This post provides a journey through the entire experiment, including sample preparation, experimental design and data evaluation.

Coral sample preparation: 200 micron thick embedded coral slices

1a) Sample labeling
→ every sample was assigned with numbers: 500 - 505
→ every sample side: a, b, c, etc.
→ p = Pocilopora
→ s = Stylophora

1a) Samples we prepared for beamtime:

2) Raw sample cutting
→ Untreated corals were cut into 1-1.5 mm thick slices:
1. Embed end of sample in thin layer of pmma, which then can be stuck to the transparent rectangle that fits in the suction plate of the bandsaw, to better control quality and thickness of slices of raw coral
→ Bandsaw (Name, company,location):

2) Embedding
→ Embed these slices in pmma, filling the mold to the top.
→ Side A = bottom of embedding mold = side of puck with sample near surface
→ Side B = top of embedding mold = far from sample
→ End up with a puck, where thin slice of sample is at one end, and the rest is pmma.
→ Embedding material:
→ Embedding melangerie:

2) Polish side A
→ Can work in batches of ~6 samples.
→ Polish side A (removes 0.1 mm):
1. Manually sand side B with 800 grit paper, just to make sure surface is clean and smooth and will stick well with tape. Wipe dust off with wet tissue and dry surface with compressed air duster.
2. Stick samples (side B stuck, side A exposed) onto transparent rectangle
3. Polishing standard procedure (Removes 0.1mm total):
- 1000 grit, 1 small weight, ~2 minutes (or more if needed) to expose surface
- 1 min @ 1000 grit, 1x small weight
- 1 min @ 1200 grit, 1x small weight
- 3 min @ 2500 grit, 1x small weight
- 3 min @ 4000 grit, 1x small weight

2) Polish side B
→removes 0.1 mm, Plastic rectangle thickness + 1 layer of tape = 2.2 mm → target thickness = 2.2 + 0.3 = 2.5mm
→ Use bandsaw to cut off excess pmma from side B, leaving pucks of ~1.5mm thick (with the coral slice inside).
→ Grind side B (800 grit, 2x small weitht + large weight) until sample is 0.3 mm thick (0.3 + 2.2 = 2.5 sample plastic tape unit). In polisher machine, can use the meter knob to set thickness at which polishing will stop. Make sure to zero without sample.
→ Stick samples (side A stuck, side B exposed) onto transparent rectangle: To allow eventual detachment of sample without damaging delicate slice, stick it with thin slivers of tape only on two sides of the puck where there is just pmma.
→ This will be slow, goes faster if use little water. Can start with 320 grit and move to 800 once approaching target thickness.
→ Then do standard polishing as above
→ Remove samples from plastic rectangle. Use fine dentistry tools to slowly lift tape off of plastic rectangle.
→ Wipe slice with kimwipe and solution of filtered 22g/L Na2CO3 (in fridge in front of the door of the room where Keyence is, in glass bottle with blue cap, labelled…you will see it).

Note: Not further polished with diamond/silica/alumina paste because in test sample this standard polishing was enough to reach < 1um roughness on side B (last polished surface).

3) At the beamtime:

Sample s504d for XRF to look into Magnesium (PTB beamline)

Plan:
Mapping 50 x 50 points, 1s exposure time to get a nice picture Then shoot at the same spots, and increase the time