Abstract. The spectromicroscopy beamline (SM) at the Canadian Light Source (CLS) will provide 100 -2000 eV photons in a high brightness, high flux, medium resolution and small spot size beam. The beamline consists of an advanced elliptically polarized undulator (EPU) source and a novel entrance slit-less plane grating monochromator which feeds two branch lines, one optimized for scanning transmission X-ray microscopy (STXM), the other for X-ray photoemission electron microscopy (X-PEEM). This article outlines the beamline design strategy, and discusses the design optimization relative to the requirements for state-of-the-art STXM and X-PEEM. DESIGN OBJECTIVES AND CONSTRAINTS Development of third generation SR sources, enhanced quality soft x-ray optics, and advances in beamline design have lead to the construction of several successful spectromicroscopy (SM) facilities around the world [1]. The SM facility at the Canadian Light Source (CLS), a dedicated soft x-ray beamline and associated scanning transmission x-ray microscope (STXM) and x-ray photoemission electron microscope (X-PEEM), will begin operation in 2004. Here we describe the design principles and solutions adopted to optimize the beamline for these two microscopies. There is a substantial difference in image formation for these two techniques. In STXM, the source is demagnified by a Fresnel zone plate (FZP) and the ultimate spatial resolution is defined by the outmost zone width, or ~30nm at current stage of FZP fabrication [2]. To keep such ultimate spot size, the phase accepted by FZP needs to be limited to a single diffraction mode or λ (wavelength of incoming radiation) [3]. As this phase space is much smaller than the emittance of existed SR sources, reduced horizontal phase acceptance can be traded for energy resolving power and overall simplicity. Following the design of the X1A spectromicroscopy beamline at the National Synchrotron Light Source (NSLS), the horizontal dispersing spherical grating monochromator has proved to be a successful choice for several STXM [3][4][5]. In PEEM, the image is formed by magnified projection of low energy photoelectrons with electrostatic or magnetic electron lenses and recorded with a CCD camera. The dominant chromatic aberrations reduce spatial resolution for most PEEM to ~50 nm in the soft x-ray regime. When this spatial resolution is matched to a megapixel high sensitivity CCD the field of view is of order 30-50 µm. Such moderate spot size can be obtained without any phase (source emittance) loss. The figure of merit analysis of different optical schemes was performed by Weiss et al [6] who concluded that a collimated plane grating monochromator is the optimal choice and further, that it allows further beam size reduction if needed . To find the optical scheme which best suits both experiments we compared two design concepts, namely a horizontally dispersed spherical grating monochromator (HD-SGM) and a collimated plane grating monochromator with vertical dispersion (PGM) with primary design goal for highest possible on-sample flux in each microscope, with a resolving power exceeding 3000 and covering the energy range 250-2000eV. The results of the comparison follow by a brief presentation of the optical properties of the PGM-based beamline, which was chosen as a best compromise. The ID10 sector was allocated for the CLS-SM facility, which limits the total length of the beamline to 37m. The lattice parameters (β x =8.5m, β y =4.6m, η x =0.15m, for ε x =18nmrad and assuming 0.2% coupling as projected for 2008 operation) result in electron beam size (FWHM) ∆x=990µ and ∆y=30µ [7]. Chiral molecules, magnetic ordering, sample texture and film orientation are among the scientific topics to be studied so full polarization contro
