Matter in Extreme Conditions

SLAC National Accelerator Laboratory
Availability in Run 2

Roughly twenty 8-hour days of short or long pulse laser time will be made available over the course of CY2020 for PRP selected LaserNetUS experiments from Cycle 2. Starting in March 2020, availability of MEC beam time for LaserNetUS experiments will be constrained to fall between scheduled LCLS MEC experiments.

Overview

The MEC instrument at LCLS fields two laser systems: a long-pulse shock drive and an ultra-short pulse high intensity Ti:sapp system, which are co-located to the LCLS hard X-ray beamline in the Far Experimental Hall.  LaserNetUS proposals give access to designated laser-only time at MEC.

Long pulse laser system

The long pulse laser at MEC is designed to provide high-energy 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. Recent upgrades have increased the energy to 60 J in a 10 ns square pulse, split between four arms, which are polarization-multiplexed into two beamlines for delivery to target. The upgrade also added 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 20 ns can be provided to users, tailored to create specific thermodynamic trajectories in a compression system. The shot rate at full energy is 1 shot per seven minutes, with 1 shot in 3.5 minutes at half energy possible by alternating pairs of arms.

The long pulse focus can be shaped by one of several phase plates available at MEC. Two sizes of continuous phase plates are currently available, along with an array of distributed phase plates. 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:Sapp 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 130 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.

The pulse cleaner was recently upgraded to provide better and more reliable performance. Now, routinely, the system achieves 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. A frequency doubling crystal and dichroic optics are available to deliver 400 nm light to target at even higher contrast.

For experiments not requiring relativistic intensities, a compressor bypass is available to deliver >1 J at 130 ps at 5 Hz.

Target chamber and diagnostics

The MEC target chamber is a versatile 2.5 m vessel designed after the Titan and (former) Trident West target chambers located at LLNL and (formerly) LANL. Experimental platforms that will utilize the LCLS beam must be designed around the beamline, which passes through a central axis of the target chamber and can’t be adjusted.  The target chamber has numerous ports on the sides, top and bottom, which can be fitted with windows, feedthrough ports, and target delivery systems. Standard target positioners to position a large array of target windows with 5-axis motion are available. Gas jet and cryogenic liquid jet targets have been fielded by users.

A number of diagnostics are available at MEC, including two vacuum X-ray Thomson spectrometers and set of four large format vacuum pixel array detectors for diffraction measurements, and a scintillator-based imaging camera. An XUV spectrometer for 35 nm down to 7 nm light is available. Optical diagnostics include a permanent line VISAR system, a Fourier domain interferometer, and a set of CCD cameras.

The LCLS facility provides a full-service user experience, from proposal development, through planning and experimental execution, to online data analysis.

Opportunities for LaserNet US at MEC

Membership in and support from LaserNet US will provide an opportunity to explicitly support optical laser experimental time for LaserNetUS members on MEC systems, outside of the LCLS run schedule, allocated through the LaserNetUS proposal process.

LCLS experiments at MEC – awarded through the LCLS call for proposals – are intensive and short beamtimes. By contrast, LaserNetUS laser-only beam times at MEC can be longer and allow for platform development that may be useful in future LCLS-MEC proposals.

Throughout CY2019, LCLS will be down for the LCLS-II upgrade, providing longer than normal periods during which laser-only time can be scheduled

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.

25 TW

Parameter Value Unit Additional Information Comments
Center Wavelength 810 nm    
Pulse duration (I FWHM) 45 fs    
Max energy on target 1 J    
Shot energy stability 5 % r.m.s.  
Focal spot at target  
F/number f/6      
intensity FWHM 7 µm    
Strehl ratio 0.35      
Energy containment 35 % in 7µm diameter  
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  
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 170 µm phase plate
Energy containment 50 % within 89 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    
intensity FWHM 50 µm  
Pointing Stability 3.8 μrad  
Pre-pulse contrast
ns scale 1E-8   @ 1 ns
Repetition Rate 5 Hz