A compact residual gas ionization profile monitor (RGIPM) system

The Accelerator Production of Tritium (APT) and Spallation Neutron Source (SNS) accelerators will produce high power density beams, which cannot be observed using conventional intercepting beam profile devices. The beam produces electrons when it ionizes the residual gas in the beam tube. These electrons, when accelerated by a uniform electric field and guided by uniform parallel magnetic field, produce a projected image of the beam on a detector perpendicular to the fields. A particle tracking program shows that this can be done with a resolution better than the needed 100 /spl mu/m There are typically no dipoles available in these accelerators to produce the needed magnetic field. Triple dipole systems are being designed which will give no net trajectory change to the beam, but will produce the needed field for the diagnostic. Although the field is not completely uniform in the electron collection region, particle tracking calculations show that the resolution is not seriously degraded relative to a uniform field. Several ways of viewing the beam profile are considered. Radiation resistant and hardened materials needed for this are discussed.