How to Make LightGwyn P. Williams

Jefferson Lab12000 Jefferson Avenue - MS 7A Newport News, VA 23606 gwyn@mailaps.org Jefferson Lab Summer Lecture July 21, 2008

Outline of Talk1. Motivation why do we need bright light?

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 thingsA nanosytem - Brownian motion. Very small is different than big

Modern nanotechnology will require an understanding of small, isolated systemsElectron 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?

(a) Freeze motion(b) Study dynamics in time domainFast Cameras

Sizes and Time-scalesseeing atomsArea of atom is 10-20 m2Area of focus of 0.1 nm beamof light is 10-20 m2Need 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

Development of Brightness of Light Sources

Back to lasers - conventional types of lasers1. Solid State2. Gas3. Excimer4. Dye5. Semiconductor6. Fiber

All work with a medium in a cavity.

LASERLIGHT

Conventional lasers have limitationsNot tunableLimited availability of different wavelengths from catalogsOutput typically limited to a few wattsNo short wavelengths x-rays

Accelerator-based light sources have no limitations.. Synchrotrons, Free Electron Lasers

TunableShort wavelengths (x-rays)High power and brightness

How do these accelerator-based light sources work?electronelectricfield

Accelerator-based Light Sources physicse is charge on electrona is accelerationc is speed of light is relativistic mass increase

2e-lightHow do we make light sources more powerful?e is charge on electrona is accelerationc is speed of light is relativistic mass increase4 times the power!!!

from Richard Sheffield LANLSchematic of next generation light sourceLASER

Principle of Jefferson Labs Energy Recovered Linac / FEL

JLabs Existing 4th Generation Light SourceE = 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

So why haven't they been built?Shorter wavelengths isky and expensive using present technology!

$ 500MSRF Linac cost

Operating and Future ERLs

Next Generation Light Sources USA ProgramsJefferson Lab, IR/THz ERL, operational LCLS, Stanford, USA, hard x-ray, DOE-BES under constructionCornell University, hard x-ray ERL, proposal to NSF, initial fundingFlorida State University, IR/THz ERL, proposal to NSF, initial fundingWiFEL, Stoughton, Wisconsin, soft x-ray, proposal to NSF Advanced Light Source, Berkeley, soft x-ray, proposal to DOEAdvanced Photon Source, Argonne, hard x-ray ERL, proposal to DOELSU, THz soft x-ray, white paper preparation to State and DOEThe Light Source of the Future (LSF), DOE-BES, TBD

FZR-Dresden, IR/THz, operationalBudker Institute, Novisibirsk, Russia, THz ERL operational FLASH, Hamburg, Germany, soft x-ray, operational Daresbury & Rutherford UK, THz-x-ray, proposal in processSTAR, Berlin, Germany, soft x-ray, proposalPaul Scherrer Inst. Switzerland, hard x-ray, proposalMaxlab, Lund, Sweden, soft x-ray, proposalXFEL, Hamburg Germany, hard x-ray, European proposalXFEL, Spring-8, Japan

Next Generation Light Sources non USA Programs

Undulator and linear accelerator at Jefferson Lab Wavelength20 cmNumber of periods12 ea.Gap26 mm

Superconducting Radio-Freq. Linac

Periodic Magnetic FieldElectron BeamTotal ReflectorNiobium SRF Cavity withOscillating Electromagnetic FieldSchematic of JLab 4th. Gen. Light Source OperationLight OutputElectron BeamDrive LaserOutput MirrorLaser Wavelength ~ Wiggler wavelength/(2Energy)2

JLab THzSynchrotronsGlobarJLab FELTable-top sub-ps lasersFEL 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, UVaElectronics - radiosPhotonics light bulbsFrequency THz Why is Terahertz Light new?

JLab THzHigh Power THz Light is New - Nature March 2007Tonouchi Nature Photonics 1, 97 (2007) Photonics- lightsourcesElectronics - 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 weapons30 GHz NOT THz

Security hidden non-metallic weaponsDavid Zimdars SPIE 5070 (2003)

Security hidden weapons, explosivesExplosive fingerprintsTHzVisible

Security fingerprint of anthrax proxy

Security hidden bio-agents, explosivesDavid Zimdars, John Federici

Medical cancer screeningBasal 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 imagingA tooth cavity shows up clearly in red. Teraview Ltd.

ConclusionBright 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.

*E.g. thermodynamic state functions are not defined for a system of a small number of particles. Then, all configurations have comparable probability and large fluctuations are observable and determine the properties of that system.*E.g. thermodynamic state functions are not defined for a system of a small number of particles. Then, all configurations have comparable probability and large fluctuations are observable and determine the properties of that system.****