The Nu-SNS proposal - ORNL Physics Division - Oak Ridge ...

New facilities, such as the Spallation Neutron Source, and existing neutrino beams can be
used to meet this essential need.
Finally, the importance of these results and the unique opportunity provided by the construction
of the Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory was highlighted in
the recent report of the Nuclear Science Advisory Council, “Guidance to Implementation of the
2002 Long Range Plan” [5], in which it was stated:
“Neutrino-nucleus interactions in a nascent supernova are an important but poorly
understood influence on the synthesis of elements in the supernova and the reverse process of
electron capture is a determining factor in the explosion dynamics. Once neutrinos from a
supernova have reached the Earth, they are detected through neutrino-nucleus interactions.
An experimental program to determined important unknown neutrino-nucleus cross
sections is now possible using the copious flux from the SNS.”
The SNS will produce, as a by-product, the world’s most intense intermediate energy neutrino
flux. This allows a long-term program of high precision neutrino-nucleus cross section
measurements on a variety of nuclear targets of interest to the astrophysics community. A unique
and fortuitous property of the SNS neutrinos is that their energy range closely matches the
energy of interest for nuclear astrophysics and supernovae dynamics. The intense flux and
advantageous time structure of the SNS allows precise measurements (~10% accuracy in one
year for a given target) to be performed using detectors of modest scale. Since neutrinos are
highly penetrating, a truly non-intrusive facility to study neutrino reactions can be built at the
SNS. We call the proposed facility Neutrinos at the Spallation Neutron Source, or ν-SNS.
We propose to build a shielded neutrino detector enclosure at a distance of 20 meters from the
SNS target [6], where the short-pulse neutrino flux will be more than 10 times greater than has
been achieved at any previous facility. The enclosure will hold two independently operable
detectors, designed so that measurements with several different targets can be performed with
little modification to the detectors. The anticipated neutrino flux at the SNS facility will allow
measurement of the charged-current neutrino-nucleus cross section for any selected nuclear
target to a statistical accuracy of better then 10%. We anticipate that this will allow doubledifferential
cross section measurements (vs. energy and angle), and that neutral current
measurements may also be possible. Measurements with this level of precision will provide a
unique test of fundamental questions in nuclear structure (allowing the resolution of the
forbidden component of the strength distribution) and will validate the complex nuclear structure
models required to compute these cross sections for nuclei that will not be measured. Armed
with measured rates and improved nuclear structure theory, we will be able to improve our
understanding of supernovae, important links in our cosmic chain of origins.
A multi-institutional collaboration with more than 30 scientists is actively involved in the
proposal to build ν-SNS (see Appendix 1 for a full collaboration list and Appendix 2 for vitae of
executive committee members). We have submitted a Letter of Intent (LOI) for our proposal to
the SNS. Following favorable review of the LOI we have received preliminary approval for
floor space in the SNS target building. As requested by SNS management we are submitting a
copy of this proposal to them for consideration.
ν-SNS Proposal 2 8/4/2005