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Usage

In 2015,  routine acquisition of 40Ar/39Ar and 4He measurements occured on 230 of 365 days.  This was manifested by 20305 total analyses.  The average time per measurement for all proceedures employed was 10 ± 2 min.  This average interval includes the time required for gas liberation, purification, and measurement.  Applying this rate of data collection yields 3384 hours of measurement time and represents 61.3 % of maximum efficiency on days where routine measurements were undertaken.  Because about 8 hours are required per sample change, most of the 38.7% down time on routine analysis days was related to the time required for bakeout and recovery of the extraction line.  Taking this necessary downtime time into account results in a steady-state productivity of about 115 analyses per day (4.8 analyses/hour) for multi-week periods of continuous operation (see accompanying graph).  The rate of He data generation is slightly higher (5.1 measurements/hr) than for Ar (4.5 measurements/hour).

Overall, about 63% of the total routine effort was allocated to 40Ar/39Ar measurements while 37%  was devoted to 4He abundance measurements in support of (U-Th)/He work.  Roughly half of the total measurements made were supporting measurements (i.e., line blanks, detector calibration, and standards/flux monitors). In all, 6438  40Ar/39Ar measurements were made for 261 geologic samples (average of 25 analyses per sample). Similarly, 4He data was produced for 875 zircon and apatite grains (3499 total analyses).  Standard analyses (flux monitors & secondary standards), line blanks, and detector calibration measurements accounted for the balance of the analyses shown on the figure to the right.  Development & maintenance time was not rigourously tracked.  Several weeks of development time was allocated to Ne isotopic measurements.  Additional laboratory time was required for extraction line hardware upgrades (new diode laser cell, modified CO2 laser cell, new getter housing, new auxiliary manifold, new Ne pipette system) prior to inplimenting the new reference gas in June 2015 and software development (CompactRIO project).  No downtime was incurred due due to instrument breakdown and repair.