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Report
NHMFL Users Committee Meeting
May 1997


The Users Committee met at Tallahassee May 16-17, 1997
Members in attendance:
C. Agosta, M. Aronson, G. Boebinger, P.M. Chaikin, W.G. Clark, J. Furdyna, R. Goodrich, M. Naughton, C. Perry, E. Zuiderweg
Members absent:
L. Kevan, R. Vold

  1. LOS ALAMOS PULSED FIELD FACILITY OPERATIONS


    The Users Committee commends the NHMFL for the increased user support at the Pulsed Field Facility, which includes the recent hiring of two postdocs and a new technician.

    We also thank the NHMFL for its flexible response in developing a floor plan for the new building in close collaboration with the user community. This final floor plan serves the needs of the user programs quite well and logically divides the laboratory into separate areas for user facilities and magnet development/support. We particularly support the plan for independent magnet cells, featuring automatic switching of the capacitor bank. Because it will have such an immediate positive impact on the scientific output of the pulsed field facility, this automatic switching should be a very high priority which, in principle, could be implemented in the present building before the move to the new building. The switch should be modular and thus easily transportable into the new building.

    The following actions would improve the effectiveness of this facility still further:
    DATA PLOTTING DURING RUNS - External users should have access to a computer (both a PC and MAC) to plot and analyze the data independent of the data collection computer. A variety of commercial plotting software packages, such as Origin, should be installed for use by users. The existing situation makes it difficult for the user to make decisions in real-time as to the quality of existing data and the strategy for future magnet pulses. It also places unnecessary burden on the NHMFL staff who now must actively participate in data plotting and analysis.
    MAXIMUM RELIABLE FIELDS - There is concern that the pulsed magnets are not being pushed to their maximum reliable fields. Because the current practices are very conservative and focus on minimizing the chance of a magnet failure during a user's experiment, there is a lack of magnet lifetime data. In order to overcome this problem, we recommend that a series of identical magnets be built and tested for reliability. One scenario is to test one to destruction, and subsequently to test the others for lifetime with a series of pulses: one magnet at 95% rating, another at 90% rating, a third at 85% rating, etc., until each magnet fails at the corresponding de-rated field. This may take hundreds of pulses, but it should provide the basis for a rational decision to replace the current "gut-feeling" decision regarding the tradeoff between de-rating a magnet and the anticipated increase in magnet lifetime.
    SMALLER BORE MAGNETS - There is considerable interest in the user community to use smaller bore magnets to obtain higher magnetic fields. Techniques are now being developed to perform a variety of measurements in a 15 mm bore. For some, and perhaps many users, the resulting increase in the achievable magnetic field is worth the effort required to work in a smaller bore. The 100T magnet appears to REQUIRE a smaller (perhaps 15 mm) bore if it is to be built from currently available materials. This potentially negative impact on the flexibility of the magnet is more than offset by the higher achievable field that it will afford.
    60-T LONG-PULSE MAGNET - We await with great anticipation the successful completion of the 60-T long-pulse magnet this summer. This magnet will put Los Alamos on the map in many users' minds, because it will have a very important set of capabilities which are unique in all the world.

  2. KECK MAGNET

    Because it appears that operation of the Keck magnet will consume so much power that no other resistive magnets can run concurrently with it, we urge that the proposal review process set high standards for acceptance and that the experiments approved for it be ones whose scientific aspects REQUIRE that the work be done at the high, homogeneous field provided by it. Its use should be managed for maximum efficiency in the use of running time during its operation. In particular, it should not be used simply to enhance sensitivity for experiments that could otherwise be carried out in a superconducting magnet. Insofar as possible, NMR experiments in the field range provided by the Keck Magnet should be carried out in the magnets currently used for condensed matter research because of their correspondingly lower power consumption. External review should be required for use of both the Keck magnet and the 45 T hybrid when they become operational.

  3. SPECIALTY MAGNETS

    The User Committee commends the magnet development group for having designed a 30 T specialty magnet with the capability of having inserts for large amplitude field modulation, high dB/dz field gradient, and field homogenizing coils.
    We have three comments regarding this magnet and its inserts:
    1. It would be more efficient for users if the functions of the inserts could be partially or fully combined so that insert change time would be saved.
    2. The scheduled start date for construction of this magnet should not be delayed past January, 1998.
    3. A report on the status of its design and discussion of the insert parameters with the Users Committee should be a part of the November, 1997 Users Committee meeting.
    20 T WIDE BORE AND SPLIT COIL MAGNETS - We doubt that the 20 T wide bore magnet now being designed will handle all of the experimental situations that could be solved with a split coil magnet. The building of a 20 T split pair should be kept on the schedule of magnets to be designed and built.
    900 MHz NMR SYSTEM AND 45T HYBRID MAGNET - Given the large investment already made in them, these systems should be completed and brought into operation as soon as possible. The 45 T hybrid will be a unique tool for high field research. If the 900 MHz system is not completed soon, it may lose its uniqueness to commercially available systems.

  4. OTHER POINTS


    We thank the laboratory management for its generally receptive response to input from the Users Committee. In addition to the items described above, we appreciate the priority given to 11 months of full operation of the resistive magnets and the support provided for the condensed matter NMR activity.

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