[PPT] - Filling the THz Gap GWYN P. WILLIAMS Jefferson Lab 12000 PowerPoint Presentation

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Thomas Jefferson National Accelerator Facility

Filling the THz Gap

GWYN P. WILLIAMS

Jefferson Lab 12000 Jefferson Avenue - MS 7A Newport News, VA 23606 gwyn@mailaps.org

CASA Seminar, Novemer 14, 2003

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Thomas Jefferson National Accelerator Facility

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200 mA Diff. Limit

3rd. Gen.
riginal design
2nd. Gen.
1st. Gen. Synch. Rad.

CDC 6600 Cray 1 Cray T90

GROWTH IN LEADING EDGE COMPUTING SPEED (Millions of operations/sec) GROWTH IN SYNCHROTRON X-RAY SOURCE BRIGHTNESS (Photons/sec/0.1%bw/sq.mm/mrad

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What ’s new? Short pulses/

Mult ipart icle coherence

Near-f ield

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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.

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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”.

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The Paper That Started it all.

1981

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1 micron

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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

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

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Radiation from Accelerated Electron

electron acceleration But unit s of power are:

2 2 3

c

MLT L ML T T

Force Distan e Time

Power

− −

× =

=

f ield

Elect ric f ield goes linear ly in t he elect ric charge and t he accelerat ion

so int ensit y (power) goes like e2a2

2 2 2

e MLT L

−

=

Now f or an elect ric charge, f orce is e2/ L2, so we can derive unit s f or e t hus: So e2a2 has unit s of :ML3 T-2×L2T-4 = ML5T-6 And if we divide by c3, or L3T-3, we get ML2T-3.

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Larmor’s Formula

2 2 3

2 3 e a c

Power=

Also we not e t hat radiat ion is emit t ed in only 2 out of 3 direct ions, so we have a 2/ 3 f act or, yielding: Not ing t hat t he unit s of power are ML2T-3, and not ing t hat M goes like gamma, L goes like 1/ gamma and T goes like gamma in t he moving f rame, in t he rest f rame t he relat ivist ic version is :

4

2 2 3

2 3 e a c

Power

γ

=

Radiation from Accelerated Electron

N.B. Radiat ed energy and elapsed t ime t ransf orm in t he same manner under Lorent z t ransf orms

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~100 V fsec laser pulse

GaAs THz

6 4 6 6 8 2 2 6 17 2

100V V E 10 m 10 m F 10 V 10 ( 3 10 ) a m .5MeV / c 0.5 10 m 10 sec

−

= = × = = = × ≅

2 8 2 17 2

c ( 3 10 ) m a 10 sec ρ 1 if ρ 1 m × = = ≅ =

fsec laser pulse

e- -> 40 MeV

GaAs THz ρ

Comparing Coherent THz Synchrotron and Conventional THz Sources

2 2 4 3

2 Larmor's Formula: Power (cgs units) 3 e a γ c =

4 7

80 80 10 !!!! and γ = =

a=acceleration c=vel. of light γ=mass/rest mass

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

Synchrotron Radiation Generation

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E l e c t r i c f i e l d time

freq. (1/time)

electron(s)

super-radiant enhancement

N

E/N I n t e n s i t y  E

2



Synchrotron Radiation Generation

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

THz

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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

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2 / ˆ i n z c

f e S z dz

ω

               

∞ ⋅ −∞

=∫

2

. nr(t ) ˆ i t c 2 2 2 2 2

d I e N[1 f ( )] N f ( ) n ˆ n ˆ e dt d d 4 c

ω

ω ω ω β ω 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

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Synchrotron Radiation - so what’s new here?

radio-freq. cavity

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Showstopper……. 3 GeV at 100 mA is 300 Megawatts!!!!! radio-freq. cavity Solution…….. Energy Recovery Synchrotron Radiation - so what’s new here?

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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

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Crystal quartz window Collimating optic Nicolet Nexus 670 FTIR bench LHe cooled Si bolometer detector

THz Setup on JLab IR-DEMO FEL

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October 2002

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1 10 100 1000 0.0 0.2 0.4 0.6

Frequency (THz)

Measured Calculated (500fs bunch length)

Watts/cm-1 Frequency (cm

1)

0.1 1 10

THz Expt and Calculation

Diffraction losses

~ 20 Watts integrated

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

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20 40 60 80 100 1000 2000 3000 4000

50 100 150 200 250 20000 40000 60000 80000 100000

Intensity (Arb. Units) Wavenumbers (cm

1)

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

Integrated THz Intensity (Arb. Units) Beam Current (µA)

Measured Intensity N

2 Fit

Coherent THz vs. Current

50 100 150 200 250 20 40 60 80 100

Measured intensity Fit to (Current)

2

Current (µA)

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Polarization of Coherent THz

25 50 75 100 500 1000 1500 2000 2500 3000 3500

I = 0.04 mA

Polarizer Vertical Polarizer Horizontal

Measured Intensity (Arb. Units) Wavenumbers (cm

1)

Expected polarization ratio for 60 mrad port at 30 cm-1 is 6:1. We observed 5:1. Good agreement.

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Why do this? Terahertz Imaging

Clery, Science 297 763 (2002)

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IR Spectroscopy & Dynamics is based on Vibrations Simple molecule More complicat ed molecule - prot ein

Slide courtesy Paul Dumas, LURE, Orsay, France

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Protein Structure / Folding Dynamics

Amide I Secondar y St r uct ure Assignment s: 1620 - 1640 β-sheet 1644 ext ended coil (D2O) 1648 - 1657 α-helix 1665 310 helix 1670 - 1695 ant i-par allel β-sheet , β-t urn

1720 1700 1680 1660 1640 1620 1600 1580

0.0 0.1 0.2

Absorbance Frequency (cm-1) α-helix β-sheet β-t urn ext ended coil

Carboxypeptidase

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1750 1700 1650 1600 0.0 0.5 1.0 random coil beta sheet 10 sec 30 sec 90 sec 180 sec 1625 1654

Absorbance 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.

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THz Spectroscopy

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

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THz Imaging

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

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The Promise of THz – novel imaging

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The Promise of THz – novel imaging

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THz Imaging

Basal cell carcinoma shows malignancy in red. Teraview Ltd.

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Terahertz computerized tomography Turkey Bone Test Object

3cm

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

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So – where are we going at JLab with THz?

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FEL upgrade, phase 1

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

THz light port

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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 mr

35 25

85 mr

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

Penetration location 1040 mm from dimad start

f bend point.

60

“View from the back of M1 looking at beam”

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625 F1 5810 Floor 1000 625 1077 2330 Dimensions in mm

not to scale

2480 Ceiling M1(ellipsoid) 705 372 M2 (plane) M3 ellipsoid F2 M4(ellipsoid) 2240 2240 e-beam 1000 F3 M1 110 x 155 M2 120 x 170 M3 183 x 258 M4 183 x 258 Neil/GPW JFEL THz Port Description Final Rev. 1 Dated 8-13-2003

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SRW SRW Calculation of Calculation of light on light on screen screen 3.0 m 3.0 m from from source source by by Paul Dum as Paul Dum as Flux after 1-st Aperture: 2.0479e+13 Photons/ s/ .1%bw

0.2m
0.1

0.0 0.1 0.2 Vertical Position

0.2m
0.1

0.0 0.1 0.2 Horizontal Position Spectral Flux / Surface at λ=100 µm 3 m from downstr. BM Edge

1.0x10

9

0.8 0.6 0.4 0.2 0.0

0.2m

0.0 0.2

Horizontal Position

200x10

6

150 100 50 Phot/s/0.1%bw/mm

2

0.2m
0.1

0.0 0.1 0.2 Vertical Position Spectral Flux / Surface vertical cut

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What is Edge Radiation?

Dipole Radiation Edge Radiation Edge Radiation is light emitted as the electrons enter the fringe field of a dipole

magnet. For long wavelengths the fringe field maybe treated as an impulse
acceleration. 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).

( )

2 2 2 2 4 2 1

e I d dF θ γ + θ γ π ω ω ∆ α = Ω

4 - 2

2 4 gq 0.05 0.1 0.15 0.2 0.25

F d dW

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1 2 1 2

[( ) ] ( ) exp[ / )] (1 )

(

e e e e

n n cR n E ec i R c d n R

ω

β β γ β ω τ β

τ

+∞ − − − −∞

× − × + − = + −

∫

ɺ
Full f ormula

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What does edge Radiation look like?

Daresbury Lab Ann Rep 1984/5

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Two Edges Interfere

Screen Interference of Two Edges in Far Field Edge 1 Edge 2 L

( ) ( )

     θ γ + λγ π Ω ≈       θ γ + λγ π − Ω ≈ Ω

2 2 2 2 1 2 2 2 2 1 2

1 2 L Sin d dF 4 1 L Exp 1 d dF d dF

Spectrum is no longer white
Opening angle depends on λ

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

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JLab’s new THz Beamline

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1 10 100 1000 1E-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 Intensity 356.6 Watts

Frequency (THz) Watts/cm

1

Frequency (cm

1)

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

2

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

0.1 1 10

JLab’s new THz Beamline

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Thomas Jefferson National Accelerator Facility 1 10 100 1000 1E-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) Watts/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

JLab’s new THz Beamline

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1 10 100 1000 10000 1E-12 1E-11 1E-10 1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1 1 10 100 1000 10000

Energy (meV) Flux (Watts/cm

1)

Wavenumbers (cm

1)

1 10 100 1000

JLab THz S y n c h r

t

r

n

s 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 & Williams Nature 420, 153 (2002)

Brightness of IR Sources

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Funded by United States DOE, DOD DE-AC05-84-ER40150 TJNAF George Neil, Fred Dylla and the Jefferson Lab FEL Team Larry 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)