Detection System for Light Ion Desorption from a Bremsstrahlung Converter Target

The Dual Axis Radiographic Hydrodynamic Test (DARHT) Facility is used to produce X-ray shadow images of hydrodynamic experiments. Both DARHT axes, comprise linear electron accelerators and a target region, where the electron beam strikes a high Z target, producing Bremsstrahlung X-rays. The radiographic image resolution is affected in large part by the electron beam spot size at the Bremsstrahlung converter target. While tuning of the accelerator and the final focusing magnet can produce a small spot size (~1 mm), light ions desorbed from the target material negate a portion of the repulsive electron beam space charge, dynamically over focusing the beam. Measurement of the desorbed ions is highly desirable for both modeling of this process and testing of mitigation methods. Electro-optical sensors can be used to measure the radial electric field produced by the electron beam and light ions, with high resolution of both field magnitude (~5 μV/m) and time (~0.5 ns). With an array of these devices, ion velocity can be inferred, and the system can be used as a time-of-flight mass spectrometer. A prototype of this system consisting of a single measurement is being tested to insure it meets resolution requirements and can operate in high radiation environments.