Transcript Pair Annihilation and Production

Physical and Applicative
Overview
Joey Goodknight
Physics 129
October 21, 2010
Getting and Getting Rid of Them
 Basic
Physical Mechanisms
 Antimatter is Everywhere
 Too Many Electrons!
How and Why the Positron?
1
•
•
•
•
gram of anti-p+
2 X 1014 Joules
4 “Little Boy”s (Hiroshima)
2 “Fat Man”s (Nagasaki)
$25,000,000,000.00 (2009 Nasa Study)
 ~GDP of Yemen
 Admittedly only 1/20 of US defense Spending
 ~Yearly Nuclear Weapons Spending (1998 )
 Containment
Unrealistic past 1012 atoms
 From Space: Classic “Doomsday Theory”
• Tungaska Event
Sorry, Back to e+/e-…
 EM
Phenomenon
 3 main methods:
• γ  e+ + e• γ + γ  e+ + e• Decay
 Other
Possibilities?
E
Conservation
• E=hυ=~mec2
• λ~1 femtometer
• υ ~1023 Hz
• Well past gamma rays
P
Conservation
• Restricts Diagrams
 Least
Expected
• Femtosecond 800nm focus
 matter+anti-matter
• “Nothing”
 Much
simpler than Prod.
 P Conservation
 Positronium
• Bound state
• L=0, annihilation!
 Dirac
• 1929
 Carl
Anderson
• 1932 under Millikan
 Cloud Chamber Tracks
 γ  208Tl
• 1936 Nobel
They’re All Around Us!
+q’
-q’
+q
Goop,
full of dipoles
E=?
E=?
-q
+q
 Vacuum
Photons
• Create Virtual Pairs
• Shield Charge
• VacuumDielectric
 QED Triumph
• spin
 1997
Confirmation
Seein’ inside you
 Weak Force Decay
 11C, 40K, 13N, 18F etc.
γ
e+
e-
γ
•Photons Come out at 180 degrees to each other
•Complex Processing
•Density Map of Tracer
Always a Friend of Solid State Physicists
γ
γ
Positron Source
Na, usually
e+
•Scan Material
•Correlate emission with annihilation
•Generate map of open volume defects
•Gets trapped
•Live longer
•Defects are what make many
semiconductors cool
γ