XLEAP Sample Prep Guide

Suitable samples for XRF

For 2D XRF techniques, samples should be relatively flat. Leaves usually work very well, and tissues like stems and fruits can be sectioned for imaging. Appropriate thickness for sections will depend somewhat on the desired spatial resolution of your measurement- please reach out if you have questions.

Not recommended:

• Fixed and embedded tissues: the chemical fixation process can lead to unpredictable mobility of light elements.

Sample mounting

Samples must be mounted on metal-free, low-scattering substrates for 2D XRF measurement. Kapton, ultralene, and silicon nitride are all suitable; the choice will depend largely on your sample size.

Most fresh or hydrated tissue samples are held between two layers of Kapton polyimide film to maintain hydration during scanning. Thinner film is preferred (1/2 mil = 0.0005" = 12.7 µm or thinner). Ultralene is also recommended (4 μm = 0.16 mil thickness), especially for best sensitivity to light elements. We frequently include a small piece of damp kimwipe in the sample "chamber" to maintain humidity during scanning.

Small or delicate samples may be mounted between one layer of Kapton tape and one layer of Kapton film (with the film side mounted towards the XRF detector).

The smallest samples and thin sections may be mounted on silicon nitride membranes.

Not recommended:

• Glass substrates: glass contains significant and unpredictable metal impurities and also leads to a large scattering background. If a thick rigid substrate is required, quartz is metal-free (but still can cause a large scattering background).

Sample holders

Our most recent sample holder designs use snap-in frames on one or both sides to hold the Kapton film taut.

Custom sample holders

Designed and printed at CHESS

We are happy to work with you to design and print custom sample holders for your experiment. Requests for custom holders must be received well in advance of beamtime (>3 weeks) to ensure time for fabrication and any troubleshooting.

Holders designed and printed by our team will remain at CHESS or be returned to CHESS after the experiment is complete.

Designed and printed by you

We encourage iteration and customization of our sample holder designs. You are welcome to download our existing designs and print them as-is or with modifications. Please check with us if you want to make the sample area much larger to ensure compatiblity with the stage scan range.

Please note: the 1" wide (25.4 mm) area with the pass-through holes must be kept clear for compatibility with our kinematic mount adapter.

Downloadable 3D printer files

30mm x 25mm window sample holder with snap-on window: Medium Window No Port 30x25.stp AND Medium No Port Snap 30x25.stp

30mm x 50mm window sample holder with snap-on window: Medium Window No Port 30x50.stp AND Medium No Port Snap 30x50.stp

100mm x 50mm window sample holder with snap-on window: Medium Window No Port 100x50.stp AND Medium No Port Snap 100x50.stp

150mm x 120mm (interior dimensions) x 7mm thick sample holder: Frame 150 x 120 x 7mm.stp

-- LouisaSmieska - 21 May 2025