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

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 Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

23 15 x10 10 200 mA Diff. Limit 22 14 10 10 GROWTH IN SYNCHROTRON X-RAY 21 13 10 10 SOURCE BRIGHTNESS 20 12 2 ) 10 10 (Photons/sec/0.1%bw/sq.mm/mrad 19 11 10 10 3rd. Gen. What ’s new? 18 10 10 10 original design 17 9 10 10 2nd. Gen. 16 8 10 10 Short pulses/ 15 7 10 10 Cray T90 Mult ipart icle coherence 14 1st. Gen. Synch. Rad. 6 10 10 13 5 10 10 Near-f ield Cray 1 12 4 10 10 11 3 10 10 CDC 6600 10 2 10 10 9 GROWTH IN LEADING EDGE 1 10 10 COMPUTING SPEED 8 0 10 10 (Millions of operations/sec) 7 -1 10 10 1960 1970 1980 1990 2000 Calendar Year Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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. Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

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”. Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

The Paper That Started it all. 1981 Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

1 micron Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Backing up….Auston Switch for producing THz light e a 2 2 2 = Larmor's Formula: Power (cgs units) c 3 3 Auston, D.H., Cheung, K.P., Valdmanis, J.A. and Kleinman, D.A., Phys. Rev.Letters 53 1555-1558 (1984). Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Radiation from Accelerated Electron 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 e 2 a 2 electron But unit s of power are: × Force Distan e = c f ield Power Time − × = = MLT L ML T 2 − 2 3 acceleration T Now f or an elect ric charge, f orce is e 2 / L 2 , so we can derive unit s f or e t hus: e 2 − = MLT 2 L 2 So e 2 a 2 has unit s of : ML 3 T -2 × L 2 T -4 = ML 5 T -6 And if we divide by c 3 , or L 3 T -3 , we get ML 2 T -3 . Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Radiation from Accelerated Electron 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: Larmor’s Formula e a Power = 2 2 2 c 3 3 Not ing t hat t he unit s of power are ML 2 T -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 : e a = 2 2 γ Power 2 4 c 3 3 N.B. Radiat ed energy and elapsed t ime t ransf orm in t he same manner under Lorent z t ransf orms Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Comparing Coherent THz Synchrotron and Conventional THz Sources a=acceleration e a γ 2 2 2 = c=vel. of light 4 Larmor's Formula: Power (cgs units) γ =mass/rest mass c 3 3 e - -> 40 MeV ~100 V THz fsec ρ fsec laser laser pulse GaAs pulse THz GaAs 100V V = = 6 E 10 m − 4 10 m × 2 8 2 c ( 3 10 ) m = = ≅ 17 a 10 × 6 6 8 2 F 10 V 10 ( 3 10 ) 2 sec ρ 1 = = = a × 2 6 m .5MeV / c 0.5 10 = if ρ 1 m m ≅ 17 10 γ = = and 4 7 2 80 80 10 !!!! sec Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Synchrotron Radiation Generation e- e- e- e- e- e- e- e- e- e- e- e- e- e- e- e- Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Synchrotron Radiation Generation electron(s)  E/N 2 E d l  e i y f t N c i s i r n t e c t e n super-radiant l I E enhancement THz time freq. (1/time) W.D. Duncan and G.P. Williams,”Infra-red Synchrotron Radiation From Electron Storage Thomas Jefferson National Accelerator Facility Rings”, Applied Optics 22, 29l4 (1983). Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Synchrotron Radiation Generation - actual situation Statistics of an electron bunch in a storage ring Time Scale 1 Time Scale 2 Hirschmugl, Sagurton and Williams, Physical Review A44 , 1316, (1991). Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Coherent Synchrotron Radiation Generation - theory 2 . nr(t ) ˆ  � ω − � i t  � ∞ c ω  � 2 2 2 d I e  � = − ω + ω × × β × 2 N[1 f ( )] N f ( ) n ˆ � n ˆ e dt  �  �  �  � ω Ω  � π  � d d 2  � 4 c � −∞  �  �  �  � f ( ω ) is the form factor – the Fourier transform of the normalized longitudinal particle distribution within the bunch, S(z) 2 ∞ ω ⋅ ω = ∫ i n z c f e S z dz / ˆ �     −∞             REFERENCES 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). Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Synchrotron Radiation - so what’s new here? radio-freq. cavity Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Synchrotron Radiation - so what’s new here? radio-freq. cavity Showstopper……. Solution…….. 3 GeV at 100 mA is 300 Megawatts!!!!! Energy Recovery Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

THz Setup on JLab IR-DEMO FEL FTIR System e - We measured the bend-magnet synchrotron radiation right before the FEL, when the beam is FTIR maximally compressed. System Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

THz Setup on JLab IR-DEMO FEL Crystal quartz window Collimating optic Nicolet Nexus 670 FTIR bench LHe cooled Si bolometer detector Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

October 2002 Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

THz Expt and Calculation Frequency (THz) 0.1 1 10 Measured Calculated (500fs bunch length) 0.6 Diffraction losses ~ 20 Watts integrated Watts/cm-1 0.4 Carr, Martin, McKinney, Neil, Jordan & Williams Nature 420 , 153 (2002) 0.2 0.0 1 10 100 1000 -1 ) Frequency (cm Thomas Jefferson National Accelerator Facility Operated by the Southeastern Universities Research Association for the U.S. Department of Energy