95 GHZ SPECTROMETER CRYO-FREE 9T MAGNET UPGRADE

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. As described and an allocation provided for in our first year grant renewal expenditures, we have acquired a 9T wide-bore magnet of the cryogen-free type for the ACERT 95 GHz spectrometer system. This unit, purchased from Cryogenic, Ltd., U.K., was installed in mid-April, 2008 and offers the benefits of both a sufficiently wide bore to accommodate a large NMR-style vacuum temperature insert (VTI) and, importantly, significant cryogen cost savings. The magnet system was initially expected to arrive in the fall season of 2007 but its delivery was delayed approximately 6 months for main coil reliability modifications and further testing. Although ACERT installation proceeded normally, with successful ramping to 9T, subsequent reliability issues with the main magnet power supply have delayed final commissioning of the magnet system. However, because the spectrometer itself is presently being rebuilt and upgraded, the magnet power supply repair/replacement downtime should not cause any additional experimental program delay. Several aspects of the spectrometer's design and configuration are affected by the transition to the new 9T magnet, and these are presently being addressed. Mechanically, the bridge, resonator and vacuum insert require an entirely new support structure that is also physically isolated from the magnet containment. To meet this requirement, a rigid framework based on heavy-duty extruded aluminum struts has been designed and will be fabricated and installed in late summer 2008. For field sweep control, a software module will be created and incorporated into the spectrometer control ensemble in order to communicate with the sweep power supply. Logging of critical magnet temperatures and field ramp profile by the spectrometer control system will be optionally implemented at a later date.