• 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).

• O. Grimm, H. Delsim-Hashemi, L. Fröhlich
  DESY, Hamburg
• E. Chiadroni
  Universita di Roma II Tor Vergata, Roma

Various activities at the TTF linear accelerator at DESY, Hamburg, that drives the VUV-FEL are geared towards measuring the longitudinal charge distribution of electron bunches with coherent far-infrared radiation. Examples are beam lines transporting synchrotron or transition radiation to interferometers mounted inside or outside the tunnel, and studies of single-shot grating spectrometers. All such approaches require a good understanding of the radiation generation and transport mechanism and of the detector characteristics to extract useful information on the charge distribution. Simulations and measurements of the expected transverse intensity distribution and polarization of synchrotron radiation emitted at the first bunch compressor of TTF have been performed. The transverse intensity scanning provided for the first time at DESY a visual image of the footprint of terahertz radiation. Detector response measurements have been performed at the FELIX facility, Netherlands, for wavelengths between 100-160 microns, and first studies with blackbody radiation and band pass filters in the terahertz regime have been done at PTB, Berlin. The paper will summarize these results.

• S. Sasaki, I. Vasserman
  ANL, Argonne, Illinois

Funding: Supported by the U.S. Dept. of Energy, BES-Office of Science, under Contract W-31-109-ENG-38.

Trajectory straightness through the undulator is critical for the success of the LCLS project. Environmental fields, including the earth’s field, will affect the trajectory. The earth’s field works as an external dipole field and, unless it is shielded or corrected, causes a bend in the electron trajectory through an undulator. We investigated the effects of the earth’s field and an iron plate which might be used as part of a girder. Modeling and calculation were performed using the code RADIA. A model with a large solenoid surrounding a seven-period undulator was used for the simulation. According to the calculations, the vertical component of the earth’s field at the undulator axis is enhanced by the undulator poles by a factor of 2.5. The horizontal on-axis component, however, is well shielded by the undulator poles and falls to less than 3% of its original strength. The effect of an iron plate located 200 mm below the undulator axis is negligibly small, so final Hall probe measurements can be done without the girder in place. However, the magnetic tuning of the undulator field must take into account the amplification of the vertical component of the environmental field in the LCLS tunnel.

• S.H. Kim
  ANL, Argonne, Illinois

Funding: Work supported by the U.S. Department of Energy under Contract No. W-31-109-ENG-38.

The peak fields on the beam axis and the maximum fields in the conductor of Nb3Sn superconducting undulators (SCUs) were calculated for an undulator period length of 16 mm. Using a simple scaling law for SCUs [1], the peak fields, as well as the conductor maximum fields and the current densities, were calculated for a period range of 8 to 32 mm. The critical current densities of commercially available Nb3Sn superconducting strands were used for the calculations. The achievable peak fields are limited mainly by the flux-jump instabilities at low fields. The possible or feasible peak field will also be compared with that achieved in prototype development of SCUs.

[1] S. H. Kim, Nucl. Instrum. Methods A, accepted for publication.