| MadSci Network: Physics |
Magnetic fields from the human body can be detected using Superconducting QUantum Interference Devices or SQUIDs. SQUIDs are based upon Josephson junctions. These junctions consist of two superconductors separated by a weak link of either non-superconducting material or a constriction in the superconducting material. The main criterion of the weak link is that superconducting electrons have to tunnel through the junction. A SQUID consists of a superconducting loop (or loops) with one or more tunnel junctions and is used to measure magnetic flux. The tunnel junctions can be operated so that a small magnetic flux change is converted into a large voltage signal across the loop. SQUIDS are operated at temperatures below that of liquid nitrogen or helium. More details are available at http://hyperphysics.phy-astr.gsu.edu/hbase/solids/squid.html#c1 In the human body, currents are generated that produce small magnetic fields. Typically, it is the neurons in the brain and excitations in muscle fibers that generate these currents. A SQUID placed outside the skull can measure these fields. The human body emits multiple different types of ionizing radiation. Natural radioactive isotopes are the primary sources of these emissions. The most common by weight is an isotope of potassium that is in the environment all around us, as well as within our bodies. Your body also contains uranium, throium, radium, tritium, carbon-14, and polonium. For more info try http://www.physics.isu.edu/radinf/natural.htm These radioactive isotopes will decay emitting gamma rays and alpha particles. The most easily measured outside of your body are the gamma rays. There are many different instruments available for measuring radiation. For more info try http://www.triumf.ca/safety/rpt/rpt_6/node1.html
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