* Corresponding author. E-mail: varfolom@lki.msk.ru. Nuclear Instruments and Methods in Physics Research A 407 (1998) 423 — 427 UCLA-KIAE focusing permanent magnet undulator for SASE experiment N. Osmanov, S. Tolmachev, A. Varfolomeev*, A.A. Varfolomeev, Jr., P. Frigola, M. Hogan, C. Pellegrini, R. Carr, S. Lidia  Coherent Radiation Laboratory, Russian Research Center **Kurchatov Institute++, Moscow 123182, Russia  Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095-1547, USA  Stanford Synchrotron Radiation Laboratory, Stanford University, CA 94309, USA  Lawrence Berkely Laboratory, CA 94720, USA Abstract A description of a new 2 m undulator is presented which was specially designed and manufactured for a SASE mode FEL experiment. It is a one section two plane focusing permanent magnet construction. The uniform period length is 2.06 cm, total number of periods is 98. The peak field on the axis is 5.4 kG for a 5 mm gap.  1998 Elsevier Science B.V. All rights reserved. PACS: 41.60.C; 07.55.G Keywords: Magnet; Undulator; Construction 1. Introduction A new pure permanent magnet undulator with total length of 2 m has been specially designed for the SASE FEL experiment at Los Alamos acceler- ator and constructed in a short time due to well- organized collaboration of some groups from dif- ferent institutes. Basic specification and mechanical fabrication was done by UCLA. The Berkeley- Stanford group made permanent magnet sorting, electron trajectory simulation in the undulator and mechanical fabrication of some small undulator components. The main part of the work was done by the Kurchatov Institute team which included common undulator design with mechanical draw- ing, control of the fabrication of mechanical com- ponents and, assembling and testing of the undula- tor. Wire technique measurements were made together with the UCLA team. All assembling and testing work was done at UCLA. A peculiarity of this work was to build a cheap undulator using Sm—Co permanent magnet blocks available from Los Alamos group as a result of disassembling of old undulators using a mechanical frame construction similar to that used earlier for 0168-9002/98/$19.00  1998 Elsevier Science B.V. All rights reserved PII S0168-9002(98)00062-X VII. OPTICS/UNDULATORS