Search Results (6 total)

Experimental results are presented from vacuum-ultraviolet free-electron laser (FEL) operating in the self-amplified spontaneous emission (SASE) mode. The generation of ultrashort radiation pulses became possible due to specific tailoring of the bunch charge distribution. A complete characterization of the linear and nonlinear modes of the SASE FEL operation was performed. At saturation the FEL produces ultrashort pulses (30–100 fs FWHM) with a peak radiation power in the GW level and with full transverse coherence. The wavelength was tuned in the range of 95–105 nm.

Electron bunches of high charge (up to 10 nC) are compressed in length in the Compact Linear Collider Test Facility magnetic chicane to less than 0.4 mm rms. The short bunches radiate coherently in the chicane magnetic field, and the horizontal and longitudinal phase space density distributions are affected. This paper reports the results of beam emittance and momentum measurements. Horizontal and vertical emittances and momentum spectra were measured for different bunch compression factors and bunch charges. In particular, for 10 nC bunches, the mean beam momentum decreased by about 5% while the rms momentum spread increased from 2% to 8%. The experimental results are compared with simulations made with the code TraFiC4.

We present the first observation of self-amplified spontaneous emission (SASE) in a free-electron laser (FEL) in the vacuum ultraviolet regime at 109 nm wavelength (11 eV). The observed free-electron laser gain (approximately 3000) and the radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width, and intensity fluctuations, are all consistent with the present models for SASE FELs.

We present a precise measurement of the left-right cross section asymmetry (A_LR) for Z boson production by e⁺e^- collisions. The measurement was performed at a center-of-mass energy of 91.26 GeV with the SLD detector at the SLAC Linear Collider (SLC). The luminosity-weighted average polarization of the SLC electron beam was (63.0 ± 1.1)%. Using a sample of 49 392 Z decays, we measure A_LR to be 0.1628 ± 0.0071 (stat) ± 0.0028 (syst) which determines the effective weak mixing angle to be sin²θ_W^eff=0.2292±0.0009(stat)±0.0004(syst).

We present the first measurement of the left-right cross section asymmetry (A_LR) for Z boson production by e⁺e^- collisions. The measurement was performed at a center-of-mass energy of 91.55 GeV with the SLD detector at the SLAC Linear Collider which utilized a longitudinally polarized electron beam. The average beam polarization was (22.4±0.6)%. Using a sample of 10 224 Z decays, we measure A_LR to be 0.100±0.044(stat)±0.004(syst), which determines the effective weak mixing angle to be sin²θ_W^eff=0.2378 ±0.0056(stat)±0.0005(syst).

It is shown that the degree of polarization of a beam in electron storage rings can be limited by nonlinear effects. The strength of a nonlinear effect depends on the amplitude of the particles. Particles performing synchrotron and betatron oscillations with high amplitudes can contribute overproportionally to depolarization. As a result, the emittance of a beam is not allowed to exceed certain boundaries, otherwise the beam will become more and more depolarized. This limit is called nonlinear spin acceptance.