measurements of Sr and Nd at the nanogram level using the Phoenix - - PowerPoint PPT Presentation

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measurements of Sr and Nd at the nanogram level using the Phoenix - - PowerPoint PPT Presentation

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High precision isotope ratio measurements of Sr and Nd at the nanogram level using the Phoenix TIMS with next generation Faraday detectors Zenon Palacz Isotopx Limited 34th IGC presentation 2958 34th IGC presentation 2958 What are the

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34th IGC presentation 2958

High precision isotope ratio measurements of Sr and Nd at the nanogram level using the Phoenix TIMS with next generation Faraday detectors

Zenon Palacz Isotopx Limited

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34th IGC presentation 2958

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34th IGC presentation 2958

What are the parameters required for high precision measurements of small samples? (on Faraday collectors)

  • High Sensitivity

– Instrument sensitivity – Use of activators

  • Low noise

– Close to theoretical Johnson noise – Baseline stability

  • Gain stability between detectors

– Required for static analyses

  • Multidynamic measurements

– Eliminates gain and efficiencies – But can it be used on small samples?

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34th IGC presentation 2958

How quiet are Xact amplifier/resistor boards

5 10 15 20 25 30 35 40 45 50 10 20 30 40 50 60 70 80 90 100 Integration time SECONDS

mV

Faraday Noise each point average of 9 channels Theoretical Measured

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34th IGC presentation 2958

How quiet are Xact amplifier/resistor boards

5 10 15 20 25 30 35 40 45 50 5 10 15 20 Integration time SECONDS

mV

Faraday Noise each point average of 9 channels Theoretical Measured

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34th IGC presentation 2958

Noise comparison between 1e11 and 1T resistors

Noise comparison between 1T and 1e11 ohm resistors 2.0E-17 6.0E-17 1.0E-16 1.4E-16 1.8E-16 2.2E-16 2.6E-16 3.0E-16 50 100 150 200 250 300 350 Integration time (seconds) Noise (amps) 1T 1e11 ohm

Noise (Amps)

Integration time (seconds) 1e12 ohm n=5 1e11 ohm n=4 1e11/1e12

1 2.3E-16 3.8E-16 1.7 5 1.0E-16 1.7E-16 1.6 10 6.5E-17 1.2E-16 1.8 20 5.1E-17 7.3E-17 1.4 40 3.6E-17 6.3E-17 1.7 60 3.6E-17 5.1E-17 1.4 300 3.5E-17 4.9E-17 1.4

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34th IGC presentation 2958

How fast are Xact resistors (1e11 ohm)?

  • 10.00
  • 5.00

0.00 5.00 10.00 15.00 20.00 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Seconds PPM of intensity

Baseline in <1 second Old specification

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34th IGC presentation 2958

1T baseline in 4 seconds

1T signal response

  • 10
  • 5

5 10 15 20

0.0 2.0 4.0 6.0 8.0 10.0 12.0 Seconds PPM of signal 5ppm of signal in 3 seconds

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34th IGC presentation 2958

Gain stability 5ppm over 1 month No drift.

CCGains H2 relative to Axial over 1 month

y = 6E-08x + 0.9977 0.99771 0.99772 0.99773 0.99774 0.99775

10 20 30 40 50 60 70 80 Measurement Gain relative to axial collector

0.997732+/-0.000005 5ppm 1RSD

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34th IGC presentation 2958

Day averages

Reduced scatter shows subtle coherent trends. Measured on factory floor with no environmental temperature control

Gain Day averages

  • 15
  • 10
  • 5

5 10 15

  • 5

10 15 20 25 30 Days Gain Drift (PPM) Series1 Series2 Series3 Series4 Series5 Series6 Series7 Series8

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34th IGC presentation 2958

Sr dynamic precision 3ppm reproducibility (5volt ion beam)

200ng NBS987 Dynamic

0.710230 0.710235 0.710240 0.710245 0.710250 0.710255 0.710260 2 4 6 8 10 12 14 16 18 20 22

Filament

87Sr/86Sr

0.7102444+/-0.0000021, 3ppm 1RSD

1RSD 200ng NBS 987

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34th IGC presentation 2958

Static precision 5ppm no gain corrections between analyses (5 volt ion beam)

200ng NBS 987 STATIC

0.710240 0.710245 0.710250 0.710255 0.710260 0.710265 0.710270 0.710275 0.710280 5 10 15 20 25 Filament

87Sr/86Sr

0.7102577+/- 0.0000035, 5ppm 1RSD

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34th IGC presentation 2958

How small a sample of Nd can be measured on Faradays

  • Nd+ ion atom efficiency is about 2.5% (triple

filament)

  • NdO+ is higher than this.
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34th IGC presentation 2958

How small an ion beam can we measure with good precision and accuracy? 50mv on 1e11, 10mv on 1T

142Nd

(amps)

142Nd

(mv)

143Nd/144Nd

%1se

145Nd/144Nd

%1se

142Nd/144Nd

%1se 7.1E-12 706 0.512095 0.0003 0.348402 0.0003 1.141827 0.0005 4.9E-12 485 0.512096 0.0004 0.348395 0.0004 1.141819 0.0006 3.0E-12 296 0.512082 0.0008 0.348399 0.0008 1.141837 0.0012 1.1E-12 105 0.512113 0.0016 0.348371 0.0020 1.141793 0.0019 4.9E-13 49 0.512057 0.0028 0.348383 0.0030 1.141822 0.0042 1.1E-13 11 0.512261 0.0106 0.348341 0.0135 1.143178 0.0139 4.9E-14 5 0.511754 0.0191 0.348499 0.0340 1.142667 0.0265 3.6E-14 4 0.512215 0.0257 0.348698 0.0274 1.142779 0.0221

142Nd

(amps)

142Nd

(mv)

143Nd/144Nd

%1se

145Nd/144Nd

%1se

142Nd/144Nd

%1se 6.88E-12 688 0.512121 0.0003 0.348419 0.0003 1.141855 0.0005 4.98E-12 498 0.512127 0.0003 0.348421 0.0003 1.141861 0.0005 2.94E-12 294 0.512117 0.0006 0.348415 0.0006 1.141837 0.0007 9.67E-13 97 0.512169 0.0010 0.348432 0.0017 1.141870 0.0013 5.16E-13 52 0.512116 0.0023 0.348425 0.0022 1.141833 0.0018 1.26E-13 13 0.512106 0.0042 0.348400 0.0050 1.141863 0.0045 4.83E-14 5 0.512418 0.0083 0.348734 0.0123 1.141554 0.0105 1E+11 1T

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Errors expand below 1e-13A

0.51140 0.51160 0.51180 0.51200 0.51220 0.51240 0.51260 0.51280 1.0E-14 1.0E-13 1.0E-12 1.0E-11 142Nd intensity (amps) 143Nd/144Nd 1.00E+11 1T

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10.5% ion/atom efficiency <20ppm reproducibility 300mv 142Nd16O

142Nd/144Nd

%1se

143Nd/144Nd

%1se

145Nd/144Nd

%1se

148Nd/144Nd

%1se

142Nd16O

amps Minutes ion/atom efficiency 1 1.141818 0.0008 0.512085 0.0006 0.348413 0.0006 0.241589 0.0012 3.3E-12 152 9.0% 2 1.141821 0.0008 0.512099 0.0008 0.348420 0.0009 0.241589 0.0015 2.9E-12 187 9.5% 3 1.141816 0.0007 0.512103 0.0007 0.348419 0.0007 0.241594 0.0010 3.1E-12 206 11.4% 4 1.141764 0.0010 0.512085 0.0007 0.348409 0.0006 0.241603 0.0013 3.1E-12 207 11.5% 5 1.141838 0.0010 0.512080 0.0007 0.348406 0.0006 0.241590 0.0015 3.1E-12 229 12.6% 6 1.141776 0.0010 0.512093 0.0007 0.348428 0.0006 0.241598 0.0015 3.1E-12 206 11.5% 7 1.141789 0.0009 0.512091 0.0007 0.348423 0.0006 0.241597 0.0014 3.2E-12 206 11.5% 8 1.141773 0.0011 0.512078 0.0007 0.348412 0.0007 0.241607 0.0016 3.1E-12 187 10.1% 9 1.141818 0.0009 0.512097 0.0007 0.348419 0.0006 0.241593 0.0013 3.2E-12 206 11.6% 10 1.141762 0.0014 0.512084 0.0009 0.348417 0.0008 0.241587 0.0014 3.2E-12 103 5.8% 11 1.141838 0.0007 0.512109 0.0006 0.348410 0.0006 0.241598 0.0011 3.0E-12 204 11.0% Mean 1.141801 0.0009 0.512091 0.0007 0.348416 0.0007 0.241595 0.0013 3.1E-12 190 10.5% 1SD 0.000029 0.0002 0.000010 0.0001 0.000006 0.0001 0.000006 0.0002 1.1E-13 35 2% 1RSD 0.0025% 0.0019% 0.0018% 0.0026%

2ng NdO 1T resistor data

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2ng Nd measured as oxide at 300mv 142Nd16O

2ng NdO

0.51205 0.51206 0.51207 0.51208 0.51209 0.51210 0.51211 0.51212 5 10 15 20 25 Sample

143Nd/144Nd

1T 1e11 ohm Isotopx preferred value 0.512104 0.512076+/-0.000007 (14ppm 1RSD) 0.512091+/-0.000010 (19ppm 1RSD)

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Total evaporation measurements

  • Widely used in nuclear applications to overcome mass

fractionation by taking the average isotopic composition

  • f the whole evaporation process.
  • Baselines , peak centring and focussing at the start of

the measurement prior to filament current ramping

  • All above must remain stable during the evaporation.
  • Used for small Sr in this application
  • Potential benefit for micro-drilled samples, ice cores?
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Total Evaporation (summed isotope ratios)

TIME INTENSITY

88Sr 87Sr 86Sr

End of analysis Ionization profile Baseline Baselines must remain constant throughout analysis

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50ng Sr ion beam profile 7v for nearly 2 hours Efficiency 3.5% (No focussing or peak centring)

50ng NBS987

0.0E+00 1.0E-11 2.0E-11 3.0E-11 4.0E-11 5.0E-11 6.0E-11 7.0E-11 8.0E-11 1000 2000 3000 4000 5000 SECONDS 88Sr (amps)

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86Sr/88Sr (summed) 50ng NBS 987

86/88 summed

1.1880E-01 1.1900E-01 1.1920E-01 1.1940E-01 1.1960E-01 1.1980E-01 1.2000E-01 1.2020E-01 1.2040E-01 1000 2000 3000 4000 5000

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87Sr/86Sr (summed)

87/86N SUMMED

7.1016E-01 7.1017E-01 7.1018E-01 7.1019E-01 7.1020E-01 7.1021E-01 7.1022E-01 7.1023E-01 7.1024E-01 7.1025E-01 7.1026E-01 1000 2000 3000 4000 5000

0.710243

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1ng Sr 3volts 88Sr for 150 minutes Efficiency= 13%

Sr88 S1 int

0.00E+00 1.00E-11 2.00E-11 3.00E-11 4.00E-11 5.00E-11 6.00E-11 7.00E-11 8.00E-11

1 000 2000 3000 4000 5000 6000 7000 8000 9000

Seconds Intensity (amps)

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Total evaporation measurements of NBS 987 <1ng

100pg 200pg 500pg 1ng 0.710244 0.710320 0.710249 0.710266 0.710255 0.710279 0.710263 0.710262 0.710285 0.710269 0.710265 0.710274 0.710242 0.710222 0.710264 0.710278 0.710256 0.710298 0.710273 0.710253 0.710320 0.710229 0.710253 0.710265 0.710299 0.710250 0.710249 0.710257 0.710229 0.710249 0.710273 0.710285 0.710272 0.710254 0.710303 0.710268 0.710258 mean 0.710272 0.710267 0.710261 0.710264 1SD 0.000031 0.000036 0.000010 0.000009 1RSD (PPM) 43 50 14 12 Total Evaporation NBS 987

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Ion/Atom detection efficiency for Sr with TaCl activator on rhenium filament

0% 5% 10% 15% 20% 25% 30% 35% 1 10 100 Sr (ng) Ion/atom efficiency Max transmission due to z focussing

?

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Conclusions

  • Sub nanogram isotope ratio measurements of Sr can be easily

made using total evaporation analyses.

  • NdO measurements at the nanogram level produce 20ppm

reproducible 143Nd/144Nd

  • 1T resistors are 1.5 to 2 times less noisy than 1e11 depending on

integration time.

  • 1e11 ohm and 1T ohm resistors produce analytically similar data

with ion beams >50mv.

  • 1T resistors show analytical advantage below 10mv. No benefit to Sr

and Nd, Probable benefit for small sample Os, Pb and U isotopes.

  • Static Isotope ratio reproducibilities of 5ppm are now possible with

new amplifier boards in a temperature controlled environment. (no need for dynamic amplifiers)

  • Boards are upgradeable on Sector 54, IsoProbe-T and IsoProbe-P

instruments.

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Thank you for your attention!