1. Johnson Noise Thermometry GSECARS

2. Overview 2004: –3 rd year of Getting’s P, T Calibration Project) –Preparation for JNT migration from UC Boulder to GSECARS, Chicago –Evaluation of electrical noise in 13-ID-D 2005: –Development of high P cell at GSECARS, continued bench test at Boulder (varying R only) –First high P test at Boulder (July), w/o JNT, for TC noise assessment 2006: –Jan - First JNT test at high P, discovered JNT circuitry problems, preamp filters added –Mar – JNT migrated to GSECARS –Nov – Takeshi Sanehira Joined GSECARS working on JNT 2007: –Jan – John Labenski (post-doc prospect) visited GSECARS, and worked with crew to solve ground loop problems –High P JNT tests throughout the year, with inconsistent results 2008: –JNT tests continue, results still inconsistent –Preparation for pyrometry using radiospectrometry –Nov – Takeshi to leave GSECARS

3. Difficulties in high P JNT tests Ground loop issues – eliminated floating voltages at microV level Electrical noise from equipment – all unnecessary equipment turned off, shielding, grounding Power supply – “clean” transformer, power conditioner to eliminate any frequencies other than 60 Hz Contamination in cell assembly – no glue, no acetone, all parts fired at 900C for 1 – 2h. Numerical filtering to eliminate 60 Hz harmonics in the JNT signal Non-white noise at high temperature persists (usually above 300C)

4. High P tests results Varying R only (bench) Wide variation in slope in various runs, cannot be contributed to electrical noise alone. Overall, slopes appear to become shallower with time (Data legends in order of time: 2006 - 2008. In situ Varying T mainly

5. “Bench test”: varying R only Bench tests (varying R only) show no significant change in slope over time

6. Alternative approach: Pyrometry PC WC anvil Fiber cable BN guide sleeve Cell assembly (TEL 10 mm) Spectrometer Steel spacer USB cable Optical window: Single crystal moissanite

7. Constant intensity light source test: source direction effects Const. current light source Moissanite window Anvil with hole o. fiber Ocean Optics spectrometer

8. Directional effects x y z anvil Window crystal 4 mm dia., 6 mm long Light source Thru 0.1 mm pinhole Y scan Z scan X scan Conclusion: Dominant signals from center of the window tip. Pyrometry feasible in MA cell

9. Bench-top W-lamp test Tungsten lamp source Use radiation at 15 Amp as standard, cross check T at 10.48 Amp by radio- spectroscopy ( both points manufacturer calibrated), Direct fit to the radiation spectrum yields T 10.48A = 2085 K To be compared with 2000 K given by manufacturer I (λ, T) = C 1 ε(λ,T)λ -5 /[exp(C 2 /λT)-1]

10. Cell assembly Pyrophyllite (Soft-Fired) Graphite Crushable alumina BN SiC lens (Single Cryst.) 14.00 mm 6.50 mm 7.00 mm 4.00 mm TEL 10 mm, ver. ２ ( cell assembly for pyrometry calibration) MgO Al 2 O 3 with double bore (0.8 mm dia.) & Thermocouple 1.00 4.70 0.80 mm 4.00 mm 5.00 mm 6.00 mm 6.60 mm WC anvil Optical fiber 1.5 mm BN guide sleeve (OD: 1.5 mm, ID: 0.4mm) T.C. BN window (2.5 mmØ) Pressure marker (MgO+Au, 10:1 by vol) 1.00

11. Tungsten lamp calibration before applying pressure anvil Moissanite window crystal Lower DIA guide block Upper DIA guide block

12. Examples of grey body (abs) fit – 1 ms data collection 1523 K 973 K 1173 K 1323 K

13. Relative T determination Assuming that a reference T 0 is known, from Wien’s approximation The ratio of two observations is a straight line give by the J (λ, T) function (Yagi and Susaki, 1992) in the J -  plot, where ω(λ) = C 2 /λ. And the slope of the line is -1/T. J (λ, T) = -(1/T)  (λ)+ln[ε(λ,T)/ε(λ, T 0 )] = ln[I(,T)/I(,T 0 )] - (1/T 0 ) ω( ) I (λ, T) = F( ) C 1 ε(λ, T)λ -5 /exp(-C 2 /λT) I (λ, T 0 ) =F  ) C 1 ε(λ, T 0 )λ -5 /exp(C 2 /λT 0 )

14. “J-function” fit, relative to 1523K 973 K 1173 K 1323 K 1573 K

15. Comparison of T measurements Pressures: 0.2 to 0.5 GPa Noise level too high at 1 ms

16. Difference plot thermal drift recognized in power- temp relation

17. Outlook Obtained optical windows (single-crystal diamond) for DIA cells between 12 and 6 mm edge length (P up to ~8 GPa) Tests under way for both W/Re and Pt/Rh thermocouples One technical paper currently in prep. Expect to obtain data up to 8 GPa and ~1800 K by Nov, 2008, results will be out 2009