This grant provides three years of continued partial support for the operation and maintenance of the Purdue Rare Isotope Measurement Laboratory (PRIME Lab)at Purdue University as a multi-user national facility for the geosciences and ancillary fields. Support for this Facility allows geoscientists access to specialized capabilities of the accelerator mass spectrometer and chemical preparation facilities at PRIME for the measurement of the very low-level cosmogenic nuclides 10Be, 14C, 26Al, 36Cl, 41Ca, and 129I for chronological and/or tracer studies. The Facility is currently developing techniques for other analysis of other rare isotopes with application to meteoritics and other fields. Funding provides minor salary support for PI faculty members, professional and technical staff members; maintenance support for the AMS system, including replacement parts; and expendable supplies for the chemistry laboratory. Additional operating expenses (about 50%) are derived from Purdue University, charges for sample measurement services, and research grants to the PI?s. The measurement of cosmogenic radionuclides by accelerator mass spectrometry (AMS) continues to support novel research in Earth surface processes and Quaternary geology, hydrology and glaciology which rely on surface exposure age dating, erosion rate estimates and isotopic tracer techniques for quantification of process rates. PRIME lab continues to be one of the only AMS labs worldwide that offers measurement and application services for AMS radionuclide systems other than radiocarbon and is currently the only laboratory that offers full service, chemical preparation through AMS measurement. PRIME Lab PIs continue to develop new AMS chemical separation and dating techniques and maintain actively funded research and research training programs that involve application of these radionuclides to a variety of geoscience problems.
PRIME Lab is a national user facility that utilizes a tandem VandeGraf accelerator to measure the radionuclides 10Be, 14C, 26Al, 36Cl, 41Ca, and 129I. This technique is referred to accelerator mass spectrometry (AMS). The technique was pioneered in the 1980s and several FN tandems were converted from nuclear physics research to AMS. Purdue University has the only FN-based multi-isotope facility based at a University in the United States, and is one of only a handful of large facilities doing geoscience AMS in the world. In the last 3 years we have undertaken a substantial upgrade of this facility, which was built in 1968. It is fair to say that within the last 10 years, especially the last 3 years, we have entirely rebuilt the facility, modernizing almost every aspect of the accelerator and all the beamlines. The result of this modernization has been a substantial improvement in both our measurement precision and our sample throughput. Listed below is a summary of some of the major accomplishments. 1 – The sample changer that plagued us for many years was replaced and throughout this proposal cycle it has proven to be extraordinarily reliable. This source of downtime has been eliminated. 2 – In 2009 we selected hardware for a new data acquisition system. This system is based on the XIA PIXIE module that is installed in a National Instruments PXI databus. In 2011 we completely switched to the new data acquisition system. It is fair to say that this has completely changed the operations at PRIME Lab. We are no longer maintaining obsolete computer hardware and unmaintainable CAMAC modules. 3 – The R45 beam-line is built, under vacuum, and under computer control. We have run 14C to a barrier detector and we have also constructed a small detector for use with 10Be. We have now had several 14C runs and are very pleased with the performance of the entire system. 4 – In 2009 we tested the fiber optics communications for the new terminal stripper. It was a spectacular failure, but we learned how not to do it. This year we have communicated with modules at the terminal through a fiber optic link. In 2011 we expanded the system to include pressure gauges. The first iteration did not survive tandem sparks but we have remedied that problem. 5 –Both 2010 and 1011 have been extremely productive years for PRIME Lab. This increase was possible because we spent less days dealing with failures and more days measuring samples. In general during our maintenance periods we either performed routine maintenance or worked on laboratory upgrades. It is also the case that in general out measurement precision has improved. For 10Be and 36Cl, in particular, our routine goal is now < 4% precision. Many samples have precisions better than 3%. 6 – Our new chemist has worked through the 10Be and 26Al backlog. It is no longer the case that we have samples backlogged for in excess of two years. Our goal is a turn-around time for these isotopes of 3-4 months. This service continues to be heavily subscribed. 7 – We have performed a major modification of the low-energy beamline that will enable to installation of the fast-switching magnet. This was done in 2011. In early 2012 we built the majority of the beamline for the low-energy injector. This has been put in place. All that remains to be done for completion of this project is the construction of the ion source and the high-voltage deck. 8 – We have tested the fast-switching components off-line. We have verified that the high voltage of the vacuum chamber of the magnet can be switched quickly with the power amplifier we obtained from TREK. 9 – We realized that with the new software we had the capability of collecting simultaneous 10Be and 9Be (using 17O as a proxy) with the new software. We have tested this and found the precision for 10Be measurements is greatly improved, < 2%. We are now routinely using this method for 10Be data acquisition. We have not yet abandoned the canonical method and for now we routinely run both methods in parallel. Summary - The last three years have been the most productive for PRIME Lab since its inception. We have measured more samples for geoscience users than we ever have, the number of scientists coming to PRIME Lab to learn cosmogenic nuclide techniques increases each year, and we are training numerous undergraduates, grad students, and post-docs to continue using these techniques in their scientific careers.
