MEC Components

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

Attenuator Pulse-Picker Assenbly

Attenuator/Pulse Picker Assembly

A single pulse shutter is used to allow only a single FEL pulse to pass through to the experimental chambers. A millisecond shutter from azsol GmbH is 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

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

LUSI Guard Slits

Guard Slits

Guard Slits

Cylinders of 3 mm diameter made of silicon nitride (Si3N4) and or Tungsten is 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-Intensity Monitors

Profile/Intensity Monitor Combo

Profile/Intensity Monitor Combo

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

 

LUSI Pop-in Intensity Monitor

Pop-in Intensity Monitor

Pop-in Intensity Monitor

The integrated intensity of the LCLS beam is measured at various locations along the MEC beamline using a photodiode which is mounted on a translation stage to allow insertion into the beam. The intensity measurement is destructive of the beam and is used for alignment and troubleshooting procedures.

 

LUSI Intensity-Position Monitor

Intensity-Position Monitor

Intensity-Position Monitor

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

 

LUSI X-ray Focusing Lens system

Lens Stack

Lens Stacks

X-ray Focusing Lens System

X-ray Focusing Lens System

Compound refractive lenses made of Beryllium is used to produce a 1 µm focus in the MEC Target chamber. An translation stage allows one of three stacks of lenses to be selected which allows focusing of photon energies from 4 to 8 keV. The lenses is approximately 4 m 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 is located within the MEC hutch. It has four arms of >15 J pulse energy each at 527 nm with a variable temporal shape and pulse width of 2-20 ns. A customized SLAC/CEO diode-pumped front end operating at 1053 nm provides the variable pulse shapes. Its output is 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 is split into four arms, and each arm is further amplified to >15 J. In standard configuration, the arms are frequency doubled and polarization multiplexed into two beams. The beams are focused at the MEC target chamber using refractive lenses and phase plates.

MEC Short Pulse Laser System

The short pulse laser is a Chirped Pulse Amplified Ti:Sapphire laser, laser at 800 nm, with pulse length as short as 35 fs, and pulse energies up to 10 mJ/pulse at 120 Hz or 1 J/pulse at 5 Hz. It consists of a master oscillator, pulse strecher and regenerative amplifier, double-CPA pulse cleaning multipass amplifier and a vacuum compressor. The laser is located within the MEC hutch.

Read more about MEC lasers on the Laser Characteristics page »


MEC Target Chamber

Target chamber

Vacuum target chamber

The MEC vacuum target chamber is an octagon with diameter of approximately 2.5 m, made out of 1 inch aluminum. It provides 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 an aluminum breadboard of approximately 2 m diameter, with a 1 inch 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 has spatial resolution of 10 µm and a temporal resolution of 10 ps, with time window ranging from 1 ns to 1 ms, a field of view of 1 mm, and a minimal velocity per fringe of 0.5 km/s/fringe.

Read more about VISAR on the VISAR Analysis page »

 

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 35 fs, and a spatial resolution of 10 µm, 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 7-35 nm, and resolution of 0.08 nm. 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 contains an X-ray Thompson Scattering Spectrometer, that looks at X-ray photons scattered from heated or compressed targets, or targets in other extreme conditions. The spectrometer is installed inside the MEC Target. The spectrometer uses 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

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 is 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 have a resolution of 7 µm, and a field of view ranging from 1-5 mm. They can acquire images on demand, or at 10 Hz synchronized with the FEL beam.

 

MEC Videos

A flyover view of the MEC instrument.

Download animation (right click and save link as):

mp4  (17.2 MB)   wmv (17 MB)  

For more MEC related videos, see the LCLS MEC playlist on YouTube.