At GSI, the Helmholtz Centre for Ion Research, the properties of scintillation screens, irradiated by an ion beam, were studied. For various materials, the different ion beams H+, C2+, Ar10+, Ni9+, Ta24+, and U28+ in the energy range from 4.8-11.4 MeV/u were applied with currents ranging from nA to some mA, delivered by the heavy ion LINAC at GSI. Scintillation screens are widely used for qualitative ion beam profile monitoring. However, precise measurements of the beam profile yield ambivalent results, especially for high beam currents. Thus, the properties (light yield, beam width, and higher statistical moments) of well-known scintillators, ceramic materials, and different quartz glasses are compared. The image of each ion beam pulse was recorded by a digital CCD camera and individually evaluated. A change of the imaged ion beam shape was observed for some materials. The recorded beam profile shows dependence on the scintillator material. Even for low beam intensities (17 nA) a difference in the beam width of about 25% was measured. Additionally, the light yield and beam width depend significantly on the screen temperature, which is increased by the ion impact. For ZrO2 : Al the influence of the screen temperature on the statistical moments was investigated. Furthermore the spectra of scintillation screens were studied in the region from 350 to 750 nm for the irradiation with H+ and Ta24+ ions. Empirical results are discussed and give rise to further investigations on the materials.

Scintillation Screen Investigations for High-Current Ion Beams

This report sums up in two volumes the first 50 years of operation of the CERN Proton Synchrotron. After an introduction on the genesis of the machine, and a description of its magnet and powering systems, the first volume focuses on some of the many innovations in accelerator physics and instrumentation that it has pioneered, such as transition crossing, RF gymnastics, extractions, phase space tomography, or transverse emittance measurement by wire scanners. The second volume describes the other machines in the PS complex: the proton linear accelerators, the PS Booster, the LEP pre-injector, the heavy-ion linac and accumulator, and the antiproton rings.

/pdf/fifty-years-of-the-cern-proton-synchrotron-volume-2-3de7u29zph.pdf

Fifty years of the CERN Proton Synchrotron : Volume 2

We recorded the in vivo emission and time-resolved spectra of the firefly Luciola praeusta Kiesenwetter 1874 (Coleoptera: Lampyridae: Luciolinae). The emission spectrum shows that the full width at half maximum (FWHM) value for this particular species is 55 nm, which is significantly narrower than the in vivo half-widths reported till now. The time-resolved spectrum reveals that a flash of about 100 ms duration is, in fact, composed of a number of microsecond pulses. This suggests that the speed of the enzyme-catalysed chemiluminescence reaction in the firefly for the emission of light is much faster than was previously believed.

/pdf/bioluminescence-emissions-of-the-firefly-luciola-praeusta-2g8fkvsgsi.pdf

Bioluminescence emissions of the firefly Luciola praeusta Kiesenwetter 1874 (Coleoptera: Lampyridae: Luciolinae)

An out-of-yoke irradiation setup using the proton beam from a cyclotron that ordinary produces radioisotopes for positron emission tomography (PET) has been developed, characterized, calibrated and validated. The current from a 20 μm thick aluminum transmission foil is readout by home-made transimpedance electronics, providing online dose information. The main monitoring variables, delivered in real-time, include beam current, integrated charge and dose rate. Hence the dose and integrated current delivered at a given instant to an experimental setup can be computer-controlled with a shutter. In this work, we report on experimental results and Geant4 simulations of a setup which exploits for the first time the 18 MeV proton beam from a PET cyclotron to irradiate a selected region of a target using the developed irradiation system. By using this system, we are able to deliver a homogeneous beam on targets with 18 mm diameter, allowing to achieve the controlled irradiation of cell cultures located in biological multi-well dishes of 16 mm diameter. We found that the magnetic field applied inside the cyclotron plays a major role for achieving the referred to homogeneity. The quasi-Gaussian curve obtained by scanning the magnet current and measuring the corresponding dose rate must be measured before any irradiation procedure, with the shutter closed. At the optimum magnet current, which corresponds to the center of the Gaussian, a homogenous dose is observed over the whole target area. Making use of a rotating disk with a slit of 0.5 mm at a radius of 150 mm, we could measure dose rates on target ranging from 500 mGy/s down to 5 mGy/s. For validating the developed irradiation setup, several Gafchromic® EBT2 films were exposed to different values of dose. The absolute dose in the irradiated films were assessed in the 2D film dosimetry system of the Department of Radiotherapy of Coimbra University Hospital Center with a precision better than 2%. In the future, we plan to irradiate small animals, cell cultures, or other materials or samples.

/pdf/development-of-a-pet-cyclotron-based-irradiation-setup-for-23vbyi375x.pdf

Development of a PET cyclotron based irradiation setup for proton radiobiology

Beam diagnostics and instrumentation are an essential part of any kind of accelerator. There is a large variety of parameters to be measured for observation of particle beams with the precision required to tune, operate, and improve the machine. In the first part, the basic mechanisms of information transfer from the beam particles to the detector are described in order to derive suitable performance characteristics for the beam properties. However, depending on the type of accelerator, for the same parameter, the working principle of a monitor may strongly differ, and related to it also the requirements for accuracy. Therefore, in the second part, selected types of accelerators are described in order to illustrate specific diagnostics needs which must be taken into account before designing a related instrument.

Beam Diagnostic Requirements: an Overview

It has been observed on different machines that scintillating ceramic screens (like chromium doped alumina) are quickly damaged by low energy ion beams. These particles are completely stopped on the surface of the screens, inducing both a high local temperature increase and the electrical charging of the material. A study has been initiated to understand the limiting factors and the damage mechanisms. Several materials, ZrO2, BN and Al2O3, have been tested at CERN on LINAC3 with 4.2MeV/u lead ions. Alumina (Al2O3) is used as the reference material as it is extensively used in beam imaging systems. Boron nitride (BN) has better thermal properties than Alumina and Zirconium oxide (ZrO2). BN has in fact the advantage of increasing its electrical conductivity when heated. This contribution presents the results of the beam tests, including the post-mortem analysis of the screens and the outlook for further measurements. The strategy for the choice of the screens for the Low Energy Ion Ring (LEIR), currently under construction at CERN, is also explained.

/pdf/scintillating-screens-study-for-leir-lhc-heavy-ion-beams-4dngx6t106.pdf

Scintillating screens study for leir/lhc heavy ion beams

The 7 TeV proton beam from the LHC ring is ejected through a long transfer line to beam dump blocks, approximately 100m downstream of the ejection septa, a series of dilution kicker magnets provide a sweeping deflection spreading the extracted beam over a 40 cm diameter area on the face of the beam dump cores. During normal operation, the quality of each dump event must be recorded and verified. The so-called “Post-Mortem” dataset will include information from the beam dumping system (logic signals, kicker pulses…) as well as from the beam diagnostics along the extraction lines. For this purpose, profile monitors in front of the dump blocks must be permanently available during machine operation. With more than 10 14 protons stored in LHC, the energy deposited in the screen becomes an issue and thermalresistant materials have to be considered. In this paper, the design of this quite unusual device is presented. The different technical options considered for the choice of the screen material are discussed first. The complete layout of the installation is then described with a special emphasis on the mechanical design, the screen assembly and the choice of the radiation-hard camera used to observe the screen.

/pdf/a-large-scintillating-screen-for-the-lhc-dump-line-4mf85eqyom.pdf

A large scintillating screen for the lhc dump line

The high charge (>6μC) electron beam produced in the CLIC Test Facility 3 (CTF3) is accelerated in fully beam loaded cavities. To be able to measure the resulting strong transient effects, the time evolution of the beam energy and its energy spread must be determined with at least 50MHz bandwidth. Three spectrometer lines are installed along the linac in order to control and tune the beam. The electrons are deflected by dipole magnets onto Optical Transition Radiation (OTR) screens which are observed by CCD cameras. The measured horizontal beam size is then directly related to the energy spread. In order to provide time-resolved energy spectra, a fraction of the OTR photons is sent onto a multi-channel photomultiplier. The overall setup is described, special focus is given to the design of the OTR screen with its synchrotron radiation shielding. The performance of the time-resolved measurements are discussed in detail. Finally, the limitations of the system, mainly due to radiation problems are discussed.

/pdf/time-resolved-spectrometry-on-the-clic-test-facility-3-3fpnbgqsjy.pdf

Time Resolved Spectrometry on the CLIC Test Facility 3

The Low Energy Ion Ring (LEIR) is central to the “Ions for LHC” project. Its role is to transform a serie of long low intensity ion pulses from Linac 3, into short high density pulses, which will be further accelerated in the PS and SPS rings, before injection into LHC. To do so the injected pulses are stacked and phase space cooled using electron cooling, before acceleration to the ejection energy of 72 MEV/u. This note describes different types of instruments which will be installed in the LEIR ring and transfer lines.

/pdf/leir-beam-instrumentation-738hfwdiua.pdf

Leir beam instrumentation

The electron gun of the CLIC Test Facility 3 (CTF3) produces 15.6‐μs‐long pulses with an energy of 140 keV and a current that can be as high as 9 A. For the nominal beam operation, a 5.4‐A beam current is generated and sent downstream into the bunching system and the rest of the accelerator. The corresponding beam charge will induce a thermal load that most of the materials, considered as radiators, would not withstand. With this problem in mind, we have built a beam imaging system, installed just after the gun and equipped with two screens. The first one is a phosphorescent screen which yields a high signal and can be for low beam currents. The second screen, a thin graphite foil, is used as a forward OTR radiator and can stand the full beam intensity. Moreover, the time resolution of OTR is very good, in the femtosecond range. This allows for observation of the evolution in time of the beam size during the pulse by using a gated camera. We present in this paper the first results obtained using this system.

/pdf/ctf3-injector-profile-monitor-54kbvs9emg.pdf

CTF3 Injector Profile Monitor

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