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An Office of Science User Facility

Matter in Extreme Conditions (MEC)

 

Components

A comprehensive overview of the MEC instrument is published in
Journal of Synchrotron Radiation, 22, (2015).

 

X-ray Optics and Diagnostics

LUSI Pulse Picker

LUSI Pulse Picker
A single pulse shutter will be used to allow only a single FEL pulse to pass through to the experimental chambers. A millisecond shutter from azsol GmbH will be incorporated into a vacuum chamber on a translation stage to allow insertion into the beam. It can be operated up to 10 Hz.
 
 
 
 
 
 
 

LUSI Attenuators

LUSI Attenuators
A set of silicon foils of varying thicknesses will be used to tailor the intensity of the LCLS beam. Multiple attenuation factors will be possible by introducing any desired combination of foils into the LCLS beam path. Ten foils of different thicknesses will be provided and can be used in any combination.
 
 
 
 
 
 

LUSI Guard Slits

LUSI Guard Slits
Cylinders of 3 mm diameter made of silicon nitride (Si3N4) and or Tungsten will be used to slit the beam. Silicon nitride will not get damaged by the LCLS beam downstream of the Near Experimental Hall, while the Tungsten slits behind the Silicon nitride will remove the Higher harmonics.
 
 
 
 
 
 
  

LUSI Pop-in Profile Monitors

LUSI Pop-in Profile Monitors
The spatial profile of the LCLS beam will be measured at various locations along the MEC beamline using a scintillating screen and a high resolution camera-lens combination. The screen will be mounted on a translation stage to allow insertion into the beam. The beam profile measurement will be destructive of the beam and will be used for alignment and troubleshooting procedures.
 
 
 
 
 
 
 
 

LUSI Pop-in Intensity Monitor

LUSI Pop-in Intensity Monitor
The integrated intensity of the LCLS beam will be measured at various locations along the MEC beamline using a photodiode which will be mounted on a translation stage to allow insertion into the beam. The intensity measurement will be destructive of the beam and will be used for alignment and troubleshooting procedures.
 
 
 
 
 
 
 

LUSI Intensity-Position Monitor

LUSI Intensity-Position Monitor
A thin foil allowing most of the beam to be transmitted will be used to measure the LCLS pulse energy on a shot-to-shot basis. Compton back-scattering from the thin foil will be measured using a set of diodes located upstream of the foil. The sensing area of the diodes will be facing the foil and they will be place in a tiled arrangement leaving a hole in the middle. The integrated intensity of all the diodes will provide a measurement of the beam intensity on every pulse. The relative signal from each tile will be used to get a measurement of the beam position.
 

 

LUSI X-ray Focusing Lens system

LUSI Intensity-Position Monitor
Compound refractive lenses made of Beryllium will be used to produce a 1 µm focus in the MEC Target chamber. An translation stage will allow one of three stacks of lenses to be selected which will allow focusing of photon energies from 4 to 8keV. The lenses will be installed approximately 4m from the target chamber center. Focusing below 4 keV is in principle possible but incurs a large intensity penalty due to the absorption below this energy.
 
 
 
 
 
 
 
 
 
 
 
 

 

MEC Laser Systems

 

 

 

 

MEC Long Pulse Laser System The MEC long pulse laser will be located within the MEC hutch. It will have two arms of 25J each per pulse at 527 nm with a variable temporal shape and pulse width of 2-20ns. A customized Continuum Agilite laser operating at 1053 nm will provide the variable pulse with and shape. Its output will be spatially filtered and image relayed to seed a pair of 25 mm diameter Nd:phosphate glass rod amplifiers. The output of the 25 mm rods will be split into two arms, and each arm will be further amplified to 25J. The beams will be focused at the MEC target chamber using refractive lenses and phase plates.

 

 

MEC Short Pulse Laser System The short pulse laser will be a Chirped Pulse Amplified Ti:Sapphire laser, laser at 800nm, with pulse length as short as 35fs, and pulse energies up to 120mJ. It will consist of a master oscillator, pulse strecher and regenerative amplifier, multipass amplifier and a vacuum compressor. The laser will be located within the MEC hutch.

 

 

 

 

MEC Target Chamber

 

The MEC vacuum target chamber is an octagon with diameter of approximately 2.5m, made out of 1inch Aluminum. It will provide a vacuum of up to 10-6 millibar. It has 10 top port, 8 side port, and 6 doors, all oriented towards target chamber. It contains a Aluminum breadboard of approximately 2m diameter, with a 1inch ¼-20 bolt pattern. In the middle of the chamber there is a motorized target alignment stage with 6 degrees of freedom.

 

 

 

 

 

 

 

 

 

MEC Target Diagnostics 

 

VISAR

VISAR
A line-imaging velocity interferometer system for any reflector (VISAR) is a widely used optical interferometric diagnostic for dynamic (e.g. shock) experiments. For opaque targets, VISAR is capable of determining shock speeds by detecting shock breakout times as a function of target thickness. In addition, free surface expansion velocities can be determined from measurement of the phase introduced in the probe beam due to the surface motion. The VISAR in the MEC station will have spatial resolution of 10µm and a temporal resolution of 10ps, with time window ranging from 1ns to1ms, a field of view of 1mm, and a minimal velocity per fringe of 0.5 km/s/fringe.

 

FDI

FDI
The primary object of the Fourier Domain Interferometer (FDI) diagnostic is to measure the phase and amplitude of the reflection of a femtosecond laser of the target. The phase information is extracted, by interfering two time-delayed pulses (one typically before, and the other after an incident pump laser pulse) in a spectrograph and gives information about the motion of the critical density surface of the target. The FDI at MEC is based on a design that originates from LULI, Ecole Polytechique, Paris. It has a time resolution of 35fs, and a spatial resolution of 10µm, and can be used in a chirped configuration.
 
 
 

 

XUV Spectrometer

XUV Spectrometer
The XUV Spectrometer for the Matter in Extreme Conditions (MECI) instrument is a diagnostic instrument for MECI experiment to resolve emissions in the XUV regime. It sits inside the MEC target chamber, has a high collection efficiency, wavelength range of 7-35nm, and resolution of 0.08nm. It is based on a design by DESY and the University of Jena (R.R. Fauestlin et al, J. Inst., 5, p02004).
 
 
 
 
 
 
 

X-ray Thompson Scattering Spectrometer

X-ray Thompson Scattering Spectrometer
The MEC target chamber will contain an X-ray Thompson Scattering Spectrometer, that will look at X-ray photons scattered from heated or compressed targets, or targets in other extreme conditions. The spectrometer will be installed inside the MEC Target. The spectrometer will use the von Hamos geometry : a cylindrically curved crystal produces a line focus with the measured x-ray spectrum dispersed along the line, and captured onto a CCD. Possible crystal choices include highly oriented pyrolytic graphite (HOPG), germanium, and silicon.
 
 

Phase contrast imaging

The instrument can image phenomena with spatial resolution of hundreds of nanometer and temporal resolution better than 100 femtoseconds. It was specifically designed for studies relevant to High Energy Density Science, such as shock fronts, phase transitions, void collapses, etc. It has the capability to perform ptychographic determination of the X-ray illumination that is used in the phase contrast imaging experiments. The imaging can be combined with X-ray diffraction for simultaneous structure determination of the imaged samples and phenomena.



 

Alignment Diagnostics

Alignment Diagnostics
MEC target chamber will be equipped with two computer controlled questar long distance microscopes. They can be mounted either at one of the 10 top ports, or on a stand bolted to the hutch floor viewing the target through a side window. The microscopes will have a resolution of 7µm, and a field of view ranging from 1-5mm. They can acquire images on demand, or at 10Hz synchronized with the FEL beam.
 

SLAC SLAC National Accelerator Laboratory, Menlo Park, CA
Operated by Stanford University for the U.S. Dept. of Energy