Slide1: 1896 1899 a, b g 1912 A History of Cosmic Rays


Slide3: The Fantastic Four ® ©1996 Marvel Comics


Slide8: 1900 Charles T. R. Wilson’s ionization chamber Electroscopes eventually discharge even when all known causes are removed, i.e., even when electroscopes are sealed airtight flushed with dry, dust-free filtered air far removed from any radioactive samples shielded with 2 inches of lead! seemed to indicate an unknown radiation with greater penetrability than x-rays or radioactive  rays Speculating they might be extraterrestrial, Wilson ran underground tests at night in the Scottish railway, but observed no change in the discharging rate.


Slide9: 1909 Jesuit priest, Father Thomas Wulf , improved the ionization chamber with a design planned specifically for high altitude balloon flights. A taut wire pair replaced the gold leaf. This basic design became the pocket dosimeter carried to record one’s total exposure to ionizing radiation. 0


Slide10: 1909 Taking his ionization chamber first to the top of the Eiffel Tower (275 m) Wulf observed a 64% drop in the discharge rate. Familiar with the penetrability of radioactive  rays, Wulf expected any ionizing effects due to natural radiation from the ground, would have been heavily absorbed by the “shielding” layers of air.


Slide11: Henri Becquerel (1852-1908) received the 1903 Nobel Prize in Physics for the discovery of natural radioactivity. Wrapped photographic plate showed clear silhouettes, when developed, of the uranium salt samples stored atop it. 1896 While studying the photographic images of various fluorescent and phosphorescent materials, Becquerel finds potassium-uranyl sulfate spontaneously emits radiation capable of penetrating thick opaque black paper aluminum plates copper plates Exhibited by all known compounds of uranium (phosphorescent or not) and metallic uranium itself.


Slide12: 1898 Marie Curie discovers thorium (90Th) Together Pierre and Marie Curie discover polonium (84Po) and radium (88Ra) 1899 Ernest Rutherford identifies 2 distinct kinds of rays emitted by uranium:  - highly ionizing, but completely absorbed by 0.006 cm aluminum foil or a few cm of air  - less ionizing, but penetrate many meters of air or up to a cm of aluminum. 1900 P. Villard finds in addition to  rays, radium emits  - the least ionizing, but capable of penetrating many cm of lead, several feet of concrete


Slide14: + Magnetic force is related to q, v and B


Slide15: Lorentz Law Experimental observations: force depends on direction of v relative to B if v is at angle q from B  F = Fmax sinq if v is parallel to B  F = 0 if v is perpendicular to B  F = Fmax


Slide16: Direction of Magnetic Force Direction of magnetic force is “sideways” force is perpendicular to both v and B use “right-hand” or “left-hand rule” to find its direction in to page out of page head tail Drawing vectors in


Slide17: Right Hand Rule Examples q q q


Slide18: + In what direction is this positive charge deflected? A. Left B. Right C. Up D. Down


Slide19: A negatively charged beam enters a magnetic field region as shown. What is the direction of B? A + y (up) B – y (down) C + x (right) D + z (out of page) E – z (into page) x y z


Slide22: From these observations alone, what definite conclusions can be made? A. as are positively charged, bs negative. B. as are negatively charged, bs positive. C. can only say a,b oppositely charged. B-field points into page


Slide23: B field out of page Particles A and B have the same charge, but particle B has more mass. When particle A enters the magnetic field, it travels along line Y. When particle B enters the magnetic field, it will follow line A) X B) Y C) Z B


Slide24: F = 2 Centripetal force: F


Slide27: 1900-01 Studying the deflection of these rays in magnetic fields, Becquerel and the Curies establish  rays to be charged particles Using the procedure developed by J.J. Thomson in 1887 Becquerel determined the ratio of charge q to mass m for : q/m = 1.76×1011 coulombs/kilogram identical to the electron! : q/m = 4.8×107 coulombs/kilogram 4000 times smaller!


Slide28: 1900-01 Noting helium gas often found trapped in samples of radioactive minerals, Rutherford speculated that  particles might be doubly ionized Helium atoms (He++) 1906-1909 Rutherford and T.D.Royds develop their “alpha mousetrap” to collect alpha particles and show this yields a gas with the spectral emission lines of helium! Discharge Tube Thin-walled (0.01 mm) glass tube to vacuum pump & Mercury supply Radium or Radon gas


Slide29: as are ionized Helium (bare Helium nuclei) 2-protons, 2-neutrons (positively charged) bs are simply electrons(negatively charged) qa = -2qb ma=7296mb


Slide30: 1911-12 Austrian physicist Victor Hess, of the Vienna University, and 2 assistants, carried Wulf ionization chambers up in a series of hydrogen balloon flights. taking ~hour long readings at several altitudes both ascending and descending radiation more intense above 150 meters than at sea level intensity doubled between 1000 m to 4000 m increased continuously through 5000 meters In 1936, Hess was awarded the Nobel prize for this discovery. Hess lands following a historic 5,300 meter flight. August 7, 1912 National Geographic photograph Dubbed this “high” level radiation Höhenstrahlung


Slide31: 50mm Cosmic ray strikes a nucleus within a layer of photographic emulsion


Slide32: 1913-14 Werner Kolhörster of Berlin’s Physikalisch-Technische Reichsanstalt ascends to 9300 m (height of Mount Everest, cruising altitude of a passenger jet!) ionization rate 50× that at sea level! 1925-26 Robert Millikan of Caltech (winner of the 1923 Nobel prize) initially fails to duplicate such results over San Antonio, Texas, found “not more than 25% of that found by European observers.” Further high-altitude measurements made in collaboration with Ira S. Bowen confirmed the existence of what Millikan coined “cosmic rays”.


Slide33: 1911 Rutherford’s assistant Hans Geiger develops a device registering the passage of ionizing particles. 1924 Walter Bothe and Geiger use multiple Geiger counters to establish the tracks followed by electron beams 1928-29 Bothe and Werner Kolhörster build Geiger telescopes and announce cosmic “rays” contain charged particles


Slide34: 1927-28 Jacob Clay from Genoa to the Dutch colony of Java ionization intensity drops ~6% minimum at magnetic equator 1929 Bothe & Kolhörster suggest Clay’s Lattitude Effect was due to deflection by earth’s magnetic field primaries are charged


Slide35: inspired by the Norwegian mathematician Carl Størmer’s calculations explaining colleague Kristian Birkland’s theory of the aurora Birkland experimented with electron beams and a phosphorous-painted globe of lodestone


Slide38: 1930-33 Arthur Compton (University of Chicago) conducts a worldwide sea- and mountain-level lattitude survey of cosmic ray intensities and confirms the Latitude Effect. The 4 curves correspond to 4 seasons. Physical Review 52 [1937]:p.808


Slide39: Størmer’s “cutoff energies”: only the fastest cosmics reach sea level near the equator  less energetic particles are observable at mid-latitudes  unrestricted energies in the polar regions September 21, 1932 Millikan completed a series of tests on the intensity of cosmic rays at various altitudes in a Condor bomber from March Field, California.


Slide40: 1933-35 Thomas Johnson (of the Carnegie Institute) and Bruno Rossi (Italy) independently mount Geiger counter telescope arrays to test for the east-west asymmetry predicted by Georges Lemaître (Belgian)


Slide41: Positive charged particles headed toward the earth from space, would tend (at mid-latitudes) to reach the surface coming down from the A. North B. South C. East D. West E. split East and West


Slide42: Although cosmic rays do come “from all directions”, at high altitudes near the equator the intensity is higher coming from the West than from the East! 1939 Johnson speculates primaries may be protons!


Slide43: Electroscopes become so robust, data can be collected remotely (for example retreived from unmanned weather balloons)


Slide44: November 11, 1935 Explorer II, a 113,000 cubic foot helium balloon ascends to a record 22,066 m while collecting atmospheric and cosmic ray data.


Slide45: 1937-1939 Studies of Extended Air Showers begin in France when by accident Pierre Auger and his Russian colleague Dimitry Skobeltzyn notice apparent coincidence between Cosmic Ray telescopes set up several hundred meters apart. Cloud chamber photographs by George Rochester and J.G. Wilson of Manchester University showed the large number of particles contained within such showers.


Slide46: 1936 Millikan’s group show that at the earth’s surface showers are dominated by electrons, gammas, and X-particles capable of penetrating deep underground (to lake bottom and deep tunnel experiments) characterized there by isolated single cloud chamber tracks


Slide47: Definite evidence for the celestial generation of Cosmic Rays came from fortuitous timing of a few high altitude balloon studies during some spectacular solar flares.


Slide48: Unusual increase in Cosmic ray intensity associated with an intense solar flare observed February 28, 1942 the same sunspot associated with this flare erupts again March 7, 1942 Similarly the June 4, 1946 solar prominence is followed by another eruption July 25, 1946 and the solar flare event of November 19, 1949 is also captured by airborne cosmic ray instruments each accompanied by a Sudden Ionospheric Disturbance which interrupts radio communications on earth


Slide49: During the June 1946 prominence, ultraviolet radiation and x-rays arrived A. shortly before B. simultaneous to C. shortly after the visual observation of the flare. Why?


Slide50: During the June 1946 prominence, charged particles causing radio blackouts arrived A. hours before B. minutes before C. simultaneous to D. minutes after E. hours later the visual observation of the flare. Particles causing radio blackouts arrived about 3 hours later. Why?


Slide51: Ground-based monitoring stations at low magnetic latitudes observed no increase. Why? However on November 14, 1960 Explorer VII detects solar flares causing “extremely severe” magnetic disturbances in the Earth's atmosphere. The sea level neutron counter at Deep River, Canada records: J.F.Steljes, H.Carmichael, K.McCracken, Journal of Geophysical Research 66 [1961]:p.1363 and the National Bureau of Standards measures extensive attenuation of radio transmissions


Slide52: May 11, 1950 A Naval Research Viking research rocket fired from the U.S.S. Norton Sound near Jarvis Island in the Pacific collects cosmic ray and pressure and temperature data. 1952-57 James A. Van Allen (University of Iowa) reports the 1st high altitude survey of total cosmic-ray intensity and latitude variation of heavy nuclei in primary cosmic radiation, from his “Rockoon” (balloon-launched rocket). February - March, 1958 U.S. Satellites Explorer I and II carry Geiger-Müller counters for Van Allen looping through highly eccentric (50 km perigee, 2600 km apogee) orbits every 2½ hours.  Cosmic ray intensities increase steadily with altitude until 2000 km when counters suddenly registered nothing.  Lab tests of duplicate counters suggested they had been overloaded by a region with a sudden 15000× increase in cosmic rays!


Slide53: 1958 Explorer IV and Sputnik III confirm, what is eventually mapped as 2 gigantic radiation belts of trapped ions. October 13, 1959 Explorer VII was launched. into an Earth orbit. By late December its data reveals inner belt mostly protons outer belt mostly electrons


Slide55: brief communications 680 © 2003 Nature Publishing Group NATURE | VOL 422 | 17 APRIL 2003 | www.nature.com Space travel Dual origins of light flashes seen in space ight flashes are unusual visual phenomena that are observed in space and are caused by the interaction of energetic cosmic-ray particles with the human visual system. Using data gathered on board the Mir space station during the Sileye-2 experiment1 , we show here that there are two separate components of cosmic rays that cause these flashes: one due to heavy nuclei and one due to protons. This indicates that perception by an astronaut’s visual apparatus could involve two complementary mechanisms. Ever since light flashes in space were predicted2 before the first space mission and subsequently reported by early Apollo astronauts, attempts to determine their cause have been made both in space and using ground-based particle accelerators3. As a result, several explanations have been proposed to account for the phenomenon ( see ref. 4 and references therein ). The measured rate of occurrence of light flashes (LF) varies for different missions: on Mir5, it is much lower ( Sileye-1, 0.18  0.02 LF min-1; Sileye-2, 0.130.01 LF min-1) than on Apollo6 ( 0.23  0.1 LF min-1), Skylab7 ( 1.3  0.1 LF min-1) and ASTP8 (0.460.05 LF min-1). This effect is probably due chiefly to a reduction in the speed of low-energy particles by Mir’s hull material (aluminium more than 3 mm thick) and the equip- ment inside the craft. As light flashes are caused by particles inter- acting with the human visual apparatus, their occur- rence should be proportional to particle rate (the so-called ‘latitude effect’). Particle rates outside the region of the South Atlantic Anomaly ( SAA ) depend on the geomagnetic cut-off, which is a function of the position-dependent geomagnetic field intensity and direction. The cut-off C represents the minimum rigidity for cosmic rays to reach Mir’s orbit without being deflected outwards; it is lower at high geomagnetic latitudes ( for Mir’s orbit, the lowest cut-off is C = 0.6 gigavolts (GV)) and higher at the geomagnetic equator ( where maximum cut-off is C = 16 GV). The lower the cut-off, the higher the rate of particles coming from outside the Earth’s magnetosphere ( we use the vertical cut-off at each location of Mir). Light-flash and particle rates measured inside Mir were divided in 3-GV bins that separated the regions outside ( C ≤ 18 GV ) and inside the SAA (3 ≤ C ≤15 GV, selected for Earth’s magnetic field B  2.510-5 tesla; Fig. 1). The light-flash rate, RLF, is plotted against the particle rate, P, for all particles (almost exclusively protons) in Fig.1a. In Fig.1b, RLF is plotted as a function of the rate of relativistic nuclei, Pn, with charge Z ≥ 6, obtained by selecting particles with high linear-energy transfer ( 20 keV m-1) to guarantee the complete removal of the proton component. From the all-particle plot (Fig. 1a), it is possible to see that RLF is not linearly proportional to proton flux in all regions: in the SAA, it is roughly independent of proton rate ( even though statistical errors preclude any further claim ). For instance, at the centre of the SAA (9≤C≤12 GV), where particle Figure 1 Rate of occurrence of light flashes on board the Mir space station as a function of particle rate for all particles and for relativistic nuclei inside(circles) and outside(squares) the South Atlantic Anomaly. a, Plot of light-flash rate against proton rate; b, light-flash rate against particle rate for particles with linear-energy transfer of §20 keV mm-1. Linear fits for each region are shown. Data are from the Sileye-2 experiment1, where astronauts wore light-excluding helmets integrated with cosmic-ray particle-flux detectors, enabling the frequency of flashes to be recorded as a function of background flux & orbit position. L


Slide56: July 31, 1961 NASA funds high-altitude balloon measurements of the proton and alpha-particle spectrum of primary cosmic radiation conducted by the University of Chicago above Uranium City, Saskatchewan, Canada. August 17, 1961 Explorer XII radios data on magnetic fields and cosmic rays from a 54,000 mile apogee (and 170 mile perigee). 1962 Enroute to Venus Mariner II detects a continuously flowing solar wind of fast and slow streams, cycling in 27 day intervals (the rotational period of the Sun). July 1969 Apollo 11 astronauts trap cosmic ray particles on exposed aluminum foil, returned to earth for analysis of its elemental and isotopic composition. With no atmosphere or magnetic field of its own, the moon’s surface provides a constant bombardment of particles.


Slide57: July 1969 Apollo 11 astronauts trap cosmic ray particles on exposed aluminum foil, returned to earth for analysis of its elemental & isotopic composition. With no atmosphere or magnetic field of its own, the moon’s surface is exposed to a constant barrage of particles.


Slide58: March 3, 1972 Pioneer 10 launched -on its flyby mission, studies Jupiter's magnetic field and radiation belts. December 1972 Apollo 17’s lunar surface cosmic ray experiment measured the flux of low energy particles in space (foil detectors brought back to Earth for analysis. October 26, 1973 IMP-8 launched. Continues today measuring cosmic rays, Earth’s magnetic field, and the near-Earth solar wind from a near-circular, 12-day orbit (half the distance to the moon). October 1975 to the present GOES (Geostationary Orbiting Environmental Satellite) An early warning system which monitors the Sun's surface for flares. 1977 The Voyager 1 and 2 spacecraft are launched. Each will explore acceleration processes of charged particles to cosmic ray energies.


Slide59: August 31, 1991 Yohkoh spacecraft launched - Japan/USA/England solar probe - studied high-energy radiation from solar flares. July 1992 SAMPEX (Solar Anomalous and Magnetospheric Particle Explorer) in polar orbit. By sampling inter- planetary & magnetospheric particles, contributes to our understanding of nucleosynthesis and the acceleration of charged particles. July 1992 IMAX (Isotope Matter-Antimatter eXperiment) balloon- borne superconducting magnetic spectrometer measured the galactic cosmic ray abundances of protons, anti-protons, hydrogen, and helium isotopes. August 25, 1997 Advanced Composition Explorer (ACE) was launched!