Low Background Physics at the Kimballton Underground Research Facility (KURF)
The next generation of ultra-low radiactive background detectors will explore the frontiers of low energy neutrino physics, neutrinoless double beta decay and direct dark matter searches. These experiments all require construction materials and environments with minimal and tightly controlled radiactive contaminants. It is the goal of this counting facility to measure the radioactivity in typical detector components and materials such as copper, electronics, plastics, shielding materials, photomultiplier tubes, etc. to very low levels. We also anticipate that these measurements will be invaluable to upcoming experiments in the proposed Homestake Deep Underground Science and Engineering Laboratory (DUSEL).
KURF is located about 25 miles from the campus of Virginia Tech in the Chemical Lime Company's Kimballton mine. The experimental area is located on the 14th level at a depth of 1700', or approximately 1400 meters of water equivalent (mwe), and has the benefit of drive-in access. This provides very easy access for personnel and equipment, and allows the establishment of self-contained laboratory modules above ground that can be transferred to the underground facility by truck. A 100' x 40' x 20' dust-exclusion enclosure has been installed. The Naval Research Laboratory (NRL) already has a self- contained laboratory in place. This trailer has been moved into the dust-exculsion enclosure and the commissioning of the detectors discussed below will commence as soon as possible. After initial background runs, we hope to start production assay work early in Spring 2008.
For livetime images of the Kimballton Underground Research Facility go here: Kimballcam.
For more information and plenty of pictures, visit the Virginia Tech Kimballton website, KURF.
The Detectors
MELISSA :
MELISSA is a 1.1 kg (50% RE) commercial low-background detector produced by
Canberra and provided to us by
NIST. It has 1.9 keV resolution (FWHM) at the 1.33 MeV line.
It is similar to other low background systems operated
by NIST in shallow underground sites at roughly 50 mwe. We estimate the background rate for
MELISSA will be about 4-8 times higher than the NRL-1 and GEMPI detectors discussed below. More
pictures of the MELISSA shield can be found in the photo gallery. It has a lead brick shield with
inner cavity dimensions of 16''x16''x18''. The cryostat can is 8'' from the top of the inner cavity
and is 3.23'' in diameter.
VT-1 :
VT-1 is an
Ortec
GEM series High Purity Germanium (HPGe) coaxial detector system with a
resolution (FWHM) of 1.76 keV at 1.33 MeV (60Co) and a relative efficiency of 35%.
It has an Ortec lead shield, and a nitrogen purge may be added to remove radon gas from the shield.
As of May 2008 VT-1 is underground at Kimballton and running. As you can see from the picture, VT-1's
lead shield is a cylinder - the inner cavity dimensions of which are 11'' diameter and 16'' tall.
The cryostat can is approximately 4.5'' from the top of the inner cavity. The can is also 2.75'' in diameter.
GeMPI 2 :
This detector is ideal for low background particle physics because it is the lowest
background germanium detector in the world. See the
Gran Sasso Low Background page for more details on NRL-1.