TOP trap

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A TOP-case ( English : "time-averaged, orbiting potential trap" or "time-Orbiting potential" trap) is an evolution of the quadrupole trap . It uses the magnetic moment of neutral atoms to capture and store them.

construction

The TOP trap consists of a magnetic quadrupole field that rotates around the axis of symmetry. The rotation is necessary because there is always a place within the trap where the magnetic field disappears. At this point the atoms can leave the trap by changing their internal angular momentum or spin ( spin-flip ).

There are three crucial frequencies:

  1. the trap frequency: This is the frequency at which a trapped atom vibrates in the trap.
  2. the Larmor frequency : With this frequency the electrons of the atom rotate around the magnetic field axis (see precession ).
  3. the frequency of rotation of the trap.

For a TOP trap to work, the rotation frequency must be greater than the trap frequency, but less than the Larmor frequency. This can be understood as follows: The rotation frequency must be much greater than the trap frequency so that the place where the atoms could leave the trap moves faster than the particles can react. Due to the rapid rotation of the potential, each atom “feels” a time-averaged (effective) potential. On the other hand, the rotation frequency has to be lower than the Larmor frequency, because otherwise the electrons can no longer follow the magnetic field. The electrons would not feel a field at all.

Further developments

The quic trap uses additional Joffe coils .