Electron-beam diagnostic for space-charge measurement of an ion beam
An electron beam diagnostic system for measuring the charge distribution of an ion beam without changing its properties is presently under development for Heavy Ion Fusion (HIF) beam physics studies. Conventional diagnostics require temporary insertion of sensors into the beam, but these capture it, or significantly alter its properties. In this new diagnostic a low energy, low current electron beam is scanned transversely across the ion beam; the measured electron beam deflection is used to calculate the line-integrated charge density of the ion beam, assuming at present a circular charge distribution that is functionally dependent only on radius. The initial application of this diagnostic is being made to the Neutralized Transport Experiment (NTX), which is exploring the physics of space charge dominated beam focusing through neutralizing plasma onto a small spot. The diagnostic system is able to scan an ion beam of up to 3 cm radius. Design and performance of this diagnostic system is presented.