The system for cooling samples in NMR radio frequency (RF) probes used in the 900 MHz magnet to cryogenic temperatures needs to be improved in several aspects. The client has a closed-cycle refrigerator capable of delivering gases to temperatures reaching -70 °C. A heat exchanger in a liquid nitrogen bath is currently used in series with this refrigerator to achieve outlet temperatures reaching -188 °C. However, this system does not account for the automatic and indefinite refill of liquid nitrogen surrounding the heat exchanger. In addition to engineering an automatic refill system, it is necessary to ensure that that the system works cohesively with the high magnetic field.

 

Figure 1- 900 MHz Magnet

Senior Design 2008—2009, Group 2

National High Magnetic Field Laboratory (NHMFL) 900 MHz NMR Probe

Project Scope