Dr. Robert J. McTaggart
312 Crothers Engineering Hall
South Dakota State University
Brookings, SD 57007
Robert.McTaggart@sdstate.edu
(605) 688-6306
Click on the picture to the right to get to the official Homestake web site.
Next DUSEL workshop: April 21-28, 2008 in Lead, South Dakota.
November 8, 2007: I gave a colloquium entitled "Homestake Update and Future Directions for Physics at SDSU" that summarized the history of Homestake, recent activities, and the DUSEL workshop at Washington, DC held November 2-4, 2007.
October 19, 2007: Dr. Dongming Mei from USD gave a presentation about opportunities at the Homestake Mine. An article summarizing the need for a purification and verification facility at Homestake can be found through the SDSU web site here.
July 10, 2007: The Homestake Mine is the candidate site selected by the National Science Foundation to become the Deep Underground Science and Engineering Laboratory. This will be renamed the Sanford Underground Science and Engineering Laboratory due to the generous $70 million donation by T. Denny Sanford to prepare the 4850 foot level for the Interim Laboratory at Homestake, the Sanford Science Center at the surface, and eventual development at the 7400 foot level.
See Dr. McTaggart's interview on KELO-TV from July 10, 2007 here.
Homestake Research:
Laser Isotope Separation Facility: This would ionize naturally-occurring and radioactive Argon-39 by laser light, and then remove it by applying a strong electric field. The technique is somewhat different than separating isotopes by centrifuge or mass spectrometry, but could eventually be used to purify various materials for use in Homestake experiments. Berkeley, Los Alamos, USD, DSU, School of Mines, and SDSU would collaborate on the project if funded by DOE EPSCoR.
Low-Level Background Counting Facility: This facility would assay materials brought into the mine for any radioimpurities that could affect the sensitivity of detectors to rare-event physics, such as the detection of neutrinos, dark matter, and proton decay. Cosmic rays reduce the amount of background radiation, but it won't do any good if you bring in construction material that is radioactive. The high-purity Germanium detectors can also be used to detect neutrinoless double-beta decay, which tells if the neutrino has mass and whether it is its own antiparticle. Radon levels in the mine would be surveyed, and a database of radioimpurity content would also be developed. Berkeley, USD, DSU, School of Mines, Augustana, and SDSU would collaborate on the project if funded by DOE EPSCoR.
Materials Free of Cosmic-Ray Defects: Surfaces and crystals as a whole should act differently in a radiation-free environment, which the Homestake Mine will approach. Dislocations and radioactive conversion of elements change the properties of materials, so this may have a lot of applications for new circuits, photovoltaics, and the study of new alloys that may be produced in the future. These studies would benefit from facilities like those above that can produce large quantities of ultrapure materials.
Biological Effects of Low Levels of Radiation: For large doses of radiation it is well-known that radiation damage and/or your risk to developing disease from radiation increases linearly with the amount of radiation absorbed. For small doses of radiation, does this linearity still hold? Will cellular mechanisms responsible for the repair of radiation actually continue unabated and produce damage to cells? Is the radiation damage due to individual DNA damage, or are other chemical and biological mechanisms at work? In general the study of the effects of low levels of radiation are important for employees in the nuclear field and the effects of Radon.
Non-Homestake Research:
Irradiation of Ethanol Feedstocks: Efforts are underway to irradiate switchgrass, DDG, and corn stalk with gamma radiation and neutrons to see if the irradiation will break up some of the lignocellulosic structure that currently hinders a net energy return from cellulosic feedstocks of ethanol. Nuclear reactors and medical sterilizers, which lose money when power levels fluctuate or they are not being used, could find a secondary use for radiation. More nuclear reactors will be built in the future to meet our growing energy demands and reduce global warming. Dedicated irradiation facilities could also be considered.
A group from Japan recently found that 500 kGy of Cobalt-60 irradiation of corn cobs and other agricultural products doubled the resulting saccharification. Currently we have irradiated switchgrass, corn stalk, and DDG with 0, 69 kGy, and 331 kGy with gamma radiation at the 3M medical sterilizer in Brookings, which has a Cobalt-60 source. Samples hydrated to 20% have also been delivered to 3M. These and samples irradiated by fast and thermal neutrons at the nuclear research reactor at Kansas State University are being analyzed by Bill Gibbons and Fathi Halaweish at SDSU.
Determination of Selenium in Soils and Plants: Selenium is an anti-oxidant that is more plentiful on average in South Dakota than other places. Certain markets desire higher selenium content in their beef and wheat. Too much of a good thing however produces selenium toxicity that can kill cattle. We are assessing the technique of neutron activation analysis (NAA) for the determination of selenium concentrations. Selenium comes in several different molecular forms that have different solubilities in water. While NAA can only yield the total amount of selenium, NAA should serve a complementary role to molecular fluoroscopy.
Se-74 is a stable isotope that is found in low abundance typically. However Se-75, which is produced when Se-74 absorbs a neutron, has a fairly long half-life. One can let other elements with shorter half-lives decay and get a clean estimate of the Se-75 concentration. Then we divide by the concentration to get the total selenium content. A short irradiation could yield information on the other isotopes to verify that the standard global concentrations of Selenium are accurate (i.e. do different processes deposit more of one isotope than another, are they absorbed preferentially by plants, etc.).
High Altitude Balloon Research: Together with Aerostar, we are preparing to launch a high-altitude balloon up to 100,000 feet above the surface in South Dakota. Pressure and temperature measurements will be used to correct Landsat satellite image data. EROS Data Center will send up a camera to take pictures and test the use of high altitude balloons for remote sensing interests. A spore trap will search for spores and other biological material in the upper atmosphere. Dosimetry will be provided by Global Dosimetry. Unijunction transistors, which are used to exhibit non-linear behavior such as periodic pulling in circuits, will also be subjected to near-space conditions and characterized in the lab.
Development of a Prototype Gamma-Ray Camera: We recently submitted a proposal to NASA EPSCoR with Augustana and Argonne National Lab to construct and test an array of Multi-Pixel Photon Counters (a.k.a. silicon photomultipliers) under different environmental conditions around the State of South Dakota, Argonne National Lab, and in near-space conditions with high-altitude balloon flights. Ultimately it would be used in the next generation of gamma-ray telescopes like VERITAS to search for evidence of dark matter, dark energy, gamma-ray bursts, new TeV sources of gamma-rays, etc. The July 2007 proposal was rejected, but the proposal may come back in a different form. Gamma-ray telescopes could benefit from several dark-sky environments available in South Dakota. Such development may also occur in using MPPC's for medical imaging.
Charmonium: The hydrogen atom is a bound state of a proton and an electron governed by a Coloumb-type interaction. The deuteron is a bound state of a proton and a neutron governed by the strong force. Charmonium is a bound state of a charmed quark and its antimatter partner also governed by the strong force. The behavior of the strong force exhibits "asymptotic freedom" at short distances, and "quark confinement" at larger distance. A non-relativistic Schrodinger equation is often applied to predict the energy eigenfunctions and their decays, but a semi-relativistic approach is needed since spin angular momentum plays a large role in splitting the degenerate states.
My Ph.D. thesis was done on the angular distribution of electron-positron pairs from Charmonium decays produced in proton-antiproton annihilations at Fermilab. I am interested in determining the energy eigenfunctions for Charmonium and reproducing the measured angular distributions seen in my thesis. Different potential models and mixing of the S and D states will eventually be included.
Fermi National Accelerator Laboratory
Los Alamos National Laboratory
Brookhaven National Laboratory
