Status of the Visible-Infrared SASE Amplifier




Aaron Tremaine




Collaborating Institutions:


BNL: M. Babzien, I. Ben-Zvi, E. Johnson,

R. Malone, G. Rakowsky, J. Skaritka, X.J.Wang, V. Yakimenko

SLAC: R. Carr, M. Cornacchia, H.-D. Nuhn,

L. Klaisner, R. Ruland

UCLA:P. Frigola, A. Murokh, P. Musumeci,

C. Pellegrini, J. Rosenzweig

LANL: D. Nguyen

LLNL: K.A. Van Bibber, G. LeSage, J.M. Hill,






Goals and Strategy




Study Self-Amplified Spontaneous Emission (SASE) in collective instability regime

-Designed for saturation

-, electron beam micro-bunching directly related to SASE FEL gain mechanism

-Needed for very short wavelength FELs

-Compare data with SASE FEL codes

-Use of many optical diagnostics


Using a strong focusing 4m (4-1m sections) planar undulator

--function of 30 cm

-Must be careful of random walk-off

-Alignment to <30mm


Electron beam needed has stringent requirements

-Using and modifying the ATF at BNL












































































Trajectories of e-beam relative to alignment laser

Alignment laser was within 300mm of undulator axis

After this alignment, alignment laser to within 30mm

Detector Signal vs. Charge


Used steering magnets to place e-beam <75mm of alignment laser

Nonlinear detector signal vs. charge indicates gain

Large acceptance angle to detector

@240pC within experimental solid angle

@240pC within coherent angle




Using Genesis gives agreement with data w/



Future Measurements



1. Power/Energy vs. distance along undulator

Exponential gain

-use pop-ins, detector

2. Micro-Bunching of electron beam

-Coherent Transition Radiation (CTR)

3. Frequency spectrum, (800nm+h.h.)

-monochromator, spectrometer

4. Fluctuations/statistics

5. Angular Spectrum


6. Electron Beam vs. distance along undulator

-Yag screens, cameras along undulator

7. Time resolution, spectrum (50 fs resolution)

-Frequency Resolved Optical Gating (FROG)

8. Put chirp in e-beam


We will need to operate into the next fiscal year









Undulator characterization finished Nov-Dec 99


1st run day Mid January

-Have had two shutdowns for interferometric alignment. 2.5 weeks offline/interferometric alignment.


Saw gain


Presently-Interferometric alignment of undulator and alignment laser to within tolerances


Move towards the more sophisticated radiation diagnostics available