How to Make Light Gwyn P. Williams Jefferson Lab 12000 Jefferson Avenue - MS 7A Newport News, VA...
-
Upload
kathleen-evans -
Category
Documents
-
view
216 -
download
0
Transcript of How to Make Light Gwyn P. Williams Jefferson Lab 12000 Jefferson Avenue - MS 7A Newport News, VA...
How to Make Light
Gwyn P. Williams
Jefferson Lab12000 Jefferson Avenue - MS 7A
Newport News, VA 23606 [email protected]
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?
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.
Need to understand small things
A nanosytem - Brownian motion.
Very small is different than big
Modern nanotechnology will require an understanding of small, isolated systems
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.
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.
What are some examples of small systems?
Molecular junction.
(a) Freeze motion
(b) Study “dynamics” in time domain
Fast Cameras
Sizes and Time-scales……“seeing atoms”
Area of atom is 10-20 m2
Area of focus of 0.1 nm beamof light is 10-20 m2
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!
0.1 nanometer
t = 10-14 secs (10fs)
Development of Brightness of Light Sources
1960 1970 1980 1990 2000 2010105
107
109
1011
1013
1015
1017
1019
1021
1x1023
1x1025
1x1027
1x1029
1x1031
1033
4th Gen.Multiparticlecoherentenhancement
3rd. Gen.original design
2nd. Gen.
1st. Gen. Synch. Rad.
GROWTH IN AVERAGE X-RAY SOURCE BRIGHTNESS
(Photons/sec/0.1%bw/sq.mm/mrad2)
Calendar Year
1960 1970 1980 1990 2000 2010105
107
109
1011
1013
1015
1017
1019
1021
1x1023
1x1025
1x1027
1x1029
1x1031
1033
MOORE'S LAWComputer Component DoublingEvery 18 months
4th Gen.Multiparticlecoherentenhancement
3rd. Gen.original design
2nd. Gen.
1st. Gen. Synch. Rad.
GROWTH IN AVERAGE X-RAY SOURCE BRIGHTNESS
(Photons/sec/0.1%bw/sq.mm/mrad2)
Calendar Year
Development of Brightness of Light Sources
Back to lasers - conventional types of lasers
1. Solid State
2. Gas
3. Excimer
4. Dye
5. Semiconductor
6. Fiber
All work with a medium in a cavity.
LASERLIGHT
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?
electron
electricfield
Accelerator-based Light Sources – physics
4Larmor's Formula: Power (cgs units)
2 2
32
3e ac
Maxwell’s equation
" "Free oPE
t tH J
e- light
e is charge on electrona is accelerationc is speed of light is relativistic mass increase
2e-
light
How do we make light sources more powerful?
42 23
2( )3
2e ac
Power
e is charge on electrona is accelerationc is speed of light is relativistic mass increase
4 times the power!!!
25102 ddE
J/cm-1/electron
from Richard Sheffield LANL
Schematic of next generation light source
LASER
laser “seed”optional
Principle of Jefferson Lab’s Energy Recovered Linac / FEL
JLab’s Existing 4th Generation Light Source
E = 150 MeV135 pC pulses up to 75 MHz(20)/120/1 microJ/pulse in (UV)/IR/THz250 nm – 14 microns, 0.1 – 5 THz
All sources are simultaneously produced for pump-probe studies
Light Sources – “The World Stage”
Light Sources – “The World Stage”
JLAB THz
JLAB FEL LCLS….
FLASH21st . Century Light Source
So why haven't they been built?
Shorter wavelengths isky and expensive using present technology!
1E-4 1E-3 0.01 0.1 1 10 100 1000 1000010
4
106
108
1010
1012
1014
1016
1018
1020
1022
1024
1x1026
1028
1x1030
4th. Generation
3rd. Generation
2nd. Generation
Gwyn Williams - file brt_1.basNov. 2007
Ave
rage
Brig
htne
ss
Pho
tons
/sec
/0.1
%B
W/m
m2/s
r
Photon Energy (eV)
$ 500M
$ 250M
$ 120M
$ 60M
SRF Linac cost
Operating and Future ERLsOperating 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
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
Next Generation Light Sources – non USA Programs
Undulator and linear accelerator at Jefferson Lab
Wavelength 20 cmNumber of periods 12 ea.Gap 26 mm
Superconducting Radio-Freq. Linac
InjectorCryomodule
Wiggler
Beam Stop Gun
Periodic Magnetic Field
Electron Beam
Total Reflector
Niobium SRF Cavity withOscillating Electromagnetic Field
Schematic of JLab 4th. Gen. Light Source Operation
Light Output
Electron Beam
Drive Laser
Output Mirror
Laser Wavelength ~ Wiggler wavelength/(2Energy)2
JLab THz
Synchrotrons
Globar
JLab FEL
Table-top sub-ps lasers
FEL proof of principle:Neil et al. Phys. Rev.Letts 84, 662 (2000)
THz proof of principle:Carr, Martin, McKinney, Neil, Jordan & WilliamsNature 420, 153 (2002)
Jefferson Lab facility unique spectroscopic range
One of the first areas of impact of next generation light source technology –
Terahertz
What is Terahertz Light?
Tom Crowe, UVa
Electronics - radios Photonics – light bulbs
Frequency THz
Why is Terahertz Light new?
JLab THz
High Power THz Light is New - Nature March 2007
Tonouchi Nature Photonics 1, 97 (2007)
Photonics- lightsources
Electronics - radios
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
Clery, Science 297 763 (2002)
Security – hidden weapons
30 GHz NOT THz
Security – hidden non-metallic weapons
David Zimdars SPIE 5070 (2003)
Security – hidden weapons, explosives
Explosive “fingerprints”
THz Visible
Security – fingerprint of anthrax proxy
Security – hidden bio-agents, explosives
David Zimdars, John Federici
Operated by the Southeastern Universities Research Association for the U.S. Department of Energy
Thomas Jefferson National Accelerator Facility
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
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-AC05-84ER40150.