Cyclotrons with Fast Variable and/or Multiple Energy Extraction

We discuss the principle possibility of stripping extraction in combination with reverse bends in isochronous separate sector cyclotrons (and/or FFAGs). If one uses reverse bends between the sectors (instead of drifts) and places stripper foils at the sector exit edges, the stripped beam has a reduced bending radius and it should be able to leave the cyclotron within the range of the reverse bend - even if the beam is stripped at less than full energy. We are especially interested in $H_2^+$-cyclotrons, which allow to double the charge to mass ratio by stripping. However the principle could be applied to other ions or ionized molecules as well. For the production of proton beams by stripping extraction of an $H_2^+$-beam, we discuss possible designs for three types of machines: First a low-energy cyclotron for the simultaneous production of several beams at multiple energies - for instance 15 MeV, 30 MeV and 70 MeV - thus allowing to have beam on several isotope production targets. In this case it is desired to have a strong energy dependence of the direction of the extracted beam thus allowing to run multiple target stations simultaneously. Second we consider a fast variable energy proton machine for cancer therapy that should allow extraction (of the complete beam) at all energies in the range of about 70 MeV to about 250 MeV into the same beam line. And third, we consider a high intensity high energy machine, where the main design goals are extraction with low losses, low activation of components and high reliability. The price that has to be paid for these advantages is an increase in size and/or in field strength compared to proton machines with standard extraction at the final energy.Comment: 10 pages, 9 figure

Minkowski Spacetime and QED from Ontology of Time

Classical mechanics, relativity, electrodynamics and quantum mechanics are often depicted as separate realms of physics, each with its own formalism and notion. This remains unsatisfactory with respect to the unity of nature and to the necessary number of postulates. We uncover the intrinsic connection of these areas of physics and describe them using a common symplectic Hamiltonian formalism. Our approach is based on a proper distinction between variables and constants, i.e. on a basic but rigorous ontology of time. We link these concept with the obvious conditions for the possibility of measurements. The derived consequences put the measurement problem of quantum mechanics and the Copenhagen interpretation of the quantum mechanical wavefunction into perspective. According to our (onto-) logic we find that spacetime can not be fundamental. We argue that a geometric interpretation of symplectic dynamics emerges from the isomorphism between the corresponding Lie algebra and the representation of a Clifford algebra. Within this conceptional framework we derive the dimensionality of spacetime, the form of Lorentz transformations and of the Lorentz force and fundamental laws of physics as the Planck-Einstein relation, the Maxwell equations and finally the Dirac equation.Comment: 36 pages, 3 figures, several typos corrected, references with title

A New Look at Linear (Non-?) Symplectic Ion Beam Optics in Magnets

We take a new look at the details of symplectic motion in solenoid and bending magnets and rederive known (but not always well-known) facts. We start with a comparison of the general Lagrangian and Hamiltonian formalism of the harmonic oscillator and analyze the relation between the canonical momenta and the velocities (i.e. the first derivatives of the canonical coordinates). We show that the seemingly non-symplectic transfer maps at entrance and exit of solenoid magnets can be re-interpreted as transformations between the canonical and the mechanical momentum, which differ by the vector potential. In a second step we rederive the transfer matrix for charged particle motion in bending magnets from the Lorentz force equation in cartesic coordinates. We rediscover the geometrical and physical meaning of the local curvilinear coordinate system. We show that analog to the case of solenoids - also the transfer matrix of bending magnets can be interpreted as a symplectic product of 3 non-symplectic matrices, where the entrance and exit matrices are transformations between local cartesic and curvilinear coordinate systems. We show that these matrices are required to compare the second moment matrices of distributions obtained by numerical tracking in cartesic coordinates with those that are derived by the transfer a matrix method.Comment: 7 pages, 2 figure

The Simplest Form of the Lorentz Transformations

We report the simplest possible form to compute rotations around arbitrary axis and boosts in arbitrary directions for 4-vectors (space-time points, energy-momentum) and bi-vectors (electric and magnetic field vectors) by symplectic similarity transformations. The Lorentz transformations are based exclusively on real $4\times 4$-matrices and require neither complex numbers nor special implementations of abstract entities like quaternions or Clifford numbers. No raising or lowering of indices is necessary. It is explained how the Lorentz transformations can be derived from the most simple second order Hamiltonian of general significance. Since this approach exclusively uses the real Clifford algebra $Cl(3,1)$, all calculations are based on real $4\times 4$ matrix algebra.Comment: Substantial rewrite of first draft. 16 pages, 1 figur

Intensity limits of the PSI Injector II cyclotron

We investigate limits on the current of the PSI Injector II high intensity separate-sector isochronous cyclotron, in its present configuration and after a proposed upgrade. Accelerator Driven Subcritical Reactors, neutron and neutrino experiments, and medical isotope production all benefit from increases in current, even at the ~ 10% level: the PSI cyclotrons provide relevant experience. As space charge dominates at low beam energy, the injector is critical. Understanding space charge effects and halo formation through detailed numerical modelling gives clues on how to maximise the extracted current. Simulation of a space-charge dominated low energy high intensity (9.5 mA DC) machine, with a complex collimator set up in the central region shaping the bunch, is not trivial. We use the OPAL code, a tool for charged-particle optics calculations in large accelerator structures and beam lines, including 3D space charge. We have a precise model of the present production) Injector II, operating at 2.2 mA current. A simple model of the proposed future (upgraded) configuration of the cyclotron is also investigated. We estimate intensity limits based on the developed models, supported by fitted scaling laws and measurements. We have been able to perform more detailed analysis of the bunch parameters and halo development than any previous study. Optimisation techniques enable better matching of the simulation set-up with Injector II parameters and measurements. We show that in the production configuration the beam current scales to the power of three with the beam size. However, at higher intensities, 4th power scaling is a better fit, setting the limit of approximately 3 mA. Currents of over 5 mA, higher than have been achieved to date, can be produced if the collimation scheme is adjusted

Evolution of a beam dynamics model for the transport lines in a proton therapy facility

Despite the fact that the first-order beam dynamics models allow an approximated evaluation of the beam properties, their contribution is essential during the conceptual design of an accelerator or beamline. However, during the commissioning some of their limitations appear in the comparison against measurements. The extension of the linear model to higher order effects is, therefore, demanded. In this paper, the effects of particle-matter interaction have been included in the model of the transport lines in the proton therapy facility at the Paul Scherrer Institut (PSI) in Switzerland. To improve the performance of the facility, a more precise model was required and has been developed with the multi-particle open source beam dynamics code called OPAL (Object oriented Particle Accelerator Library). In OPAL, the Monte Carlo simulations of Coulomb scattering and energy loss are performed seamless with the particle tracking. Beside the linear optics, the influence of the passive elements (e.g. degrader, collimators, scattering foils and air gaps) on the beam emittance and energy spread can be analysed in the new model. This allows for a significantly improved precision in the prediction of beam transmission and beam properties. The accuracy of the OPAL model has been confirmed by numerous measurements.Comment: 17 pages, 19 figure