which arc automatically pushed in or pulled out from narrow channels drilled through the reacting fissionable material as soon as the rate of neutron production drops below or exceeds the desired level.
We have already mentioned that Fermi-piles were unsuitable for purposes of nuclear power production because ofthe high dilution of uranium by carbon; they should be considered rather as "alchemicalplants" in which plutonium is produced. For the purpose of nuclear power production, we use the controlled nuclearehain reactions in pure fissionable materials, such as U235 or Pu234, which can be run at quite high temperatures. In the so-called "swimming pool" reactor (реактор бассейнового типа) in which several cylindrical containers filled with pure fissionable material arc placed at the bottom of a large water tank, the water circulating through the tank carries away the heat produced in the fission process and also protects the observer from the deadly nuclear radiation. The color of the water turns blue as a result of the so-called Cherenkoffs radiation produced in water by high-energy electrons.
• Explain how you understand the italicized words and phrases in the text.
• Give an adequate translation of the sentences marked with an asterisk.
• Give a summary of the passage in English or in Russian.
• Give a free translation of the text.
У каждого элемента есть радиоактивные изотопы, которые либо существуют в природе, либо возбуждаются искусственно бомбардировкой устойчивых ядер такими частицами, как протоны, альфа-частицы или нейтроны. Частица, однако, не будет поглощаться ядром мишени, если ее скорость не будет соответствовать (correspond with) одному из энергетических уровней (level) ядра. Тяжелые ядра, имеющие больше энергетических уровней, чем легкие, осуществляют захват частицы с большей вероятностью, и этот факт помогает объяснить значение урана, тория и других очень тяжелых атомов в ядерном исследовании.
Так как нейтрон не заряжен, на него не влияют заряженные электроны и протоны, и поэтому более вероятно, что он, а не другая частица, будет захвачен. В случае захвата нейтрона массовое число ядра увеличится и ядро станет неустойчивым и радиоактивным. По мере того как излучение продолжается, уровень радиоактивности уменьшается экспоненциально, и время, которое требуется для того, чтобы он достиг половины своей первоначальной (исходной) величины, известно как период полураспада изотопа (half-life).
HOMEWORK
(to be done in writing)
1. Translate into Russian.
1. The predicted accuracy was found to be difficult to obtain in practice.
2. Light was assumed to leave a source as an indefinite number of particles travelling in straight lines.
3. Collisions between electrons and neutral molecules in solids appear to be frequent.
4. The moon appears to be a particularly good gravitational antenna.
5. The new lasers were expected to work in principle at least at a very high efficiency in comparison with other lasers.
6. An intense beam of light is observed to emerge from the mirror ends of the crystal: the entire process is called light amplification by stimulated emission of radiation (hence the acronym "laser").
7. Solid-state lasers already exist and although they have not had the spectral purity of gas lasers, this situation seems to be changing.
8. At first the concept of charge density in an atom seems to bear little resemblance to Bohr's picture of an electron orbiting the nucleus, but the two views are closely related.
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