Gurgen Askaryan - AbsoluteAstronomy.com

Gurgen Askaryan (December 14, 1928 – 1997) was a prominent Soviet physicist, famous for his discovery of the self-focusing

Self-focusing

Self-focusing is a non-linear optical process induced by the change in refractive index of materials exposed to intense electromagnetic radiation. A medium whose refractive index increases with the electric field intensity acts as a focusing lens for an electromagnetic wave characterised by an...

of light, pioneering studies of light-matter interactions, and the discovery and investigation of the interaction of high-energy particles with condensed matter. (See Askaryan effect

Askaryan effect

The Askaryan effect is the phenomenon whereby a particle traveling faster than the phase velocity of light in a dense dielectric produces a shower of secondary charged particles which contain a charge anisotropy and thus emits a cone of coherent radiation in the radio or microwave part of the...

)

Biography

Gurgen Askaryan was born in 1928 in Moscow, Russia to Armenian

Armenians

Armenian people or Armenians are a nation and ethnic group native to the Armenian Highland.The largest concentration is in Armenia having a nearly-homogeneous population with 97.9% or 3,145,354 being ethnic Armenian....

parents. Both parents were doctors: father Ashot Askaryan, was a general practitioner, and his mother Astgik Askaryan was a dentist. At the age of 18 Gurgen entered the Department of Physics at the Moscow State University

Moscow State University

Lomonosov Moscow State University , previously known as Lomonosov University or MSU , is the largest university in Russia. Founded in 1755, it also claims to be one of the oldest university in Russia and to have the tallest educational building in the world. Its current rector is Viktor Sadovnichiy...

, where he started his first research project specializing in the physics of atomic nuclei. Graduated in 1952 and was accepted to the graduate school at the Institute of Chemical Physics (ICP) in Moscow. In 1953 transferred to the Lebedev Institute of Physics, and graduated with PhD in 1957. An author of over 200 articles, Askaryan made a significant contribution to the field of high energy physics (see Askaryan effect

Askaryan effect

and ANITA

ANtarctic Impulse Transient Antenna

The AA experiment has been designed to study ultra-high-energy cosmic neutrinos by detecting the radio pulses emitted by their interacting with the Antarctic ice sheet...

(Antarctic Impulsive Transient Antenna)), acoustics

Acoustics

Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...

, and optics

Optics

Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...

. For his famous discovery of the self-focusing

Self-focusing

of light, he received the highest scientific award at the time in Soviet Union. Shortly after receiving a degree of the Doctor of Science

Doctor of Science

Doctor of Science , usually abbreviated Sc.D., D.Sc., S.D. or Dr.Sc., is an academic research degree awarded in a number of countries throughout the world. In some countries Doctor of Science is the name used for the standard doctorate in the sciences, elsewhere the Sc.D...

in 1992, Gurgen experienced health problems, which were also accompanied by worsening of his sister Gohar’s health. He and his sister died the same day on 2 March 1997 in their apartment in Moscow, both because of similar heart disease.

Past Nobel Prize

During the third year of his education G. Askaryan proposed a new method of
registration of fast charged particles. His idea was the following. Suppose, there
is an overheated transparent liquid. A very small amount of energy is sufficient to
make it boil. Let a fast charged particle penetrate through this overheated liquid.
The particle expends its energy on ionization of atoms located near its trajectory.
This energy loss is transformed into heat in amount which is sufficient to induce
boiling along particle’s trajectory. Then the trajectory becomes observable because
many bubbles are created along it.

G. Askaryan discussed this proposal with some of his teachers and fellow students. No one objected. However, no one supported him, no one helped to realize
the idea. G. Askaryan then was inexperienced in forms and methods of scientific
investigation. He even did not publish his proposal. Several years later, in 1952,
the same idea was set forth independently by an American physicist Donald Arthur
Glaser

Donald A. Glaser

Donald Arthur Glaser , is an American physicist, neurobiologist, and Nobel Prize in Physics laureate for his invention of the Bubble chamber used in subatomic particle physics....

. He put the idea into practice having assembled the device known now as
bubble chamber

Bubble chamber

A bubble chamber is a vessel filled with a superheated transparent liquid used to detect electrically charged particles moving through it. It was invented in 1952 by Donald A. Glaser, for which he was awarded the 1960 Nobel Prize in Physics...

. This instrument proved to be so useful in high energy physics
that D. A. Glazer was awarded with the Nobel Prize

Nobel Prize

The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. The will of the Swedish chemist Alfred Nobel, the inventor of dynamite, established the prizes in 1895...

in 1960. This event gave rise
to Askaryan’s deep concern. Of course, he was shaken that Nobel Prize was so near
and, so to say, he let it slip. On the other hand, this event helped him to get faith
in himself.

Cosmic rays and sound waves

G. Askaryan discovered and investigated in details various effects accompanying passage of high energy particles through dense matter (liquids or solids). He showed that hadron-electron-photon showers and even single fast particles may produce sound pulses. Ionization losses are quickly converted into heat, and the small region adjacent to trajectory undergoes quick thermal expansion thus generating sound waves. These results gave a new approach to the study of cosmic rays. Before, investigations of cosmic rays were based on direct interaction of cosmic ray particle with a detector. Askaryan’s results made it possible to detect showers and single particles using sound receivers situated at some distance from the event.

Several years ago, the registration of energetic particles and showers with sound detectors in sea water was planned as an important part of global monitoring.

Cosmic rays and electromagnetic waves

G. Askaryan also showed that cosmic ray

Cosmic ray

Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...

showers emit electromagnetic radiation, thus giving yet another way for their detection. Before him it was commonly assumed that electron-photon showers do not emit electromagnetic radiation since the electrons and positrons are created in pairs. Askaryan’s analysis led to the conclusion that in an electron-photon shower there is an excess of negative charge (excess of electrons). These excess electrons are knocked out from atoms either by photoeffect or by shower electrons and positrons (ionization). At the same time, due to the annihilation process the number of positrons decreases. Thus, there is an electric current created by the excess electrons associated with shower. This variable current is the source of electromagnetic radiation. Therefore, every shower is the source of electromagnetic radiation. These studies opened new perspectives for distant registration of cosmic ray showers.

These investigations paved the way for distant registration of cosmic ray showers. Now many radio-astronomical stations are conducting observations on cosmic ray showers.

Intense laser beams and radiation acoustics

Later G. Askaryan showed that intense laser beam passing through matter also generates sound waves This effect may be used for processing and for destruction of matter. As a result of this series of investigations, a new branch of physics was created, radiation acoustics, and G. Askaryan was the founder.

Interaction of laser beam with substances

After discovery of lasers, G. Askaryan began to investigate interaction of laser
beam with various substances. At that time physicists who worked with lasers,
used to break through thin metal specimens (usually, razor blades) with laser beam.
It was something like a game. G. Askaryan also rendered tribute to this game. He
noticed that holes made by laser beam were of two kinds. When he used laser
of moderate power, the edges of aperture were smooth, as if the aperture was
melted through (indeed, it was melted). However, the hole made by powerful laser
had rough uneven edges, as if the hole was broken through, not melted. At first
G. Askaryan supposed that it was the light pressure which knocked out the part of
razor blade in the light spot, however, simple estimates showed that the assump-
tion was wrong.

The problem was later cleared up by G. A. Askaryan and E. M. Moroz.
The explanation was the following. The beam from a powerful laser heats metallic surface
so intensely that surface layer turns into a vapor before the heat penetrates into
next layers. The vapor is ejected from the surface. Thereby, a force arises which
acts on the part of surface within the spot. This force is numerically equal to the
momentum of vapor ejected during a unit of time. Such is the reaction of vapor
on the surface. And in the case of powerful laser this reaction is so strong that
the metal within the spot is torn out. The reaction of the vapor gives pressure
that is many orders greater than the light pressure. Vaporizing ablation is now
used for compressing the nuclear fuel in the problem of laser induced controlled
thermonuclear reactions.

Self-focusing of waves

Perhaps one of the most brilliant of Askaryan’s discoveries was the self-focusing

Self-focusing

of light. In the medium with third order nonlinear polarization, the refractive index can be represented as n = n₀ + n₂I, where n₀ is the linear refractive index, n₂ is an optical constant characterizing the strength of the optical nonlinearity, and I is the Gaussian intensity profile of the beam. The phenomenon of self-focusing may occur if a beam of light with nonuniform transverse intensity distribution, for example Gaussian profile, propagates through a material in which n₂ is positive. If a strong beam of light passes through a medium with this type of nonlinearity also called Kerr

Kerr effect

The Kerr effect, also called the quadratic electro-optic effect , is a change in the refractive index of a material in response to an applied electric field. The Kerr effect is distinct from the Pockels effect in that the induced index change is directly proportional to the square of the electric...

nonlinearity, then the refractive index of the medium inside the beam is greater than that outside of the beam. If the electric field is strong enough then the beam will create a dielectric waveguide, which reduces or entirely eliminates the divergence of the beam. Askaryan called this effect self-focusing

Self-focusing

. Discovery of self-focusing opened a new chapter in non-linear elec-
trodynamics and optics.

Askaryan effect

The Askaryan effect

Askaryan effect

, which was theoretically predicted by Askaryan in 1962, describes a phenomenon, similar to the Cherenkov effect, whereby a particle travelling faster than the speed of light in a dense radiotransparent medium such as salt, ice or the lunar regolith produces a shower of secondary charged particles which contain a charge anisotropy and thus emits a cone of coherent radiation in the radio or microwave part of the electromagnetic spectrum. This phenomenon is of primary interest in using bulk matter to detect ultra-high energy neutrinos.

Other

Askaryan was the first to note that the outer few metres of the Moon's surface, known as the regolith, would be a sufficiently transparent medium for detecting microwaves from the charge excess in particle showers. The radio transparency of the regolith has since been confirmed by the Apollo missions.

Askaryan also found (together with M. L. Levin) a combination of auxiliary high-frequency elds which could secure stability of electron bunch during acceleration.

Selected works

Source: ISI Web of Knowledge

Askaryan GA, 'O GENERATSII RADIOVOLN MILLIMETROVOGO DIAPAZONA PRI PROKHOZHDENII ELEKTRONNOGO SGUSTKA CHEREZ TORMOZYASHCHUYU SREDU', ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI 27 (6): 761-761 1954
Askaryan GA, 'ACCELERATION OF CHARGED PARTICLES IN RUNNING OR STANDING ELECTROMAGNETIC WAVES', SOVIET PHYSICS JETP-USSR 9 (2): 430-430 1959
Askaryan GA, 'RADIATION OF VOLUME AND SURFACE COMPRESSION WAVES DURING IMPINGEMENT OF A NONRELATIVISTIC ELECTRON STREAM AT THE SURFACE OF A DENSE MEDIUM', SOVIET PHYSICS-TECHNICAL PHYSICS 4 (2): 234-235 1959
Askaryan GA, 'ELECTROMAGNETIC RADIATION FROM ELECTRON DIFFUSION', SOVIET PHYSICS JETP-USSR 12 (1): 151-152 1961
Askaryan GA, 'DIAMAGNETIC PERTURBATIONS IN MEDIA CAUSED BY IONIZING RADIATION', SOVIET PHYSICS JETP-USSR 14 (1): 135-137 1962
Askaryan GA,'INTERACTION BETWEEN LASER RADIATION AND OSCILLATING SURFACES', SOVIET PHYSICS JETP-USSR 15 (6): 1161-1162 1962
Askaryan GA,'EXCESS NEGATIVE CHARGE OF AN ELECTRON-PHOTON SHOWER AND ITS COHERENT RADIO EMISSION', SOVIET PHYSICS JETP-USSR 14 (2): 441-443 1962
Askaryan GA,'CERENKOV RADIATION AND TRANSITION RADIATION FROM ELECTROMAGNETIC WAVES', SOVIET PHYSICS JETP-USSR 15 (5): 943-946 1962
Askaryan GA, IOVNOVICH ML, LEVIN ML, et al.,'TRANSPORT AND CONTAINMENT OF MOVING PLASMA CONCENTRATIONS (HIGH FREQUENCY AND MAGNETIC PLASMA WAVE-GUIDES)', NUCLEAR FUSION : 797-800 Suppl. 2 1962
Askaryan GA,'PROJECTION OF PLASMOIDS THROUGH MAGNETIC FIELDS (MAGNETODYNAMIC TRAPS)', SOVIET PHYSICS-TECHNICAL PHYSICS 7 (6): 492& 1962
Askaryan GA, PROKHOROV AM, CHANTURIYA GF, et al.,'THE EFFECTS OF A LASER BEAM IN A LIQUID', SOVIET PHYSICS JETP-USSR 17 (6): 1463-1465 1963
Askaryan GA,'DIRECTED COHERENT RADIATION DUE TO BREAKDOWN NEAR THE TRACK OF AN IONIZING PARTICLE', SOVIET PHYSICS JETP-USSR 17 (4): 901-902 1963
Askaryan GA,'EXCITATION AND DISSOCIATION OF MOLECULES IN AN INTENSE LIGHT FIELD', SOVIET PHYSICS JETP-USSR 19 (1): 273-274 1964
Askaryan GA,'EMISSION OF RADIO WAVES UPON MODULATION OF AN INTENSE BEAM OF LIGHT IN A MEDIUM', SOVIET PHYSICS JETP-USSR 18 (2): 441-443 1964
Askaryan GA,'COHERENT RADIO EMISSION FROM COSMIC SHOWERS IN AIR AND IN DENSE MEDIA', SOVIET PHYSICS JETP-USSR 21 (3): 658& 1965
Askaryan GA, GOLTS EY, RABINOVI.MS, 'USE OF ARTIFICIAL METEORS FOR LASER PUMPING', JETP LETTERS-USSR 4 (11): 305& 1966
Askaryan GA, 'OPTOCALORIC EFFECT (AMPLIFICATION OF ATOMIC INTERACTION AND COOLING OF MEDIUM) IN A LASER BEAM', JETP LETTERS-USSR 3 (4): 105& 1966
Askaryan GA, 'SELF-FOCUSING AND FOCUSING OF ULTRASOUND AND HYPERSOUND', JETP LETTERS-USSR 4 (4): 99& 1966
Askaryan GA,'SELF-FOCUSING OF A LIGHT BEAM UPON EXCITATION OF ATOMS AND MOLECULES OF MEDIUM IN BEAM' JETP LETTERS-USSR 4 (10): 270& 1966
Askaryan GA, RABINOVI.MS, SMIRNOVA AD, et al.,'CURRENTS PRODUCED BY LIGHT PRESSURE WHEN A LASER BEAM ACTS ON MATTER' JETP LETTERS-USSR 5 (4): 93& 1967
Askaryan GA, 'NONLINEARITY OF MEDIA DUE TO INDUCED DEFORMATION OF MOLECULES ATOMS AND PARTICLES OF A MEDIUM', JETP LETTERS-USSR 6 (5): 157& 1967
Askaryan GA, 'WAVEGUIDE PROPERTIES OF A TUBULAR LIGHT BEAM', SOVIET PHYSICS JETP-USSR 28 (4): 732& 1969
Askaryan GA, STUDENOV VB,'BANANA SELF FOCUSING OF BEAMS', JETP LETTERS-USSR 10 (3): 71& 1969
Askaryan GA, CHISTYI IL,'THERMAL SELF-FOCUSING IN A LIGHT BEAM WITH LOW INTENSITY NEAR AXIS', SOVIET PHYSICS JETP-USSR 31 (1): 76& 1970
Askaryan GA, PUSTOVOI.VI,'SELF-FOCUSING AND FOCUSING OF ULTRASOUND AND HYPERSOUND IN METALS AND SEMICONDUCTORS', SOVIET PHYSICS JETP-USSR 31 (2): 346& 1970
ARUTYUNYAN.IN, Askaryan GA, POGOSYAN VA, 'MULTIPHOTON PROCESSES IN FOCUS OF AN INTENSE LASER BEAM WITH EXPANSION OF INTERACTIVE REGION TAKEN INTO CONSIDERATION', SOVIET PHYSICS JETP-USSR 31 (3): 548& 1970
Askaryan GA, STEPANOV VK, 'SIMULTANEOUS EXTENDED ACTION OF A HIGH-POWER LIGHT BEAM ON MATTER', SOVIET PHYSICS JETP-USSR 32 (2): 198& 1971
Askaryan GA, 'SELF-FOCUSING OF POWERFUL SOUND DURING PRODUCTION OF BUBBLES'JETP LETTERS-USSR 13 (7): 283& 1971
Askaryan GA, TARASOVA NM, 'INITIAL STAGE OF OPTICAL EXPLOSION OF A MATERIAL PARTICLE IN AN INTENSE LIGHT FLUX', SOVIET PHYSICS JETP-USSR 33 (2): 336& 1971
Askaryan GA, DIYANOV KA, MUKHAMAD.M,'NEW EXPERIMENTS ON FORMATION OF A SELF-FOCUSING FILAMENT FROM FOCUS OF BEAM ON SURFACE OF A MEDIUM', JETP LETTERS-USSR 14 (8): 308& 1971
Askaryan GA, RAKHMANI.TG,'SCATTERING, REFRACTION AND REFLECTION OF SOUND UNDER ACTION OF INTENSE LIGHT ON MEDIUM', SOVIET PHYSICS JETP-USSR 34 (3): 639& 1972
Askaryan GA, MANUKYAN SD, 'PARTICLE ACCELERATION BY A MOVING LASER FOCUS, FOCUSING FRONT OR FRONT OF AN ULTRASHORT LASER PULSE', ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI 62 (6): 2156-2160 1972
Askaryan GA, 'EFFECT OF SELF-FOCUSING',USPEKHI FIZICHESKIKH NAUK 111 (2): 249-260 1973
Askaryan GA, DIYANOV KA, MUKHAMAD.MA, 'SUPPRESSION OF NONLINEAR PROCESSES OF STIMULATED SCATTERING, BEAM COLLAPSE, AND BREAKDOWN OF MEDIUM DURING BEAM SCANNING - SELF-FOCUSING OF STROLLING-BEAMS', JETP LETTERS 19 (5): 172-174 1974
Askaryan GA, NAMIOT VA, RABINOVI.MS, 'UTILIZATION OF OVERCOMPRESSION OF A SUBSTANCE BY LIGHT-REACTIVE PRESSURE FOR PREPARATION OF MICROCRITICAL MASS OF FISSIONABLE ELEMENTS, SUPER-STRONG MAGNETIC-FIELDS AND PARTICLE ACCELERATION', USPEKHI FIZICHESKIKH NAUK 113 (4): 716-718 1974
Askaryan GA, NAMIOT VA, 'COMPRESSION AND FOCUSING OF A NEUTRON GAS BY MOVING MODERATOR', JETP LETTERS 20 (5): 148-149 1974
Askaryan GA, DOLGOSHEIN BA, 'ACOUSTIC REGISTRATION OF HIGH-ENERGY NEUTRINOS', JETP LETTERS 25 (5): 213-214 1977
Askaryan GA, DOLGOSHEIN VA,'MICROELECTROSTRICTION IN AN IONIZED MEDIUM', JETP LETTERS 28 (10): 571-574 1978
Askaryan GA, RAEVSKII IM, 'EXCITATION OF HIGH-FREQUENCY OSCILLATIONS BY A LASER-PULSE', JETP LETTERS 32 (2): 104-108 1980
Askaryan GA, MUKHAMADZHANOV MA, 'NON-LINEAR DEFOCUSING OF A FOCUSED BEAM - A FINE BEAM FROM THE FOCUS', JETP LETTERS 33 (1): 44-48 1981
Askaryan GA, 'INCREASE OF LASER AND OTHER RADIATION TRANSMISSIONS THROUGH SOFT OPAQUE PHYSICAL AND BIOLOGICAL MEDIA', KVANTOVAYA ELEKTRONIKA 9 (7): 1379-1383 1982
Askaryan GA, MANZON BM, 'LASER DRAGON DIRECTED BY THE BEAM OF LIGHT DISCHARGE EJECTION INTO THE ATMOSPHERE', USPEKHI FIZICHESKIKH NAUK 139 (2): 370-372 1983
Askaryan GA, 'NEUTRINO STUDY OF THE EARTH, THE NEUTRINO GEOLOGY', USPEKHI FIZICHESKIKH NAUK 144 (3): 523-530 1984
Askaryan GA, 'DECAY OF A HIGH-ENERGY PION BEAM IN A MEDIUM - FORMATION OF A DECAY CHANNEL', JETP LETTERS 41 (12): 651-654 1985
Askaryan GA, YURKIN AV, 'NEW STUDIES IN OPTOTHERMOACOUSTICS', JETP LETTERS 43 (4): 221-225 FEB 25 1986
Askaryan GA, 'Cherenkov Radiation
Cherenkov radiation
Cherenkov radiation is electromagnetic radiation emitted when a charged particle passes through a dielectric medium at a speed greater than the phase velocity of light in that medium...

FROM OPTICAL PULSES', Physical Review Letters
Physical Review Letters
Physical Review Letters , established in 1958, is a peer reviewed, scientific journal that is published 52 times per year by the American Physical Society...

57 (19): 2470-2470 NOV 10 1986
Askaryan GA, RAEVSKII IM, 'LASER SIMULATION OF THE LIGHT AND PLASMA ACTION ON COMETS AND PLANETS', KVANTOVAYA ELEKTRONIKA 14 (2): 229-231 FEB 1987
Askaryan GA, BATANOV GM, KOSSYI IA, et al., 'CONSEQUENCES OF MICROWAVE EMISSIONS IN THE STRATOSPHERE', USPEKHI FIZICHESKIKH NAUK 156 (2): 370-372 OCT 1988
Askaryan GA, YURKIN AV, 'NANOSECOND PHOTOGRAPHY OF FAST PROCESSES IN INVISIBLE (UV) LIGHT WITH A NITROGEN LASER AND NEW STUDY OF A TRAIN OF SHOCK-WAVES', JETP LETTERS 58 (7): 563-567 OCT 10 1993
Askaryan GA, Bulanov SV, Dudnikova GI, et al., 'Magnetic interaction of ultrashort high-intensity laser pulses in plasmas', PLASMA PHYSICS AND CONTROLLED FUSION 39 (5A): 137-144 Sp. Iss. SI MAY 1997

Biography

Past Nobel Prize

Cosmic rays and sound waves

Cosmic rays and electromagnetic waves

Intense laser beams and radiation acoustics

Interaction of laser beam with substances

Self-focusing of waves

Askaryan effect

Other

Selected works

See also