Beamline Elements Research Articles

Beam-Based Beamline Element Alignment for the Main Linac of the 380 GeV Stage of CLIC

Beam-Based Beamline Element Alignment for the Main Linac of the 380 GeV Stage of CLIC

A study of muon collider background rejection criteria in silicon vertex and tracker detectors

The hit response of silicon vertex and tracking detectors to muon collider beam background and results of a study of hit reducing techniques are presented. The background caused by decays of the 750 GeV/c μ+ and μ− beams was simulated using the MARS15 program, which included the infrastructure of the beam line elements near the detector and the 10̂ nozzles that shield the detector from this background. The ILCRoot framework, along with the Geant4 program, was used to simulate the hit response of the silicon vertex and tracker detectors to the muon decay background remaining after the shielding nozzles. The background hit reducing techniques include timing, energy deposition, and hit location correlation in the double layer geometry.

Confining continuous manipulations of accelerator beam-line optics

Altering the optics in one section of a linear accelerator beamline will in general cause an alteration of the optics in all downstream sections. In circular accelerators, changing the optical properties of any beamline element will have an impact on the optical functions throughout the whole machine. In many cases, however, it is desirable to change the optics in a certain beamline section without disturbing any other parts of the machine. Such a local optics manipulation can be achieved by adjusting a number of additional corrector magnets that restore the initial optics after the manipulated section. In that case, the effect of the manipulation is confined in the region between the manipulated and the correcting beamline elements. Introducing a manipulation continuously, while the machine is operating, therefore requires continuous correction functions to be applied to the correcting quadrupole magnets. In this paper we present an analytic approach to calculate such continuous correction functions for six quadrupole magnets by means of a homotopy method. Besides a detailed derivation of the method, we present its application to an algebraic example, as well as its implementation at the seeding experiment sFLASH at the free-electron laser FLASH located at DESY in Hamburg.

Optical pseudomotors for soft x-ray beamlines.

Optical elements of soft x-ray beamlines usually have motorized translations and rotations that allow for the fine alignment of the beamline. This is to steer the photon beam at some positions and to correct the focus on slits or on sample. Generally, each degree of freedom of a mirror induces a change of several parameters of the beam. Inversely, several motions are required to actuate on a single optical parameter, keeping the others unchanged. We define optical pseudomotors as combinations of physical motions of the optical elements of a beamline, which allow modifying one optical parameter without affecting the others. We describe a method to obtain analytic relationships between physical motions of mirrors and the corresponding variations of the beam parameters. This method has been implemented and tested at two beamlines at ALBA, where it is used to control the focus of the photon beam and its position independently.

Benchmarking Monte Carlo simulations against experimental data in clinically relevant passive scattering proton therapy beamline configurations

Monte Carlo simulations are widely used to calculate secondary neutron doses in proton therapy. When using the passive scattering technique, a small variation in the tumor size or location requires a full adjustment of the beamline configuration. This work thus focuses on modeling all possible beamline elements of the local facility with the MCNPX code while covering the entire clinical range of proton beam energies. This paper documents the experimental validation of realistic beamline configurations dedicated to intracranial tumor treatments, with different sources and beamline elements. Simulations were compared against measurements and treatment planning system (TPS) data considering percentage depth dose distributions (PDD) and relative lateral dose profiles. The results show that simulated and measured PDD distributions differ by no more than 1.6 mm on the proton beam range (tolerance set at 2 mm/2%) for the 162 MeV configuration. Meanwhile, for the modulated lateral dose profiles, the 219 MeV configuration presented the largest difference for the in-plane field width at 90% with 2 mm difference in measurements. The modeled proton sources and beamline elements were validated, and the new realistic geometries can be used to calculate secondary neutron doses to healthy tissues.

Interaction region design and auxiliary detector systems for an EIC

There are a number of exciting physics opportunities at a future electron-ion collider facility. One possible design for such a facility is eRHIC, where the current RHIC facility located at Brookhaven National Lab would be transformed into an electron-ion collider. It is imperative for a seamless integration of auxiliary detector systems into the interaction region design to have a machine that meets the needs for the planned physics analyses, as well as take into account the space constraints due to the tunnel geometry and the necessary beam line elements. In this talk, we describe the current ideas for integrating a luminosity detector, electron polarimeter, roman pots, and a low Q2 -tagger into the interaction region for eRHIC.

Long bunch trains measured using a prototype cavity beam position monitor for the Compact Linear Collider

The Compact Linear Collider (CLIC) requires beam position monitors (BPMs) with 50 nm spatial resolution for alignment of the beam line elements in the main linac and beam delivery system. Furthermore, the BPMs must be able to make multiple independent measurements within a single 156 ns long bunch train. A prototype cavity BPM for CLIC has been manufactured and tested on the probe beam line at the 3rd CLIC Test Facility (CTF3) at CERN. The transverse beam position is determined from the electromagnetic resonant modes excited by the beam in the two cavities of the pickup, the position cavity and the reference cavity. The mode that is measured in each cavity resonates at 15 GHz and has a loaded quality factor that is below 200. Analytical expressions for the amplitude, phase and total energy of signals from long trains of bunches have been derived and the main conclusions are discussed. The results of the beam tests are presented. The variable gain of the receiver electronics has been characterized using beam excited signals and the form of the signals for different beam pulse lengths with the $2/3\text{ }\text{ }\mathrm{ns}$ bunch spacing has been observed. The sensitivity of the reference cavity signal to charge and the horizontal position signal to beam offset have been measured and are compared with theoretical predictions based on laboratory measurements of the BPM pickup and the form of the resonant cavity modes as determined by numerical simulation. Finally, the BPM was calibrated so that the beam position jitter at the BPM location could be measured. It is expected that the beam jitter scales linearly with the beam size and so the results are compared to predicted values for the latter.

SU‐E‐J‐142: Prompt Gamma Emission Measurements From a Passively Scattered Proton Beam On Targets Containing 16O, 12C and 14N

Purpose:To measure the prompt gamma emission from the important elements found in tissue (1 6O,1 2C and1 4N) in a clinical passive‐scatter treatment environment.Methods:The targets (composed of water, Perspex, graphite and liquid nitrogen) were irradiated with a 200 MeV passive‐scatter proton beam and the discrete prompt gamma energy spectra was detected by a high resolution 2′ × 2′ LaBr. detector. In order to reduce the high level of radiation produced by the beam line elements, the detector was surrounded by 10 cm of lead to attenuate the scattered gamma‐rays entering the detector with an extra 5 cm thick layer of lead added along the beam direction. A 10 cm thick collimator with a 5 cm × 10 cm rectangular opening was also used.Results:The prompt gamma peaks at 6.13 MeV and 4.44 MeV were clearly identified as a Result of the inelastic nuclear reaction between the protons and the 16O atoms found in the water target. The 6.13 MeV peak was 5% higher than the peak at 4.44 MeV for the water target. The 4.44 MeV peak was the only identified emission in the prompt gamma energy spectra from the graphite target (1 2C). The expected 2.313 MeV peak form the1 4N (liquid nitrogen target) was identified, but the other expected1 4N peaks could not be resolved.Conclusion:Prompt gamma measurements with a passive‐scatter proton beam are possible, but the presence of a high amount of background radiation from the patient final collimator presents a challenge at the treatment isocenter. The prominent prompt gamma peaks at 6.13 MeV and 4.44 MeV were identified from the water, Perspex and graphite targets. The prompt gammas from the liquid nitrogen target were difficult to see, but may not be significant in the in‐vivo verification process.

Secondary doses to healthy tissues during proton therapy treatments: influence of irradiation parameters

Secondary doses to healthy tissues during proton therapy treatments: influence of irradiation parameters

Cleaning of carbon layer from the gold films using a pulsed Nd:YAG laser

Hydrocarbon cracking and carbon contamination of optical elements in soft X-ray spectrometers and synchrotron radiation beamlines is a severe problem. Carbon contamination seriously affects the optics performance. In the present work, an Nd:YAG laser providing 2mJ of pulse energy and 100ns of pulse duration has been used for carbon cleaning experiments. The laser cleaning is a non-contact, accurate, efficient and safe process. A surface area of 48cm2 having ∼20nm thick carbon layer on gold surface has been removed with six number of laser passes and with 80% laser spot overlapping without any change in surface roughness of the underneath gold film. Effect of laser beam on gold film after carbon removal has been analyzed using X-ray photoelectron spectroscopy, soft X-ray reflectivity techniques. Atomic force microscopy was used to analyze surface morphology before and after laser cleaning process. Power spectral density function was calculated over large frequency range of 10−1 to 10−4nm−1 to understand topographic data.

Study of the secondary neutral radiation in proton therapy: Toward an indirect in vivo dosimetry

Introduction The proton therapy facility at Centre Antoine Lacassagne in Nice uses the 65 MeV isochronous cyclotron MEDICYC to treat eye tumors. The passive scattering allows to deliver a ‘‘plateau” percentage depth dose (or Spread-Out-Bragg-Peak), in order to cover the target volume in depth. This modulation is given by a range shifter and a range modulator wheel, which are adapted to each patient treatment. At the end of the beam line, the patient collimator reduces the beam laterally to protect healthy tissues. Secondary particles are produced in the collision of protons with beam line elements: photons and neutrons, which are able to escape from the patient and can be used, in theory, for in vivo dosimetry and quality assurance measurements. The secondary particles production is closely linked through the modulation accessories. Materials and methods The aim of this study is to investigate the relationship between proton dose and secondary particle production. Monte Carlo calculations, using MCNPX code, and measurements were extended to 100 clinical Spread-Out-Bragg-Peak covering the whole range of therapeutic dose rates (D/MU). The measurements were performed for validation of Monte Carlo calculations. Results This work highlights the existence of a correlation function between proton dose and secondary particle production. Knowing this relation in one point of the tratment room, it is possible to develop a quality assurance system which controls the effective proton dose rate delivered to the patient. Conclusion This system has been installed and is now used routinely. It allows the delivered dose to be monitored independently of the beam monitor reading and offers a new approach to the conventional in vivo dosimetry in protontherapy.

Monte-Carlo calculations of the activation of the accelerator target holder and shadow cone during the calibration of the ITER diagnostic devices with monoenergetic neutrons

Abstract The ITER International Fusion Energy Organization has solicited IRSN Laboratory for Neutron Metrology and Dosimetry to study the possibility to calibrate, in monoenergetic neutron fields at 14 and 2.45 MeV, the neutron detectors to be placed inside the future fusion reactor. In addition to the estimate of the necessary irradiation times, the dose equivalent rates from some of the neutron activated beam line elements had been calculated to consider the cooling time mandatory before access. Neutron activation calculations have been performed with the Fluka Monte-Carlo code. The resulting dose equivalent rates depend strongly of the neutron beam intensity as well as the neutron energy. In the worst case, for 14 MeV neutrons at an emission rate of 1012 s−1, a cooling time of 24 h would be needed for a close access to the shadow cone. Several days would be mandatory in the case of the target holder.

上海光源储存环恒流注入束流安全性模拟

For the safety issue for top-up injection, the trajectory of the injection beam was tracked to find out in what kinds of conditions the injection beam would get through the synchrotron light beam pipe and cause radiation hazards. The forward tracking method is used with Accelerator Toolbox (AT) code. We enlarge injection beam phase space volume and reduce the beam line element to simplify the calculation while covering all the possibility. According to this simulation, the interlock criteria are set up for top-up operation.

How good can our beamlines be?

The accuracy of X-ray diffraction data depends on the properties of the crystalline sample and on the performance of the data-collection facility (synchrotron beamline elements, goniostat, detector etc.). However, it is difficult to evaluate the level of performance of the experimental setup from the quality of data sets collected in rotation mode, as various crystal properties such as mosaicity, non-uniformity and radiation damage affect the measured intensities. A multiple-image experiment, in which several analogous diffraction frames are recorded consecutively at the same crystal orientation, allows minimization of the influence of the sample properties. A series of 100 diffraction images of a thaumatin crystal were measured on the SBC beamline 19BM at the APS (Argonne National Laboratory). The obtained data were analyzed in the context of the performance of the data-collection facility. An objective way to estimate the uncertainties of individual reflections was achieved by analyzing the behavior of reflection intensities in the series of analogous diffraction images. The multiple-image experiment is found to be a simple and adequate method to decompose the random errors from the systematic errors in the data, which helps in judging the performance of a data-collection facility. In particular, displaying the intensity as a function of the frame number allows evaluation of the stability of the beam, the beamline elements and the detector with minimal influence of the crystal properties. Such an experiment permits evaluation of the highest possible data quality potentially achievable at the particular beamline.

Laser‐driven beam lines for delivering intensity modulated radiation therapy with particle beams

Laser-accelerated particles are a promising option for radiation therapy of cancer by potentially combining a compact, cost-efficient treatment unit with the physical advantages of charged particle beams. To design such a treatment unit we consider different dose delivery schemes and analyze the necessary devices in the required particle beam line for each case. Furthermore, we point out that laser-driven treatment units may be ideal tools for motion adaptation during radiotherapy. Reasons for this are the potential of a flexible gantry and the time structure of the beam with high particle numbers in ultrashort bunches. One challenge that needs to be addressed is the secondary radiation produced in several beam line elements. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Spin flipping in rings with Siberian Snakes II: Simulations with localized orbit excursions

A new program eilms is used to perform spin tracking simulations, for spin flippers in model rings with full strength Siberian Snakes, at a spin tune of 12. eilms employs canonical variables and symplectic–unitary integrators for all beamline elements. In particular, tracking studies are presented for a new design of a spin flipper proposed for stored polarized proton beams in RHIC. The induced coherent vertical betatron oscillations are localized within the flipper system. Points of detail which require further study are elucidated.

J-PARC Muon Facility, MUSE

Abstract The muon science facility (MUSE) is located in the Materials and Life Science Facility (MLF), which is a building integrated to include both neutron and muon science programs. For Phase 1, we succeeded in installing one super conducting decay/surface muon beamline, so called D-line, with a modest-acceptance pion injector of about 45 mSr in the summer of 2008. In November 2009, by iterative beam tuning and developing new beamline elements such as a larger separator, the surface muons (μ +) extraction rate was significantly increased up to 1.8 × 106/s with the use of a 120 kW proton beam from the RCS. The achieved intensity is equivalent or even larger than that at the RIKEN-RAL muon facility, and would correspond to 1.5 × 107/s surface muons when in the future the proton beam will reach a power of 1MW. Recently, the Superomega muon beamline, so called U-line, with a large acceptance of 400 mSr was funded for construction, delivering 4 × 108/s surface muons to the experimental area, aiming at creating a new type of muon source; an intense ultra-slow muon source of 1 × 105-6/s for the study of thin film magnetism, etc.

ILCRoot Tracker and Vertex Detector Hits Response to MARS15 Simulated Backgrounds in the Muon Collider

Abstract Results from a simulation of the background for a muon collider, and the hits response of a silicon tracking detector to this backgroundare presented.The backgroundcausedbydecaysofthe750 GeV/ c beam μ + and μ − was simulated using the MARS15 program, which included the infrastructure of the beam line elements near the detector and the 10 ∘ nozzles that shield the detector from this background. The ILCRoot framework, along with the Geant4 program, was used to simulate the hits response of the tracker and vertex silicon detectors to the muon-decay background remaining after the shielding nozzles. Results include the hit distributions in these detectors, the fractions of type-specific background particles producing these hits and illustrate the use of timing of the hits to suppress the muon beam background.

Comparison of dc and superconducting rf photoemission guns for high brightness high average current beam production

A comparison of the two most prominent electron sources of high average current high brightness electron beams, DC and superconducting RF photoemission guns, is carried out using a large-scale multivariate genetic optimizer interfaced with space charge simulation codes. The gun geometry for each case is varied concurrently with laser pulse shape and parameters of the downstream beamline elements of the photoinjector to obtain minimum emittance as a function of bunch charge. Realistic constraints are imposed on maximum field values for the two gun types. The SRF and DC gun emittances and beam envelopes are compared for various values of photocathode thermal emittance. The performance of the two systems is found to be largely comparable provided low intrinsic emittance photocathodes can be employed.

A simple, high-yield, apparatus for NEG coating of vacuum beamline elements

Non-Evaporable Getter (NEG) materials are extremely useful in vacuum systems for achieving Ultra High Vacuum. Recently, these materials have been used to coat the inner surfaces of vacuum components, acting as an internal, passive, vacuum pump. We have constructed a low cost apparatus, which allows coating of very small diameter vacuum tubes, used as differential pumping stages. Despite the relative ease of construction, we are routinely able to achieve high coating yields. We further describe an improvement to our system, which is able to achieve the same yield, at an even lower complexity by using an easily manufactured permanent magnet arrangement. The designs described are extendible to virtually any combination of length and diameter of the components to be coated.