RF voltage and current (V-I) sensors and measurement methods

1. A radio frequency (RF) sensor assembly comprising:

a sensor casing disposed around a central hole, the sensor casing comprising a first conductive cover and a second conductive cover;

a cavity disposed around the central hole and comprising a first dielectric material, the cavity being bounded by a first major outer surface and a second major outer surface along a radial direction from a center of the central hole, the first major outer surface comprising a continuous ring shaped region in physical contact with the central hole, and the second major outer surface at a radial distance greater than a radius of the first major outer surface, wherein the first conductive cover is electrically coupled to the second conductive cover through a coupling region beyond the second major outer surface of the cavity and, wherein the first conductive cover is electrically insulated from the second conductive cover by the cavity and the central hole; and

a current sensor electrically insulated from the sensor casing and comprising a current pickup disposed symmetrically around the central hole, the current pickup being disposed within the cavity and being insulated from the sensor casing.

2. The sensor assembly of claim 1 , wherein the current sensor comprises a mandrel shaped like a toroid.

3. The sensor assembly of claim 2 , wherein the mandrel comprises a second dielectric material around a continuous hollow passage, the hollow passage coiling symmetrically around an internal circular axis, wherein the current pickup comprising a continuous conductive wire with two opposite ends, and wherein the wire is shaped like a coil threading through the hollow passage.

4. The sensor assembly of claim 3 , further comprising:

a plurality of access holes extending from an outer surface of the mandrel to the hollow passage; and

two electrical terminals insulated from the sensor casing, wherein the two electrical terminals are electrically connected to the respective two opposite ends of the wire extending out of the mandrel through the plurality of access holes.

5. The sensor assembly of claim 2 , wherein the mandrel comprises a second dielectric material having grooves on an outer major surface of the mandrel, the grooves coiling symmetrically around an internal circular axis, wherein the current pickup comprises a continuous conductive wire with two opposite ends, wherein the wire is shaped like a coil disposed in the grooves of the toroid.

6. The sensor assembly of claim 5 , further comprising:

two electrical terminals insulated from the sensor casing, wherein the two electrical terminals are electrically coupled to the respective two opposite ends of the wire outside the mandrel.

7. A radio frequency (RF) sensor assembly comprising:

a sensor casing disposed around a central hole, the sensor casing comprising a first conductive cover and a second conductive cover;

a cavity disposed around the central hole and comprising a first dielectric material, the cavity being bounded by a first major outer surface and a second major outer surface along a radial direction from a center of the central hole, the first major outer surface comprising a continuous ring shaped region in physical contact with the central hole, and the second major outer surface at a radial distance greater than a radius of the first major outer surface, wherein the first conductive cover is electrically coupled to the second conductive cover through a coupling region beyond the second major outer surface of the cavity and, wherein the first conductive cover is electrically insulated from the second conductive cover by the cavity and the central hole:

a current sensor electrically insulated from the sensor casing and comprising a current pickup disposed symmetrically around the central hole, the current pickup being disposed within the cavity and being insulated from the sensor casing;

a voltage sensor, the voltage sensor comprising a voltage pickup and an electrical terminal,

wherein the voltage pickup is disposed in the cavity interposed between the current sensor and the central hole, and

wherein the electrical terminal is electrically connected to the voltage pickup; and

wherein the voltage sensor is electrically insulated from the sensor casing.

8. The sensor assembly of claim 7 ,

wherein the voltage pickup is an electrode shaped like a ring disposed symmetrically around the central hole, and

wherein the voltage pickup is mechanically supported by a third dielectric material in the cavity disposed between the first conductive cover and the second conductive cover.

9. The sensor assembly of claim 8 , wherein the third dielectric material is a solid dielectric material and the first dielectric material is a gas.

10. The sensor assembly of claim 8 , wherein the voltage pickup is electrically insulated from the sensor casing by a slit region, the slit region comprising a continuous zig-zag region shaped like a ring, and wherein the slit region is in physical contact with the central hole, the voltage pickup, and the current sensor.

11. A plasma system comprising:

a radio frequency (RF) sensor assembly comprising:

a sensor casing disposed around a central hole, the sensor casing comprising a first conductive cover and a second conductive cover;

a cavity disposed around the central hole and comprising a first dielectric material, the cavity being bounded by a first major outer surface and a second major outer surface along a radial direction from a center of the central hole, the first major outer surface comprising a continuous ring shaped region in physical contact with the central hole, and the second major outer surface at a radial distance greater than a radius of the first major outer surface, wherein the first conductive cover is electrically coupled to the second conductive cover through a coupling region beyond the second major outer surface of the cavity and, herein the first conductive cover is electrically insulated from the second conductive cover by the cavity and the central hole; and

a current sensor electrically insulated from the sensor casing and comprising a current pickup disposed symmetrically around the central hole, the current pickup being disposed within the cavity and being insulated from the sensor casing.

12. The plasma system of claim 11 , wherein the current sensor comprises a mandrel shaped like a toroid.

13. The plasma system of claim 12 , wherein the mandrel comprises a second dielectric material around a continuous hollow passage, the hollow passage coiling symmetrically around an internal circular axis, wherein the current pickup comprising a continuous conductive wire with two opposite ends, and wherein the wire is shaped like a coil threading through the hollow passage.

14. The plasma system of claim 13 , further comprising:

a plurality of access holes extending from an outer surface of the mandrel to the hollow passage; and

two electrical terminals insulated from the sensor casing, wherein the two electrical terminals are electrically connected to the respective two opposite ends of the wire extending out of the mandrel through the plurality of access holes.

15. The plasma system of claim 12 , wherein the mandrel comprises a second dielectric material having grooves on an outer major surface of the mandrel, the grooves coiling symmetrically around an internal circular axis, wherein the current pickup comprises a continuous conductive wire with two opposite ends, wherein the wire is shaped like a coil disposed in the grooves of the toroid.

16. The plasma system of claim 15 , wherein the sensor assembly further comprises:

two electrical terminals insulated from the sensor casing, wherein the two electrical terminals are electrically coupled to the respective two opposite ends of the wire outside the mandrel.

17. The plasma system of claim 11 , further comprising a voltage sensor, the voltage sensor comprising a voltage pickup and an electrical terminal,

wherein the voltage pickup is disposed in the cavity interposed between the current sensor and the central hole, and

wherein the electrical terminal is electrically connected to the voltage pickup; and

wherein the voltage sensor is electrically insulated from the sensor casing.

18. The plasma system of claim 17 ,

wherein the voltage pickup is an electrode shaped like a ring disposed symmetrically around the central hole, and

wherein the voltage pickup is mechanically supported by a third dielectric material in the cavity disposed between the first conductive cover and the second conductive cover.

19. The plasma system of claim 18 , wherein the third dielectric material is a solid dielectric material and the first dielectric material is a gas.

20. The plasma system of claim 18 , wherein the voltage pickup is electrically insulated from the sensor casing by a slit region, the slit region comprising a continuous zig-zag region shaped like a ring, and wherein the slit region is in physical contact with the central hole, the voltage pickup, and the current sensor.