Recent advances in insertion devices

Demand for more and better insertion devices (IDs) at new third-generation synchrotron radiation facilities has led to significant advances in ID technology at different laboratories around the world. In this overview of this progress, focus is on those results that apply to IDs in general rather than one specific ID or laboratory. The advances fall into two general categories: those that reduce the net effect that the ID has on the particle beam, and those that enhance the quality of the emitted light spectrum. The need for these advances, factors that are most important inaachieving them, and the current state of the art are discussed

Characterization of a novel elliptically polarized wiggler

We report on the initial characterization of an elliptically polarized wiggler built by a collaboration between the Advanced Photon Source, the Institute of Nuclear Physics, and the National Synchrotron Light Source. The wiggler has recently been installed in the X13 straight section of the NSLS X-Ray ring. The device consists of a vertical permanent-magnet wiggler and a horizontal electromagnet wiggler. The electromagnets allow the wiggler to produce on-axis circularly polarized soft x-rays with the capability of AC modulation of the polarization. The maximum switching frequency that can be reached is 100 Hz. The degree of circular polarization of the radiation from the wiggler was characterized by making magnetic circular dichroism measurements using the X13A soft x-ray beamline. For a vertical deflection parameter, K{sub x}, of 1.6, the dichroism effects at the Fe L{sub 2,3} edges indicate a degree of circular polarization of approximately 75% using an aperture with a vertical acceptance of 87 {mu}rad. Because both the left- and right-circularly polarized photons traverse identical paths through the beamline optical system, significantly smaller intensity fluctuations associated with switching of the polarization were observed that are typically possible at bending magnet beamlines. This, together with the relatively fast modulation rate, means that it will now be feasible to perform a variety of experiments that have not been possible using bending magnet sources

Soft x-ray spectroscopy undulator beamline at the Advanced Photon Source

Construction of the high-resolution soft x ray spectroscopy undulator beamline, 2ID-C, at the Advanced Photon Source (APS) has been completed. The beamline, one of two soft x ray beamlines at the APS, will cover the photon energy range from 500 to 3,000 eV, with a maximum resolving power between 7,000 and 14,000. The optical design is based on a spherical grating monochromator (SGM) giving both high resolution and high flux throughput. Photon flux is calculated to be approximately 10{sup 12}--10{sup 13} photons per second with a beam size of approximately 1 x 1 mm{sup 2} at the sample

The advanced photon source low-energy undulator test line

There are a number of fully commissioned 3rd-generation synchrotron light sources in the world today. So far they have met the demanding requirements of the user community; however, there is always a desire to go beyond what is presently available or even desirable. The Advanced Photon Source (APS) Low-Energy Undulator Test Line (LEUTL) was conceived to address the advancement of synchrotron light sources. The LEUTL uses the existing APS linac and a low-emittance electron gun, and by means of measurements of the beam and generated light, will test new and innovative undulators and push the technology and physics of single-pass, coherent light sources. The design and status of the LEUTL will be described along with its immediate capabilities and those planned for the future

Beamline and exposure station for deep x-ray lithography at the Advanced Photon Source

APS is a third-generation synchrotron radiation source. With an x-ray energy of 19.5 keV and highly collimated beam ( 1 mm) using deep x-ray lithography (DXRL). The 2-BM beamline was constructed and will be used for DXRL at APS. Selection of appropriate x-ray energy range is done through a variable-angle mirror and various filters in the beamline. At the exposure station, the beam size will be 100(H) x 5(V) mm{sup 2}. Uniform exposure will be achieved by a high-speed (100 mm/sec) vertical scanner, which allows precise angular ({approximately}0.1 mrad) and positional (< 1 {mu}m) control of the sample, allowing full use of the highly collimated beam for lateral accuracy and control of sidewall slopes during exposure of thick resists, as well as generation of conicals and other profiles. For 1-mm-thick PMMA, a 100 x 25 mm{sup 2} area can be fully exposed in about 1/2 hr, while even 10-mm-thick PMMA will require only 2-3 hours

Beamline and exposure station for deep x-ray lithography at the advanced photon source

APS is a third-generation synchrotron radiation source. With an x-ray energy of 19.5 keV and highly collimated beam ( 1 mm) using deep x-ray lithography (DXRL). The 2-BM beamline was constructed and will be used for DXRL at APS. Selection of appropriate x-ray energy range is done through a variable-angle mirror and various filters in the beamline. At the exposure station, the beam size will be 100(H) x 5(V) mm{sup 2}. Uniform exposure will be achieved by a high-speed (100 mm/sec) vertical scanner, which allows precise angular ({approximately}0.1 mrad) and positional (< 1 {mu}m) control of the sample, allowing full use of the highly collimated beam for lateral accuracy and control of sidewall slopes during exposure of thick resists, as well as generation of conicals and other profiles. For 1-mm-thick PMMA, a 100 x 25 mm{sup 2} area can be fully exposed in about 1/2 hr, while even 10-mm-thick PMMA will require only 2-3 hours

The LIL for UU-statistics in Hilbert spaces

We give necessary and sufficient conditions for the (bounded) law of the iterated logarithm for $U$-statistics in Hilbert spaces. As a tool we also develop moment and tail estimates for canonical Hilbert-space valued $U$-statistics of arbitrary order, which are of independent interest

Moments of unconditional logarithmically concave vectors

We derive two-sided bounds for moments of linear combinations of coordinates od unconditional log-concave vectors. We also investigate how well moments of such combinations may be approximated by moments of Gaussian random variables.Comment: 14 page