2,365 research outputs found
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 -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 -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 -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 , all calculations are based on real
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
Thiadizoloquinoxaline-Based Low-Bandgap Conjugated Polymers as Ambipolar Semiconductors for Organic Field Effect Transistors
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
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