# A Fast-Ion Source for LAPD by wulinqing

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The Lighter Side of Physics

Prof. Roger McWilliams

Department of Physics & Astronomy
University of California, Irvine 92697, USA
Email: mcw@uci.edu
949-824-6228 lab phone and fax

The slides of this talk are posted at
http://HAL9000.ps.uci.edu
How did we get to today?
• Civilization – the combination of culture and
technology, both at relatively high levels.
– Science and engineering create and make technology.
– Science and engineering contribute to culture as well,
but we shall focus on technology here.

• Mechanical Age – previous societies were in
ages described by mechanical names (stone,
bronze, iron, steam)
• Electrical Age – a new type of age
The Electrical Age
• Professors Maxwell & Faraday, and others, gave us the electrical
• From the following Maxwell’s Equations, we get modern
civilization: Electricity, Magnetism, Electromagnetic Waves,
Light come from understanding these equations (motors, power
generators, lasers, transistors, et cetera).
• To understand how important these equations are, try turning off
your electrical power at home and work.
• Maxwell’s Equations:

  D   Free

B  0

     B
 E  
t

         D          
  H  jFree      jFree  jDisplacement
t

Result:
Generators
Time-changing
Electric power plants for
magnetic fields
all electrical appliances
make electric fields
and lights
The Discovery of Electromagnetic Induction
The experiment was conducted
on 29 August 1831. When the
primary circuit was closed, there
was a displacement of the
galvanometer needle in the
secondary winding. Deflections
of the galvanometer were only
observed when the current in the
electromagnet was switched on
and off. This was the discovery of
electromagnetic induction.
James Clerk Maxwell
Scotland’s Greatest Physicist

Celebrating the 175th
Anniversary of
Maxwell’s birth and
the opening of the
James Clerk Maxwell
Laboratories at the
Albert Einstein (1931)
“We may say that, before Maxwell, Physical Reality, in so
far as it was to represent the process of nature, was
thought of as consisting in material particles, whose
variations consist only in movements governed by partial
differential equations. Since Maxwell’s time, Physical
Reality has been thought of as represented by continuous
fields, governed by partial differential equations, and not
capable of any mechanical interpretation. This change in
the conception of Reality is the most profound and the
most fruitful that physics has experienced since the time of
Newton.”
James Clerk Maxwell – A Commemorative Volume 1831-1931
Maxwell as a college student:
Edinburgh University (1847-1850)
Lecture courses attended
Publications in
Mathematics – Kelland             Transactions of the
Natural Philosophy – Forbes
Royal Society of
Logic – William Hamilton
Edinburgh
Books borrowed from library
Cauchy: Calcul Différential
On the Theory of
Fourier: Théorie de la Chaleur      Rolling Curves
Monge: Géometrie Desciptive
Newton: Optics                    The Equilibrium of
Poisson: Mechanics                  Elastic Solids
Taylor: Scientific Memoirs
Willis: Principles of Mechanism
Maxwell’s Equations
Maxwell figured out how electromagnetic phenomena could
be described by the mathematics in these four equations.
Maxwell is responsible for dreaming up that last term in the
last equation.


•   Electric charges make electric
fields
  D   Free

•   Magnetic charges would make            B  0
magnetic fields, but we’ve never                    
seen any                                         B
•   Time-changing magnetic fields           E  
make electric fields                              t

•   Electric currents or time-changing                   D          
electric fields make magnetic fields     H  jFree      jFree  jDisplacement
t
A Dynamical Theory of the Electromagnetic Field (1865)

Maxwell's own view of this paper is revealed
in what Francis Everitt calls “a rare moment
of unveiled exuberance” in a letter to his
cousin Charles Cay:

“I have also a paper afloat,
containing an electromagnetic
theory of light, which, till I am
convinced to the contrary, I hold
to be great guns”.
A Treatise on Electricity & Magnetism (1873)

• “The most important aspect of any phenomenon from a
mathematical point of view is that of a measurable quantity.
I shall therefore consider electrical phenomena chiefly with
a view to their measurement, describing the methods of
measurement, and defining the standards on which they
depend.”
• “The internal relations of the different branches of the
science which we have to study are more numerous and
complex that those of any other science hitherto developed.”
• “It appears to me, therefore, that the study of
electromagnetism in all its extent has now become of the
first importance as a means of promoting the progress of
science.”

And, once more,                 D   Free

B  0
Maxwell’s Equations                         
     B
 E  
t

         D          
  H  jFree      jFree  jDisplacement
t

Let’s see now, hmm, if that third equation says time-changing
magnetic fields make electric fields, then the electric fields
must be changing in time also (because we can start with zero
magnetic field). And the fourth equation says time-changing
electric fields make magnetic fields! Ah, ha! Does this mean
that time-changing electric and magnetic fields can make each
other with no other assistance? Can they go together through
space on their own? Gee whillikers, you betcha!
http://www.nrao.edu/

The combination of time-changing electric and magnetic fields
propagating through space or matter is what we call
electromagnetic waves or light waves.
Voodoo Science: A Trick with a Scientific-
Sounding Premise
False claim: This experiment shows how ESP makes successful
predictions. Recent statistics suggest that this system can
predict the correct outcome of your choice with 98% accuracy.
Let me repeat. I am conducting an experiment. There are six
small cards below. Select a card, stare at it, and be sure to
remember it. By detecting your electromagnetic energy after

Prediction: I know your card and
will now remove it from the cards.
I have removed your card! Quantum consistency is: 671.

This is not science. Even though scientific terms are used and
there is a claim of predictive capability, there is no proof that
your card was known via ESP sensing of electromagnetic
energy.
trick is no cards shown above were on the previous page. But
careful examination is needed to see that. Many people believe
this trick actually shows ability to know the card you selected.
Be skeptical of claims of predictive capability unless verified by
scientists independent of those who would profit from claims.
From Nasa
Maxwell’s Colour Triangle

Maxwell’s original version   Modern version
Light comes out of many plasmas.
A solar flare, viewed through a blue filter, on our
most important plasma, the Sun. Photo: NASA
The Northern Lights
(Aurora Borealis).
Photo: J. Curtis

Collisionally-induced fluorescence

Temporal evolution of emitted photons can be observed.
This is collisionally-induced fluorescence from electrons
raining down upon neutrals.
Comet Hale-Bopp.
Photo: D. Toohey

Ultraviolet-induced fluorescence
Visible and near-visible photons can provide non-
intrusive diagnosis of plasmas. Blue comet plasma tail is
visible due to fluorescence induced by ultraviolet
photons from the Sun. White tail is sunlight scattered
from comet dust tail.
When light travels through matter, it is slowed down by the
electrons in the atoms. Different frequencies/wavelengths are
slowed different amounts depending on the atoms in the
material.
Prism of quartz example below. Diamonds have very strong
wavelength dependence (spread the colors a lot) and are very
durable (Zircon nearly as good). Leaded glass is great, too.
Now let’s go look at some fun
atmospheric light effects
http://www.atoptics.co.uk
Rainbow – large drops (refraction, reflection) primary, secondary, higher,
supernumerary (wave interference)
Corona – small drops (diffraction)
Glory and Heiligenschein (not same)
Halo – parhelic circle, sun dog, tangential arc
Green flash

Corona are caused by diffraction around small water
mist in the atmosphere. Typically seen around 15
degrees from the sun or moon. Can have rainbow-
What is a laser; why do we care to know?

• Light Amplification of Stimulated Emission
Radiation (LASER). Often laser light is:
– Aimed pretty much in one direction,
– Pretty much near one wavelength (color)
• Lasers are described by Maxwell’s Equations,
with a little bit of quantum mechanics thrown in.
• There are lasers in nature, but most interest is for
Theodore Maiman (my mother was
acquainted with him) got the patent for
the first laser.

Maiman with a ruby laser on the
laser’s 25th anniversary. Photo
courtesy of Kathleen Maiman

1960 invention
1961 patent application
1967 patent issued
A double Laser-Induced Fluorescence (LIF)
system: Two pump plasma ion lasers, in
background, drive two tunable dye lasers (one
with cover removed). (This photo is 15 years old,
but was hard to make; we are not doing it again).
How your airplane follows its flight path
Subtitle: Ring laser gyroscopes, plasma etching, the US
Supreme Court, and Doctrine of Equivalents, which may put
you in a fog (fiber optic gyroscope).
Author: Willy Makeit         Illustrator: Betty Wont

In 1978 a man and his dog found
a way to make incredibly-highly
reflecting mirrors. He did not
know why this way worked and
the dog would not say, but Litton
Industries was very happy.
Among the pleasant people
assembled for the Litton team
was attorney John Roberts.

You know him now as Chief
Justice of the US Supreme Court.
Tissue Discrimination via LIF
Purpose
• To find a practical,
inexpensive, and non-
invasive method of
discriminating healthy
from unhealthy biological
tissue

Picture by Medicine Net
<http://www.medicinenet.com/images/illustrations/skin.jpg>
Hopes and Dreams

• Fluorescence on human skin might be done without
damage
• Fluorescence might allow discrimination of different
types of skin conditions and growths
• Perhaps various skin cancers can be detected by
fluorescence instead of skin biopsy technique
presently used
• Potential for much lower cost, very fast analysis
while the patient is in the office, and no biopsy
wound requiring healing
And finally, how do lasers and
Optical fibers carry your
conversations to their destinations
• Your voice is converted into pulses of light
traveling down “light tubes” called optical fibers.
• Fibers are especially useful for long lines, like
from US to Japan.
• Still, while traveling on long lines, the signal gets
weaker and needs to be amplified occasionally.
• Putting atoms which can lase directly into the
fiber allows the fiber to become the amplifier.
Erbium-doped Fiber Amplifiers (EDFA)
can give you clear communication
anywhere a fiber can be run
On the 1550 nm voice signal where one
might want a stable, low-power laser
source
• UC Irvine worked with New Focus to develop small,
inexpensive tunable, stable diode lasers.
• New Focus was another Milton Chang startup (like
Newport Corporation).
• New Focus now owned by Bookham Technologies
(whose president worked for me in graduate school).
New Focus laser in blue box in middle. Note how
small it is compared to person in photo.
On the 980 nm amplifying laser pump
power where one might want a stable,
high-power laser source

• UC Irvine worked with SDL to develop 0.5W
single-pass diode laser amplifiers.
SDL MOPA with diffraction grating cavity removed. The
0.5 W output active semiconductor chip diode is white
dot in center of gold holder. Chip is about 2 mm wide.
Shakespeare’s King Henry VI, Part III, Act II, Scene I

EDWARD: Dazzle mine eyes, or do I see three suns?

RICHARD: Three glorious suns, each one a perfect sun;
Not separated with the racking clouds, But sever'd in a
pale clear-shining sky. See, see! they join, embrace, and
seem to kiss, As if they vow'd some league inviolable:
Now are they but one lamp, one light, one sun. In this the
heaven figures some event.
Conclusions
• Every person in this room is relying on
electromagnetism around the clock for their
participation in civilization.
• The lighter side of physics is fun to observe
and understand.

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