A beam profile monitor for heavy ion beams at high impact energies

A beam profile monitor for heavy ion beams has been developed for the use in experiments at the Heavy Ion Synchrotron SIS at Gesellschaft für Schwerionenforschung Darmstadt (GSI). Four thin scintillation fibres are mounted on one wheel and scan the ion beam sequentially in two linearly independent directions. They are read out via one single photomultiplier common to all four fibres into one time spectrum, which provides all information about beam position, beam extension, time structure and lateral homogeneity of the beam. The system operates in a wide dynamic range of beam intensities.     

Energy modulations of a polarized proton beam associated with polarization reversal

The energy change associated with polarization reversal was studied for protons from an atomic beam polarized ion source after acceleration by a tandem accelerator. The modulation was found to be ≦0.5 eV.     

Intrabeam scattering at high energies

The growth of a beam of charged particles due to intrabeam scattering is studied in the high energy limit. The variation of the β-functions and the dispersion around the accelerator are included. In the high γ limit, analytical results are found for the horizontal, vertical and longitudinal growth rates. For a lattice consisting only of regular cells, with no insertions, a time invariant is found and the longitudinal and transverse growth rates are simply related. The dependence of the final state of the beam on the final energy is also studied.     

A proton and neutron beam polarimeter at SATURNE II

A beam polarimeter using CH₂ and carbon targets has been used to measure proton and neutron beam polarization in the energy range 0.4–2.8 GeV in one of the beam lines at the SATURNE II accelerator. The analyzing power for np-scattering is calibrated against the known analyzing power for pp-scattering by using the polarized deuteron beam to measure simultaneously the asymmetries for scattering of quasifree protons and neutrons in the deuterons. A low level of systematic errors is achieved by pulse to pulse polarization reversal at the ion source of the accelerator, and by measuring left and right scattering simultaneously. The detailed operation procedure and the beam polarizations measured during all experiments from 1981 to 1984 are presented.     

Microdosimetric investigation at the therapeutic proton beam facility of CATANA

Proton beams (62 Mev) are used by the Laboratori Nazionali del Sud of the Italian Institute of Nuclear Physics to treat eye melanoma tumours at the therapeutic facility called CATANA. A cylindrical slim tissue-equivalent proportional counter (TEPC) of 2.7 mm external diameter has been used to compare the radiation quality of two spread-out Bragg peaks (SOBP) at the CATANA proton beam.     

Wide-angle, nonmechanical beam steering with high throughput utilizing polarization gratings

We introduce and demonstrate a ternary nonmechanical beam steering device based on polarization gratings (PGs). Our beam steering device employs multiple stages consisting of combinations of PGs and wave plates, which allows for a unique three-way (ternary) steering design. Ultrahigh efficiency (～100%) and polarization sensitive diffraction of individual PGs allow wide steering angles (among three diffracted orders) with extremely high throughput. We report our successful demonstration of the three-stage beam steerer having a 44° field of regard with 1.7° resolution at 1550 nm wavelength. A substantially high throughput of 78%-83% is observed that is mainly limited by electrode absorption and Fresnel losses.     

Performance of a lead glass spectrometer at high energies

The performance of a photon detector consisting of two lead glass arrays and three planes of proportional tubes is reported. The detector was designed to measure the energies and positions of photons in the energy range 3–50 GeV. An energy resolution of $\text{1.0\% +}\text{5.0\%}\text{√E}$ (standard deviation) and a spatial resolution approaching 3 mm (standard deviation) were achieved during calibration with a low intensity positron beam. The energy resolution was degraded during use with a high intensity hadron beam whereas the spatial resolution was only slightly affected.     

Radiation protection at high energy proton accelerators

The radiological problems associated with proton accelerators having maximum energies higher than a few GeV are discussed. Examples are given from accelerators where the authors have had practical experience for a number of years. The main focus will be on those problems which are unique to high energy proton accelerators, and which may not be necessarily associated with the proton beam operation itself.     

Absolute calibration of accelerator beam energies by the crossover technique

An absolute method for the determination of the energy of a charged particle beam is described. The method is based on 0423 0450 V 2 scattering kinematics and exploits the variation with angle of the energy of particles scattered by elastic and inelastic processes 0423 0450 V 3 from different target nuclei. A determination of the angle at which particles scattered by two different reactions have the same 0423 0450 V 3 energy allows a precise calculation of the energy of the incident ion beam if the relativistic corrections are taken into account. A 0423 0450 V 3 simple system capable of supplying an absolute and accurate information on the beam energy in a short time has been designed and 0423 0450 V 3 tested. The system allows beam energy determinations over a wide energy range, from a few MeV up to several tens MeV and is not limited to some energy values in particular, in contrast with the use of resonance or threshold reactions. The system can in particular be employed for the calibration of accelerator beam energies in the energy interval typical of medium-energy commercial 0423 0450 V 3 cyclotrons, an increasing number of which are in operation in industry and in many fields of applied research. The paper briefly illustrates the theory underlying the “crossover” technique, describes the experimental apparatus and procedure and reports on experimental results for 12–36 MeV protons. The correction factors to be considered to fully exploit the accuracy of the technique 0423 0450 V 3 are discussed. The application of the method to the energy calibration of beams of deuterons and helium ions is described. A secondary and faster calibration procedure is also reported. This is derived from the main technique and can be routinely used once a number of energies have been determined and a sufficient data base of energy values has been built up. It is demonstrated that this secondary method is almost as accurate as the main technique.     

Measurement of the antiproton/proton ratio at TeV energies with the ARGO-YBJ detector

Cosmic ray antiprotons provide an important probe for the study of cosmic-ray propagation in the interstellar space and to investigate the existence of Galactic dark matter. Cosmic rays are hampered by the Moon, therefore a deficit of cosmic rays in its direction is expected (the so-called Moon shadow). The Earth–Moon system acts as a magnetic spectrometer. In fact, due to the geomagnetic field the center of the Moon shifts westward by an amount depending on the primary cosmic ray energy. Paths of primary antiprotons are therefore deflected in an opposite sense in their way to the Earth. This effect allows, in principle, the search of antiparticles in the opposite direction of the observed Moon shadow.The ARGO-YBJ experiment, in stable data taking since November 2007 with an energy threshold of a few 100s of GeV, is observing the Moon shadow with high statistical significance. Using about 1 year data, an upper limit of the flux ratio in the few-TeV energy region is set to a few percent with a confidence level of 90%.     

Acceleration of the polarized proton beam at the KEK 12 GeV ps

Acceleration of the polarized proton beam at the KEK PS up to 3.5 GeV is described. In the booster synchrotron, 75% of the linac beam polarization was preserved without any correction for the depolarizing resonances. In the main ring, almost 100% of the booster beam polarization was preserved at 3.5 GeV by the fast passage method for the intrinsic resonances and by the closed orbit correction for the imperfection resonances. The KEK PS is the first cascaded synchrotron which has demonstrated acceleration of a polarized beam.     

Proton target polarization measured with a polarized neutron beam at 477 MeV

The polarization of a proton target is determined with elastic neutron-proton scattering at 477 MeV. The results agree well with the nuclear magnetic resonance measurements at the error level of 4%.     

Note on polarization of electron beam

Based on the classical theory of electrodynamics, we show the feasibility of using superconductors to realize transversal and longitudinal polarizations of electron beams. The results can in principle be used with beams of positron and/or other particles with magnetic moments without major modifications. We briefly discuss applications of polarized electron beams in physical sciences and technology.     

Spectral polarization measurements by use of the grating division-of-amplitude photopolarimeter

The grating division-of-amplitude photopolarimeter (G-DOAP) is an instrument that exploits the multiple-beam-splitting, polarizing, and dispersive properties of diffraction gratings for the time-resolved measurement of the complete state of polarization of collimated broadband incident light, as represented by the four Stokes parameters as a function of wavelength across the spectrum. It is a compact, high-speed sensor that has no moving parts and is simple to install and operate. These characteristics make the G-DOAP well suited for in situ spectroscopic ellipsometry (SE) applications for monitoring and controlling thin-film processes. The design and performance of a prototype instrument are presented. Precise SE measurements, to +/-0.04 degrees in psi and +/-0.1 degrees in delta, are demonstrated in the 550-940-nm wavelength range.     

Pendulum sensor for location of vertical by using polarization measurements

We consider a fast contactless sensor for information about the position of a pendulum relative to a platform; the sensor is based on the use of polarization modulation of a light beam. We investigate problems on reducing the moment of force due to friction in the axial system of the pendulum. Translated from Izmeritel’naya Tekhnika, No. 1, pp. 18–21, January, 1998.     

Final-state angular momentum distributions in charge transfer collisions at high energies

We investigate the influence of different terms of the Born series on the final-state angular momentum (l) distribution and the anisotropy of the captured electron. A variety of different l distributions depending on the projectile velocity v and the charge asymmetry Z_p/Z_T of the collision system can be found, revealing different underlying mechanisms for charge transfer. We compare the predictions of perturbation theories such as the first and second Born approximation, the continuum distorted wave (CDW) approximation and the post-collision interaction (PCI) model valid at high velocities with those of the “quasi-resonant over barrier” model of charge transfer valid at intermediate velocities.