University of Liverpool
Design, Construction and Tests of a Full Set of Diagnostics for Future Low-energy Storage Rings
ESR: Janusz Harasimowicz (janusz.harasimowicz@quasar-group.org)
Supervisor: Carsten Welsch (c.p.welsch@liverpool.ac.uk)
To enable the efficient investigation of some very essential questions regarding the physics with low-energy antiprotons, a novel electrostatic cooler synchrotron, the ultra-low energy storage ring (USR) is being developed in the QUASAR group at the Cockcroft Institute in close collaboration with experts at the MPI for Nuclear Physics and the GSI Atomic Physics Division.
The aim of the USR will be to slow down antiprotons to very low energies between 300 and 20 keV. This will provide world-wide unique conditions for both in-ring studies with an intensity of up to 1012 cooled and stored antiprotons per second, as well as for experiments requiring extracted slow beams. The boundary conditions of the USR project put very high demands on the machine’s instrumentation: The extremely low vacuum pressure of the USR, together with a beam energy of only 20 keV and low currents of antiprotons between 1 nA and 1 μA require the development of new diagnostic methods as most of the standard techniques will no longer work.
In this project the beam diagnostics elements as they are required for a successful operation of this storage ring have been developed. Prototypes of a purpose-built Faraday Cup, a capacitive beam position monitor and a secondary emission monitor have been designed and built up. This was complemented by investigations into scintillating screen materials. Close collaboration with DITANET partners MPI for Nuclear Physics, CERN, Stockholm University and INFN-LNS took place throughout the project.
Development of a Modified Neutral Beam Scanner
ESR: Massimiliano Putignano (massimiliano.putignano@quasar-group.org)
Supervisor: Carsten Welsch (c.p.welsch@liverpool.ac.uk)
At the lowest beam energies and low intensities that will become available in future low-energy ion storage rings, existing beam profile monitors cannot provide
the necessary information. Therefore, new diagnostic techniques have to be developed. The aim of this project is to develop a modified neutral beam scanner, which relies on an ultra-thin extended (4 cm x 4 cm) gas-target “curtain” and on the three-dimensional detection of the ions created via charge exchange or ionization.
The image of these ions will provide complete information about the stored beam over a wide range of stored particle numbers, for all beam energies and for any particle species in the accelerator. The design of this monitor requires careful optimization of all its components, in particular detailed studies into the dynamics of the gas jet shaping and control. Within the project, the monitor has been designed, built up and is now being used for detailed studies with beam.
Beam Diagnostics for Medical Accelerators
ESR: Tomasz Cybulski (tomasz.cybulski@quasar-group.org)
Supervisor: Carsten Welsch (c.p.welsch@liverpool.ac.uk)
The Clatterbridge Centre for Oncology hosts one of the best-equipped radiotherapy centres in the UK. Facilities include nine linear accelerators, a cobalt unit, superficial and orthovoltage X-ray machines, two simulators, two scanners - a wide bore single slice Computer Tomography (CT) simulator and a multi-slice helical Computer Tomography (CT) simulator. In addition, the centre’s cyclotron facility remains as the only patient treatment cyclotron in the UK, providing a service with proton therapy for eye tumours. While the precise measurement of beam intensity and position is very important for many accelerators, it is crucial for medical accelerators.
Within this project, beam instrumentation for the precise measurement of the proton beam position and intensity is being developed. This includes Monte Carlo studies into the energy deposition of the proton beam in different target materials for the design of current and energy spread monitors, as well as the utilization of the LHCb VELO detector for the purpose of least-destructive beam monitoring. Ultimately, this work will lead to a detector phantom able to measure all important characteristic parameters of the therapeutic particle beam.