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    Where the Lab is Headed

    Jefferson Lab is headed toward new scientific questions - the ones being turned up in the dynamic research process now going on. Answering them will require even better particle-detection and data-acquisition technology. This second generation of CEBAF science will also require upgrading the accelerator to 12 GeV, double the present energy.

    A prototype seven-cell superconducting accelerating cavity. Each present cavity has five cells. All cryomodules contain eight cavities each. Cavities in the new cryomodules will look like this one.
    The 12 GeV CEBAF will enable a major new scientific initiative in meson spectroscopy, a technique for investigating how quark-antiquark pairs hold together. The upgraded accelerator will also help reveal the quark substructure of nuclei through deep inelastic scattering experiments, involving larger transfers of energy as quarks deflect electrons inside target nuclei. Higher energy in CEBAF will mean sharper views into nuclei, just like increasing a microscope's magnification. That's why the nation's Nuclear Science Advisory Committee and the National Academy of Sciences endorse the upgrade's scientific opportunities.

    Increasing the energy means improving the accelerating cavities and building the upgraded cryomodules that will contain them - ten cryomodules to be added to the accelerator outright, and, depending on performance, up to six more to replace some of the present ones. The new seven-cell cavities in the upgraded cryomodules will have higher gradient, boosting the beam's energy faster within a given length. They will also operate with a better Q, or quality factor, reducing power consumption and cost.

    Together with constructing a fourth experimental hall, Hall D, the upgrade also requires increasing the fields in the magnets that transport the beam, adding a tenth beam-recirculation arc between the two linacs (linear accelerators), and doubling the capacity of the central helium refrigeration plant. (The accelerating cavities can operate superconductively because they are immersed in liquid helium at 2 degrees Kelvin, some 456 degrees Fahrenheit below zero.)

    When CEBAF was originally planned for 4 GeV, its designers, mindful of the future, made sure to accommodate the possibility of future upgrades. That same principle will apply in 12 GeV preparations. In the still longer term, the energy might well be doubled yet again, to 24 GeV - for a third generation of Jefferson Lab science.

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