How to Make Light
Gwyn P. Williams
Jefferson Lab
12000 Jefferson Avenue - MS 7A
Newport News, VA 23606
gwyn@mailaps.org
Jefferson Lab Summer Lecture July 21, 2008
Outline of Talk
1. Motivation – why do we need bright light?
2. How do we make ultrabright light sources?
……what is brightness anyway?
Need to understand small things
Very small is different than big
Typical
thermodynamic
system - heat
moves from hot
(boiler) to cold
(condenser) and
work is extracted.
Small is different. Small things such as
pollen grains in a water solution are endlessly
buffeted by the random motion of the water
molecules. (This is termed Brownian motion).
Macroscopic machines – like steam engines –
are far too massive to be affected by these
small fluctuations.
We cannot calculate the power/efficiency
trade-off for a nanomachine or derive design
rules. Neither thermodynamics nor
stationary-state quantum mechanics helps.
Molecular junction.
A nanosytem Brownian motion.
What are some examples of small systems?
Modern nanotechnology will require an understanding of small, isolated systems
A powerful molecular
motor (yellow)
translocates the
twisted strands of
DNA (right) of a virus
into a protein capsid.
By using optical
tweezers to pull on
the DNA while it is
being packed, it was
determined that the
motor can pack DNA
to a pressure of
about 60
atmospheres, 10x
that of a champagne
bottle.
Molecular junction.
Electron transport has been observed
across molecules with only a few
monomers (a few Angstrom). Charge
transfer through single molecular devices
is presently one the most fascinating and
fastest developing fields in the range
between mesoscopic physics and
chemistry.
Fast Cameras
(a) Freeze motion
(b) Study “dynamics”
in time domain
Sizes and Time-scales……“seeing atoms”
Area of atom is
10-20
m2
t = 10-14 secs (10fs)
Area of focus of 0.1 nm beam
of light is 10-20 m2
0.1 nanometer
Need 1012 photons/sec to get good data, into this area
- which means a:
desired BRIGHTNESS of 1026 photons/sec/mm2/mrad2
Brightness is photon flux/(area x angle)
– or photons on target!
Development of Brightness of Light Sources
33
10
31
1x10
29
1x10
27
1x10
GROWTH IN AVERAGE X-RAY
SOURCE BRIGHTNESS
2
(Photons/sec/0.1%bw/sq.mm/mrad )
4th Gen.
Multiparticle
coherent
enhancement
25
1x10
23
1x10
3rd. Gen.
original design
21
10
19
10
2nd. Gen.
17
10
15
10
1st. Gen. Synch. Rad.
13
10
11
10
9
10
7
10
5
10
1960
1970
1980
1990
Calendar Year
2000
2010
Development of Brightness of Light Sources
33
10
31
1x10
29
1x10
27
1x10
GROWTH IN AVERAGE X-RAY
SOURCE BRIGHTNESS
2
(Photons/sec/0.1%bw/sq.mm/mrad )
4th Gen.
Multiparticle
coherent
enhancement
25
1x10
23
1x10
3rd. Gen.
original design
21
10
19
10
2nd. Gen.
17
10
15
10
1st. Gen. Synch. Rad.
13
10
11
10
MOORE'S LAW
Computer Component Doubling
Every 18 months
9
10
7
10
5
10
1960
1970
1980
1990
Calendar Year
2000
2010
Back to lasers - conventional types of lasers
1.
2.
3.
4.
5.
6.
Solid State
Gas
Excimer
Dye
Semiconductor
Fiber
All work with a medium in a cavity.
LASER
LIGHT
Conventional lasers have limitations…
•
•
•
•
Not tunable
Limited availability of different wavelengths from catalogs
Output typically limited to a few watts
No short wavelengths – x-rays
Accelerator-based light sources have no limitations…..
Synchrotrons, Free Electron Lasers
•
•
•
Tunable
Short wavelengths (x-rays)
High power and brightness
How do these accelerator-based light sources work?
electric
field
electron
Accelerator-based Light Sources – physics
light
e
Maxwell’s equation
H  J
"Free"
Larmor's Formula:
 E  P
o
t
2a2 4
2
e
Power 
3c3
t
e is charge on electron
a is acceleration
c is speed of light
 is relativistic mass increase
(cgs units)
How do we make light sources more powerful?
2elight
2 a2 4
2(
2e
)
Power 

3c3
4 times the power!!!
dE
 2 10  25 J/cm-1/electron
d
e is charge on electron
a is acceleration
c is speed of light
 is relativistic mass increase
Schematic of next generation light source
LASER
laser “seed”
optional
from Richard Sheffield LANL
Principle of Jefferson Lab’s Energy Recovered Linac / FEL
JLab’s Existing 4th Generation Light Source
E = 150 MeV
135 pC pulses up to 75 MHz
(20)/120/1 microJ/pulse in (UV)/IR/THz
250 nm – 14 microns, 0.1 – 5 THz
All sources are simultaneously
produced for pump-probe studies
Light Sources – “The World Stage”
1x10
30
28
10
Average Brightness
2
Photons/sec/0.1%BW/mm /sr
1x10
26
Electron Beam Energy = 3 GeV
Bending Radius = 5m
1 nc @ 100 MHz (100 mA)
rs
e
24
10
m
s li
5x5microns 50fs FWHM
10
(x10 for multiparticle)
a
20
10
18
a
sic
y
h
4th. Generation
lp
22
10
10
it
iv
g
f
o
ar
p
n
te
me
d
Fu n
a
nt
e
m
10 x 500 microns)
(x500 for ID) 50ps FWHM
16
10
14
10
3rd. Generation
12
10
10
2nd. Generation
10
500x1000 microns)
500 ps FWHM
8
10
6
10
4
10
1E-4
1E-3
0.01
0.1
1
10
Photon Energy (eV)
100
1000
10000
Gwyn Williams - file brt_1.bas
Nov. 2007
Light Sources – “The World Stage”
1x10
30
28
10
Average Brightness
2
Photons/sec/0.1%BW/mm /sr
1x10
26
Electron Beam Energy = 3 GeV
Bending Radius = 5m
1 nc @ 100 MHz (100 mA)
rs
e
24
10
m
s li
5x5microns 50fs FWHM
10
(x10 for multiparticle)
a
20
10
18
a
sic
y
h
4th. Generation
lp
22
10
10
it
iv
g
f
o
ar
p
n
te
me
d
Fu n
a
nt
e
m
10 x 500 microns)
(x500 for ID) 50ps FWHM
16
10
14
10
3rd. Generation
12
10
10
2nd. Generation
10
500x1000 microns)
500 ps FWHM
8
10
6
10
4
10
1E-4
1E-3
0.01
0.1
1
10
Photon Energy (eV)
100
1000
10000
Gwyn Williams - file brt_1.bas
Nov. 2007
So why haven't they been built?
Average Brightness
2
Photons/sec/0.1%BW/mm
/sr
Shorter wavelengths isky and expensive using present technology!
1x10
30
10
28
1x10
26
10
24
10
22
10
20
10
18
10
16
10
14
10
12
10
10
10
8
10
6
$ 500M
$ 250M
4th. Generation
3rd. Generation
SRF
Linac
cost
$ 120M
2nd. Generation
$ 60M
4
10
1E-4
1E-3
0.01
0.1
1
10
Photon Energy (eV)
100
1000
10000
Gwyn Williams - file brt_1.bas
Nov. 2007
Operating and Future ERLs
Operating ERLs
ERL Test Facilities
ERL Conceptual designs
Next Generation Light Sources USA Programs
1. Jefferson Lab, IR/THz ERL, operational
2. LCLS, Stanford, USA, hard x-ray, DOE-BES under construction
3. Cornell University, hard x-ray ERL, proposal to NSF, initial funding
4. Florida State University, IR/THz ERL, proposal to NSF, initial funding
5. WiFEL, Stoughton, Wisconsin, soft x-ray, proposal to NSF
6. Advanced Light Source, Berkeley, soft x-ray, proposal to DOE
7. Advanced Photon Source, Argonne, hard x-ray ERL, proposal to DOE
8. LSU, THz – soft x-ray, white paper preparation to State and DOE
9. The Light Source of the Future (LSF), DOE-BES, TBD
Next Generation Light Sources – non USA Programs
1.
FZR-Dresden, IR/THz, operational
2.
Budker Institute, Novisibirsk, Russia, THz ERL operational
3.
FLASH, Hamburg, Germany, soft x-ray, operational
4.
Daresbury & Rutherford UK, THz-x-ray, proposal in process
5.
STAR, Berlin, Germany, soft x-ray, proposal
6.
Paul Scherrer Inst. Switzerland, hard x-ray, proposal
7.
Maxlab, Lund, Sweden, soft x-ray, proposal
8.
XFEL, Hamburg Germany, hard x-ray, European proposal
9.
XFEL, Spring-8, Japan
Undulator and linear accelerator at Jefferson Lab
Wavelength
20 cm
Number of periods 12 ea.
Gap
26 mm
Superconducting Radio-Freq. Linac
Schematic of JLab 4th. Gen. Light Source Operation
Niobium SRF Cavity with
Oscillating Electromagnetic Field
Electron Beam
Drive Laser
Cryomodule
Light Output
Injector
Gun
Beam Stop
Wiggler
Total Reflector
Output Mirror
Periodic Magnetic Field
Electron Beam
Laser Wavelength ~ Wiggler wavelength/(2Energy)2
Jefferson Lab facility unique spectroscopic range
Energy (meV)
1
10
100
1000
10000
1000
100
JLab THz
-1
Flux (Watts/cm )
10
JLab FEL
1
0.1
Table-top sub-ps
lasers
0.01
1E-3
1E-4
1E-5
1E-6
1E-7
1E-8
1E-9
THz proof of principle:
Carr, Martin, McKinney, Neil, Jordan & Williams
Nature 420, 153 (2002)
1E-10
1E-11
1E-12
1
10
100
1000
-1
Wavenumbers (cm )
10000
FEL proof of
principle:
Neil et al. Phys.
Rev.Letts 84, 662
(2000)
One of the first areas of
impact of next generation
light source technology –
Terahertz
What is Terahertz Light?
Why is Terahertz Light new?
Photonics – light bulbs
Electronics - radios
THz
0.1
1
10
100
0.01
2000K Black Body
1E-6
-1
2
Watts/cm /mm /sr
1E-4
1E-8
1E-10
Frequency THz
1
Tom Crowe, UVa
10
100
1000
-1
Frequency (cm )
10000
High Power THz Light is New - Nature March 2007
Electronics
- radios
JLab THz
Tonouchi Nature Photonics 1, 97 (2007)
Photonics
- light
sources
What is Unique about Terahertz Light?
• THz light passes through many materials, such as
packaging material, clothing, carpet, walls.
• THz light is non-ionizing – unlike x-rays.
• THz light can “recognize” and distinguish materials that
x-rays cannot, such as plastics & proteins.
• THz light allows high speed & safe communications.
- Tera is 1000 times faster than Giga…
• THz does not pass through metal and water, and will always
be complimentary to x-rays.
Why make Terahertz Light?
Many applications, new discoveries every month.
•
•
•
•
•
•
Security
Medical screening (skin cancer)
Pharmaceuticals (drug verification and testing)
Non-destructive evaluation
Environmental monitoring
High speed communication
Security – hidden weapons
30 GHz NOT THz
Clery, Science 297 763 (2002)
Security – hidden non-metallic weapons
David Zimdars SPIE 5070 (2003)
Security – hidden weapons, explosives
THz
Visible
Explosive “fingerprints”
Security – fingerprint of anthrax proxy
Security – hidden bio-agents, explosives
David Zimdars, John Federici
Medical – cancer screening
Basal cell carcinoma shows malignancy in red. Teraview Ltd.
1 mW source images 1 cm2 in 1 minute
100 W source images whole body (50 x 200cm) in few seconds
Thomas Jefferson National Accelerator Facility
Operated by the Southeastern Universities Research Association for the U.S. Department
of Energy
Medical – improved dental imaging
A tooth cavity shows up clearly in red. Teraview Ltd.
Conclusion
Bright Light has a Bright Future.
Quest is now on to shorten wavelength.
FEL Team at JLab
This work supported by the Office of Naval Research, the Joint
Technology Office, the Commonwealth of Virginia, the Air Force Research
Laboratory, Army Night Vision Lab, and by DOE Contract DE-AC0584ER40150.