Research and development in pulsed power, plasma physics and fusion energy sciences since 2005

Diagnostics

Products Model Number Spec Sheet References
B-dot probes M1-B-Single Diagnostics-Magnetics-Single References Get a Quote »
Linear arrays M1-B-Array Diagnostics-Magnetics-Array References Get a Quote »
Rogowskis M1-R Diagnostics-Magnetics-Rogowski References Get a Quote »
Rogowskis for banks M1-R-Air Request spec sheet References Get a Quote »
Insitu calibration jig M1-C-IS Request spec sheet References Get a Quote »
Calibration jigs M1-C Request spec sheet References Get a Quote »
Insertable rogowskis M1-R-Vac Diagnostics-Magnetics-Rogowski References Get a Quote »
Flux loops in Air M1-FL-Air Request spec sheet References Get a Quote »
Flux loops in a Vacuum M1-FL-Vac Request spec sheet References Get a Quote »
Electrostatic Model Number Spec sheet Reference
Voltage monitors (HV, voltage dividers) E1-Vdiv Request spec sheet Electrostatic References Get a Quote »
Langmuir probe – static E1-L-[# of tips] Diagnostics-Electrostatic-Langmuir Electrostatic References Get a Quote »
Langmuir probe – reciprocating E1-L-R Diagnostics-Electrostatic-Langmuir Electrostatic References Get a Quote »
Retarding Grid Energy Analyzers E1-RFA Diagnostics-Electrostatic-RFEA Electrostatic References Get a Quote »
Ball pen probe E1-Bpp Request spec sheet Electrostatic References Get a Quote »
Faraday cup E1-FC Request spec sheet BElectrostatic References Get a Quote »
Mach probes E1-M Request spec sheet Electrostatic References Get a Quote »
Refractive index Model Number Spec sheet References
CO2 Interferometer R1-CO2 Request spec sheet Refractive Index References Get a Quote »
HeNe interferometer R1-HeNe Diagnostics-Refractive-HeNe Get a Quote »
Microwave interferometer R1-M Diagnostics-Refractive-Microwave Get a Quote »
Polarimetry R1-P Request spec sheet Refractive Index References Get a Quote »
mmWave Reflectometer R1-R Request spec sheet Get a Quote »
Fiber-Coupled Interferometer R1-F Request spec sheet Get a Quote »
Fiber-Coupled, Two-Color Interferometer R1-F-2C Request spec sheet Get a Quote »
Scattering Model Number Spec sheet References
Profile Thomson Scattering-YAG S1-T-YAG Request spec sheet Scattering References Get a Quote »
Profile Thomson Scattering-RUBY S1-T-RUBY Request spec sheet Scattering References Get a Quote »
Radiation Model Number Spec sheet References
Photodiode bolometer SP1-B Request spec sheet Get a Quote »
3 channel filtered bolometer array SP1-B-3 Request spec sheet Get a Quote »
1 channel thermistor SP1-B-T Request spec sheet Get a Quote »
Charge exchange particle neutral analyzer SP1-NPA Request spec sheet Get a Quote »
Visible spectrometer SP1-SP-VIS Request spec sheet Get a Quote »
Hard X-ray Request spec sheet Get a Quote »
VUV monochrometers SP1-SP-VUV Request spec sheet Get a Quote »
H-alpha array SP1-SP-Ha Request spec sheet Get a Quote »
TV cameras SP1-SP-TV Request spec sheet Get a Quote »
Microwave Imaging Reflectometer Request spec sheet Get a Quote »
Scintillator SP1-S Request spec sheet References Get a Quote »
Neutral Particle Analyzer Request spec sheet References Get a Quote »
Gas Model Number Spec sheet References
Residual gas analyzer RGA-1 Request spec sheet Get a Quote »


WSI has nearly a decade of experience designing and manufacturing diagnostics for plasma experiments. Browse our product listings to the left or download a flyer (pdf).

Recently WSI was awarded a Phase I and Phase II SBIR to examine the role that Additive Manufacturing can play in the development of plasma diagnostics.

During the last 50 years, plasma diagnostics have matured into a standard set that now measure most of the dominant parameters needed to understand plasma confinement. New diagnostics are being developed that allow new parameters to be measured. However, when presented with the opportunity to start a new facility or maintain an existing facility with failures in diagnostics occurring relatively frequently, the recourse is to utilize techniques and technologies dating back 50 years or more, resulting in expensive, large and often time-consuming diagnostic development activities.

A principal cost associated with any new fusion system is the subsystem comprising all of the measurements needed to ensure that the plasma is reaching the temperature, density and confinement time needed for fusion conditions. This `diagnostic' subsystem relies on technology that is decades old, and any custom system is expensive. Some diagnostic components are known to fail regularly (such as plasma-facing mirrors on larger devices), and solutions for their cleaning or replacement are not straightforward to implement. Additive manufacturing with vacuum compatible and plasma-compatible materials could therefore significantly impact the costs of the diagnostic subsystems, allowing in some possible cases for in-situ manufacture in vacuum, thereby reducing costs and shortening time-lines for commercial deployment.

Diagnostic costs are also prohibitive for entry into fusion research: typically a magnetic system can cost several thousand dollars, and usually custom made. Open source designs are now eliminating design costs - optical mount components are now available free for download and a few cents for printing. We provide magnetic system components on our website for download and printing already. Having a complete set of diagnostic designs available to academics and students will significantly impact development costs and time, and significantly reduce barriers to entry into plasma physics as a field.

Fostering a community of 'open-source diagnosticians' can only help to improve the development of fusion technology and expedite transfer of technology to areas of high tech industry. All of the diagnostic designs (not printer technology) that we will develop during the Phase I SBIR will therefore be offered as open-source on one of the available forums (or through our website). The designs will be available to serious academic studies and a wider sphere of high school educational projects.

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Magnetic Probes

For magnetic fusion energy (MFE) systems, measurements of the magnetic field and associated current are the primary diagnostic interest. Faraday's law states that a time-varying magnetic field, B(t), will induce an electric field, E(t), in a loop of wire: ∇×E = -dB/dt. For n loops of wire with cross-sectional area, A, the resulting electric potential is φ(t) = nAdB/dt (where B is the component of B along the axis of the loops). Measuring the voltage produced by such a coil will therefore give the time- variation of B, which after integration (numerical or passive) will yield B(t). Magnetic probes typically comprise many loops of magnet wire wound around a plastic form. These coils are commonly mounted around the perimeter of an experiment and designed either to measure either the slow or fast variations in B (so-called equilibrium coils or fluctuation coils). Coils can also be wound to be sensitive to multiple orthogonal components of B, measuring all at the same time. A similar type of probe called a Rogowski coil measures the time-variation of the current passing through it, which is integrated to find I(t). We have engineered various ultra-high vacuum (UHV) compatible magnetic probes for various purposes, including single coils and arrays. We have also developed Helmholtz coil arrays used to calibrate these coils either in-situ or on a bench. A good reference for magnetic probes is Hutchinson's Principles of Plasma Diagnostics. References for specific applications can be found in Magnetics References.

When requesting a quote for a magnetic diagnostic, please consider the following:
  • Expected magnitude of the measured quantity and digitizer dynamic range. These determine the minimum and maximum nA of the coil.
  • Frequency response. What is the frequency (or range of frequencies) that need to be measured? This determines the required inductance, L, and resistance, R, of the coil.
  • Vacuum environment. Is the probe intended to be used in air or vacuum? High vacuum (HV, 10-3 - 10-9 torr) or ultra-high vacuum (UHV, 10-9 - 10-12 torr)? This helps us determine the materials that can be used for your application.
  • Thermal environment. Will the probe experience high heat loads (for example, behind first wall tiles) or low heat loads? Will it experience thermal cycling? Will it be used at a high or low ambient temperature (will the chamber be baked)? This information also places restrictions on the materials that can be used.
  • Mounting interface. Will the probe be mounted to a vacuum flange, a custom mounting structure on the chamber wall, or something else?
  • Size constraints. Width of gap behind wall tiles, diameter of port through which the coil must be inserted, perturbation to the plasma, et cetera.

Magnetic Field Coils (B-dot)


Download this coil for 3D-Printing (.stp file)



Magnetic Field Coil Spec Sheet

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Rogowski Coils




Download Coil Form for CNC Milling: Coil Form
Download Coil Case for CNC Milling: Case (lower), Case (upper)

Rogowski Coil Spec Sheet

Rogowski Coil Probe Spec Sheet

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Linear Array of Magnetic Coils



Magnetic Coil Array Spec Sheet

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Calibration Jigs

Coil1

Coil2

Coil4

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Plasma Particle Flux

A Fundamental technique for measuring the properties of plasmas is the use of electrostatic probes, most notably the Langmuir probe, Mach probe, and retarding field analyzer (RFA). These probes are inserted into the plasma and thus allow local measurement of several plasma properties. The Langmuir probe measures the electron energy, temperature, and density and comes in single, double, and triple tip configurations, which have various effects on the plasma. Some of these configurations are able to measure the floating potential and/or plasma potential. A Mach probe is used to measure the ion flow velocity. Retarding field analyzers can measure the ion or electron energy and temperature in specific directions. Each electrostatic probe configuration has its advantages and disadvantages and the scientists at WSI can help you decide which probe is right for you. Two excellent references for electrostatic probes are Hutchinson's Principles of Plasma Diagnostics and Noah Hershkowitz's chapter in Plasma Diagnostics: Discharge Parameters and Chemistry. References for specific applications of each type of probe are provided in the sections below.

When requesting a quote for an electrostatic diagnostic, please consider the following:
  • Quantity to be measured and its expected magnitude. Electron or ion measurements? Is electron density of interest? Ion flow velocity or energy and temperature? Are floating and/or plasma potential of interest?
  • Frequency response. What is the frequency (or range of frequencies) that need to be measured? What is the timescale of evolution of the measured quantitiy?
  • Digitizer dynamic range. What is the peak-to-peak signal amplitude that your data acquisition system can handle?
  • Vacuum environment. Is the probe intended to be used in air or vacuum? High vacuum (HV, 10-3 - 10-9 torr) or ultra-high vacuum (UHV, 10-9 - 10-12 torr)? This helps us determine the materials that can be used for your application.
  • Thermal environment. Will the probe experience high heat loads (for example, behind first wall tiles) or low heat loads? Will it experience thermal cycling? Will it be used at a high or low ambient temperature (will the chamber be baked)? This information also places restrictions on the materials that can be used.
  • Mounting interface. Will the probe be mounted to a vacuum flange, a custom mounting structure on the chamber wall, a reciprocating drive, or something else?
  • Size constraints. Diameter of port through which the probe must be inserted, distance from the mount to the measurement location within the plasma, perturbation to the plasma, et cetera.

Langmuir Probes

  • Langmuir Probes
    • Single Tip
    • Double Tip
    • Quad Tip
    • Flat


Double-tip Langmuir Probe

Langmuir Probes References

Langmuir Probe Spec Sheet

Available in Single, Double, Triple, or Quad tip configurations. Built for UHV environments. Probe size customizable depending on plasma parameters. Reciprocating probes available. Flat probes also available.

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Gridded Ion Energy Analyzers

Ion Energy References

Retarding Field Analyzer Spec Sheet


Retarding Field Analyzer

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Refractive-Index Measurements

The refractive index of a plasma is a robust indicator of the electron density. Interferometers are commonly used to take a chord-averaged measurement of the refractive index, thereby measuring the density along the beam line. An interferometer is favored for its non-perturbing measurement, at the expense of point resolution. Interferometers are often deployed in sets, sampling several chords to build up profile information for the target plasma. Woodruff Scientific provides interferometers in microwave, infrared (CO2), and visible (HeNe) wavelengths to meet your specifications for sensitivity range and vibration tolerance. Density profile information can also be recovered through additional refractive-index diagnostics such as reflectometry (in which the beam is reflected by a surface at the cutoff density) and refractometry (in which the deflection or spread of the transmitted beam is used to infer the density profile). Finally, one can also use the difference in refractive index between left and right circularly polarized waves in a polarimeter to achieve a chord-averaged measurement of the magnetic field component parallel to the beam. An excellent reference for refractive index diagnostics is Hutchinson's Principles of Plasma Diagnostics 2nd Edition.

HeNe Interferometer


HeNe Interferometer Spec Sheet

Microwave Interferometer


Microwave Interferometer Spec Sheet

Fiber-Coupled Interferometer

Fiber-coupled interferometers are very flexible and robust systems, often allowing for lines of sight to be quickly changed without the need for optical realignment.


Fiber-Coupled Interferometer Spec Sheet

Fiber-Coupled, Two-Color Interferometer

This two-color system provides vibration compensation in addition to the flexibility and robustness of fiber-coupled systems.


Fiber-Coupled, Two-color Interferometer Spec Sheet

CO2 Interferometer

CO2 Interferometer References

Polarimeter

Polarimeter References

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Optical Mount Components for 3D Printing

Over time, we plan to develop a whole range of mechanical components for use in our diagnostics, passing on cost savings to customers in the diagnostics. It is also possible that we can design the entire optical system as a single monolithic structure to be printed with alignment built-in. Check back in the coming months as we add more information here, and to our thingiverse pages.

3D printed mirror mount

3D printed mirror mount

Download files ready for 3D-printing: Optical Mount, Optical Mount Adjust

3D printed beam splitter mount

3D printed beam splitter mount

Download files ready for 3D-printing: Beam splitter Mount (for 40mm cube beam splitter)

3D printed laser mount

3D printed laser mount

Download files ready for 3D-printing: Laser Mount (uses 1/4 20 nuts and screws)

Scattering

Scattering of electromagnetic radiation from the plasma is a non-perturbing method of determining detailed information about the electron distribution function, and sometimes of the ions. Excellent references for Thomson scattering include Sheffield's Plasma Scattering of Electromagnetic Radiation 2nd Edition

Thomson Scattering

Thomson Scattering References

Thomson Scattering
Thomson beamline, dump, and collection optics

Thomson collector
Thomson collection optics: primary lens to fibers

YAG laser resources

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Spectroscopic

Line radiation from the plasma due to bound state transitions of the electrons can yield information about the power losses and impurity concentrations, and also about the velocities of impurities. An excellent secondary reference summarizing the physics is Hutchinson's Principles of Plasma Diagnostics 2nd Edition

Soft X-Ray Diode Imaging

Soft X-Ray References

Bolometer

Bolometer References

VUV Spectrometer

VUV Spectrometer References

Visible Spectrometer

Visible Spectrometer References

Ion Doppler Spectrometer

Ion Doppler Spectrometer References

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Neutral Particles

Neutral particles are able to escape the confining magnetic field since they are not charged. It is also possible to use neutral particles as probes, which then relies on radiation of some other sort from the plasma for diagnosis. An excellent resource for neutral particle analysis is Hutchinson's Principles of Plasma Diagnostics 2nd Edition

Neutral Particle Analyzer

Neutral Particle Analyzer References

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Neutrons

Neutrons escape readily from fusion plasmas, generated in the fusion of deuterium and tritium. Neutron diagnostics can provide information about the rate and also temperature of the fusion plasma. Primary reference for neutron detection is Harvey and Hill's 1979 article Scintillation detectors for neutron physics research

Scintillator Type

Scintillator References

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