NEH 2.2

NEH 2.2

The combination of exceptionally high flux of monochromatic photons, far exceeding that at current state-of-the-art instruments, delivered in the form transform-limited femtosecond X-ray pulses, will make the NEH 2.2 Instrument at LCLS-II one with transformational capabilities. It will enable new ways to capture rare chemical events, characterize fluctuating heterogeneous complexes, and reveal quantum phenomena in matter, using multidimensional and coherent X-ray techniques that are possible only with X-ray lasers. This facility will provide access to the “soft X-ray” regime (250 eV to 1.6 keV) to provide fully coherent X-rays in a uniformly spaced series of pulses with programmable repetition rate and rapidly tunable photon energies.

Endstation Descriptions

NEH 2.2 will host initially 2 endstations, Resonant Inelastic X-ray Scattering (RIXS) Endstation and Liquid Jet Endstation (LJE), that will be placed in series with attention paid to X-ray focal requirements, vacuum compatibility and beam pass-through capabilities. The LJE instrument is comprised of a sample chamber, designed with emphasis on soft X-ray spectroscopy experiments on liquid samples, and 2 X-ray emission spectrometers, the Varied Line Spacing (VLS) portable spectrometer and the Transition Edge Sensor (TES) spectrometer. For rapid XAS measurements and direct beam detection (in the case of transmissive samples), a suite of in-vacuum detectors will be implemented on a rotating arm. The endstation shall be designed with the goal to support automated sample transfer.

The RIXS instrument is comprised of a sample chamber and a rotatable spectrometer consisting of grating and detector assemblies (and auxiliary components), continuously covering the range of scattering angles 40-160 degrees in the horizontal plane. The spectrometer has to achieve a target resolving power of 50,000 at 1 keV, with the option for lower resolving power, ~10,000, and higher throughput through the use of a second grating in the spectrometer.

The sample chamber will be designed also to accommodate the technique of Resonant Elastic X-ray Scattering (REXS). For this, a suite of in-vacuum point and 2D detectors will be implemented on a rotating arm to allow for rapid X-ray Absorption Spectroscopy (XAS) and (super)structural peak finding for sample orientation. In addition, the spectrometer arm shall be designed so that X-ray Photon Correlation Spectroscopy (XPCS) experiments on solid samples could be performed as well.

Provisions for a third, roll-up station shall be considered.

Specifications

Parameter Required Goal Comment
Photon Energy Range [eV] 250-1600  
  • Oxygen K-edge 3rd harmonic rejection of >10-5
  • Experiments on rare earth M-edges
Beamline Transmission [%] 20 40
  • For zero order (grating reflection) operating mode below 1000 eV. Required transmission shall be maintained.
Bandwidth Control
[Resolving Power]
50,000
10,000
5,000
>50,000 in higher order

1,000-2,000
  • Ref: Mono Requirements RP in the 1,000-2,000 range is needed for experiments needing very high temporal resolution.

Specifications Experimental Spot Size Range

  1. Horizontal [μm]
  2. Vertical [μm]
2-1,000
2-1,000
 
  • Spot size adjustable to each end station interaction location
Beam Position Stability
[% of FWHM]
<10    
Pulse Stretching <2  x TL  
  • This requirement should be achievable for all RP modes of operation and at all photon energies in the range specified

Advisory Panel

LJE:

  • Jinghua Guo - LBNL – ALS
  • Andreas Scherz - EuXFEL
  • Philippe Wernet - BESSY
  • Wilfried Wurth - DESY - FLASH
  • Anders Nilsson - Stockholm U., Stanford
  • Steve Kevan - LBNL – ALS

RIXS:

  • Yi-De Chuang- LBNL - ALS
  • Joe Dvorak - NSLS-II
  • Giacomo Ghiringhelli - Politecnico di Milano
  • Wei-Sheng Lee - SLAC
  • Ruben Reininger - APS
  • Tony Warwick - LBNL - ALS
  • DJ Huang - NSRRC
  • Alexander Fohlisch - BESSY
  • Gabriel Aeppli - PSI