A non-invasive beam profile monitor for charged particle beams

Abstract

Non-interceptive beam profile monitors are highly desirable in almost all particle accelerators. Such techniques are especially valuable in applications where real time monitoring of the beam properties is required while beam preservation and minimal influence on the vacuum are of the greatest importance. This applies to many kinds of accelerators such as high energy machines where the normal diagnostics cannot withstand the beam's power, medical machines where treatment time is valuable and cannot be allocated to diagnostics and also low energy, low intensity accelerators where the beam's properties are difficult to measure. This paper presents the design of a gas-jet based beam profile monitor which was developed and commissioned at the Cockcroft Institute and can operate in a very large background pressure range from 10−7 down to below 10−11 millibars. The functioning principle of the monitor is described and the first experimental results obtained using a 5 keV electron beam are discussed.

Gas dynamics considerations in a non-invasive profile monitor for charged particle beams

“…12. Example of acquired profile and measurements [15], conversion factor equals to around 12 pixels/mm. and the optimization of the system so it can be more efficient in terms of pumping requirements.…”

Laser diode self-mixing interferometry for velocity measurements

“…Gas ions, created in the jet, are then extracted, allowing two-dimensional beam profile imaging. 10,11 The gas jet consists of a high density (10 9 to 10 12 particles∕cm 3 ) of neutral molecules, which could be molecular nitrogen, argon, or helium. The gas-jet curtain is expected to have a velocity range of 100 to 2000 m∕s, and the diameter of the jet itself is 1 to 20 mm.…”

Beam profile assessment in spectral CT scanners

“…A broad definition of the beam profile analysis encompasses all beam properties, such as spatial, temporal and spectral characteristics, power, and propagation. The characterization of a beam is specific to the type of beam, which could be monochromatic or polychromatic . For a laser beam, parameters such as alignment, focus spot size, and beam uniformity are typically analyzed to optimize laser performance .…”

“…For a laser beam, parameters such as alignment, focus spot size, and beam uniformity are typically analyzed to optimize laser performance . Characterizing the beamlines is also essential in particle accelerators for them to be operated with optimal output . The polychromaticity of the x‐ray beams used in the computed tomography (CT) scanners necessitates the accurate modeling of beam profile in these machines.…”