Generation of quadrupole magnetic field for trapping atoms in Cs fountain being developed at NPL India
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We describe the development of a constant current source for magneto-optical trap (MOT) coils. The system is designed to supply maximum 5 A current in continuous or pulsed mode to the anti-Helmholtz (AH) coils which produce quadrupole magnetic field inside the chamber for trapping of Cs atoms. To obtain a stable field gradient the coils are operated at low current to minimize current fluctuations. With AH coils having 100 turns and 5 Ω resistances, we achieved rise and fall times of current as 5 ms and 7 ms, respectively. With a field gradient of 6 G/cm at the center of the MOT, 7 number of atoms trapped is about 10. To prevent burning of coils due to failure of current source, a thermal protection circuit has been incorporated. Measurements made for switching times of current profile in coils is also reported.
KeywordsMagnetic Field Gradient Constant Current Source Metrology Society Maximum Power Dissipation Quadrupole Magnetic Field
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