Lorentz Scanning Electron/Ion Microscopy

We have developed an observation and measurement method for spatial electromagnetic fields by using scanning electron/ion microscopes, combined with electron holography reconstruction technique. A cross-grating was installed below the specimen, and the specimens were observed under the infocus condition, and the grating was simultaneously observed under the defocus condition. Electromagnetic fields around the specimen were estimated from grating-image distortions. This method is effective for low and middle magnification and resolution ranges; furthermore, this method can in principle be realizable in any electron/ion beam instruments because it is based on the Lorentz force model for charged particle beams. Mini Abstract We have developed a visualization technique for spatial electromagnetic fields by using scanning electron/ion microscopes, combined with electron holography reconstruction technique. A specimen and a cross-grating installed below the specimen were observed simultaneously. The distorted grating image caused by electromagnetic fields around the specimen were quantitatively measured and visualized.

Biological Rationale and Clinical Evidence of Carbon Ion Radiation Therapy for Adenoid Cystic Carcinoma: A Narrative Review

Adenoid cystic carcinoma (ACC) is a rare, basaloid, epithelial tumor, arising mostly from salivary glands. Radiation therapy can be employed as a single modality for unresectable tumors, in an adjuvant setting after uncomplete resection, in case of high-risk pathological features, or for recurrent tumors. Due to ACC intrinsic radioresistance, high linear energy transfer (LET) radiotherapy techniques have been evaluated for ACC irradiation: while fast neutron therapy has now been abandoned due to toxicity concerns, charged particle beams such as protons and carbon ions are at present the beams used for hadron therapy. Carbon ion radiation therapy (CIRT) is currently increasingly used for ACC irradiation. The aim of this review is to describe the immunological, molecular and clinicopathological bases that support ACC treatment with CIRT, as well as to expose the current clinical evidence that reveal the advantages of using CIRT for treating ACC.

A novel non-adiabatic approach to transition crossing in a circular hadron accelerator

Crossing the transition energy is always a delicate process, representing a potential source of strong perturbations of the dynamics of charged particle beams in a hadron circular accelerator. Since the first generation of multi-GeV rings, intense studies have been devoted to understanding the possible harmful mechanisms involved in transition crossing and to devise mitigation measures. Nowadays, several circular particle accelerators are successfully operating across the transition energy and this process is well mastered. In a completely different context, stable resonances of the traverse phase space have been proposed as new means of manipulating charged particle beams. While the original aim of such a proposal was multi-turn extraction from the CERN Proton Synchrotron to the Super Proton Synchrotron, many more applications have been proposed and studied in detail. In this paper, the two topics, i.e. transition crossing and stable resonances, have been brought together with the goal of providing a novel and non-adiabatic approach to perform a clean transition crossing. The idea presented here is that by judiciously using sextupoles and octupoles it is possible to generate stable islands of the horizontal phase space. These islands represent a second closed orbit whose properties can be selected independently of those of the standard, i.e. central, closed orbit. This provides a means of performing a non-adiabatic change of the transition energy experienced by the charged particles by displacing the beam between the two closed orbits.

Cyclotron trap

The cyclotron trap was developed at SIN/PSI to increase the stopping density of negatively charged particle beams for the formation of exotic atoms in low pressure gases. A weak focusing magnetic field, produced by superconducting solenoids, is used. Particles are injected radially through the fringe field to a moderator, which decelerates them into orbits bound by the field. Further deceleration by moderators and/or low-pressure gases leads the particles to the centre of the device, where they can be stopped or eventually extracted. Experiments became feasible with this technique, such as those dealing with pionic hydrogen/deuterium at SIN/PSI. Muonic hydrogen laser experiments also became possible with the extraction of muons from the cyclotron trap. The formation of antiprotonic hydrogen in low pressure targets led to successful experiments at LEAR/CERN.

ABOUT THE POSSIBILITY OF CREATING AN EFFICIENT ENERGY ANALYZER OF CHARGED PARTICLE BEAMS BASED ON AXIALLYSYMMETRIC OCTUPOLE-CYLINDRICAL FIELD

One of the problems in creating systems for energy analysis of charged particles beams is to determine the deflecting field and calculation the shape of the deflecting electrodes. This article is devoted to the study of the possibility of creating an effective energy analyzer of charged particle beams based on multipole electrode systems. A previously unstudied type of a multipole-cylindrical field - an electrostatic axially-symmetrical octupole-cylindrical field was chosen as the deflecting field. The field is formed by using the superposition of an electrostatic cylindrical field and a circular octupole of various contributions. The family of the equipotentials of cylindrical octupoles with planes of symmetry and antisymmetry is calculated. The calculation and analysis of equipotential portraits of the electrostatic axially-symmetric octupole-cylindrical fields with different weight contributions of the cylindrical field and circular octupole are carried out.

AFFECT OF ULTRASHORT ELECTRON BEAMS ON THE ESCHERICHEA COLI SURVIVAL

The paper represents the study of ultrashort electron beams impact on some Escherichia coliK-12strains with different radiosensitivity. The charged particle beams generated by ultrashort bunch accelerators differ by short duration of particle direct exposure, relatively long intervals between bunches and by high values of instantaneous dose rates. Because of these characteristics, the nature of ultrashort beams impact on biological objects may sufficiently differ from conventional sources of radiation. As a source of ultrashort beams linear electron accellerator AREAL of SichrotronResearcinstitut CANDLE (Yerevan, Armenia) was used. The dependence of E.coli cells survival from electron bunches repetition rate and irradiation media was investigated. It is shown that the dose dependence of the survival degree of microorganisms has a qualitatively different unusual concave shape. Such behavior of the survival curves does not depend on the ionic composition of the irradiation medium as well as on the time of preliminary incubation of microorganisms in this medium. To explain the observed phenomenon, it was assumed that the compensatory capacity of the irradiated object increases with an increase of the irradiation dose.The proposed mathematical model described well the behavior of the survival curves. It is assumed that this change of the compensatory capacity may be determined by oxygen.

Charged particle guiding and beam splitting with auto-ponderomotive potentials on a chip

Electron and ion beams are indispensable tools in numerous fields of science and technology, ranging from radiation therapy to microscopy and lithography. Advanced beam control facilitates new functionalities. Here, we report the guiding and splitting of charged particle beams using ponderomotive forces created by the motion of charged particles through electrostatic optics printed on planar substrates. Shape and strength of the potential can be locally tailored by the lithographically produced electrodes’ layout and the applied voltages, enabling the control of charged particle beams within precisely engineered effective potentials. We demonstrate guiding of electrons and ions for a large range of energies (from 20 to 5000 eV) and masses (from 5 · 10−4 to 131 atomic mass units) as well as electron beam splitting for energies up to the keV regime as a proof-of-concept for more complex beam manipulation.