4
Impacts of a National Underground Facility

An underground research facility could be as simple as two or more co-located experiments that share infrastructure or as complete, wide-ranging, and integrated as the proposed DUSEL facility or anything in between. The committee’s assessment of the impact of such a facility on the relevant research communities has so far been limited to a discussion of the importance of individual science questions and the scope and ability of the experiments in the program to address those questions. In any case, however, a facility’s impact on these communities could extend beyond the particular experiments that have been discussed and even beyond these particular communities. For instance, a centralized and integrated infrastructure would not only support the experiments under consideration but also provide opportunities to pursue future research and support for the communities pursuing that research. A highly integrated facility such as the one proposed by the DUSEL program would also allow for educating the general public and benefiting nearby communities. This chapter discusses some of the impacts of such a facility.

SHARED INFRASTRUCTURE AND INTEGRATED OVERSIGHT

Conducting experiments underground requires substantial infrastructure and technical support. Co-location of underground experiments at a single site would



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4 Impacts of a National Underground Facility An underground research facility could be as simple as two or more co- located experiments that share infrastructure or as complete, wide-ranging, and integrated as the proposed DUSEL facility or anything in between. The commit - tee’s assessment of the impact of such a facility on the relevant research com - munities has so far been limited to a discussion of the importance of individual science questions and the scope and ability of the experiments in the program to address those questions. In any case, however, a facility’s impact on these commu- nities could extend beyond the particular experiments that have been discussed and even beyond these particular communities. For instance, a centralized and integrated infrastructure would not only support the experiments under consid - eration but also provide opportunities to pursue future research and support for the communities pursuing that research. A highly integrated facility such as the one proposed by the DUSEL program would also allow for educating the general public and benefiting nearby communities. This chapter discusses some of the impacts of such a facility. SHARED INFRASTRUCTURE AND INTEGRATED OVERSIGHT Conducting experiments underground requires substantial infrastructure and technical support. Co-location of underground experiments at a single site would 88

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imPacts n at i o na l U n d e rg ro U n d f ac i l i t y 89 of a enable researchers to efficiently share that infrastructure and support.1 The require- ments include access to adequate space, power, ventilation, and ready ingress and egress. Safety is of utmost concern, because most of the proposed experiments have measurable safety risks, especially given that they may be conducted a mile or more underground. Because it is expensive to excavate and support underground space, almost all underground experiments would need laboratory space on the surface for assembling and maintaining apparatus as well as developing future work. There is typically also a need to set aside underground laboratory space for low radioactivity studies to reduce background signals. In addition, technical person- nel are needed to maintain, operate, and manage the infrastructure. Much of this infrastructure and its associated staff could be shared by co-located experiments. The economies of scale could reduce construction and operating costs, although the extent of savings would need to be quantified by comparing alternate sites. The existence of a central location for underground physics research would also allow carrying out other science experiments. Integration of infrastructure for co-located experiments would need to be accompanied by at least limited coordination. For example, an integrated safety program would be needed to ensure that all experimenters are safe from risks of their own and other experiments. The location of any given experiment at a site would also need to consider possible interference of other experiments during construction or operations. While infrastructure could also be shared for some experiments by locating them here or abroad, this section considers the impact of a national facility. The mere co- location of experiments would give to the research communities some, but not all, of the advantages of a more integrated program, as described in the next section. Co-location alone would also not have such a broad impact on education and the public as would a national research facility similar to the proposed DUSEL program.2 1 The term co-location is used to refer to two or more experiments located at a single site. For instance, the three main physics experiments could be co-located in the Homestake mine, or a dark matter experiment could be co-located with existing experiments at an existing laboratory. The proposed DUSEL program co-locates all of the experiments and foresees a more integrated program that includes additional aspects of a national laboratory, including a surface campus, a large user community, mechanisms for developing a future program, and an education/outreach facility. 2 The committee notes that while the DUSEL program was developed with the expectation that the proposed experiments would be placed at the Homestake mine in Lead, South Dakota, the committee’s conclusions on the advantages of co-locating experiments are not limited to that site and should still prevail, regardless of the site chosen. The balance of advantages and disadvantages of a site, including safety issues, will depend on the specifics of the site and experiments proposed to be installed at that site.

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an assessment science ProPosed dUsel 90 of the for the The benefits of shared infrastructure and integrated oversight provided by co-location of experiments, as well as some of the benefits discussed in the next sections, lead to the following conclusions: Conclusion: The co-location of the three main underground physics experi- ments at a single site would be a means of efficiently sharing infrastructure and personnel and of fostering synergy among the scientific communi- ties. The infrastructure at the site would also facilitate future underground research, either as extensions of the initial research program or as new research initiatives. These additional benefits, along with the increase in visibility for U.S. leadership in the growing field of underground science, would be important considerations when choosing a site for the three main physics experiments. Conclusion: If co-located with one or more of the main underground physics experiments in the United States, a small underground accelerator facility to enable measurements of low-energy nuclear cross sections important to nuclear astrophysics would benefit from shared infrastructure, personnel, and expertise. Conclusion: In light of the potential for valuable experiments in subsurface engineering, the geosciences, and the biosciences that could be offered by an underground research facility, if such facility is constructed in the United States for physics experiments, scientists in other fields would greatly benefit by having a mechanism in place that would allow them to perform research there. STEWARDSHIP FOR THE RESEARCH COMMUNITIES One of the committee’s tasks is to assess “the impact of the proposed program on the stewardship of the research communities involved.”3 Stewardship is a broad concept and can take many forms, although an essential aspect is that it provides a scientific community the opportunity to pursue its research. The degree to which a program provides stewardship for a community is reflected in the types of ques- tions it allows the community to address, including how closely those questions are aligned with that community’s strategic plans. That impact is enhanced by qualitative factors such as the intellectual atmosphere the program fosters; the ease with which the research can be pursued, including the proximity of the research site to researchers; the degree to which the program is able to meet future as well as 3 Statement of Task, Appendix A.

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imPacts n at i o na l U n d e rg ro U n d f ac i l i t y 91 of a current research needs; and the opportunities and intellectual excitement that the program provides that allows it to attract and train not only the current generation of scientists but also the next one. As described in Chapter 3, the physics program proposed for the DUSEL facil- ity would address questions of tremendous scientific importance and so would have a strong, positive impact on the stewardship of the communities engaged in underground physics research. Further, those physics experiments play a prominent role in the long-range plans of the nuclear and particle physics communities and, hence, in the stewardship of these communities. The strategic plan prepared in 2008 by the Particle Physics Project Prioritization Panel (P5) of the High Energy Physics Advisory Panel (HEPAP) for the Department of Energy (DOE) and the National Science Foundation (NSF) emphasized the need for “a strong, integrated research program at the three frontiers of the field: the Energy Frontier, the Inten- sity Frontier and the Cosmic Frontier”4 in order to answer the important questions in particle physics. The proposed DUSEL program would serve as a key element in this plan for both the Intensity Frontier and the Cosmic Frontier. The long-baseline neutrino oscillation experiment, coupled with a new high-intensity proton source at Fermilab, is a critical component of the Intensity Frontier program, along with neutrinoless double-beta decay experiment and the search for proton decay. Experi- ments aimed at the direct detection of dark matter are a critical component of the Cosmic Frontier program, which also includes the study of neutrinos from space, such as neutrinos arising from supernovas. The most recent long-range plan of the Nuclear Science Advisory Committee (NSAC) for DOE and NSF identified the construction of DUSEL as “vital to U.S. leadership in core aspects” of the initiative to investigate neutrino properties and fundamental symmetries.5 This strategic plan for the nuclear physics field identi- fied neutrinoless double-beta decay experiments and the discovery of neutrino properties through neutrino oscillation studies as core aspects of the field. The plan built on similar support for construction of DUSEL in the 2002 NSAC long- range plan, as well as recommendations in the NRC decadal study for elementary particle physics.6 The scientific programs foreseen in these strategic plans represent the prioritization of the science opportunities within each field, under budget assumptions provided by the agencies. Clearly, the realization of DUSEL is of high priority to both the nuclear and the particle physics communities and would have great positive impacts on the stewardship of those communities. 4 DOE/NSF. 2008. US Particle Physics: Scientific Opportunities: A Strategic Plan for the Next Ten Years, Report of the Particle Physics Project Prioritization Panel, p. 2. 5 DOE/NSF. 2007. The Frontiers of Nuclear Science: A Long Range Plan. Report of the Nuclear Science Advisory Committee, p. 7. 6 NRC. 2006. Revealing the Hidden Nature of Space and Time. Washington, D.C.: The National Academies Press.

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an assessment science ProPosed dUsel 92 of the for the The research communities involved in the proposed DUSEL program would include not only those engaged in particle and nuclear physics, but also segments of the biological, geological, and engineering science communities. The DUSEL program would give communities outside of physics the opportunity to per- form valuable, long-term experiments in a regulated environment, thus advancing research potentials for those fields. Although important to research communities of all fields, an environment that offers robust research opportunity will be of great consequence for the subsurface engineering research community. As noted in a recent DOE report, Chronic underinvestment in federal R&D in . . . [the engineering and geosciences] disci- plines has eroded the nation’s capacity to educate and train the next generation workforce necessary for industry, academia, and government. As a result, the U.S. faces the prospect of ceding its historic leadership role in these disci- plines, and thereby undermining its resource security.7 For this community, the opportunity to undertake scientific and engineer- ing research experiments in situ in an underground facility such as the proposed DUSEL site would be critical in the effort to address these shortfalls. It would help revitalize programs in subsurface engineering at universities, allowing researchers to at long last move beyond small-scale tests on rock specimens and numerical modeling of rock mass behavior to the testing of theoretical concepts in the field. This, in turn, would give U.S. engineers the knowledge and skills to lead the sus- tainable development of subsurface resources. Facilitating the development of future research opportunities is a one of the significant ways that the DUSEL program would provide ongoing stewardship of the research communities. As the proposed DUSEL evolves, it will implement a process for evaluating the merit of proposed future experiments. It can be expected that important underground experiments beyond the proposed initial DUSEL suite will emerge. For instance, the initial suite does not include all the experiments proposed in the course of developing the DUSEL design. These include efforts spe- cialized to detect certain proton decay modes, solar neutrinos, or geoneutrinos, the last of which would constitute particularly interesting cross-disciplinary research. Nor does the initial DUSEL experimental suite include the next-generation physics experiments that can be expected to follow some of the initial ones. The committee was briefed on a future antineutrino oscillation experiment to measure the matter- antimatter asymmetry in neutrinos and on future underground gravitational wave experiments. Moreover, for dark matter and/or double-beta decay studies, larger, 7 DOE. 2009. Energy Research and Development (Document END09278): Strengthening Educa - tion and Training in the Subsurface Geosciences and Engineering for Energy Development, Section 33, Subtitle C, p. 3.

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imPacts n at i o na l U n d e rg ro U n d f ac i l i t y 93 of a more sensitive experiments or experiments that use different technologies may be required to either follow up on the observations of initial experiments or take fresh steps in case those experiments fail to reach the sensitivities needed to observe the desired events. DUSEL’s planning process is intended to integrate selected experi- ments with the current suite of experiments, either by incorporating them into existing experimental space or by developing and implementing plans for excavat- ing new space and expanding support services. The biological, geological, and engineering science experiments described in the proposed program are simply representative of the interesting, and relatively modest, experiments that could also be staged at DUSEL in coming years. One may anticipate that many new concepts for experiments will emerge as the potential of DUSEL for underground research in these fields is realized and appreciated. Indeed, it is likely that, as in the past, the advantages afforded by the existence of the facility will suggest scientific opportunities far beyond those anticipated in the initial DUSEL program. As an example, the Amundson-Scott South Pole Scientific Station, originally developed for geophysics studies, created unique opportunities for astrophysics and cosmology. The proposed DUSEL program, in bringing together particle and nuclear physicists at a single experimental site, will also provide a venue and program for interactions among scientists and an enriched, synergistic intellectual atmosphere that enhances their research. Having researchers from the biological, geological, and engineering sciences conduct experiments alongside physicists may result in the application of experimental techniques to new fields just as, in the past, the rapid development of particle astrophysics and dark matter experiments relied on techniques and facilities developed to support accelerator- and space-based experiments. In practice, it is more convenient, easier, and less costly in terms of travel expenses for U.S. research communities to perform experiments at a single location such as the proposed DUSEL site. Such a site would also make it easier to attract students and postdoctoral researchers to a research program, to allow faculty to more efficiently split their time between teaching and research commitments, and to give all researchers the chance to optimize their time at their experimental site. Indeed, the siting of at least some research facilities on U.S. soil is essential to a vital and healthy scientific program. By providing underground research space and a planning process for realiz- ing meritorious underground science, the proposed DUSEL program will afford individual U.S. scientists and research groups a context in which they can pursue their concepts. This context, together with the exceptional scientific opportuni- ties planned, will help ensure that they attain their full intellectual and research potential. It may also smooth the way for U.S. scientists to maintain the intellec- tual leadership roles that they have played in underground science, particularly in

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an assessment science ProPosed dUsel 94 of the for the the face of the growing scale of experiments, increased demand for underground laboratory space, and shrinkage in the numbers of experiments tackling certain critical science questions. On the larger international stage where the U.S. nuclear and particle physics communities play their part, the proposed DUSEL program, coupled with the U.S. Intensity Frontier program based on the Fermilab accelerator complex, would give the United States the leadership role in a field of great scientific interest over at least the next two decades, when research at the Energy Frontier will be led by the Euro- pean Large Hadron Collider. Such a leadership role would contribute significantly to the sense of scientific opportunity needed to steward these communities. Indeed, the proposed DUSEL program, being world class, would be able to attract consid- erable international interest and participation, which, in turn, would enhance the quality of research at the facility and the intellectual environment. The research environment provided by DUSEL would offer an ideal venue for training students and postdoctoral scholars in research, with the international context contributing to the value of that training. The importance of the science, the vibrant research environment, and the intellectual opportunity on frontier sci- ence would all help attract talented young students into the science and technology workforce. The committee recognizes that the proposed DUSEL program would not be the only way to provide stewardship to these research communities. For instance, as discussed more fully in the following section, other underground laboratory space is available and new underground research space can be created in other contexts. Research training and interdisciplinary interactions could also be pro - vided in other contexts. Nevertheless, as outlined above, the proposed DUSEL program would provide strong stewardship to the research communities in several different ways. It would be much more extensive than the simple co-location of experiments and would provide many advantages to the research communities that are not available in a limited facility where experiments are simply co-located. Moreover, the proposed DUSEL program is intended to complement, rather than duplicate, existing facilities or their experiments. While the final decision on whether a national underground facility should be built should take into account many other factors, including the programmatic goals of the funding agencies and the financial costs of different options, significant advantages would accrue to the U.S. research communities involved in these research areas were such a facility be sited in the United States. Conclusion: A facility for underground research would have a significant positive impact on the stewardship of the research communities involved. Such a facility would offer the particle and nuclear physics communities access to the underground research space they need to undertake a range of

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imPacts n at i o na l U n d e rg ro U n d f ac i l i t y 95 of a scientifically critical experiments, and it would allow the bioscience, geosci- ence, and subsurface engineering communities to perform valuable long- term experiments in a regulated environment. NEED TO DEVELOP SUCH A PROGRAM IN THE UNITED STATES In addition to providing stewardship of research communities, other factors are relevant for assessing whether to develop the proposed DUSEL program, or components of that program, in the United States. Some of these factors are specific to a given experiment and others are of a more general nature. Those factors are discussed in this section. General Considerations While the United States is uniquely well positioned for mounting the long- baseline neutrino oscillation experiment, its ability to mount the other physics experiments in the proposed DUSEL program is not unique. These experiments, which do not need a beam from an external accelerator, could, in principle, be mounted in an underground research facility anywhere in the world. Nonetheless, there are good reasons to mount these experiments in the United States. General considerations pertaining to mounting experiments in the United States rather than abroad include the availability of suitable laboratory space, efficient approval procedures, cost savings, partner commitment, and recognition of the U.S. role. Laboratories in other countries, most notably at Gran Sasso in Italy and at the Sudbury Neutrino Observatory Laboratory (SNOLAB) in Canada, and possibly at the proposed Chinese Underground Laboratory at some future date, appear to have some space where experiments could be sited. However, in order to be placed there, the experiments proposed for the DUSEL program would need to compete for space with experiments from the host nations. Competition would include experiments that are part of the worldwide program for tackling some of the same research questions—for instance, from the dark matter and neutrinoless double- beta decay programs, both of which call for multiple experiments. Unfortunately, it is difficult to foresee how much space might be available abroad for future U.S.-led experiments, because future programs or expansions of overseas laboratories are not yet well defined. A U.S.-led experiment at a foreign laboratory would need to be approved by the host laboratory, with some associated uncertainties. In order to gain approval, U.S. scientists would need to submit a proposal to the laboratory that would then be reviewed by its program or scientific advisory committee, with approval depen- dent not only on the scientific merits of the proposal but also on how the proposed project fits within the overall objectives of the laboratory. If no space is available

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an assessment science ProPosed dUsel 96 of the for the abroad for a U.S.-led experiment, the United States could pay for the excavation of a new space in a foreign underground laboratory. However, obtaining the necessary approval for such excavation is usually very difficult, and the excavation could be quite costly. Some foreign underground research facilities that might be considered can- didates for a U.S.-led experiment such as SNOLAB are in operating mines, which presents a separate set of issues. There are trade-offs to be considered in choosing between an experimental site at a dedicated research facility and one in an operat- ing mine. On the one hand, ongoing mining operations usually absorb some of the rather large costs of access for underground research. On the other hand, research in an operating mine is subject to the interests of the mine operator and to its continued agreement to support research in the mine. Considering that some of the lines of research for the proposed DUSEL program, such as dark matter and double-beta decay, will probably be carried on for decades, and that some of the experiments require many years to mount, the need for the continued agreement of the mine owner and the risk that economic conditions might cause the owner to cease operating the mine, contribute uncertainty to constructing and conducting an experiment in an operating mine. Issues of liability and decision making in the event of an accident present additional complications. These insecurities counterbalance at least some of the achievable cost savings associated with such a facility, so that the cost savings by funding an experiment at a foreign site must be determined on a case-by-case basis. Although enhancing a foreign underground laboratory might be less costly in the short term, the uncer- tainties surrounding space and approvals might favor a U.S. facility, which could ensure or at least facilitate the participation of U.S. scientists, who have historically been leaders in underground science. Furthermore, if significant discoveries are made by a U.S.-led experiment abroad, much of the recognition would go to the host country despite the U.S investment. To summarize, in order for a foreign site to be deemed appropriate for a U.S.- funded experiment, a number of conditions should be satisfied. In addition to adequate space, infrastructure, and other technical criteria, there should be clear, well-established cost savings advantages over a U.S. site. Furthermore, it would have to be understood that the important scientific programs—for instance, in dark matter and double-beta decay—would probably take decades. A foreign site would therefore have to guarantee continuing access, the long-term sharing of operating costs, and the ability and permission to expand laboratory space in the future. Such assurances will probably call for high-level agreements between gov- ernments and private corporations if operating mine sites are used. Furthermore, because it is important that the U.S. science achievements be recognized, it must be clear that a U.S.-funded experiment is part of the U.S. science program, despite the participation of international partners.

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imPacts n at i o na l U n d e rg ro U n d f ac i l i t y 97 of a Specific Considerations In addition to the general considerations, the experiments in the proposed DUSEL program have specific considerations that should be taken into account in determining whether to install those experiments at a U.S.-based facility or abroad. Neutrino Oscillation Experiments Although design studies for a very large neutrino detector are currently under way in Japan (Hyper-Kamiokande), in Europe (LAGUNA), and in China, a large neutrino oscillation experiment in the United States could be coupled with the pres- ent and future capabilities of the Fermilab accelerator complex to provide an intense neutrino beam at a suitably long baseline. No other region can currently offer a fully competitive combination of an intense neutrino source and an appropriate under- ground laboratory site for a very large neutrino detector. No existing underground laboratory has space for such an enormous detector, so a new large underground cavern would have to be excavated wherever the experiment is built. Furthermore, the huge cost of such an ambitious detector and cavern makes it fairly unlikely that more than one such experiment would be built. Thus, mounting the long-baseline neutrino experiment here would allow the United States to lead the world in neutrino physics, as well as serve the world neutrino physics community. Moreover, if a second large neutrino detector were someday built elsewhere in the world, the programs here and abroad undoubtedly would be designed to be complementary and not duplicative. Different experimental techniques would allow important cross-checks of delicate, sensitive measurements. Different detector technologies—for example, water Che- renkov and liquid argon—might be used, and the combination of neutrino energy and baseline would probably be different. In addition to affording cross-checks, different baselines would have different “matter effects,” which would help untangle contradictions between the mass hierarchy and the charge-parity (CP) angle, δ. In addition, results from two experiments could be combined to improve sensitivity to small effects in these delicate experiments. Dark Matter and Double-Beta Decay Experiments The considerations for mounting the experiments in direct detection of dark matter and neutrinoless double-beta decay are similar. They include the need for multiple experiments and for deep sites and/or large caverns, as well as an acknowl- edgement of the global nature of these programs. There is general recognition everywhere that at the present stage of these programs and probably also at the next stage, multiple, complementary experi- mental efforts using diverse techniques are needed. Complementary experiments

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an assessment science ProPosed dUsel 98 of the for the are needed because a particular technique may prove most effective—for instance, for background suppression. Moreover, multiple techniques will provide essential cross-checks if a signal is detected (see Chapter 3). Competition and diversity will increase the likelihood of success for these extremely important efforts. When the results of two or more experiments are combined, the overall sensitivity to these exceptionally rare occurrences will be increased. Even if discovery claims are made in the next few years, independent confirmation will be needed using a wide variety of techniques, including different target nuclei in the case of the dark matter experi- ments or different isotopes for the neutrinoless double-beta decay experiments. In the case of double-beta decay, if and when a signal is detected measurements must be made with multiple isotopes to differentiate between the quantitative effects of nuclear matrix elements and neutrino mass. As these international programs evolve, it becomes reasonable to expect that hosting and supporting future large experiments would be shared by underground laboratories in different countries. U.S.-based dark matter and double-beta decay experiments will be part of the required complement of experiments needed in both fields. Relatively few underground sites would at present be able to host a large third- generation dark matter or double-beta decay experiment. These experiments call for deep sites, although background mitigation mechanisms (large water shields, neutron vetoing) may be possible. In that case, the shielding structures will neces- sarily be thicker and require correspondingly larger experimental halls (say, about 20 m). These space needs mean fewer underground sites would be available for hosting these experiments, making a case for excavating new caverns. The size and complexity of future dark matter and double-beta decay experi- ments, the potential scarcity of specific target materials for dark matter experi- ments and of specific nuclear isotopes for double-beta decay experiments, and the substantial costs of the experiments will probably necessitate global collaborations to amass the effort, material, and financing required. As stated previously, at least two dark matter experiments and at least two double-beta decay experiments are needed worldwide to successfully address these two key scientific questions. Real- ization of the required experiments depends upon the existence of appropriate underground sites to host them. If it fails to provide such a site to host some of these experiments, the United States will be abdicating its share in these critical discovery programs, as well as missing an opportunity to provide stewardship of them, ensuring opportunities for U.S. scientists to become involved in these pro- grams in a major way, and ensuring continued U.S. leadership. Proton Decay and Supernova Neutrinos Searches for proton decay and for neutrinos from supernovae would also ben- efit from multiple experiments. For instance, in proton decay, sensitivity depends

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imPacts n at i o na l U n d e rg ro U n d f ac i l i t y 99 of a on detector mass. Therefore, multiple experiments would be complementary sim- ply by combining their results. Furthermore, multiple experiments using different technologies could enable greater advances on many fronts. For instance, differ- ent detector technologies (i.e., water Cherenkov and liquid argon) have different sensitivities to different proton decay modes. Adopting variations in technique, such as gadolinium doping or different segmentation or photodetector coverage, might increase sensitivity to different ranges of neutrino energy, which would provide further complementarity. To the extent that the search for proton decay is background limited, multiple techniques might enable greater sensitivity as well as provide cross-checks that would be critical if a signal is detected. Finally, if supernova neutrinos are detected, multiple observations would be needed as cross-checks for this very rare event. Nuclear Astrophysics Experiment While the cross-section measurements to be made by the nuclear astrophysics accelerator experiment are delicate and challenging, they are not as scientifically uncertain as the searches for dark matter and neutrinoless double-beta decay. Nev- ertheless, having more than one nuclear astrophysics facility in the world would be of scientific value, particularly because the number of cross-section measure- ments to be made in order to determine astrophysical processes is more than the existing LUNA facility at the Gran Sasso laboratory can accomplish on its own. The proposed DIANA facility will have much to measure; moreover, it has reduced backgrounds with respect to LUNA, making it capable of producing measurements more quickly and with improved results. The two facilities together will more rap- idly complete the set of fundamental measurements needed to elucidate important astrophysical processes. Experiments in Subsurface Engineering and the Geosciences and Biosciences For subsurface engineering, the geosciences, and the biosciences, special con- siderations include characteristics of the proposed DUSEL program as well as the need for multiple research environments. Existing underground research labora- tories around the world for subsurface engineering were all developed for studies related to radioactive waste isolation. They are all relatively shallow (ca. 500 m) and none are comparable to DUSEL in size or in scope. DUSEL would provide the opportunity for a broad range of experiments directed at a general understanding of the subsurface and enabling validation of computer modeling. In situ rock is a complex system. It is affected by tectonic forces and unstable slip events, including earthquakes, and contains networks of fractures that have a profound influence on rock deformability and strength and that serve as pathways for groundwater

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an assessment science ProPosed dUsel 100 of the for the flow. Sophisticated numerical models are now available to describe this system over a wide range of temporal and spatial scales, but further advances depend on experimental verification of the model predictions. The regulated environment of DUSEL would offer this opportunity. For the first time, it would be possible to define the engineering characteristics of the subsurface. This ability would have profound and far-reaching implications for the wide variety of engineering activi- ties involving the subsurface, and for this reason DUSEL is attracting considerable international interest. However, an individual underground research facility basically provides only a single geological and biological environment for study. The development of multiple underground facilities around the world for geological and biological observation and experimentation would overcome this limitation, enable comple- mentary experiments, and provide the ability to compare and contrast observations in different environments. Furthermore, the site proposed for the DUSEL program offers some special features that would be attractive for particular subsurface engi- neering experiments. Considerations related to revitalization of the U.S. academic subsurface engineering community (as discussed previously) are of particular relevance to the proposed DUSEL program. Summary of the Need As suggested above, a national underground research facility in the United States would provide the world with much-needed laboratory space for experi- ments in the burgeoning international field of underground science. A growing, widespread appreciation of the importance of the scientific questions that can be addressed by underground experiments and the need for large underground laboratories for the next-generation experiments with the sensitivities needed by the science drive the demand for increased underground laboratory space. More- over, in order to address the experimental challenges of this important science, multiple experiments are needed worldwide to address each major science subject. The United States has a role to play in this flourishing field by not only providing leadership in particular areas or in the field as a whole but also hosting a portion of the ambitious worldwide program that is required to address these challeng- ing science questions. Finally, a U.S.-based underground research facility would reinforce stewardship of the U.S. research communities by providing a research site that does not involve distant or international travel and that would facilitate graduate student training. In summary, a number of reasons exist for developing an underground facility in the United States. As discussed in the preceding section, some of these reasons relate to the stewardship of research communities. In addition, a long-baseline neu- trino experiment located in the United States would benefit from the combination

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imPacts n at i o na l U n d e rg ro U n d f ac i l i t y 101 of a of an intense Fermilab neutrino source and a suitably long baseline between source and detector site. For other experiments, there are general considerations related to the global availability of appropriate laboratory space for underground experi- ments and to access to foreign laboratory space for U.S. experiments. There are also a number of reasons specific to certain experiments. For instance, the global research programs in direct detection of dark matter and neutrinoless double-beta decay each require at least two experiments somewhere in the world. There are also reasons relating to co-location of experiments, discussed in a preceding section. An underground facility would provide a venue for future underground experiments as well as the initial set. The final reason is the benefits of a major U.S. role as a partner in the expanding field of underground research. Conclusion: Development of an underground research facility in the United States would supplement and complement underground laboratories around the world. A U.S. facility could build upon the unique position of the United States that would allow it to develop a long-baseline neutrino experiment using intense beams from Fermilab. It could accommodate one of the large direct detection dark matter experiments and one of the large neutrinoless double-beta decay experiments that are needed by the interna- tional effort to delve into these critical scientific issues, while sharing infra- structure among the three experiments, which are of comparable import. It could also host and share infrastructure with other underground physics experiments, such as an accelerator to study nuclear astrophysics, and with underground experiments in other fields. An underground research facil- ity would benefit the U.S. research communities, and would guarantee the United States a leadership role in the expanding global field of underground science. BROADER IMPACTS In addition to providing stewardship of the involved communities, other fac- tors pertinent to the assessing the value of the DUSEL program include its posi- tive effect on raising the visibility of scientific accomplishments of U.S. scientific communities and the opportunities it offers to provide education and outreach to the general public. Visibility of the U.S. Scientific Accomplishment A national underground research facility such as the proposed DUSEL would also advance more general national interests. It is well recognized that a vigorous and visible national scientific research program will significantly contribute to the

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an assessment science ProPosed dUsel 102 of the for the future health of the U.S. economy. The 2007 NRC study Rising Above the Gathering Storm: Energizing and Employing America for a Brighter Economic Future8 argues persuasively that the long-term economic health of the United Sates depends criti- cally on maintaining a strong scientific and technical base. The study presented four recommendations: increasing America’s talent pool by vastly improving K-12 science and mathematics education; sustaining and strengthening the nation’s commitment to long-term basic research that has the potential to be transforma- tional; making the United States the most attractive setting in which to study and perform research; and ensuring that the United States is the premier place in the world to innovate. A strong program of deep underground science with a number of cutting-edge experiments at a single location would be a powerful focus for activities that address these recommendations. The excitement of the scientific program and the potential for discoveries that would fundamentally change our description of the world would attract world-class scientists and help maintain the preeminent role the United States plays in scientific research. Further, the technical challenges associated with an underground facility would lead to the development of innovative engineering techniques and provide a focus for engineering research. Educational and Outreach Opportunities The science to be explored by the proposed DUSEL program is world-class and transformative, highlighting experiments that aim at understanding the basic nature of the Universe. Any such program will typically attract and excite students at all levels and the public at large and would provide excellent opportunities for science education. The current and proposed education and outreach program at Sanford Laboratory is an excellent model of what the educational component of an underground research facility could provide. The program has two main goals: enhancing the understanding of science at all levels and bringing scientific educa- tion to historically underrepresented groups. In particular, the geographical loca- tion of the proposed DUSEL facility would bring science to Native Americans. The compelling nature of the science and the unique opportunities of an underground research facility would inspire students and prepare them for careers in technical and scientific fields. Summer research programs would bring high school teachers and students to the site and provide a hands-on chance to do research. Collabora- tions with local universities would help those universities recruit and retain faculty and expand their programs in physics and engineering. Components of such a program might include the following: 8 NAS, NAE, and IOM. 2007. Rising Above the Gathering Storm: Energizing and Employing America for a Brighter Economic Future. Washington, D.C.: The National Academies Press.

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imPacts n at i o na l U n d e rg ro U n d f ac i l i t y 103 of a • Internships for high school and college teachers to allow them to contribute to the scientific output of the experiments and to help them craft innovative educational programs for their students. • Summer programs for high school and college students to encourage them to consider careers in science. • Outreach programs where top-notch scientists travel out to the community to work with K-12 school groups. These programs could have especially important effects on underrepresented communities. • Collaborations with faculty at local colleges and universities An underground research facility such as the proposed DUSEL laboratory would take advantage of the public’s curiosity about what lies below Earth’s sur- face to attract them to the facility, where they can be exposed to frontier science and state-of-the-art technology. The Soudan Underground Laboratory has been successful in attracting the public. Of course, safety is important, so visitors would have to be well protected if outreach programs take them underground.

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