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Low-Level Counting ( llc ) At NIST

Low-Level Counting ( llc ) At NIST. George A. Klouda Surface and Microanalysis Science Division National Institute of Standards and Technology Gaithersburg, MD. “Synergies in Low Background , Ultra-Sensitive Radiation Techniques,” University of Minnesota, 25-26 July 2005.

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Low-Level Counting ( llc ) At NIST

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  1. Low-Level Counting (llc) At NIST George A. Klouda Surface and Microanalysis Science Division National Institute of Standards and Technology Gaithersburg, MD “Synergies in Low Background , Ultra-Sensitive Radiation Techniques,” University of Minnesota, 25-26 July 2005 NIST Surface and Microanalysis Science Division

  2. Outline • Beta Counting (37Ar, 14C and 85Kr) • 1970’s – 2002: BNL Logic Interface, + Waveform (Davis et al., 1972; Cleveland et al., 1998; Currie et al., 1983; 1998) • 2002 – Present: NIST Interrupt Driven System, + Waveform (A. Band) • Accelerator Mass Spectrometry Atom Counting (14C) • 1980 – 2002: Collaborations with Many AMS Groups, e.g., Univ. of Rochester, Univ. Arizona and Woods Hole Oceanographic Institute • Source Attribution of Atmospheric Particulate and Volatile Carbon (L.A. Currie, J. Res. Natl. Inst. Stand. Technol. 109, 185, 2004) • Neutron Activation Analysis • UltraPure Materials Analysis (R. Lindstrom) NIST Surface and Microanalysis Science Division

  3. Shielding and Counters • Passive Shield: World War I Iron Gun Barrel • 20 cm Thickness; 147 cm Length • Location: Basement, ca. 2 m of Concrete Floor Above • Active Shield • OFHC Cu Proportional Annulus • NaI(Tl) Annulus and Plugs (Bicron) • Proportional and Geiger Muller Counters • NIST Miniature Quartz Proportional Counters (5 and 15 mL) • LND GM Counter (45 mL) NIST Surface and Microanalysis Science Division

  4. Counting Hardware Bicron NaI(Tl) Annulus & Plugs (61 cm Length; 14.5 cm ID; 26 cm OD; 5.7 cm Thickness; 10 cm Plugs) Iron Gun Barrel LND 45 mL GM Counter Bkg = 0.1 cpm NIST 5 mL Quartz Proportional Counter Bkg = 0.02 cpm Gun Barrel with NaI(Tl)

  5. Low Background Quartz Proportional Counter (5 mL) NIST Surface and Microanalysis Science Division

  6. Parameters Monitored by llc Electronics • Time-of-Arrival (TOA) • Rise Time (ADP) and Amplitude (E) • Digitized Waveform • Barometric Pressure • Live Display: Counts, Rates, ADP vs. E Plot and Waveform • Post Data Analysis • ADP v. E, E Distrib., ADP Distrib. • TOA and dt Distrib. • Wave–Browser (–Filter) AfterPulses Commercial GM Counter NIST Surface and Microanalysis Science Division

  7. NIST llc Electronics Schematic Hybricon 3-Slot Pizza Box VMEbus Enclosure NIST Surface and Microanalysis Science Division

  8. Analog Pulse Processing • GM and Proportional Counter • BNL Fast Preamp for PC • Linear Amplifier: Tennelec 213, Canberra 814A • Timing Filter Amplifier: Ortec 454, Canberra 2111 • Fast Stretcher: BNL NIM • NaI(Tl) Photomultiplier Tubes (n = 14) • Three Separate Circuits: Annulus Left & Right Bank, Plugs • Canberra 2005 Preamps NIST Surface and Microanalysis Science Division

  9. VME Enclosure Modules SBS 620 VMEbus – PCI Adapter with DMA, High Speed (35 M byte/sec) Fiber-Optic Connection SIS 3300, 8 Channel, 100 MHz, 12-bit A/D, VMEbus Digitizer for Pulse Height And Rise Time Signals

  10. Industrial PC SBS 620 VMEbus – PCI Adapter with DMA, High Speed Fiber-Optic Connection NuPRO-770 PICMG Single Board Computer, 800 MHz Pentium III Processor, Bridges ISA bus and PCI bus Boards GT657 Time Interval Analyzer, Records Time of Event with 25 ns Resolution

  11. NIST llc Facility NIST Surface and Microanalysis Science Division

  12. Post Data Analysis – GM Pulses (Currie et al., Radiocarbon, 40(1), 113, 1998) Overlay of Coincidence Waveforms from GM Tube: Expected Constant Pulse Amplitude and a Rare Saturated Event Snapshot of Pulse Stream: - Amplitude - dt Between Coinc. and Antic. - Saturated Event - DT Between Antic. and Next Antic. NIST Surface and Microanalysis Science Division

  13. Dual Distribution Plot of dt v. Time of Arrival (Currie et al., Radiocarbon, 40(1), 113, 1998) Afterpulses, Fairly Uniformly Distributed In Time NIST Surface and Microanalysis Science Division

  14. 85Kr Measurement Precision (RSD):Dependence on Counter Size and Shielding (Currie and Klouda, J. Radioanal. & Nucl. Chem., 248(1), 239, 2001) Projections assume 2 Liter air sample at 1.4 Bq m-3 and a non-Poisson background variability of 5% rsd. NIST Surface and Microanalysis Science Division

  15. Atmospheric 85Kr in Northern Mid-Latitude(Wilhelmova et al., 1994) NIST Surface and Microanalysis Science Division

  16. 85Kr Measurement Capabilities:Detection and Quantification Limits in Bq m-3 (Currie and Klouda, J. Radioanal. & Nucl. Chem., 248(1), 239, 2001) NIST Surface and Microanalysis Science Division

  17. 14C Accelerator Mass Spectrometry (AMS) • Comparative Study of Small Targets, 10 – 1000 g (Klindinst et al., NIM B 92, 166, 1994) • Woods Hole Oceanographic Institute (NOSAMS) Small Target Preparation, 25 g (Pearson et al., Radiocarbon, 40, 61, 1998) • NIST Combustion – Dilution Facility for Small Samples Approaches the Limit of AMS, 1 g Modern Carbon, e.g. Black Carbon in Greenland Snow (Currie et al., NIM B 172, 440, 2000) (Tandem Accelerator at ETH, Zurich) NIST Surface and Microanalysis Science Division

  18. 14C Modern Carbon Standard vs. Carbon Mass (Klinedinst et al., Nucl. Instr. Meth. B 92, 166, 1994) NIST Surface and Microanalysis Science Division

  19. AMS 14C Precision, Accuracy and Mass Dependence (Klinedinst et al., Nucl. Instr. Meth. B 92, 166, 1994) NIST Surface and Microanalysis Science Division

  20. Atmospheric Volatile Organic Carbon (VOC): Source Attribution Using 14C/13C Ratio (Klouda et al., JGR, 107(D8) 2002; Klouda et al., ES&T, 30 (4) 1996) SCOS97 – Azusa, CA Canister Sample w/ CO2 Removal Biogenic VOC Summary • Median Percentage: 18  11% (95% CI) • Median Mixing Ratio: 80  50 nmol mol-1 (95% CI) • Source Region for High Biogenics: North to East

  21. Acknowledgements Alan Band (NIST Electron Physics Group) - for design and configuration of new electronics system hardware and software for processing and storage of individual pulses to replace existing BNL Interface Stephen Pheiffer (Contractor) - for software development to support new electronics system

  22. NIST Surface and Microanalysis Science Division

  23. BNL llc Electronics Schematic, + Waveform NIST Surface and Microanalysis Science Division

  24. NIST Counting Electronics (Alan Band and Stephen Pheiffer, 2002) Captured Pulses Risetime v. Energy Distribution • Electronics/Software Capabilities • Time of Arrival to 25 ns Resolution • (GT675 Time Interval Analyzer) • Energy and Rise Time (Canberra PAD 814A & • TFA 2111 • - Digitized Waveforms (SIS 3300 Digitizer) • - Mu-meson Spectrum • - Inter-Channel Events AfterPulses NIST Surface and Microanalysis Science Division

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