Magnetic Field Vector Measurements Using Doppler-Free Saturation Spectroscopy

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Oak Ridge, Tennessee
Project Term:
05/01/2020 - 10/31/2021

Technology Description:

Knowing the magnetic field inside a fusion device is essential for understanding and validating performance, but measuring the magnetic field without perturbing it is exceedingly challenging. This Capability Team will build a non-perturbative, portable diagnostic to measure the topology of the equilibrium magnetic field vector in potentially transformative, magnetically confined fusion devices. The technique to be used, Doppler-free saturation spectroscopy (DFSS), is a pump/probe laser-based technique that has demonstrated magnetic field measurement accuracy of <10 G in laboratory experiments. The new DFSS diagnostic will be built and tested during this project, and will be ready to deploy to multiple fusion experiments around the country through public-private partnerships such as DOE’s Innovation Network for Fusion Energy program. Directly comparing the topology of experimental and theoretical magnetic-field equilibria will provide critical information required to optimize and accelerate the development of lower-cost fusion concepts.

Potential Impact:

Accelerating and lowering the costs of fusion development and eventual deployment will enable fusion energy to contribute to:


Fusion energy will ensure the U.S.’s technological lead and energy security.


Fusion energy will improve our chances of meeting growing global clean-energy demand and realizing cost-effective, net-zero carbon emissions, while minimizing pollution and avoiding long-lived radioactive waste.


As a disruptive technology, fusion energy will likely create new markets, opportunities, and export advantages for the U.S.


ARPA-E Program Director:
Dr. Scott Hsu
Project Contact:
Dr. Elijah Martin
Press and General Inquiries Email:
Project Contact Email:


University of Tennessee

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