Magnetic nanoparticle spectrometer

1. An apparatus, comprising:

an electrical source configured to generate a time-varying current supply;

an excitation coil coupled to the electrical source to generate a time-varying magnetic field based on the time-varying current supply for application to a magnetic sample;

a sensing coil system that senses a magnetic response of the magnetic sample, the magnetic response comprising an induced voltage generated in response to the time-varying magnetic field, the sensing coil system comprising a pick-up coil and a balancing coil to cancel a portion of the time-varying magnetic field that is induced from the excitation coil into the pick-up coil, the sensing coil system comprising a mechanically adjustable fine-tuning coil that modifies an effect of the cancellation of the time-varying magnetic field induced from the excitation coil, the adjustable fine-tuning coil being electrically coupled with the pick-up coil and the balancing coil; and

a data acquisition system that measures the induced voltage generated by the sensing coil system.

2. The apparatus of claim 1 , wherein the excitation coil is a gapped solenoid excitation coil.

3. The apparatus of claim 1 , wherein the data acquisition system further comprises a magnetic field sensor that measures the time-varying magnetic field.

4. The apparatus of claim 1 , further comprising a structure to tilt the balancing coil with respect to a tilt axis to modify an amount of the cancellation of the induction from the excitation coil.

5. The apparatus of claim 1 , wherein the pick-up coil is internally molded in epoxy resin to minimize a distance between the pick-up coil and the magnetic sample.

6. The apparatus of claim 1 , wherein the balancing coil is coupled in series with the pick-up coil, and the balancing coil is wound in a direction opposition of the pick-up coil.

7. The apparatus of claim 1 , wherein the data acquisition system is configured to measure the time-varying current supply to assess a reference phase of the time-varying magnetic field.

8. The apparatus of claim 1 , further comprising a resonant matching circuit coupled to the electrical source.

9. A magnetic particle spectrometer, comprising:

an electrical source configured to generate a time-varying current supply;

an excitation coil system coupled to the electrical source to generate a time-vary magnetic field for application to a sample;

a sensing coil system that senses a magnetic response of the sample in response to the time-varying magnetic field, wherein the sensing coil system comprises a pick-up coil and a balancing coil that can be translated or rotated, the balancing coil being configured to cancel a feed-through induction signal, wherein the sensing coil system comprising a mechanically adjustable fine-tuning coil that modifies an effect of the cancellation of the feed-through induction signal from the excitation coil system, the adjustable fine-tuning coil being electrically coupled with the pick-up coil and the balancing coil; and

a data acquisition system that measures the magnetic response from the sensing coil system.

10. The magnetic particle spectrometer of claim 9 , wherein:

the magnetic response is representative of a magnetization change of the sample based on the time-varying magnetic field; and

the magnetic response generates an inducted voltage in the sensing coil system.

11. The magnetic particle spectrometer of claim 9 , wherein the balancing coil is translated or rotated to modify an amount of the cancellation of the feed-through induction signal.

12. The magnetic particle spectrometer of claim 9 , wherein the excitation coil system is coupled to the electrical source via a resonant matching circuit.

13. The magnetic particle spectrometer of claim 12 , wherein the resonant matching circuit comprises at least one pair of capacitors designed for a current gain greater than one at a plurality of discrete frequencies in a non-linear mode.

14. The magnetic particle spectrometer of claim 9 , wherein the excitation coil system comprises a plurality of coils with different orientations to generate a rotating magnetic field.

15. A system, comprising:

an electrical source configured to generate a time-varying current supply;

an excitation coil coupled to the electrical source to generate a time-varying magnetic field based on the time-varying current supply for a magnetic sample; and

a sensing coil system to detect an induced voltage from a magnetic response of the magnetic sample in response to the time-varying magnetic field, the sensing coil system comprising a pick-up coil and a balancing coil to cancel a feed-through induced signal, the sensing coil system comprising a mechanically adjustable tuning coil that is magnetically coupled to the pick-up coil and the balancing coil, the adjustable tuning coil being configured to adjust the cancellation of the feed-through induced signal.

16. The system of claim 15 , further comprising a structure to rotate the balancing coil with respect to an axis to adjust the cancellation of the feed-through induced signal.

17. The system of claim 15 , wherein the excitation coil is coupled to the electrical source via a resonant matching circuit.

18. The system of claim 15 , wherein the excitation coil is directly coupled to the electrical source.

19. The system of claim 15 , further comprising a data acquisition system that measures, records, and applies signal processing techniques to the induced voltage from the sensing coil system.

20. The system of claim 15 , wherein the adjustable tuning coil is mechanically rotated to adjust the cancellation of the feed-through induced signal.