RF impedance measurements on the DARHT-II accelerator intercell assembly
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RF impedance measurements on the DARHT-II accelerator intercell assembly

  • Author(s): Fawley, William M.
  • Eylon, Shmuel
  • Briggs, Richard
  • et al.
Abstract

We report upon recent experimental measurements made of RF properties of the intercell assembly of the second axis accelerator[1] of Dual Axis Radiographic Hydrodynamic Test (DARHT) facility at LANL. The intercells provide both pumping and diagnostic access to the main DARHT-II beamline. Their design includes a pumping plenum separated from the main beam pipe by return current rods together with RF shielding provided by a copper-coated stainless steel mesh. Measurements using the twin lead technique (see Ref. [2]) at low frequencies (f < 200 MHz) suggest a constant value for the ratio h of the radial and azimuthal magnetic field components to which the transverse impedance is linearly related. We find that these results compare favorably to predictions from a simple analytic, lumped circuit model which includes the effects of the mesh and return current rods. We also present RF loop-to-loop frequency scans above beam pipe cutoff (~;600 MHz) showing the existence of many RF modes with relatively high Q's.

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