Low Energy Beam Transfer Research Articles

Quasi-Alvarez drift-tube linac structures for heavy ion therapy accelerator facilities

Next generation heavy ion therapy and research facilities require efficient accelerating structures. Particularly, at low beam energies, right after the standard scheme of the ion source, low-energy beam transfer, and radio-frequency quadrupole (RFQ), several options for accelerating structures are available including the classic drift-tube linac (DTL), the interdigital H-mode DTL (IH-DTL), and superconducting quarter-wave resonators. These structures need to integrate the beam acceleration with the focusing channel, nowadays typically provided by permanent-magnet quadrupoles (PMQs). The frequency of operation needs to be in line with that of the RFQ structure, and it has been chosen at 750 MHz for practical considerations for the Next Ion Medical Machine Study (NIMMS) that is the application focus of this manuscript. While classic DTL structures at low ion beam energies do not provide enough space for PMQs at that frequency within a single $\ensuremath{\beta}\ensuremath{\lambda}$ period, IH-DTL structures do not provide the regular focusing channel with consequences on the beam quality. For these reasons, quasi-Alvarez drift-tube linac (QA-DTL) structures are reevaluated in this manuscript as they might fill this gap. They have not received much attention in the literature so far and therefore their design is described in detail. The design procedure presented here may serve as a blueprint for DTL design in general. In addition to the overall rf design, axial field stabilization with a new technique and multiphysics studies of the rf structure are described. A cost estimation completes the NIMMS QA-DTL study.

First injector commissioning results with helium beam at MedAustron Ion Therapy Center

MedAustron is a synchrotron-based Particle Therapy Accelerator located in lower Austria which delivers clinical proton and carbon beams in the range of 62-252.7 MeV/u and 120-400 MeV/u respectively in two clinical treatment rooms. A proton Gantry was recently commissioned in a third clinical treatment room and a fourth experimental beamline is dedicated to non-clinical research activities. Within the latter, the injector commissioning has recently started for He2+ beam generation. The long-term goal is to use helium for cancer treatment due to its favourable physical and biological properties. The helium beam properties from the source up to injection further downstream into the accelerator, i.e. from the Low Energy Beam Transfer line to the Linear Accelerator are discussed in terms of beam emittance, intensity and transmission efficiency. Furthermore, a comparison with simulated data is presented.

Testing residual gas profiler at SARAF

A Residual Gas Monitor (RGM) developed at GANIL was tested with pulsed and CW proton beams at currents up to 1 mA at SARAF Phase I. Response of the detector as a function of beam current and duty cycle was measured. Beam profiles were measured at different beam size and position values and compared with measurements performed with a multi-wire grid profiler. Influence of the low-energy beam transfer (LEBT) optical settings on intense CW beams was studied for the first time. The obtained data enabled a better analysis and understanding of the current ramp-up process.

Development of ion injection into the BNL test electron beam ion source using a prototype low energy beam transfer switchyard and a hollow cathode ion source (abstract)

In order to provide a variety of ion species to the BNL relativistic heavy ion collider (RHIC) and NASA Space Radiation Laboratory facilities on a pulse-to-pulse basis, the BNL RHIC electron beam ion source (EBIS) will use injection of primary “seed” ions from external low charged ion sources. As part of the prototype for the RHIC EBIS low energy beam transport line, a switchyard for seed ion injection and extracted EBIS ion beams has been constructed. The ion injection line includes a hollow cathode ion source (HCIS), four quadrupole lenses, a switchyard, gridded lenses, and other deflection optics. The HCIS is based on one obtained from CEA Saclay [B. Visentin et al., Phys. Scr., T 71, 204 (1997).] and has been used in bench studies in the production of low charged metal and gas ions, as well as in BNL test EBIS injection studies for the production of highly charged ions. The HCIS geometry and extraction optics have been modified to be able to reach the output currents necessary to seed the test EBIS. Ion currents greater than 60μA Cu+ and 130μA Ne+ have been extracted from the modified HCIS at 12–15kV and plasma aperture of 1–1.5mm. The HCIS discharge is initiated by a rf coil and can be operated stably at pulse rates from 1to100Hz. Measurement of the emittance of injector beam before and after the injection switchyard will be provided, as well as results from ion injection into the test EBIS using the new injector configuration.

Status Report on the Centro Nazionale di Adroterapia Oncologica (CNAO)

The Centro Nazionale di Adroterapia Oncologica (National Center for Oncological Hadrontherapy, CNAO) will be the first Italian center for deep hadrontherapy. It is presently under construction in Pavia. It will be based on an evolution of the PIMMS synchrotron capable to accelerate carbon ions up to 400 MeV/u kinetic energy and protons up to 250 MeV, energies which are necessary to treat deep seated tumors. Four treatment lines, in three treatment rooms, and a dedicated facility for clinical and radiobiological researches are foreseen in a first stage. Space for two additional rooms eventually equipped with gantries has been left aside the center and the synchrotron has been designed to work with these two additional lines, but they are intended as a future upgrade. The beam is injected into the synchrotron from the inside, to allow positioning all the injection chain inside the synchrotron ring itself, and also to better exploit the two nondispersive regions in the synchrotron. The injection chain is made by a 8 keV/u Low Energy Beam Transfer line (LEBT), a RFQ accelerating the beam to 400 keV/u, a LINAC to reach the injection energy of 7 MeV/u and a Medium Energy Beam Transfer line (MEBT) to transport the beam to the synchrotron. This report describes the design and the performances of the CNAO, and reports about the status of the construction of the center

Magnets for the Heavy-Ion Cancer Therapy Accelerator Facility (HICAT) for the Clinic in Heidelberg

The Heavy Ion Cancer Therapy Accelerator facility (HICAT) for the university hospital in Heidelberg is now under construction and will be completed in 2006. The facility consists of 2 ion sources, low-energy beam transfer lines, a linear accelerator, a medium energy beam transfer line, a synchrotron, high-energy beam transfer lines, and 3 treatment locations. One of the treatment locations will be equipped with a gantry. All magnets were designed at GSI. The design of the magnets will be reviewed. Wherever possible, a conservative design approach was used. Special design efforts were necessary for the huge 90/spl deg/ gantry dipole and the tiny internal quadrupoles for the IH-type drift tube linac, so that prototypes of these magnets were built and tested. The design, construction, and measurements of the quadrupoles for the IH-type drift tube linac will also be discussed in detail.

A version of the Trasco Intense Proton Source optimized for accelerator driven system purposes

A full set of measurements of the magnetic field has been carried out to define a different design of the TRASCO Intense Proton Source (TRIPS) magnetic system, based on permanent magnets, in order to increase the reliability of the source. The two coils of the source generate a maximum field of 150 mT and the optimum field was determined around 95 mT. The OPERA-3D package was used to simulate the magnetic field and a new magnetic system was designed as a combination of three rings of NdFeB magnets and soft iron. The high voltage insulation has been completely modified, in order to avoid any electronics at 80 kV voltage. The description of the magnetic measurements and the comparison with the simulations are presented, along with the mechanical design of the new version permanent magnet TRIPS (PM-TRIPS) and the new design of the extraction system. Finally the modification of the low energy beam transfer line (LEBT), which now includes a 30° bending magnet, will be outlined, with special regard to the accelerator availability improvement which can be obtained with the installation of two PM-TRIPS sources or more on the LEBT.