• A. Sessler
  LBNL, Berkeley, California

The impact of the work of Albert Einstein on accelerator physics is described. Because of the limit of time, and also because the audience knows the details, the impact is described in broad strokes. Nevertheless, it is seen how his work has affected many different aspects of accelerator physics. In the second half of the talk, Albert Einstein's impact on the world will be discussed; namely his work on world peace (including his role as a pacifist, in the atomic bomb, and in arms control) and his efforts as a humanitarian (including his efforts on social justice, anti-racism, and civil rights).

• A. Meseck, M. Abo-Bakr, J. Bahrdt, B.C. Kuske
  BESSY GmbH, Berlin

Funding: Funded by the Bundesministrium für Bildung, und Forschung, the state Berlin and the Zukunftsfonds Berlin

BESSY proposes a soft X-ray free electron laser (FEL) multi-user facility. It will consist of three undulator lines, each based on cascaded High-Gain Harmonic-Generation (HGHG) scheme delivering photons in energy range of 24 eV to 1 keV. Start-to-end Simulations including error sources from the injector, and linac structure have been performed to provide realistic information about the expected radiation field (B. Kuske, FEL2005). However, the beamline designer needs to know the exact location and the size of the photon beam waist to maximize the brightness at the sample. This information can be derived from results of longitudinal propagation of the electric field distribution, which can be extracted from simulation results using the code GENESIS. The results of the Start-to-End simulation are used for realistic prediction of the photon beam properties of the BESSY Soft X-ray FEL.

• R. Tatchyn
  SLAC, Menlo Park, California

The temporal resolution of pump-flash interactions in the ultrashort (fs-as) regime is limited by the characteristic time constants of the excited states in the detector material. If the relaxation time constant is appreciably longer that the time interval between the pump and probe signals the response of the detector material to the probe represents a temporal convolution of the pump and probe responses, setting a lower limit on the resolution to which the interval between the two pulses can be measured. In most of the solid state ultrafast detection schemes that are being considered for the ultra-short pulse x-ray sources under current development at SLAC and elsewhere the characteristic time constants are related to the bound states of the atoms comprising the material or to the relaxation times of phase transitions or charge carrier populations of the lattice, setting a probable lower limit on the attainable resolution on the order of ~0.1 ps. In this paper we consider a novel detection principle predicated on the excitation of specially prepared unbound states in an ionized plasma and estimate its potential for extending the lower limit of resolution into the as regime.

• O. Williams, A. Doyuran, R.J. England, C. Joshi, J. Lim, J.B. Rosenzweig, S. Tochitsky, G. Travish
  UCLA, Los Angeles, California

An Inverse Compton Scattering (ICS) experiment investigating the polarized harmonic production in the nonlinear regime has begun which will utilize the existing terawatt CO2 laser system and 15 MeV photoinjector in the Neptune Laboratory at UCLA. A major motivation for a source of high brightness polarized x-rays is the production of polarized positrons for use in future linear collider experiments. Analytical calculations have been performed to predict the angular and frequency spectrums for various polarizations and different scattering angles. Currently, the experiment is running and we report the set-up and initial results. The advantages and limitations of using a high laser vector potential, ao, in an ICS-based polarized positron source are expected to be revealed with further measurement of the harmonic spectrum and angular characteristics.

• R. Bonifacio
  INFN-Milano, Milano
• N. Piovella
  Universita' degli Studi di Milano, MILANO

We formulate a quantum linear theory of the N-particle free-electron laser Hamiltonian model, quantizing both the radiation field and the electron motion, in the steady state regime. Quantum effects such as frequency shift, line narrowing, quantum limitation for bunching and energy spread and minimum uncertainty states are described. Using a second quantization formalism we demonstrate quantum entanglement between the recoiling electrons and the radiation field.

• G. De Ninno, E. Allaria, F. Curbis, M.B. Danailov, B. Diviacco, M. Marsi, M. Trovo
  ELETTRA, Basovizza, Trieste
• M. Coreno
  CNR - IMIP, Trieste
• S. Günster, D. Ristau
  Laser Zentrum Hannover, Hannover

Thanks to an intensive technological effort in the framework of the EEC Contract HPRI CT-2001-50025 (EUFELE), the European FEL at ELETTRA was able to break the previous record for the shortest wavelength of an FEL oscillator. Novel solutions were adopted for multilayer mirrors to allow FEL operation in the wavelength region between 160 and 190 nm, which is one of the main targets of the project. The characteristics of the FEL pulses measured at 176 nm (spectral profiles, high intensity, meV bandpass, MHz repetition rate) make it a competitive light source for spectroscopy, in particular for fluorescence studies in the VUV spectral range. Proof of principle experiments have been performed on different types of silica glasses, yielding information on the mechanisms of light absorption in this material.

• G.L. Orlandi
  ENEA C.R. Frascati, Frascati (Roma)

In the electromagnetic radiative phenomena originated by relativistic charged beams, angular distortions as well as variations of the photon flux are commonly observed as a function of the ratio between the beam transverse size and the observed wavelength, even at a wavelength shorter than the longitudinal bunch length. In the framework of a single particle theory of the transition radiation, diffractive alterations of the spectrum due, for instance, to the finite size of the radiator screen are already known. For relativistic three-dimensional charged beams, it could be interesting to check if the transition radiation emission undergoes modifications depending on the finite value of the beam transverse size with respect to the observed wavelength. Taking into account the beam diagnostics applications of the transition radiation in a linear accelerator, such an experimental check can offer promising perspectives. The theoretical background and physical basis of the spatial coherence effects affecting the spectral distribution of the transition radiation intensity in conditions of temporal incoherence will be presented. The main beam diagnostics applications will be also contoured.

• S.J. Park, J.Y. Huang, I.S. Ko, J.-S. Oh, Y.W. Parc, P.C.D. Park, J.H. Park
  PAL, Pohang, Kyungbuk
• C. Kim
  POSTECH, Pohang, Kyungbuk
• X.J. Wang
  BNL, Upton, Long Island, New York
• D. Xiang
  TUB, Beijing

Funding: Work supported by the MOST and the POSCO.

The PAL XFEL, an X-Ray Free Electron Laser (XFEL) project based on the Self-Amplified Spontaneous Emission (SASE), is under progress at the Pohang Accelerator Laboratory (PAL). Successful completion of the project is expected to impose stringent requirements on the beam qualities such as the normalized emittance (< 1.2 mm-mrad) and the un-correlated energy spread (~10(-5)). This requires careful and systematic planning for ensuring the generation and the preservation of high-brightness beams in the whole machine. The PPI (Pohang Photo-Injector) is to achieve these requirements with high reliability and stability. In this article, we discuss various physics and engineering issues involved in the design and construction of the PPI. We also report on the R&D status of photo-cathode RF gun at the PAL.

• R. Bonifacio, R. Bonifacio
  Universidade Federal de Alagoas, Maceio
• N. Piovella
  Universita' degli Studi di Milano, MILANO
• G.R.M. Robb
  Strathclyde University, Glasgow

We present a proof of principle of the novel regime of quantum SASE with propagation effects. Using a self-consistent system of Schrodinger-Maxwell equations, we show that the dynamics of the system is determined by a properly defined "quantum FEL-parameter", ρ', which rules the number of photons emitted per electron, as well as the electron recoil in units of ћk. In the limit ρ'>>1 the quantum model reproduces the classical SASE regime with random spiking behavior and broad spectrum. In this limit we show that the equation for the Wigner function reduces to the classical Vlasov equation. In the opposite limit, ρ'<1, we demonstrate "quantum purification" of SASE: the classical spiking behavior disappears and the power spectrum becomes very narrow so that the temporal coherence of the SASE spectrum is dramatically improved. Photon statistics, electron-photon entangled states, minimum uncertainty states and quantum limitations on bunching and energy spread will be discussed.