Signedunsigned
FunctionThis is part of an experiment for the advanced undergraduate physics class at Harvard involving NMR called "negative spin temperature". The system inside the box (meant to protect the students from electric hazard) is basically a set of circuits, one RC (resistor-capacitor) and one LR (inductance-resistor) with the switch alternating between the two. When the RC is activated, the capacitor is charged by an external 5000-volt DC power supply (2004-1-0413). Then, once the capacitor is fully charged, the experimenter lowers a sample crystal of lithium fluoride (safely mounted on an insulating lucite rod, 2004-1-0412c) through the small hole on the top of the box into the coil on the red platform. Then she switches to the LR circuit, discharging the capacitor through the coil creating a very large magnetic field that aligns the majority of the substance's atoms' spins in one direction.
The gradual decay of of this spin alignment (the "negative spin temperature") can then be detected by its emission of radiation, for instance with the 2004-1-414 radio receiver. Wolf Rueckner notes that the experiment only worked with the first LiF crystal they used; the crystal in 2004-1-0412c was apparently too pure, as were the crystals left in their packing box (2004-1-0412b).
ProvenanceUsed in Harvard's advanced undergraduate physics class (Physics 191r) before coming to the collection.