CONTROLLED-TEMPERATURE INSERT FOR 95 GHZ CW/PULSE SPECTROMETRY

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. ACERT is scheduled for installation of a Cryogenic, Ltd. 9T cryogen-free magnet and low-temperature insert in late August, 2007. This schedule represents a 3-month delay from the original installation date. For impending step-frequency 95 GHz DEER experiments on protein systems in our existing 6T Oxford magnet, we have therefore proceeded with specification and design of a significant interim upgrade to our earlier JOMO-I temperature control system. The Controlled Temperature Insert (CTI) upgrade that we are presently assembling consists of an added closed-loop gas pre-heater section, construction of a low time-constant temperature control heater within the existing "ambienstat" insert structure and temperature monitoring of one or both of the vacuum-retaining warm bore "O"-ring seals. The existing Lakeshore model 331 temperature controller, with input from an appropriate sensor at the sample, will be retained as the primary temperature regulating system. Temperature control down to 100¿K at 0.1¿K stability is expected. All components for the interim CTI upgrade have been acquired, and the insert structure has been modified to accept a heater/armature assembly in a position of close proximity (7 cm) to the sample. A rack chassis with front panel Omega controller/monitors and heater power driver circuitry for preheater regulation and O-ring seals temperature monitoring (and, optionally, control) is currently under construction. We intend to complete construction and debug of the rackmount CTI preheater control system within a few weeks, at which time the controller will be installed in the 95 GHz magnet in concert with the revised ambienstat and cryostat O-ring seal monitors.