This powerpoint presentation was prepared for physics seminar class that I am enrolled in as a graduate student at Creighton University. I reviewed a paper published in Scientific Instrument journal. The paper focused on active cancellation of stray magnetic field.

1. Shouvik Kanti Bhattacharya
PHY791 | 04.10.2014
“Active Cancellation of stray magnetic
fields in a Bose-Einstein Condensation
experiment”
C. J. Dedman, R. G. Dall, L. J. Byron, and A. G.
Truscott
Review of Scientific Instruments
78, 024703(2007)[1]

2. Phase transition of a graduate
student
 Moved to Omaha from Boston on the 10th
of August, 2013.
 Went through 3 different orientations in
the following 8 days (August 12- August
20, 2013).
 Engaged in analytical solution of finding
an optimum setup for cancelling magnetic
fields and presented my work on October
30, 2013.
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3. A common example of phase transition
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Figure 1. The front yard of my residence, picture taken April 4, 2014, 8:42 am
CST.

4. Sublimation/Evaporation
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Figure 2. The front yard of my residence, picture taken April 4, 2014, 3:03 pm
CST.

5. Let’s remind us about the Bose-
Einstein condensate
 Bose-Einstein condensation is a phase
transition.
 All bosons are at the ground state.
 The condensate occurs at a thermal
equilibrium.
 Superfluidity of helium and
superconductivity of an electron gas are
caused by the Bose Einstein condensate.
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6. Experimental Setup of the BEC
 “The possibility of creating optical fields
with many photons in a single mode of a
resonator was realized with the creation of
the laser in 1960. The possibility of
creating a matter-wave field with many
atoms in a single mode of an atom trap-
the atomic equivalent of an optical
resonator-was realized with the
achievement of Bose-Einstein
condensation(BEC) in 1995.” Wolfgang
Ketterle[2]
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7. History of the BEC Experiments
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Figure 3. History of the BEC publications over time[2]

8. Controlling the Magnetic fields
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 A Stable magnetic field where the bosons
are trapped in is a key requirement for
many BEC and ultra cold atom
experiments.
 Examples: Quantum information
processing, quantum simulation with
qubits encoded in field sensitive atomic
spin states.[3]

9. Controlling the Magnetic fields (cont.)
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 A complete shielding of the exterior
magnetic field is also desired in some
cases.
 Experiment on the spinor condensates
require to suppress the background
magnetic field.[3]

10. Bhattacharya 10
Figure 4. Magnetic Noise [1]

11. What did they do?
 An active system that responds to an
abrupt change in magnetic field up to 3
kHz noise.
 Their main objective was stabilizing the
magnetic field by one part in ten thousand
(10-10 T).
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12. Some ways to shield a magnetic field
 Shielding by a high permeable material
 Shielding by Eddy current
 Using 3-pairs of “active” Helmholtz
Coil
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13. Bhattacharya 13
Figure 5. Experimental Design[1]

14. Integrator
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Figure 6. A Schematic Diagram of an Integrator Circuit, Image courtesy:
http://www.electronics-tutorials.ws/opamp/opamp_6.html

15. Integrating Vin
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Figure 7.Image courtesy: http://www.electronics-
tutorials.ws/opamp/opamp_28.html

16. Differentiator
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Figure 8. A Schematic Diagram of a Differentiator Circuit, Image Courtesy:
http://www.electronics-tutorials.ws/opamp/opamp_7.html

17. Differentiating Vin
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Figure 9 Image courtesy: http://www.electronics-
tutorials.ws/opamp/opamp_42.html

18. Result
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19. Scope of work
 Currently enrolled in PHY582 and hoping
to finish the geomagnetic field
suppression (passive system) experiment
this semester.
 Planning to enroll in PHY799 in summer
and start making progress in the active
magnetic field suppression.
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20. Helmholtz Coils
20
1
2
Figure 10. A pair of Helmholtz coils. Image Courtesy:
http://physicsx.pr.erau.edu/HelmholtzCoils/HelmholtzCoils.jpg

21. Radia
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Figure 11. Changing the separation parameter and reporting associated
magnetic field with it.

22. Acknowledgements
 I would like to primarily thank to Dr.
Jonathan Wrubel, Dr. Andrew Baruth, and
Dr. Michael Nichols.
 Dr. David Sidebottom and Dr. Kyle Watters
 Nathan Holman and the AMO Research
group at Creighton University (Spring
2014)
Bhattacharya 22

23. References
[1] C. J. Dedman, R. G. Dall, L. J. Byron, and A. G. Truscott. 2007.
Review of Scientific Instruments 78, 024703.
[2] Ketterle, Wolfgang. December, 1999. Physics Today.
[3] A Smith, B E Anderson, S Chaudhury, and P S Jessen, J. Phys. B:
At. Mol. Opt. Phys. 44 (2011) 205001 (7ppm).
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24. Questions
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Figure 12. Bose Residency: Image Courtesy:
http://upload.wikimedia.org/wikipedia/commons/2/22/Bose_Institute_-
_Kolkata_7354.JPG