Standard Configurations

Configuration LPL

MEC Long Pulse Standard Configuration for Run 18

Types of Experiments

Two variations of the LP standard configuration are available: the X-ray diffraction variation (XRD) and X-ray Thomson scattering variation (XRTS). A user supplied detector cannot be fielded in either standard configuration. Users may request any standard MEC beamline devices and diagnostics, but the request must be explicitly mentioned in the proposal.

X-ray Diffraction Variation: CSPAD Configuration and Layout

This variation consists of the ns laser drive beams, VISAR, the backward XRTS (optionally) and four CSPADs. Fig.1 shows the layout.

Figure 1. Geometry for XRD standard configurations using two nanosecond, 527nm drive beams. The lasers hit the sample at an angle of 20° from each side of the x-ray axis. The angle between the target normal and the LCLS x-ray axis is 0° (so that each drive beam is incident at 20°). VISAR is collected normal to the back of the target. 4 Quad detectors are arranged to capture diffraction rings.

Four Quads (CSPAD-560k) will be used for the x-ray diffraction measurement, with fixed position. They will cover the scattering angle θ=2θB from 20 degrees to 82 degrees. The approximate angular phase space that is covered is shown in Fig.2.

Figure 2. Scattering angles collected by the various CSPAD in the X-ray diffraction variation. Y-axis is the scattering angle θ=2θB , the x-axis is the azimuthal angle, φ, with θ=90, φ=0 is scattering along the horizontal direction. Black / grey


XRTS Variation: CSPAD Configuration and Layout

This variation consists of the ns drive beams, VISAR, backward XRTS and Forward XRTS, and two out of four of the Quads from the XRD configuration. See Fig.3 for the layout. The coverage in θB is unchanged, but coverage in phi is reduced.

F-XRTS will be located at the south-side next to the two Quads that has an angle of 36 degrees horizontally. The center of X-ray photon energy accessible by this configuration is from 4.3 keV to 8 keV. The spectral coverage from the center of X-ray photon energy is +/- 320 eV. Due to a collision with VISAR lens and the other two Quads, there is a limitation of scattering angle. For details, please contact instrument scientists.

Figure 3. Geometry for F-XRTS standard configurations using two nanosecond, 527nm drive beams. Use of the Forward XRTS requires removal one pair of CSPADs. The horizontal angle of the F-XRTS is 36° and the vertical angle of the spectrometer can be changed from 0° to 55° at a photon energies of 7.5-8 keV, for a total angle from the x-ray axis of 36° to 62°. Angular coverage of F-XRTS changes with photon energy. For more details, please contact instrument scientists.


Geometry and Optical Laser Parameters

The MEC ns glass laser will be delivered to the target as shown in Fig.1 and 3. Two beamlines, each containing two multiplexed laser arms. Both beamlines can be used simultaneously (7 minutes between shots), or staggered (one shot every 3.5 minutes). The 72 mm beams are focused using 250 mm focal length aspheric lenses (F/3.5), and the focal plane relative to the target can be adjusted from best focus to a ~100 µm spot. MEC uses phase plates generating circular focal spots of 150, 200, 300, and 500 micron through HPP and 150 and 600 micron by CPP. Phase plates can be manually exchanged during a standard configuration run.

Pulse length can vary between 5 ns and 20 ns. Flat top temporal profiles will be available by default; custom profiles can be provided, but must be requested at least 2 months in advance. The total laser energy is dependent on pulse length and profile. For 10ns square pulses the maximum beam energy on target will be 60 J. The arrival time of the optical laser with respect to the x-ray can be changed during the experiment, and is accurate to within 25 ps RMS.

X-ray Parameters

X-ray beam operation with be in the standard SASE mode (no seeding) for Run 18. Seeding will not be available for any experiments in this run. Photon energy and spot size are chosen by users.

VISAR

The MEC line VISAR will be available as a diagnostic (See Fig.1 and 3). Table 1 lists the etalons available at MEC; alternatively, users can bring their own. Users can take up to 15 test shots with the laser drive beam and VISAR before the start of their X-ray beam time.

Optical layout of the MEC VISAR system

Figure 4. Optical layout of the MEC VISAR system. Two VISAR beds with streak cameras are provided. Etalons for each bed can be chosen from table below, or user can bring their own.

 

Etalon thickness (mm) Etalon diameter (mm)​
5.072, 5.077, 8.087, 8.096, 11.006,14.999,15.01 ​25
25.036, 25.034, 49.96, 75.04 ​50

Table 1. VISAR etalons available at MEC. All etalons are fused silica. User can bring their own etalons, provided the diameter is either 25 or 50mm. Maximum etalon length that can be supported is 110mm.

Read more about VISAR on the VISAR Analysis page »

Targets

The user provided targets will need to be mounted on target frames that are compatible with the MEC target holder.

Figure 5. Drawing of an example target frame that is compatible with the MEC alignment stage. The targets are mounted on the right side of the side view (on reference plane A). In the side view, the laser comes from the left, and the VISAR beam from the right. Dimensions are in inches. The spacing and size of the target holes may be changed, but all other dimension need to stay unchanged. Depending on the phase plate that is used, and the ablator surface on the target, the wings of the laser drive beam can damage neighboring targets. To avoid this damage, the targets should be spaced at least 5mm apart (e.g. in the drawing above, each target should have an empty hole around it in all directions) (Download detailed drawing)

MEC Instrument Staff

Gilliss Dyer, Bob Nagler, Hae Ja Lee, Eric Galtier, Philip Heimann

Laser Contact

Eric Cunningham, Michael Greenberg

Parameter Table

To be considered for scheduling in this standard configuration, users will be required to include a table in the proposal that lists the specific experimental parameters to ensure compatibility with these configurations. If the experimental parameters are not compatible with the standard configuration or if the table of parameters is incomplete, the proposal will be reviewed and considered for scheduling as general user proposal. Please see the table of required parameters. No fundamental changes to the standard configurations will occur, but some details of the configuration may be updated in response to inquiries, so users should recheck the website before submitting your proposal to confirm that you have the latest information. Address any questions to the instrument staff.

 

Configuration SPL

MEC Short Pulse Laser Standard Beam Delivery Configuration for Run 18

A standard short pulse laser (SPL) beam delivery is introduced for Run 18 to allow block scheduling and reduce setup time. All SPL experiments are encouraged to conform to this beam delivery scheme if possible. In this configuration, the short pulse laser (SPL) beam path delivery geometry, from the entrance port in the target chamber down to the focus position of the final focusing optics, is fixed and cannot be altered. The target sample plan orientation vs the X-ray beam path can be altered but a minimum angle of incidence between the target normal and the laser beam at the final focusing optics is required to be a minimum of 35°. Users may request any standard MEC beamline devices and diagnostics, but the request must be explicitly mentioned in the proposal. For more details, please contact an MEC beamline scientist.

Short pulse laser beam delivery geometry

Delivery of the beam to target from the chamber input consists of a set of 5” dielectric mirrors and a motorized final focusing optics assembly arranged in the target chamber. Fig.1 shows the layout. The input beam in the south-west port of the chamber goes through a chicane to allow for a beam pointing monitoring system which is located in the red shaded area and makes use of a small amount of the beam leaking through the first mirror the short pulse laser encounter in the chamber. This beam pointing monitoring assembly is located outside the chamber and provides shot-to-shot pointing offset. After reflecting off the first motorized mirror (tip and tilt), the SPL beam is then transported with dielectric mirrors down to the Off-Axis parabola (OAP). It has an effective focal length of 330.4 mm and an off axis angle of 35.21°. The clear aperture is 4” and the protected silver coating has a surface figure of λ/22.6 Peak-to-Valley (at 633 nm) over 90% of the clear aperture. The OAP mount is motorized in XYZ (X is lateral, Y is vertical and Z is longitudinal to the input optical laser beam) to allow for less than 5 mm corrections of the position of the optical laser spot. The other mirror mounts are using manual tip/tilts. The preferred target stage sample plan orientation is at 45° vs the LCLS X-ray beam to allow for the use of the Earth as additional radiation protection. Rotating the sample plan is allowed for other geometries as long as:

  • The target holder translation stage do not collide with the final mirror before the OAP
  • The preponderance of accelerated particles originating from the target are travelling south and south-east

The red shaded area indicates a keep-out zone for user diagnostics, while the green shaded area is considered open. A 4” motorized iris is located at the beam entrance of the target chamber short pulse laser port to allow for synchronization between X-rays and SPL. The short pulse laser energy can be checked while the target chamber is pumped down using a vacuum power meter located between this motorized iris and the first dielectric mirror encountered by the SPL.

         

Figure 1. Geometry for SPL standard beam delivery configurations. The lasers hit the target at an angle of 35° from the target normal. The angle between the target normal and the LCLS x-ray axis is 45°.

Optical Laser Parameters

The MEC fs laser will be delivered to the target as shown in Fig.1. Both compressed and chirped delivery are available. The beam size is 65 mm at the entrance of the target chamber. The laser spot size is about 10 µm FWHM and 40 fs compressed. It delivers up to 1 J on target at a repetition rate is 5 Hz. See the laser characteristics page for more information on the laser parameters.

X-ray Parameters

There is no constraint on the X-ray beam parameters linked to the SPL standard beam delivery.

Targets

The user provided targets will need to be mounted on target frames that are compatible with the MEC target holder.

          

Figure 2. Drawing of the target frames that are compatible with the MEC alignment stage. The targets are mounted on the right side of the side view (on reference plane A). In the side view, the laser comes from the left. Dimensions are in inches. The spacing and size of the target holes may be changed, but all other dimension need to stay unchanged. The chamfer in the front side of the target hole is 60°. (Download detailed drawing)

MEC Instrument Staff

Gilliss Dyer, Bob Nagler, Hae Ja Lee, Eric Galtier, Philip Heimann

Laser Contact

Eric Cunningham, Michael Greenberg

Parameter Table

For experiments submitted as standard short pulse delivery, users will be required to include a table in the proposal that lists the specific experimental parameters to ensure compatibility with these configurations. If the experimental parameters are not compatible with the standard configuration or if the table of parameters is incomplete, the proposal will be considered for scheduling as general user proposal. Please see the table of required parameters. No fundamental changes to the standard delivery will occur, but some details of the configuration may be updated in response to inquiries, so users should recheck the website before submitting your proposal to confirm that you have the latest information. Address any questions to the instrument staff.

  LCLS proposals are submitted through the User Portal.