[email protected] gwyn p. williams filling the thz...

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Thomas Jefferson National Accelerator Facility

Filling the THz Gap

GWYN P. WILLIAMS

Jefferson Lab12000 Jefferson Avenue - MS 7A

Newport News, VA [email protected]

CASA Seminar, Novemer 14, 2003



1960 1970 1980 1990 2000107

108

109

1010

1011

1012

1013

1014

1015

1016

1017

1018

1019

1020

1021

1022

x1023

200 mA Diff. Limit

3rd. Gen.original design

2nd. Gen.

1st. Gen. Synch. Rad.

CDC 6600

Cray 1

Cray T90

GROWTH IN LEADING EDGECOMPUTING SPEED(Millions of operations/sec)

GROWTH IN SYNCHROTRON X-RAY SOURCE BRIGHTNESS(Photons/sec/0.1%bw/sq.mm/mrad2)

Calendar Year

10-1

100

101

102

103

104

105

106

107

108

109

1010

1011

1012

1013

1014

1015

What’s new?

Short pulses/Multiparticle coherence

Near-field



The THz Gap

Many important dynamical processes occur in the THz region (5 meV). Superconducting band-gaps, protein conformational modes, phonons….

With high coherent power the key niche areas are non-linear dynamics and imaging.



THz – Brief History

After Nichols left Berlin, Rubens continued the work, and in 1900 he isolated wavelengths of 6THz (50 microns) and made careful measurements which he gave to Max Planck who derived the Radiation Law. Planck wrote in 1922 “Without the intervention of Rubens the formulation of the radiation law, and consequently the formulation of quantum theory would have taken place in a totally different manner, and perhaps even not at all in Germany”.



The Paper That Started it all.

1981



1 micron



Backing up….Auston Switch for producing THz light

Auston, D.H., Cheung, K.P., Valdmanis, J.A. and Kleinman, D.A., Phys. Rev.Letters 53 1555-1558 (1984).

2 2

3

2Larmor's Formula: Power (cgs units)3e ac

=



Radiation from Accelerated Electron

electron

acceleration

But units of power are:

2 2 3

c

MLT L ML TT

Force Distan eTimePower

− −× =

×

=

=field

Electric field goes linearly in the electric charge and the acceleration- so intensity (power) goes like e2a2

2 22

e MLTL

−=

Now for an electric charge, force ise2/L2, so we can derive units for e thus:

So e2a2 has units of :ML3 T-2×L2T-4 = ML5T-6

And if we divide by c3, or L3T-3, we get ML2T-3.



Larmor’s Formula2 2

323e ac

Power=

Also we note that radiation is emitted in only 2 out of 3 directions, so we have a 2/3 factor, yielding:

Noting that the units of power are ML2T-3, and noting thatM goes like gamma, L goes like 1/gamma and T goes likegamma in the moving frame, in the rest frame the relativistic version is :

42 23

23e ac

Power γ=

Radiation from Accelerated Electron

N.B. Radiated energy and elapsed time transform in the same manner under Lorentz transforms



~100 V

fseclaserpulseGaAs

THz

64

6 6 8 2

2 6

172

100V VE 10 m10 mF 10 V 10 ( 3 10 )am .5MeV / c 0.5 10

m10 sec

−= =

×= = =×

≅

2 8 217

2c ( 3 10 ) ma 10 secρ 1

if ρ 1 m

×= = ≅

=

fseclaserpulse

e- -> 40 MeV

GaAsTHz

ρ

Comparing Coherent THz Synchrotron and Conventional THz Sources

2 24

3

2Larmor's Formula: Power (cgs units)3e a γc

=

4 780 80 10 !!!!andγ = =

a=accelerationc=vel. of lightγ=mass/rest mass



e-e-e-e-e-e-e-e-e-e-e-e-e-

e-e-

e-

Synchrotron Radiation Generation



E lec

t ric

fi eld

time freq. (1/time)

electron(s)

super-radiantenhancement

N

E/N

Inte

nsity

E2

Synchrotron Radiation Generation

W.D. Duncan and G.P. Williams,”Infra-red Synchrotron Radiation From Electron Storage Rings”, Applied Optics 22, 29l4 (1983).

THz



Statistics of an electron bunch in a storage ring

Synchrotron Radiation Generation - actual situation

Hirschmugl, Sagurton and Williams, Physical Review A44, 1316, (1991).

Time Scale 2

Time Scale 1



2/ˆi n z cf e S z dzωω

∞ ⋅−∞= ∫

2.n r( t )ˆi t c2 2 22

2d I eN[1 f ( )] N f ( ) n n e dtd d 4 c

ωωω ω βω Ω π

−∞

−∞= − + × × ×

S.L. Hulbert and G.P. Williams, Handbook of Optics: Classical, Vision, and X-Ray Optics, 2nd ed., vol. III. Bass, Michael, Enoch, Jay M., Van Stryland, Eric W. and Wolfe William L. (eds.). New York: McGraw-Hill, 32.1-32.20 (2001).S. Nodvick and D.S. Saxon, Suppression of coherent radiation by electrons in a synchrotron. Physical Review 96, 180-184 (1954).Carol J. Hirschmugl, Michael Sagurton and Gwyn P. Williams, Multiparticle Coherence Calculations for Synchrotron Radiation Emission, Physical Review A44, 1316, (1991).

Coherent Synchrotron Radiation Generation - theory

f(ω) is the form factor – the Fourier transform of the normalized longitudinal particle distribution within the bunch, S(z)

REFERENCES



Synchrotron Radiation - so what’s new here?

radio-freq.cavity



Showstopper…….3 GeV at 100 mA is 300 Megawatts!!!!!

radio-freq.cavity

Solution……..Energy Recovery

Synchrotron Radiation - so what’s new here?



FTIR System

e-

FTIR System

We measured the bend-magnet synchrotron radiation right before the FEL, when the beam is maximally compressed.

THz Setup on JLab IR-DEMO FEL



Crystal quartz window

Collimating optic

Nicolet Nexus 670 FTIR bench

LHe cooled Si bolometer detector

THz Setup on JLab IR-DEMO FEL



October 2002



1 10 100 10000.0

0.2

0.4

0.6

Frequency (THz)

Measured Calculated (500fs bunch length)

Wat

ts/c

m-1

Frequency (cm-1)

0.1 1 10

THz Expt and Calculation

Diffraction losses ~ 20 Watts integrated

Carr, Martin, McKinney, Neil, Jordan & WilliamsNature 420, 153 (2002)



0 20 40 60 80 1000

1000

2000

3000

4000

50 100 150 200 2500

20000

40000

60000

80000

100000

In

tens

ity (A

rb. U

nits

)

Wavenumbers (cm-1)

50 µA 80 µA 105 µA 110 µA 170 µA 230 µA

Inte

grat

ed T

Hz

Inte

nsity

(Arb

. Uni

ts)

Beam Current (µA)

Measured Intensity N2 Fit

Coherent THz vs. Current

0 50 100 150 200 2500

20

40

60

80

100

Measured intensity Fit to (Current)2

Current (µA)



Polarization of Coherent THz

0 25 50 75 1000

500

1000

1500

2000

2500

3000

3500 I = 0.04 mA

Polarizer Vertical

Polarizer Horizontal

Mea

sure

d In

tens

ity (A

rb. U

nits

)

Wavenumbers (cm-1)

Expected polarization ratio for 60mrad port at 30 cm-1 is 6:1.

We observed 5:1. Good agreement.



Why do this? Terahertz Imaging

Clery, Science 297 763 (2002)



IR Spectroscopy & Dynamics is based on Vibrations

Simple molecule

More complicatedmolecule - protein

Slide courtesy Paul Dumas, LURE, Orsay, France



Protein Structure / Folding Dynamics

Amide I Secondary Structure Assignments:

1620 - 1640 β-sheet1644 extended coil (D2O)1648 - 1657 α-helix1665 310 helix1670 - 1695 anti-parallel β-sheet,

β-turn

1720 1700 1680 1660 1640 1620 1600 1580

0.0

0.1

0.2

Abs

orba

nce

Frequency (cm-1)

α-helix

β-sheetβ-turn

extended coil

Carboxypeptidase



1750 1700 1650 1600

0.0

0.5

1.0

random coilbeta sheet10 sec30 sec90 sec180 sec

162516

54

Abs

orba

nce

Frequency

Protein Folding Dynamics - Silk Fiber Formation

SCAN PARAMETERS:

• %T: silk fibroin on BaF2 disk• 32 scans at 200 KHz (2.3 sec)• 4 cm-1 resolution• MCT detector

Lisa Miller, Mark Chance et al.



THz Spectroscopy

Anthrax proxy DNA

Globus et al. University of Virginia J. App. Phys. 91 6105 (2002)



THz Imaging

A tooth cavity shows up clearly in red. Teraview Ltd.



The Promise of THz – novel imaging



THz Imaging

Basal cell carcinoma shows malignancy in red. Teraview Ltd.



Terahertz computerized tomography

Turkey Bone Test Object

3cm

Ferguson et. al. Phys. Med. Biol. 47 3735 (2002)



So – where are we going at JLabwith THz?



FEL upgrade, phase 1

Jefferson Lab’s new ERL/FEL/THz sourceTurned-on June 2003!!

THz light port



0o

10.2o = 173 milliradians

JFEL THz Port Description Final Rev. 1 Dated 8-13-2003

ρ =1.2 meter

s

M1 (110 x 155) mm

M1 to “dimad”“start of bend” = 667mm

120 mr

0o 3.58o

50 mr

146 mr35 25

85 mr

Beamline Center Line to be: 20 tangent, 35 mrads from zero degrees 7/24/03 GPWThis puts F1=667-(1200×0.035)=625Penetration location

1040 mm from dimad startof bend point.

60

“View from the back of M1 looking at beam”



625F1

5810

Floor1000

625

1077

2330

Dimensions in mmnot to scale

2480

Ceiling

M1(ellipsoid)

705

372M2 (plane) M3

ellipsoid

F2

M4(ellipsoid)

2240

2240

e-beam

1000

F3

M1 110 x 155M2 120 x 170 M3 183 x 258M4 183 x 258

Neil/GPW

JFEL THz Port Description Final Rev. 1 Dated 8-13-2003



SRW SRW Calculation of Calculation of light on light on screenscreen 3.0 m 3.0 m from from source source by by Paul DumasPaul Dumas

Flux after 1-st Aperture: 2.0479e+13 Photons/s/.1%bw

-0.2m

-0.1

0.0

0.1

0.2

Ver

tical

Pos

ition

-0.2m -0.1 0.0 0.1 0.2Horizontal Position

Spectral Flux / Surface at λ=100 µm 3 m from downstr. BM Edge

1.0x109

0.8

0.6

0.4

0.2

0.0-0.2m 0.0 0.2

Horizontal Position

200x106

150

100

50

0

Phot

/s/0.

1%bw

/mm

2

-0.2m -0.1 0.0 0.1 0.2

Vertical Position

Spectral Flux / Surface vertical cut



What is Edge Radiation?

Dipole Radiation

Edge Radiation

Edge Radiation is light emitted as the electrons enter the fringe field of a dipolemagnet. For long wavelengths the fringe field maybe treated as an impulseacceleration. Thus edge radiation has characteristics similar to transition radiation.In the far field approximation for a single edge the angular spectral flux is “white”up to a cutoff determined by the details of the fringe and is given by,

Reference: R.A. Bosch, Nuclear Instr. & Methods A431 320 (1999).

( )222

24

2 1eI

ddF

θγ+θγ

πωω∆α=

Ω- 4 - 2 0 2 4

gq

00.05

0.10.15

0.20.25

FddW



1 21

2[( ) ] ( ) exp[ / )]

(1 )(e e e

e

n n cR nE ec i R c dn Rω

β β γ β ω τβ

τ+∞ − −

−

−∞

× − × + −= +−∫

Full formula



What does edge Radiation look like?

Daresbury LabAnn Rep 1984/5



Two Edges Interfere

Screen

Interference of Two Edges in Far Field

Edge 1 Edge 2

L

( )

( )

θγ+λγπ

Ω≈

θγ+λγπ−

Ω≈

Ω

222

2

1

222

212

12

LSinddF4

1LExp1ddF

ddF

•Spectrum is no longer white

•Opening angle depends on λ

Near Field Calculation of Two Edges using SRW (Chubar& Elleaume, ESRF)



JLab’s new THz Beamline



1 10 100 10001E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

0.1

1

10

100

1000

10000

100000

Integrated Intensity356.6 Watts

Frequency (THz)

Wat

ts/c

m-1

Frequency (cm-1)

Jlab Demo 5mA 100pc 500 fsecs fwhm 60hX60v Synchrotron radiation (NSLS, Brookhaven) 800 mA 90X90 2000K Black Body 10 mm2

JLab Upgrade 135 pc 75 MHz (10mA) 300fs 150x150

0.1 1 10




1 10 100 10001E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

0.1

1

10

100

1000

10000

100000

JLab FEL - THz Port

Frequency (THz)

W

atts

/cm

-1

Frequency (cm-1)

75 MHz 135 pc (10 mA) 150 x 150 mr Int. Power

100 fs FWHM 1.1kW 400 fs FWHM .26kW 800 fs FWHM .11kW

0.1 1 10




1 10 100 1000 100001E-121E-111E-101E-91E-81E-71E-61E-51E-41E-30.010.1

110

1001000

10000

Energy (meV)

Flux

(Wat

ts/c

m-1)

Wavenumbers (cm-1)

1 10 100 1000

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)

Brightness of IR Sources



Funded byUnited States DOE, DOD

DE-AC05-84-ER40150 TJNAF

George Neil, Fred Dylla and the Jefferson Lab FEL TeamLarry Carr (Brookhaven National Laboratory)Lisa Miller (Brookhaven National Laboratory)Carol Hirschmugl (UW Milwaukee)Paul Dumas (University of Paris, France)Oleg Chubar (Soleil project, Saclay, France)Mike Martin (Berkeley Lab)Wayne McKinney (Berkeley Lab)

Thanks to…………………….

[email protected] gwyn p. williams filling the thz...

Documents