Laser Heating at Description of simultaneous Laser Heating and XRD. Pt and NaCl. Sander Caldwell, Dylan Spaulding, Simon Clark

Description of Activity Loaded DAC with small Pt foil, NaCl, and Ruby Increased P to 9 GPa at which point the gasket started to blowout Put on ES2 and centered wrt beam and rotation center of goniometer. Did 2D diode scan (transmission of x-rays) to determine where the sample was Took Preheat XRD (Pattern #5), confirmed that main XRD peak is from Pt Did test heating and confirmed that alignment of heating optics was on Pt foil (both sides). Next confirmed that the alignment of temperature optics (to spectrometer) was proper (meaning hotspot light centered on entrance slit) Previous day had done Ne Calibration, aligned temperature optics on x-ray beam (hotspot on entrance slit), and took W-lamp calibration spectrum Started heating from lowest laser power (10 amps) incrementally up to 25 amps. At each laser power took XRD of 100 secs and temperature spectra of 10 secs (at low power) to 0.1 secs at highest power.

Refl&Trans TransLight ReflLight 300 microns 122 pixels ~2.5micron/pixel 1024 pixels 124 pixels Aligning the temperature Optics Use the existing diffraction grating as mirrors (set them to 0 wavelength) and open slits fully Image Taken with Leica Put sample on x-ray beam and goniometer rotation center Adjust mirrors so that hotspot is centered on CCD. Close down slits and make sure that hotspot (slice thru hotspot) stays visible

Sample = Pt + NaCl + small Ruby 9GPa Damn! Gasket blowing out. Fortunate to catch it before hit edge of culet Do a 2D diode scan to find Pt

Temp Analysis PtHeat7_Downstream Acquire spectra during heating and XRD

Temp Analysis (MJW Matlab code) Is the peak temp really 5100? Hand analyze the center of the peak to check

First look at Wlamp and System Response

Wien Plot w/ W Lamp as Unknown

Reciprocal of Derviative (=Temp) of Wien Plot yields discrimant for Temp measurement

1/(Deriv. of Wien) plotted vs wavelength W Lamp

Now look at the heating data (PtHeat7). Planck fit to PtHeat7DS

Wien Fits to PtHeat7DS

PtHeat7DS Wien plot, and smooth Wien plot, and (dJ/dw)-1. As you can see the deriv data is too noisy to be of use, even though the Wien data was smoothed before differentiating

previous graph shows derivative of Wien plot. Because slope of Wien plot is proportional to 1/T, then plotting (WienDeriv) -1 should show the Temp as a function of wavelength (or normalized wavelength) and can be used as a test of the wavelength range used in fitting the Wien data. That is, a perfect Wien plot would yield a derivative plot that shows a constant value. In the above plot, there is obviously a problem for w > -19 The Wien plots for real data are not linear over the full wavelength range. How to know which wavelength range to use? Also, the Planck fits yield different temps depending upon the wavelength range. At least the Wien and Planck fits yield similar values. And the values that I get by processing thru Igor are similar to MJW’s Matlab code. In general, the temps need to be verified by some ambient pressure method. Summary of analysis

Now look at the results of testing Heating Temp vs Laser Power note: practically all avg hotspot temps above Pt Melt Temp (Tm)

Heating Temp vs Laser Power

Analyzing diffraction patterns of Pt lines Jan25 Preheat5 Here we see the Pt lines 2.24, Pt a / Pt P 7.1 +/- 0.6 NaCl a / NaCl P 6.1 +/- 0.1 Ambient Temp

Laser Power = 12 Amps heating 7, lines still visible, but 1.94 appears to be getting smaller (is Pt starting to melt?) Pt a = / NaCl a = /

Laser Power = 25 Amps heating 15, Pt lines at 1.94, 2.24 are gone. Are we still sampling an area where there is no Pt, or did it really melt??

Pt Heat Summary Main result is that there is huge scatter in temperatures, almost all temps are above Pt Tmelt, yet no melting was seen except for maybe #14 and 15 (Laser Power = 25 Amps) Thus should pursue ambient pressure temperature validation before attempting high-pressure temperature validation (thermal expansion and melting)

XRD Data Summary