Vasilis Tzoganis

A non-invasive beam profile monitor for charged particle beams

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 beams power, medical machines where treatment time is valuable and cannot be allocated to diagnostics and also low energy, low intensity accelerators where the beams 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.

Laser diode self-mixing interferometry for velocity measurements

Abstract. A diode laser velocimeter based on laser self-mixing has been developed and characterized as a reliable, precise, comparably cheap, and compact monitor. The resolution of this sensor at different incident angles and for a variety of solid and liquid targets moving at velocities between 0.1 and 50  m/s is presented. This includes a theoretical analysis of the underlying measurement principle, highlighting possibilities to extend the measurement capabilities to even higher velocities by altering the sensor design. Finally, an outlook on future applications of the sensor for detailed studies of supersonic gas jets used in beam diagnostics and atomic physics applications is given.

Self-mixing diode laser interferometry for velocity measurements of different targets

Supersonic gas jets can be used as a profile monitor for charged particle beams, as well as a cold target for collision experiments. For the optimisation of these experiments, it is important to know the velocity and density distribution of the jet. In these applications, gas jet velocities can be up to 2000 m/s. A diode laser velocimeter based on laser self-mixing method is currently being developed as an easy to build and compact alternative measurement technique. The technique seems a promising way for a complete characterisation of the gas jet parameters. It should be pointed out, however, that laser self-mixing is usually used for measurement of low velocities and vibrations. In this contribution, the heterodyne principle and design of the laser diode velocimeter are first discussed. The laser velocimeter is a self-aligning device, based on the self-mixing method where the laser is both, transmitter and receiver of the signal. The here presented theoretical analysis shows the possibility to extend measurement capabilities also to high velocities by altering the design. Experimental results from measurements with different targets are presented. The set-up for testing the sensor allows investigations into the limitation of the method to be made as well as the amount of feedback which is required for a detailed study of a gas jet.

Physical Society of Japan : Beam diagnostics for low energy antiprotons

This paper presents a comprehensive set of beam diagnostics that has been developed to characterize low energy antiproton and ion beams (during initial machine commissioning) and subsequent facility operation. It shows results from simulations and experiments using invasive and non-invasive monitors for absolute beam current measurements; capacitive pickups for position detection; scintillating screens, secondary emission monitors and micro channel plate detectors for transverse profile monitoring, as well as an ultra-cold gas jet for minimally-invasive profile measurements and in-ring experiments. The identified limits are discussed for each technique, and options for further improvements are indicated.