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Beamline U5UA

General Information

Source Type
Insertion Device

Status
Operational

General User Beamtime
50%

Energy Range Category
Ultraviolet

Energy Range
15-150 eV

Beamline Type
Facility Beamline

Technique(s)
Ultraviolet photoelectron spectroscopy (UPS), angle-resolved
Ultraviolet photoelectron spectroscopy (UPS), spin-resolved

Institution(s)
Brookhaven National Laboratory - CFN
NSLS

Research Types
Branch I: Valence band photoemission; core level photoemission; angular-resolved photoemission; spin polarized photoemission. Branch II: LEEM/PEEM spectromicroscopy

Contact Information

Spokesperson The person from each beamline who acts as a contact point between the beamline management and NSLS administration. Contact for questions about the beamline scientific program, experimental capabilities, and beamline management.
Elio Vescovo, Brookhaven National Laboratory, vescovo@bnl.gov, 344-7399

Local Contact The beamline staff member who is typically responsible for overseeing the daily operation and maintenance of the beamline. Contact for questions about beamline instrumentation, experimental details, and training.
Elio Vescovo, Brookhaven National Laboratory, vescovo@bnl.gov, 344-7399
Qing-Yi Dong, Brookhaven National Laboratory, qdong@bnl.gov, 344-5358

Beamtime Scheduler The beamline staff member responsible for coordination of beamline schedule every trimester. Contact for questions about beamtime scheduling.
Elio Vescovo, Brookhaven National Laboratory, vescovo@bnl.gov, 344-7399

Beamline Phone
631-344-5505

Instrumentation

Beamline Characteristics

Energy Range Mono Crystal or Grating Resolution (ΔE/E) Flux Spot Size (mm) Total Angular Acceptance (mrad)
10 – 20 eV 300 lines/mm 10-4 - 10-3 1 x 1014 ph/sec/0.1%bw (@ 500 mA) 1.0H x 0.2V 2.7H x 1.4V
20 – 40 eV 600 lines/mm 10-4 - 10-3 1 x 1014 ph/sec/0.1%bw (@ 500 mA) 1.0H x 0.2V 2.7H x 1.4V
40 – 80 eV 1200 lines/mm 10-4 - 10-3 8 x 1013 ph/sec/0.1%bw (@ 500 mA) 1.0H x 0.2V 2.7H x 1.4V
80 – 160 eV 2400 lines/mm 10-3 8 x 1013 ph/sec/0.1%bw (@ 500 mA) 1.0H x 0.2V 2.7H x 1.4V

Source Type
7.5 cm, 57-pole undulator

Optical System
The beamline optical design, as reconfigured in 1995, is relatively simple; it is based on a 3.5 m spherical-grating monochromator (R = 10 m) coupled to a pre-focusing spherical mirror and a post-focusing toroidal one. The undulator source is demagnified 4:1 onto the entrance slit. Both the entrance and exit slits are mounted on linear slides, thereby enabling operation of the monochromator in the Rowland-circle geometry over an extended photon energy range. The small angular divergence of the undulator source permits the use of relatively inexpensive postage stamp-size gratings (150 x 20 mm). The beamline is equipped with 4 gratings (300, 600, 1200, 2400 lines/mm ruling densities) for optimum matching in the photon energy ranges 10-20 eV, 20-40 eV, 40-80 eV, 80-160 eV, respectively (see table above). The exit slit is refocused (2:1 demagnification) onto a small spot-size (1H x 0.2V mm2) at the upstream sample position. The U5UA photon energy range (15 < hv < 160 eV) and its high-photon flux are particularly suited to the demanding requests of spin-polarized, angular-resolved photoelectron spectroscopy, which is performed in the upstream endstation.

An extension of the U5UA beamline was designed and constructed in FY2003-4 in order to serve VUV/soft x-ray users who need a small focused beam spot. The refocusing optics consist of two figured ellipsoidal mirrors with the following parameters: first ellipsoid: 1250mm input: 350mm output: 5o grazing angle of incidence (3.6:1 demagnification), second ellipsoid: 1500 mm input, 900 mm output, 5o grazing angle of incidence (1.7:1 demagnification). This produces a focal spot ~20m in diameter with a flux similar to that in the upstream endstation, since the reflectivity at in the VUV 5o grazing angle of incidence in the VUV is relatively high. No endstation is permanently installed in the second endstation position; to date, it has been used for high resolution angle-resolved photoemission and VUV emission spectroscopies. In late FY2005, we expect this second endstation to begin serving the LEEM/PEEM microscope in conjunction with the BNL Center for Functional Nanomaterials.

Experimental Apparatus
Upstream end-station for spin- and angular-resolved photoemission. The experimental apparatus is equipped with the standard instruments for the preparation and characterization of surface, interfaces and thin-films (LEED/Auger, differential sputtering, e-beam evaporators). The electron energy analyzer is a commercial Omicron 125mm hemispherical electron energy analyzer that has been custom-fitted with a 30 kV micro-Mott spin polarimeter (Rice Univ.).

Computer System Hardware & Software
Hardware: EPICS/VME system running RTEMS; plus McLennan stepping motor controller for the beamline stepping motors (serial interface), and PCI GPIB for other stepping motors and electron energy analyzer control. User-level software interface is via the "Un" program (S. Hulbert, E. Vescovo (NSLS USD)) running on a Debian Linux PC.

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