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G-line map

G-line history and mission:

Commissioned in 2002, Gline is the most recent addition to CHESS. Its three x-ray stations make use of radiation from the same 49-pole wiggler that feeds the A1 and A2 hutches in CHESS West: the 5.3 GeV electron beam circulates counterclockwise and produces X-rays for A1 and A2, while the positron beam circulates clockwise and feeds G1, G2 and G3. The high intensity available at these stations is used by a wide variety of research groups from Cornell University and around the world to study the structure and dynamics of matter at the atomic scale.

G-line's two-fold mission is to serve both as a lightning rod for new research directions and a training ground for future leaders in synchrotron-based research.  It explicitly brings together CHESS's strong tradition of synchrotron science and applications development with the Cornell Center for Materials Research (CCMR).  As part of its research and training roles, G-line hosts biannual symposia featuring student research based at G-line or elsewhere at CHESS.

G1 and G3 were principally designed for time-resolved studies requiring high flux but modest spatial and energy resolution. Both stations generally operate from 8-12 keV, and combine horizontal and vertical focusing with synthetic multilayer monochromator pairs to deliver upwards of 5x1013 photons/sec/mm2 at the sample. G2 employs a single-crystal transmission monochromator to obtain a fraction of the G3 beam for high resolution diffraction.  It features a custom-built six-circle kappa diffractometer, and houses a variety of research projects examining detailed studies of the structure and dynamics of organic and inorganic thin films.

G-line Front End Summary:

The 2 milliradian fan of radiation from the CHESS West wiggler is approximately 50 mm wide by the time it reaches G-cave, where it is split into two components by a pair of synthetic multilayer monochromators. The southern 25 mm of beam is deflected upwards and eventually becomes the G1 beam. The northern half is deflected downwards and then guided through a lead-shielded pass-through pipe in G1. Upon reaching G2 cave, a narrow bandpass transmission crystalline monochromator deflects a small portion of the beam into G2, while the undeflected beam proceeds to G3. Further details and specs may be found here.

Source: Number of Poles 49
  Period (cm) 12
Peak Magnetic Field (T) 0.8
Critical Energy, (keV)@5.3GeV 14.9
Deflection Parameter, K 9
Length, m 3
Source size: FWHM (horizontal) = 3.61 mm, FWHM (vertical) = 1.07 mm
Source-to-Hutch Distances: G1: 33.5-38 m
G2: 38.3-41 m
G3: 41.2-44.8 m
Beam Position Monitors (BPM):
Photoelectron Monitor (PE) 19.5 m from source
Video Beam Position Monitor (VBPM) 25.0 m from source
Filters and Windows:
Graphite Filter 0.5 mm
Total Thickness of Be Windows 2.0 mm
White-Beam Mirror
Rh coated, electroless-nickel-plated Glidcop. 1000 mm x 80 mm x 80 mm, bendable mount.
Mirror constant: 60 keV-mrad. theta = 4 mrad
  Distance from source: 23 m
G1/G3 vertical beam separation: 200mm
Monochromatic Mirrors
Rh coated single-crystal silicon, 1000 mm x 80 mm x 80 mm, bendable for vertical focusing.
Mirror constant: 60 keV-mrad. nominal theta = 4mrad
G1 Mirror distance from source: 32.2 m
G2/3 Mirror distance from source: 30.7 m
First Monochromator Box
Base pressure: 5x10-9 Torr. No in-vacuum motors
Multilayers are mounted to internally-water-cooled copper blocks
G1 mono distance from source: 27 m
G2/3 mono distance from source: 26 m
Second Monochromator Box
Base Pressure: 1x10-8 Torr
G1 1st-2nd crystal distance: 0.9-2.3 m
G2/3 1st-2nd crystal distance: 1.75-3.3 m
Standard Monochromator Optics:
G1 multilayers
d-spacing, Å Material Substrate Refl ΔE/E,%
23.59 W/B4C 200x50x10mm, flat; SiC 0.73 1.5
23.65 W/B4C 200x50x10mm, flat; Si 0.77 1.5
(23.57) W/B4C 200x50x25mm, curved; Si (0.74) (1.5)
G3 multilayers
27.11 W/B4C 200x50x25mm, SiC 0.75 2.1
27.13 W/B4C 200x50x25mm, Si 0.77 2.1
(27.11) W/B4C 200x50x25mm, curved; Si (0.75) (2.1)
Parentheses indicate measurements of flat witness samples
G2 Transmission Monochromator: Single crystal beryllium (002).
Thickness: 0.5 mm. D-spacing: 1.79 Angstroms

Additional Links:
Student Symposia
Documentation
Faculty
G-line Design
Safety

 

 

 

2013 X-ray Runs

Feb 13th - April 2nd
May 8th - June 18th


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