Author: Zhang, L.
Paper Title Page
WEPH19
 Positioning Behavior of a Lead-Screw Type In-Vacuum Actuator  
 
  • L. Lee, D.S. Morton, M.L. Ng, L. Zhang
    SLAC, Menlo Park, California, USA
  
  In-vacuum actuators are under consideration for operating the bending flexturs of the new Kirkpatrick-Baez focusing mirrors as part of the upgrade to LCLS-II. To achieve an mechanical accuracy of better than 104, the characteristics of the actuators need to be explored. We designed a testing procedure in terms of both setup and actuator excursion program to understand various behaviors of the actuator in a simulated typical operating condition. Multiple independent sensors were used, including optical linear encoder, laser interferometer and capacitive sensors. In this presentation, I will show the testing procedure and results obtained for a commercially available high-precision leadscrew type in-vacuum linear actuator with a stroke of 10 mm and a resolution of 2.5 nm. It was found that under typical static operation conditions, an accuracy of 104 can be achieved without external encoder feedback. Detailed behaviors regarding repeatability and backlash are also discussed.  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THOAMA02
 LCLS NEH Floor Thermal Deformation and Mitigation Plan  
 
  • L. Zhang, J.C. Castagna, M. R. Holmes
    SLAC, Menlo Park, California, USA
  
  The key features of LCLS-II upgrade are the high repetition rate up to 1 MHz, and two variable-gap undulators (SXR and HXR). To take the advantages of this major upgrade, LCLS, SLAC is designing and building new soft and tender X-ray beamlines (TMO, TXI, RIXS, XPP). The laser pump FEL probe, or SXR FEL pump HXR probe experiments need sub-micron stability in a time range from 5 ms to a few hours. Dynamically bendable KB mirror can focus X-ray beam down to 300 nm. The overlap of the pump laser (or FEL), probe FEL beam and sample is challenging. Some measurements on vibration and long term stability have been carried out on the floor in the Near Experimental Hall (NEH) to host the new beamlines. The vibration displacement in the frequency range of 1 to 200 Hz is at the level of 25 nm. The floor deformation over hours and days measured by HLS and interferometer, however, show tens micro-meters displacement variation. This huge floor deformation is incompatible with the stability requirement. In this paper, we will present the simulation of the whole NEH building, comparison with measurement results, describe mitigation plan and predict the performance.  
slides icon Slides THOAMA02 [15.109 MB]  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THOPMA05
 Using Resistive Element Adjustable Length (REAL) Cooling to Increase Optical Design Flexibility in High Power XFELS  
 
  • C.L. Hardin, D. Cocco, L. Lee, D.S. Morton, M.L. Ng, L. Zhang
    SLAC, Menlo Park, California, USA
  
  With the onset of high power XFELs and diffraction limited storage rings, there is a growing demand to maintain sub nanometer mirror figures even under high heat load. This is a difficult issue as the optimum cooling design for an optic is highly dependent on the power footprint on the mirror, which can be highly dynamic. Resistive Element Adjustable Length cooling can be utilized to change the cooling parameters during an experiment to adapt for changing beam parameters. A case study of the new soft x-ray monochromator for the LCLS L2SI program is presented that utilizes this new capability to allow the beam to translate across the mirror for different operation modes, greatly simplifying the monochromator mechanics.  
slides icon Slides THOPMA05 [22.095 MB]  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPH34
 Design & Validation of Adaptive Bendable Mirrors for the LCLS-II Soft X-Ray Beam Lines  
 
  • D.S. Morton, D. Cocco, C.L. Hardin, L. Zhang
    SLAC, Menlo Park, California, USA
  
  Funding: SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.
One of the key components of the photon beam transport system, in the LCLS-II SXR beamlines is the bendable focusing mirror system. For the first time in the Synchrotron or FEL beamlines, the large bending needed to focus the beam will be coupled with a direct cooling system, since almost the entire FEL power is de-livered through the optics to the sample. While cooling and bending the mirror, height errors shall be preserved below one nanometer RMS, to not distort the wavefront of the coherent FEL beam. This has required an extensive study of the mechanical properties of the thermal interface material, Gallium Indium (GaIn). Aside from the challenges introduced by the cooling, the mechanical requirements of the bender have resulted in an extensive design effort. This effort has yielded a prototype system that has been tested to validate our design decisions, and the FEA models of the system. In this paper, the key design elements of the bendable mirror system will be reviewed. We then discuss FEA models of the system and the expected performance. This is followed by results from laboratory tests and comparison to simulations. We finalize with the design changes and future work. 		 
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THPH36 Engineering Challenges for the NEH2.2 Beamline at LCLS-II 409
 
  • F.P. O'Dowd, D. Cocco, G.L. Dakovski, J. Defever, S. Guillet, C.L. Hardin, D.S. Morton, T.O. Osier, M.A. Owens, D.W. Rich, L. Zhang
    SLAC, Menlo Park, California, USA
  
  SLAC National Accelerator Laboratory is developing LCLS-II, a superconducting linear accelerator based FEL capable of repetition rates up to 1MHz. The NEH2.2 Instrument at LCLS-II will use this combination of exceptionally high flux of monochromatic photons to achieve multidimensional and coherent X-ray techniques that are possible only with X-ray lasers. The challenges, which emanate from delivering the beam from the sub-basement level to the basement of the Near Experimental Hall (NEH) along with the stringent requirements for providing a stable beam at the interaction points, necessitate unique engineering solutions. With this paper we present the conceptual design for the NEH2.2 Instrument along with an overview of the R&D program required to validate design performance. Furthermore, it will additionally show the design of the proposed Liquid Jet Endstation (LJE) and Resonant Inelastic X-Ray Scattering Endstation (RIXS) that will be installed on the beamline. After introducing the context and layout of the beamline, this paper will focus on the technical challenges and present the mechanical design solutions adopted for beam delivery and other strategic components.  
poster icon Poster THPH36 [2.220 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-MEDSI2018-THPH36  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
FROAMA01
 Mechanical Engineering Instrument Design and Development for LCLS-II  
 
  • L. Zhang
    SLAC, Menlo Park, California, USA
  
  The high-repetition-rate FELs will enable a broad range of high-resolution, coherent pump probe experiments over a large photon energy range. On top of the extreme high peak power of the FEL, the average power of this high-repetition-rate FEL reaches several hundred watts. This combination of extreme high peak power and high average power becomes very challenging for the X-ray optics to preserve the FEL beam quality. As an example for X-ray optics - water cooled and dynamically bendable KB mirror, minimizing thermal deformation, bending the mirror to perfect ellipse shape. Managing the beam power of soft X-ray FEL with high energy per pulse and high average power needs windowless gas attenuator with differential pumping system. FEL beam from two different sources (SXR and HXR) or to split femtosecond FEL pulses and recombine them with a precisely adjustable delay opens numerous scientific applications such X-ray pump X-ray probe. The complexity of a delay system for LCLS-II includes multiple bounce crystals requiring femtosecond time delay accuracy and with the possibility of photon energy scan. In this paper, we will highlight design and development of these systems at LCLS.  
slides icon Slides FROAMA01 [17.486 MB]  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)