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Matter in Extreme Conditions (MEC)

MEC Long Pulse and Short Pulse Optical Lasers

  • SLAC National Accelerator Laboratory
  • Laser Types: shaped nanosecond shock drive and high intensity Ti:Sapp lasers

Menlo Park, California is the birthplace of Google, home to Facebook HQ, and is known for Sand Hill Road — the Main Street of venture capital. Across the street, scientists at SLAC explore how the universe works at the biggest, smallest, and fastest scales at the vibrant multi-disciplinary laboratory managed by Stanford University.

Capabilities

Gilliss Dyer

Gilliss Dyer

Office: M/S 010, 2575 Sand Hill Rd, Menlo Park, CA 94025

Phone: (650) 926-3414

Email: Gilliss@slac.stanford.edu

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Overview

The Matter in Extreme Conditions (MEC) instrument of LCLS is provided part time to LaserNetUS users as a laser facility for optical-laser-only experiments using either or both of its long and short pulse lasers in the 2 m target chamber. The two laser systems may be used together or separately. The same expert staff that operates MEC as part of the LCLS national user facility is available to support LaserNetUS experiments.

(left to right) Instrument scientists Hae Ja Lee, Eric Galtier, and Bob Nagler

Long pulse laser system

The long pulse laser at MEC is designed to provide up to 10s of Joule shapeable pulses at 527 nm to create high pressure states (typically ~ 0.1 to 4 Mbar), warm dense matter conditions, high strain rate material states, or the formation of a plasma environment. The maximum energy deliverable to target will depend greatly on pulse shape, with a reference point of >60 J deliverable in a 10 ns square pulse. This energy is split between four arms, which are polarization-multiplexed into two beamlines for delivery to target. The laser system features a diode pumped front end with exquisite pulse shaping capabilities and excellent stability. A variety of pulse shapes, from as short as 3 ns  to as long as 35 ns can be provided to users, tailored to create specific thermodynamic trajectories in a compression system. The shot rate of the main amplifiers is 1 per seven minutes.

Marc Welch (left) and Eric Cunningham (right) discuss the MEC long pulse laser system

The long pulse focus can be shaped by one of several phase plates available at MEC. These phase plates produce nominally 150 µm, 300 µm, and 600 µm spot sizes with the standard aspheric lens sets, and measured beam profiles can be provided on request. Uniaxial shocks above 3 Mbar have been demonstrated in plastic ablators using the 150  µm spot; higher pressures can be reached through impedance mismatch.

Short pulse laser system

MEC employs a Ti:Sapphire double CPA laser system to enable dense plasma studies and relativistic particle production. A CPA regenerative amplifier front end is delivered compressed to a pulse cleaner, the output of which is stretched to 180 ps and amplified in two bowtie amplifiers to up to 1.5 J, compressed to 1 J in 40 fs for delivery to target, at up to 5 Hz repetition rate.

MEC Laser Scientist Eric Cunningham with a diffractive grating mirror optic used in chirped pulse amplification.

A robust pulse cleaner based on a Topas-Prime colinear OPA allows the system to achieve a pulse contrast of better than 10-8 at 4 ps, and better than 10-11 at 30 ps. This is currently the measurement threshold for the full energy output; the front end contrast reaches the noise floor of 10-12 at 5 ps.

The short pulse laser has been used in a number of specialized configurations:

  • Frequency doubled to 400 nm for extreme contrast, with over 400 mJ to target at up to 5 Hz, or mJ level at up to 120 Hz
  • A frequency doubling crystal and dichroic optics are available to deliver 400 nm light to target at even higher contrast.
  • An uncompressed mode for over 1.5 J in 130 ps at up to 5 Hz 
  • In specialized demonstration experiments, generation of betatron, HHG, or THz probes for interaction with matter heated and/or compressed either with part of the short pulse energy laser energy or the long pulse.

Target chamber and diagnostics

The MEC target chamber is a versatile 2 m vessel designed after the LLNL Titan and LANL Trident West target chambers. The target chamber has numerous ports on the sides, top and bottom, which can be fitted with windows, feedthrough ports, and target delivery systems. A standard target positioner with 5-axis motion and a large rastering target frame are used most frequently, but a number of custom target types have been fielded by users including rotating cylinder, gas jet and cryogenic liquid jets.

Commonly used diagnostics at MEC include dual line VISARs, a set of X-ray spectrometers covering photon energy ranges from 5 to 25 keV, a set of X-ray cameras including four large format vacuum pixel array detectors for diffraction measurements, and an X-ray imaging platform including compound refractive lenses and an Optique Peter X-ray microscope. Less commonly used diagnostics at MEC include a fourier domain interferometer and XUV spectrometer. Users should contact MEC with questions  regarding existing hardware and accommodation of user-provided hardware.

MEC User Support

MEC is an instrument of the LCLS user facility, which typically runs 10 months per year. MEC provides optical-laser-only beam time to LaserNetUS users as the LCLS schedule allows, typically 1-2 user experiments per year. A professional staff provides direct experimental support with each experiment dedicated points of contact for experiment setup, controls/data systems, detectors, lasers, and mechanical engineering. The LCLS facility provides a full-service user experience, from proposal development, through planning and experimental execution, to online data analysis.

Graduate student Meriame Berboucha adjusts a shielding slit in a Cauchois-type transmission crystal X-ray spectrometer in the MEC hutch

Facility access

All members of an experimental team expecting to be present at MEC must be registered with LCLS through the SLAC User Portal and complete all required courses before arriving (some courses are only required for specific activities). The spokesperson for an accepted LaserNetUS proposal (e.g. they who submitted the proposal) will be asked to name a principal investigator (PI) for the experiment. An MEC Instrument Scientist Point Of Contact (POC) will be assigned, who will guide the PI through the steps of preparing for their laser time.

https://lcls.slac.stanford.edu/instruments/mec
Gilliss Dyer, Gilliss@slac.stanford.edu
 

An in-vacuum variable filter mount, with Eric Galtier and the MEC target chamber in the background

Inside the MEC target chamber

The MEC target chamber during an experimental setup (ca. 2017), with VISAR enclosure to the right.

Eric Cunningham adjusts an internal diagnostic of the long pulse laser system

25 TW

Parameter Value Unit Additional Information
             
Center Wavelength 810 nm  
Pulse duration (I FWHM) <50 fs  
Max energy on target 1 J  
Shot energy stability 5 % r.m.s.      
Focal spot at target      
F/number f/6    
intensity FWHM 9 µm  
Strehl ratio 0.7    
Energy containment 74 % within 9.5 µm radius
Pointing Stability 8 µrad r.m.s.
Pre-pulse contrast      
ns scale 1E-12   @ 1 ns
ps scale 1E-10   @ 30 ps
  1E-09   @ 5 ps
  1E-07   @ 1 ps
Repetition Rate 5 Hz    

Compression Laser

Parameter Value Unit Additional Information
Center Wavelength 527 nm frequency doubled
Pulse duration (I FWHM) 5-35 ns  
Max energy on target >2x30 J for 10 ns square pulse
Shot energy stability 5 % r.m.s.
Focal spot at target      
F/number 3.5    
intensity FWHM 30 μm  
Energy containment 69 % within 20 µm radius
F/number 3.5    
intensity FWHM 150 μm phase plate
Energy containment 61 % within 76 µm radius
F/number 3.5    
intensity FWHM 200 μm phase plate
Energy containment 83 % within 108 µm radius
F/number 3.5    
intensity FWHM 370 μm phase plate
Energy containment 50 % within 200 µm radius
Pointing Stability < 20 μrad        
Repetition Rate 1/7 min-1        

Uncompressed CPA

Parameter Value Unit Additional Information
Center Wavelength 810 nm  
Pulse duration (I FWHM) 130 ps linearly chirped
Max energy on target 1.5 J  
Shot energy stability 5 % r.m.s.      
Focal spot at target      
F/number 30   representative value: contact facility
intensity FWHM 50 µm  
Pointing Stability 3.8 µrad  
Pre-pulse contrast      
ns scale 1E-8   @ 1 ns
Repetition Rate 5 Hz    

Contacts

Have a question or need assistance with your research?

Please address
inquiries to:

Email: Gilliss@slac.stanford.edu