The Fresh-Bunch' technique in FELs

Conference · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5113476

Ben-Zvi, I; Yang, K M; Yu, L H

The 'Fresh Bunch' technique is being proposed as a method of increasing the gain and power of FEL amplifiers in which the length of the optical radiation pulse is shorter than the length of the electron bunch. In multi-stage FEL, electron beam energy spread is increased by the FEL interaction in the early stages. In the 'Fresh Bunch' technique, the low energy spread of the electron beam is recovered by shifting the radiation pulse to an undisturbed part of the electron bunch, thus improving the gain and trapping fraction in later stages. A test case for the application of the Fresh Bunch method is demonstrated by numerical simulation. In this particular example we examine a subharmonically seeded VUV Free-Electron Laser. We begin with the generation of harmonic radiation, which takes place over one part of the electron bunch. Then the radiation is shifted by means of a strong dispersive section to a fresh part of the bunch for exponential amplification and tapered wiggler amplification. By starting over with a new ensemble of electrons, the energy spread introduced by the bunching in the fundamental is removed, leading to an increased gain. Furthermore, it is possible to use a much stronger seed in the fundamental without incurring the penalty of a large energy spread later on. We note that more than a single application of the 'Fresh Bunch' method may be done in a single FEL multiplier-amplifier. Thus x-ray wavelengths may be reached by successive multiplication in a chain of FEL amplifiers starting from a tunable seed laser. 5 refs., 2 figs., 2 tabs.

• Research Organization: Brookhaven National Lab., Upton, NY (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5113476
• Report Number(s): BNL-46688; CONF-9108118--16; ON: DE92002066
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
426002 -- Engineering-- Lasers & Masers-- (1990-)
43 PARTICLE ACCELERATORS
430303* -- Particle Accelerators-- Experimental Facilities & Equipment
AMPLIFICATION
BEAM BUNCHING
BEAM DYNAMICS
BEAMS
ELECTRICAL EQUIPMENT
ELECTROMAGNETIC RADIATION
ELECTROMAGNETS
ELECTRON BEAMS
ENERGY SPECTRA
EQUIPMENT
FAR ULTRAVIOLET RADIATION
FREE ELECTRON LASERS
FREQUENCY MIXING
GAIN
HARMONIC GENERATION
LASERS
LEPTON BEAMS
MAGNETS
PARTICLE BEAMS
PULSES
RADIATIONS
SPECTRA
ULTRAVIOLET RADIATION
WIGGLER MAGNETS