1 / 11

Quantum Noise in (High-Gain) FELs

Quantum Noise in (High-Gain) FELs. Kwang -Je Kim Argonne National Laboratory March 8, 2012 Future Light Sources WS Jefferson Laboratory Newport News, VA. EM Field Operator. Complex field amplitude  operator  ( Hermitian conjugate) Intensity = ,

kele
Télécharger la présentation

Quantum Noise in (High-Gain) FELs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Quantum Noise in (High-Gain) FELs Kwang-Je Kim Argonne National Laboratory March 8, 2012 Future Light Sources WS Jefferson Laboratory Newport News, VA

  2. EM Field Operator • Complex field amplitudeoperator •  ( Hermitian conjugate) • Intensity= • , • =(annihilation, creation operator) • =1, = number operator • from vacuum fluctuation Quantum Noise KJK FLS 2012

  3. Linear amplifier • =(input, output) field operator • ; =amplitude gain • operator for gain medium; = • | • =+; 2 =power gain • In the absence of initial photons; • Can show • The minimum noise is ½ input photon from VF and ½ input photon from amplifier reaction • Low noise in gain device (oscillator) Quantum Noise KJK FLS 2012

  4. Proof (C. M. Caves, PRD, 1817 (1982)) •  • : •  • Condition for minimum noise: =0 Quantum Noise KJK FLS 2012

  5. FEL equation • Classical • : • Field energy density • Quantum:=1 •  : • , • ; Quantum Noise KJK FLS 2012

  6. Heisenberg FEL equation in collective variables (R. Bonifacio, et.,al.) • Bunching factor • Collective momentum • Assume . =classical, and small • , , • Formally identical to classical equation Quantum Noise KJK FLS 2012

  7. Solution exp(ilt) • , maximum growth • ; Quantum Noise KJK FLS 2012

  8. Amplified power • The first two terms are classical coherent amplification and SASE, respectively • Random electron distribution • Noise suppression schemes ( A. Gover,..)  • Classical (KJK and RRL, FEL 2011) and quantum limitation of the suppression Quantum Noise KJK FLS 2012

  9. Quantum noise • ; • representation • Assume Gaussian wavefunction Cross terms do not contribute (C. Schroder, C. Pellegrini, P.Chen) • Minimum =3/2 • However the minimum should be 1=1/2+1/2 Quantum Noise KJK FLS 2012

  10. Minimum noise wavepacket • Require:  : minimum noise • To understand phase space distribution, look at Wigner function • Tilted phase space, or chirped Quantum Noise KJK FLS 2012

  11. Magnitude of minimum quantum noise relative Random SASE • Small but not negligible Quantum Noise KJK FLS 2012

More Related