Most methods for measuring the properties of a relativistic charged particle beam are generally destructive to the beam. That is, the methods require inserting an object, such as a element, phosphor screen, or wire, which intercepts the beam. Intercepting the beam also disturbs the beam and complicates tuning accelerator systems used to accelerate and transport the beam. Older measurement methods also suffer from being cumbersome, requiring multiple sensing stations that prevent real-time measurements, and being unable to measure all parameters of interest with a single device. The cumbersome nature of older methods is a result of the need to insert screens and beam collimators. The need for multiple sensing stations is illustrated by wire scanners and wire scanners combined with focusing magnets.
More recent diagnostics based upon transition radiation overcome many of the limitations and problems of the older methods based on diffraction radiation. However, a transition radiation diagnostic requires an intercepting element and, hence, is also a concurrently disruptive measurement process. Prior art noninterceptive beam diagnostics, such as wall current monitors, do exist. However, these prior art diagnostics require placement at multiple stations along the transport line of the beam accelerator. The prior art diagnostics also require elaborate mathematical analysis to produce any parameters other than the simplest beam parameters (for example, to produce the centroid position of the beam). In addition, the prior art noninterceptive beam diagnostics are highly susceptible to electrical noise within the transport line of the accelerator beam.
Other nondestructive monitors require complex, cumbersome waveguide structures designed for a machine-specific beam parameter range and long time scales to produce their results. Included among such other monitors are monitors of centroid position and bunch length, such as cavities coupled to the beam's field. Furthermore such other nondestructive monitors cannot measure other important beam properties such as the beam divergence, spatial distribution, energy, and emittance.
Only one highly specific use of diffraction radiation has been demonstrated and reported in the literature. That use was as a bunch length measurement device, and is reported in Y. Shibata, et. al., Phys. Rev. E 52, 6787 (1995). However, this device suffers from a number of serious difficulties. Because of the geometry of its design, the bunch length measurement device of Shibata is destructive to the particle beam. This fact restricts the observations and measurements of Shibata's bunch length measurement device to forward-directed (zero degrees) and backward-directed (180 degrees) diffraction radiation.
This geometry necessitates the use of mirrors. The mirrors intercept the beam in the course of the measurement and produce transition radiation as a result. The transition radiation produced with the diffraction radiation from the aperture severely complicates both the measurement and the analysis of the diffraction radiation. The analysis of the diffraction radiation is used to diagnose the bean's bunch shape.
The bunch length measurement device is restricted to bunch length measurements in the far infrared region of the spectrum and, hence, is limited in its applicability. Furthermore, the bunch length measurement device does not diagnose the beam divergence, beam position, spatial distribution, energy, or emittance, and is not capable of real time monitoring. The charged particle beam diagnostic device of the present invention overcomes the limitations and complications of the prior art.