Status of the
Visible-Infrared SASE Amplifier
(VISA@800nm)
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,
A.Toor
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
@240pC within
experimental solid angle
@240pC within coherent angle
and
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
-cameras
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
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