NSLS and Beamline X28C ceased operations on September 30, 2014. Stay tuned for XFP@NSLS-II.

General Information

  • Beamline Operating Procedures
  • Research Program: Time-Resolved X-ray Footprinting (DNA, RNA, and protein)
  • Ring: X-Ray
  • Status: Operational
  • Time Dedicated to General User Program: 25%
  • Participating Institutions: Case Western Reserve University



Energy Range (keV)OpticsSource Type/Angular AcceptanceFlux (photons/sec)Size of Focus (mm)
White BeamToroidal focusing mirror (optional)Bending Magnet/ 6 mradUnfocused beam: 4.2 x 1016 ph/s; Fully focused beam: 2.9 x 1016 ph/s0.5 H x 0.5 V

Optical and Beamline Configuration

X28C is a white-light capable beamline which accepts 6mrad of horizontal radiation from the bending magnet X-ray source. The optical transport system operates under high vacuum and includes a tapered Cu aperture with 5 mm vertical x 123 mm horizontal exit dimensions; two 0.01" thick Be windows, at 8.96 m and 15.5 m from the source, respectively, and a focusing mirror centered at 9.378 m from the source. The mirror is a single Si crystal coated with Pd which has a cylindrical cut bendable to a toroidal shape that allows both horizontal and vertical focusing of the X-ray beam. The remaining section of beam transport pipe is kept at millitorr vacuum during operations and cycled to atmosphere to change transport pipe length and Al exit window thickness (0.003" Al exit window is standard).

Beam size and shape, flux density, and associated X-ray spectrum are adjustable through manipulation of the toroidal mirror from a full focus of 0.5 x 0.5 mm (~6-15 keV broadband spectrum) through complete removal of the mirror for full white beam at 2.5 V x >30 H mm (5 keV-100 keV). Standard configurations include a beam appropriate for exposure of a droplet at the bottom of a PCR tube (held by surface tension as the tube is held horizontally) and a beam appropriate for flow cells.

Experimental Apparatus

The lead-lined experimental hutch contains apparatus to perform a variety of steady-state and time-resolved experiments. These include a computer controlled Pre-shutter, XZ transition table, heavy jack for moving the beampipe, a millisecond (Unibilitz®) shutter, several specialized Kintek® quench flow apparatus (temperature controlled), multiple sample (23) holder (with temperature regulation), micro fluidic flow set-up connected to syringe and/or M50 pumps, a fraction collector, an in-line incubator for live cell experiments, and a dark room facility for exposure of photosensitive samples.

Computer System Hardware and Software

Beamline control is provided by a PC running Windows XP and a specialized LabView interface that interacts with the motor control units: KinTek® controller, Uniblitz shutter controller (Vincent Associates), XDAC-Parker Compumotor 6K8, Harvard Syringe pump, Vici M50 pump (Valco Instruments), and the fraction collector. Also provided is a Windows 8 computer for data analysis (includes Xcalibur, Origin, Excel), connected to the internet. Both computers can access the beamline printer.