Measuring magnetic fields stronger than 100 teslas using miniature b-dot probes on COBRA

Summary form only given. The MagLIF [1] concept relies on magnetic field compression to limit electron losses to the liner wall and reach fusion parameters. To measure magnetic field compression, B-dot probes could be used at the beginning of the implosions. However, this probe will fail as the magnetic field becomes large when the liner compresses. Our goal is to measure a 100T field created on two coaxial solenoids using the IMA 100ns rise time pulse power generator COBRA. The experimental setup is presented in another poster at this conference [2]. The miniature B-dot probes are fabricated using a 1mm in diameter coaxial cable. The center conductor is soldered to the outer jacket, forming a single turn loop of a quarter square millimeter area. An epoxy and kapton sleeve protects the central conductor from plasma generated in the load region of COBRA. The B-dot probe has a bandwidth greater than 1GHz. The magnetic field measurements were done at different locations on the plane of symmetry of the coil system to map the field topology between the two coils. Plasma shorting near the B-dot probe was avoided by connecting the two central conductors of the coils to the cathode of the machine, which is grounded. The magnetic field computed by an analytical code was compared to experimental measurements and excellent agreement was found.