The need for a National Underground Science Laboratory

 

Underground science includes studies at the frontiers of particle physics, nuclear physics, astronomy, geology, and biology, as well as applied areas such as materials science and nuclear proliferation.  In the past decade, fundamental progress has been made in underground experiments in such diverse and exciting fields as nucleon decay, atmospheric neutrino oscillations, the solar neutrino measurements, searches for dark matter, the measurement of nuclear fusion cross sections at stellar temperatures, and the discovery of novel microorganisms that live deep in the earth.  In order to participate in these discoveries, U.S. scientists have had to either take their equipment to other countries or, in a few cases, to make use of non-optimal facilities in the U.S.

 

The questions addressed by underground experiments are among the most fundamental and exciting problems in modern science. Underground experiments will continue to be at the forefront of fundamental science in the coming decade. Many of the science projects are described in some detail in the accompanying document `Underground Science.’

 

 

The next generation of underground experiments is more challenging technically than previous studies and will therefore require both significant resources and good planning and management to succeed. Creating a National Underground Science Laboratory (NUSL) will establish the conditions that will enable the science, which must be done with large, sophisticated equipment, to succeed in a cost effective way. A well run NUSL will have a coherent research program whose priorities are constantly reviewed in order to produce the best science results.

 

There are advantages in centralizing most of the experiments in one underground laboratory:

• Sharing of common infrastructure including access, machine shops, administrative support, computing, and telecommunications;
• Provision for a common safety support that  must oversee equipment and procedures for dangerous components such as flammable and cryogenic materials;
• Synergistic interactions among scientists doing different experiments in an environment where they can easily exchange ideas;
• Establishment of common facilities that can be used by different groups interested in, for example, low radioactivity materials or low level counting measurements;
• Creation of a support organization that can make possible the testing and implementation of new ideas within an established coherent scientific program.
• Providing a critical mass for outreach to the local population, especially K-14, and to the public at large.
• Provide a research center that would be a base for international collaborations to maintain scientific and technical staff for developing and carrying out large scale projects.
• Provide a nurturing and exciting scientific environment in which students and young scientists would develop.
• Provides a center for international scientific meetings,

 

The committee believes that the arguments in favor of a National Underground Science Laboratory are compelling and urgent.

 

In order to be world-class, the NUSL must be deep. A depth of approximately 6000-7000 meters of water equivalent (m.w.e) is desirable for many classes of experiments and is required for certain experiments such as the next generation of solar neutrino and double beta-decay experiments. Above this level, interference from the cosmic ray related backgrounds constitute the limiting factor for high sensitivity experiments.  The next generation solar neutrino detectors, dark matter searches, and double beta-decay studies require as low a cosmic ray produced muon flux as possible. The simplest and most reliable way to achieve lower cosmic-ray induced backgrounds is to do experiments at greater depths.

 

The Committee has received many Letters of Interest by scientists throughout the world who would like to perform pioneering experiments in different subjects using such a deep underground laboratory. Currently, he deepest available general underground scientific laboratory is located at a depth of 3800 m.w.e. in the Gran Sasso National Laboratory in Italy.

 

We believe that the United States will be in a position to lead the world in pioneering scientific investigations by establishing a National Underground Science Laboratory with a depth extending to 7000  m.w.e. .