Showing papers on "Linear particle accelerator published in 2012"

Time-gated Cherenkov emission spectroscopy from linear accelerator irradiation of tissue phantoms

Abstract: Radiation from a linear accelerator induces Cherenkov emission in tissue, which has recently been shown to produce biochemical spectral signatures that can be interpreted to estimate tissue hemoglobin and oxygen saturation or molecular fluorescence from reporters The Cherenkov optical light levels are in the range of 10−6 to 10−9 W/cm2, which limits the practical utility of the signal in routine radiation therapy monitoring However, due to the fact that the radiation is pulsed, gated-acquisition of the signal allows detection in the presence of ambient lighting, as is demonstrated here This observation has the potential to significantly increase the value of Cherenkov emission spectroscopy during radiation therapy to monitor tissue molecular events

Radiobiological effectiveness of laser accelerated electrons in comparison to electron beams from a conventional linear accelerator.

Abstract: Laser particle acceleration/Laser radiotherapy/Cell response to electrons/Pulsed irradiation. The notable progress in laser particle acceleration techn ology promises potential medical application in cancer therapy through compact and cost effective laser devices that are suitable for already existing clinics. Previously, consequences on the radiobiological response by laser driven particle beams characterised by an ultra high peak dose rate have to be inves tigated. Therefore, tumour and non-malignant cells were irradiated with pulsed laser accelerated electrons at the JETI facility for the comparison with continuous electrons of a conventional therapy LINAC. Dose res ponse curves were measured for the biological endpoints clonogenic survival and residual DNA double strand breaks. The overall results show no significant differences in radiobiological response for in vitro cell experiments between laser accelerated pulsed and clinical used electron beams. These first systematic in vitro cell response studies with precise dosimetry to laser driven electron beams represent a first s tep toward the long term aim of the application of laser accelerated particles in radiotherapy.

Generation of tunable, 100–800 MeV quasi-monoenergetic electron beams from a laser-wakefield accelerator in the blowout regime

Abstract: In this paper, we present results on a scalable high-energy electron source based on laser wakefield acceleration. The electron accelerator using 30–80 TW, 30 fs laser pulses, operates in the blowout regime, and produces high-quality, quasi-monoenergetic electron beams in the range 100–800 MeV. These beams have angular divergence of 1–4 mrad, and 5%–25% energy spread, with a resulting brightness 1011 electrons mm−2 MeV−1 mrad−2. The beam parameters can be tuned by varying the laser and plasma conditions. The use of a high-quality laser pulse and appropriate target conditions enables optimization of beam quality, concentrating a significant fraction of the accelerated charge into the quasi-monoenergetic component.

Generation and characterization of electron bunches with ramped current profiles in a dual-frequency superconducting linear accelerator.

Abstract: We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radio frequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced ~700-MeV bunches have peak currents of the order of a kilo-Ampere. Data taken for various accelerator settings demonstrate the versatility of the method and, in particular, its ability to produce current profiles that have a quasilinear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak accelerating electric fields with transformer ratios larger than 2 in dielectric-lined waveguides.

Beam properties and stability of a flattening-filter free 7 MV beam—An overview

Abstract: Purpose: Several works have recently focused on flattening-filter-free (FFF) beams of linear accelerators of various companies (in particular, Varian and Elekta), but no overview as yet exists for the flattening-filter free 7XU beam (Siemens Artiste). Methods: Dosimetric properties of the 7XU beam were measured in May and September 2011. We present depth dose curves and beam profiles, output factors, and MLC transmission and assess the stability of the measurements. The 7XU beam was commissioned in the Pinnacle³ treatment planning system (TPS), and modeling results including the spectrum are presented. Results: The percent depth dose curve of the 7XU beam is similar to the flat 6X beam line, with a slightly smaller surfacedose. The beam profiles show the characteristic shape of flattening-filter free beams, with deviations between measurements of generally less than 1%. The output factors of the 7XU beam decrease more slowly than for the 6X beam. The MLC transmission is comparable but slightly less for the 7XU beam. The 7XU beam can be adequately modeled by the Pinnacle³ TPS, with successful dosimetric verification. The spectrum of the 7XU beam has lower photon fluence up to approximately 2.5 MeV and higher fluence beyond, with a slightly higher mean energy. Conclusions: The 7XU beam has been commissioned for clinical use after successful modeling, stability checks, and dosimetric verification.

Development and beam test of a continuous wave radio frequency quadrupole accelerator

Abstract: The front end of any modern ion accelerator includes a radio frequency quadrupole (RFQ). While many pulsed ion linacs successfully operate RFQs, several ion accelerators worldwide have significant difficulties operating continuous wave (CW) RFQs to design specifications. In this paper we describe the development and results of the beam commissioning of a CW RFQ designed and built for the National User Facility: Argonne Tandem Linac Accelerator System (ATLAS). Several innovative ideas were implemented in this CW RFQ. By selecting a multisegment split-coaxial structure, we reached moderate transverse dimensions for a 60.625-MHz resonator and provided a highly stabilized electromagnetic field distribution. The accelerating section of the RFQ occupies approximately 50% of the total length and is based on a trapezoidal vane tip modulation that increased the resonator shunt impedance by 60% in this section as compared to conventional sinusoidal modulation. To form an axially symmetric beam exiting the RFQ, a very short output radial matcher with a length of 0:75 was developed. The RFQ is designed as a 100% oxygen-free electronic (OFE) copper structure and fabricated with a two-step furnace brazing process. The radio frequency (rf) measurements show excellent rf properties for the resonator, with a measured intrinsic Q equal to 94% of the simulated value for OFE copper. An O5þ ion beam extracted from an electron cyclotron resonance ion source was used for the RFQ commissioning. In off-line beam testing, we found excellent coincidence of the measured beam parameters with the results of beam dynamics simulations performed using the beam dynamics code TRACK, which was developed at Argonne. These results demonstrate the great success of the RFQ design and fabrication technology developed here, which can be applied to future CW RFQs.

Time-gated Cherenkov emission spectroscopy from linear accelerator irradiation of tissue phantoms

Abstract: A time-gated-acquisition method is introduced to measure the Cherenkov emission from linear accelerator (LINAC) in tissue mimic phantom and shown to be an effective way to enhance the intensity of the Cherenkov emission over the ambient light.

Systems and methods for cargo scanning and radiotherapy using a traveling wave linear accelerator based x-ray source using pulse width to modulate pulse-to-pulse dosage

Abstract: Provided herein are systems and methods for operating a traveling wave linear accelerator to generate stable electron beams at two or more different intensities by varying the number of electrons injected into the accelerator structure during each pulse by varying the electron beam current applied to an electron gun The electron beams may be used to generate x-rays having selected doses and energies, which may be used for cargo scanning or radiotherapy applications

Acceleration tests of a 3 GHz proton linear accelerator (LIBO) for hadrontherapy

Abstract: This paper describes the acceleration tests performed at the Catania LNS Laboratory on a 3 GHz linac module of the side coupled type, which boosts the proton energy of a beam extracted from a cyclotron from 62 to 72 MeV. The output proton energy was measured with two devices: a NaI(Tl) crystal and a bending magnet. The experimental spectra are in good agreement with the calculated ones. From their shape it is obtained that (18±3.0)% of the transmitted protons fall in a ±2 MeV interval centered around 72 MeV. This result is in good agreement with the 20% value derived from the simulation of the acceleration process. The measured energy of the accelerated protons was used to check that the shunt impedance of the structure is equal to the computed one within 3%. This was the first time that a 3 GHz structure has been used to accelerate protons, and the results of the tests have demonstrated that a high frequency linac can be used as a cyclotron booster.

Note: Absolute calibration of two DRZ phosphor screens using ultrashort electron bunch

Abstract: This article gives the absolute calibration of two types phosphor screens (DRZ) that were used to detect and characterize electron bunches driven by laser-plasma accelerator. The test was performed with picoseconds electron bunch at a radio frequency linear electron accelerator in Tsinghua University. The photons emitted from DRZ screens showed good linear responses to the charge of incident electron bunch and cosine angular distribution in space. An energy conversional efficiency of effective scintillant matter was also calculated.

Next generation light source r&d and design studies at lbnl

Abstract: LBNL is developing design concepts for a multi-beamline soft x-ray FEL array powered by a superconducting linear accelerator, operating with a high bunch repetition rate of approximately one MHz. The cw superconducting linear accelerator is su pplied by an injector based on a high-brightness, high-repetition-rate photocathode electron gun. Electron bunches are distributed from the linac to the array of independently configurable FEL beamlines with nominal bunch rates up to 100 kHz in each FEL, and with even pulse spacing. Individual FELs may be configured for different modes of operation, and each may produce high peak and average brightness x-rays with a flexible pulse format, and with pulse durations ranging from sub-femtoseconds to hundreds of femtoseconds. In this paper we describe conceptual design studies and optimizations. We describe recent developments in the design and performance parameters, and progress in R&D activities.

Scintillating Screen Applications in Accelerator Beam Diagnostics

Abstract: Scintillation screens are widely used for transverse beam profile diagnostics at particle accelerators. The monitor principle relies on the fact that a charged particle crossing the screen material deposits energy which is converted into detectable light. The resulting photon emission leads to a direct image of the two-dimensional beam distribution and can be measured with standard optical techniques. Simplicity and low cost make this kind of diagnostic very attractive. During the last years, scintillating screen monitors were mainly deployed in hadron and low energy electron machines. Most recent experiences from modern LINAC-based light sources showed that optical transition radiation (OTR) diagnostics commonly used as standard profile measurement system might fail for high energy and high brilliance electron beams. This makes again the usage of scintillating screens very attractive. Studies showed that the response of scintillating materials depends on many parameters such as particle energy, intensity, species and time structure of the beam. Therefore, scintillating materials have to be tailored with respect to the application demands required at large accelerator facilities. Measured properties, as light yield or imaged beam shape, show a strong dependency on the scintillating material and change significantly with screen temperature as observed for high current ion beams at low energies. In addition, the spectral response of inorganic material might change with intense ion irradiation. Many investigations on scintillating screen properties were performed for particle ιuxes much higher than for typical applications in medical imaging or high energy physics.

Upgrade of the MIT Linear Electrostatic Ion Accelerator (LEIA) for nuclear diagnostics development for Omega, Z and the NIF

Abstract: The MIT Linear Electrostatic Ion Accelerator (LEIA) generates DD and D3He fusion products for the development of nuclear diagnostics for Omega, Z, and the National Ignition Facility (NIF). Significant improvements to the system in recent years are presented. Fusion reaction rates, as high as 107 s−1 and 106 s−1 for DD and D3He, respectively, are now well regulated with a new ion source and electronic gas control system. Charged fusion products are more accurately characterized, which allows for better calibration of existing nuclear diagnostics. In addition, in situ measurements of the on-target beam profile, made with a CCD camera, are used to determine the metrology of the fusion-product source for particle-counting applications. Finally, neutron diagnostics development has been facilitated by detailed Monte Carlo N-Particle Transport (MCNP) modeling of neutrons in the accelerator target chamber, which is used to correct for scattering within the system. These recent improvements have resulted in a versatile platform, which continues to support the existing nuclear diagnostics while simultaneously facilitating the development of new diagnostics in aid of the National Ignition Campaign at the National Ignition Facility.

Observation of parametric X-ray radiation by an imaging plate

Abstract: We have demonstrated experimentally the application of an imaging plate for registering the angular distribution of parametric X-ray radiation. The imaging plate was used as a two-dimensional position-sensitive X-ray detector. High-quality images of the fine structure in the angular distributions of the yield around the reflection of the parametric X-ray radiation produced in a silicon crystal by a 255-MeV electron beam from a linear accelerator have been observed in the Laue geometry. A fairly good agreement between results of measurements and calculations by the kinematic theory of parametric X-ray radiation is shown. Applications of the imaging plates for the observation of the angular distribution of X-rays produced by accelerated particles in a crystal are also discussed.

First observation of intrabeam stripping of negative hydrogen in a superconducting linear accelerator.

Abstract: We report on an experiment in which a negative hydrogen ion beam in the Spallation Neutron Source (SNS) linear accelerator was replaced with a beam of protons with similar size and dynamics. Fractional beam loss in the superconducting part of the SNS accelerator was measured to be at least 2×10(-5) for the H(-) beam, and it was an order of magnitude lower for the protons. Also beam loss has a stronger dependence on intensity with H(-) than with proton beams. These measurements verify a recent theoretical explanation of unexpected beam losses in the SNS superconducting linear accelerator based on an intrabeam stripping mechanism for negative hydrogen ions. This previously unidentified mechanism for beam loss is important for the design of new high current linear ion accelerators and the performance improvement of existing machines.

Interleaving multi-energy x-ray energy operation of a standing wave linear accelerator using electronic switches

Abstract: The disclosure relates to systems and methods for fast-switching operating of a standing wave linear accelerator (LINAC) for use in generating x-rays of at least two different energy ranges with advantageously low heating of electronic switches. In certain embodiments, the heating of electronic switches during a fast-switching operation of the LINAC can be kept advantageously low through the controlled, timed activation of multiple electronic switches located in respective side cavities of the standing wave LINAC, or through the use of a modified a side cavity that includes an electronic switch.

VMAT testing for an Elekta accelerator

Abstract: Volumetric-modulated arc therapy (VMAT) has been shown to be able to deliver plans equivalent to intensity-modulated radiation therapy (IMRT) in a fraction of the treatment time. This improvement is important for patient immobilization/localization compliance due to comfort and treatment duration, as well as patient throughput. Previous authors have suggested commissioning methods for this modality. Here, we extend the methods reported for the Varian RapidArc system (which tested individual system components) to the Elekta linear accelerator, using custom files built using the Elekta iComCAT software. We also extend the method reported for VMAT commissioning of the Elekta accelerator by verifying maximum values of parameters (gantry speed, multileaf collimator (MLC) speed, and backup jaw speed), investigating: 1) beam profiles as a function of dose rate during an arc, 2) over/under dosing due to MLC reversals, and 3) over/under dosing at changing dose rate junctions. Equations for construction of the iComCAT files are given. Results indicate that the beam profile for lower dose rates varies less than 3% from that of the maximum dose rate, with no difference during an arc. The gantry, MLC, and backup jaw maximum speed are internally consistent. The monitor unit chamber is stable over the MUs and gantry movement conditions expected. MLC movement and position during VMAT delivery are within IMRT tolerances. Dose rate, gantry speed, and MLC speed are accurately controlled. Over/under dosing at junctions of MLC reversals or dose rate changes are within clinical acceptability.

Enhancement of x-rays generated by a guided laser wakefield accelerator inside capillary tubes

Abstract: Electrons accelerated in the nonlinear regime in a laser wakefield accelerator experience transverse oscillations inside the plasma cavity, giving rise to ultra-short pulsed x-rays, also called the betatron radiation. We show that the fluence of x-ray can be enhanced by more than one order of magnitude when the laser is guided by a 10 mm long capillary tube instead of interacting with a 2 mm gas jet. X-rays with a synchrotron-like spectrum and associated critical energy ∼5 keV, with a peak brightness of ∼1×1021 ph/s/mm2/mrad2/0.1%BW, were achieved by employing 16 TW laser pulses.

Beam generation and planar imaging at energies below 2.40 MeV with carbon and aluminum linear accelerator targets.

Abstract: Purpose : Recent work has demonstrated improvement of image quality with low-Z linear accelerator targets and energies as low as 3.5 MV. In this paper, the authors lower the incident electron beam energy between 1.90 and 2.35 MeV and assess the improvement of megavoltage planar image quality with the use of carbon and aluminumlinear accelerator targets. Methods : The bending magnet shunt current was adjusted in a Varian linear accelerator to allow selection of mean electron energy between 1.90 and 2.35 MeV. Linac set points were altered to increase beam current to allow experimental imaging in a practical time frame. Electron energy was determined through comparison of measured and Monte Carlo modeled depth dose curves. Planar image CNR and spatial resolution measurements were performed to quantify the improvement of image quality. Magnitudes of improvement are explained with reference to Monte Carlo generated energy spectra. Results : After modifications to the linac, beam current was increased by a factor greater than four and incident electron energy was determined to have an adjustable range from 1.90 MeV to 2.35 MeV. CNR of cortical bone was increased by a factor ranging from 6.2 to 7.4 and 3.7 to 4.3 for thin and thick phantoms, respectively, compared to a 6 MV therapeutic beam for both aluminum and carbon targets. Spatial resolution was degraded slightly, with a relative change of 3% and 10% at 0.20 lp/mm and 0.40 lp/mm, respectively, when reducing energy from 2.35 to 1.90 MV. The percentage of diagnostic x-rays for the beams examined here, ranges from 46% to 54%. Conclusion : It is possible to produce a large fraction of diagnostic energy x-rays by lowering the beam energy below 2.35 MV. By lowering the beam energy to 1.90 MV or 2.35 MV, CNR improves by factors ranging from 3.7 to 7.4 compared to a 6 MV therapy beam, with only a slight degradation of spatial resolution when lowering the energy from 2.35 MV to 1.90 MV.

Systems and methods for generating X-rays and neutrons using a single linear accelerator

Abstract: Systems and methods for generating X-rays and neutrons using a single linear accelerator are disclosed. Such system and methods may interrogate an object at times with X-rays and at other times with neutrons, e.g., after suspicious material is detected based on the X-rays. A system may include a single linear accelerator for generating first and second electron beams; first and second targets; a magnet configured to control irradiation of the first and second targets by the first and second electron beams; and a controller that (a) causes the linear accelerator to generate the first electron beam and causes the magnet to direct the beam to first target to generate X-rays; and (b) causes the linear accelerator to generate the second electron beam and causes the magnet to direct the beam to the second target to generate neutrons.

Observation of Shot Noise Suppression at Optical Wavelengths in a Relativistic Electron Beam

Abstract: Control of collective properties of relativistic particles is increasingly important in modern accelerators. In particular, shot noise affects accelerator performance by driving instabilities or by competing with coherent processes. We present experimental observations of shot noise suppression in a relativistic beam at the Linac Coherent Light Source. By adjusting the dispersive strength of a chicane, we observe a decrease in the optical transition radiation emitted from a downstream foil. We show agreement between the experimental results, theoretical models, and 3D particle simulations.

A simple quality assurance test tool for the visual verification of light and radiation field congruent using electronic portal images device and computed radiography

Abstract: Background The radiation field on most megavoltage radiation therapy units are shown by a light field projected through the collimator by a light source mounted inside the collimator. The light field is traditionally used for patient alignment. Hence it is imperative that the light field is congruent with the radiation field.

A european proposal for the compton gamma-ray source of eli-np

Abstract: A European proposal is under preparation for the Compton gamma-ray Source of ELI-NP. In the Romanian pillar of ELI (the European Extreme Light Infrastructure) an advanced gamma-ray beam is foreseen, coupled to two 10 PW laser systems. The photons will be generated by Compton back-scattering in the collision between a high quality electron beam and a high power laser. A European collaboration formed by INFN, Univ. of Roma La Sapienza, Orsay-LAL of IN2P3, Univ. de Paris Sud XI and ASTeC at Daresbury, is preparing a TDR exploring the feasibility of a machine expected to achieve the Gamma-ray beam specifications: energy tunable between 1 and 20 MeV, narrow bandwidth (0.3%) and high spectral density, 10 4 photons/sec/eV. We will describe the lay-out of the 720 MeV RF Linac and the collision laser with the associated optical cavity, as well as the optimized beam dynamics to achieve maximum phase space density at the collision. The predicted gamma-ray spectra have been evaluated for the case at 360 MeV.

Technique and instrumentation for bunch shape measurements

Abstract: Bunch shape is one of the most important, interesting but difficult to observe characteristics of a beam in ion linear accelerators. Different possibilities of bunch shape measurements are considered but the emphasis is put on the Bunch Shape Monitors (BSM) developed in INR RAS. The operation of BSM is based on coherent transformation of a longitudinal structure of a beam under study into a transverse distribution of a secondary electron beam through rf scanning. BSM characteristics found both by simulations and experimentally are presented. Modifications of BSM are described. Some experimental results of bunch observations are demonstrated.

Real-time imaging dosimeter systems and method

Abstract: A radiation therapy system including a linear accelerator configured to emit a beam of radiation and a dosimeter configured to detect in real-time the beam of radiation emitted by the linear accelerator. The dosimeter includes at least one linear array of scintillating fibers configured to capture radiation from the beam at a plurality of independent angular orientations, and a detection system coupled to the at least one linear array, the detection system configured to detect the beam of radiation by measuring an output of the scintillating fibers.

H -mode accelerating structures with permanent-magnet quadrupole beam focusing

Abstract: We have developed high-efficiency normal-conducting rf accelerating structures by combining $H$-mode resonator cavities and a transverse beam focusing by permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. The shunt impedance of interdigital $H$-mode (IH-PMQ) structures is 10--20 times higher than that of a conventional drift-tube linac, while the transverse size is 4--5 times smaller. Results of the combined 3D modeling---electromagnetic computations, multiparticle beam-dynamics simulations with high currents, and thermal-stress analysis---for an IH-PMQ accelerator tank are presented. The accelerating-field profile in the tank is tuned to provide the best propagation of a 50-mA deuteron beam using coupled iterations of electromagnetic and beam-dynamics modeling. Measurements of a cold model of the IH-PMQ tank show a good agreement with the calculations. Examples of cross-bar $H$-mode structures with PMQ focusing for higher beam velocities are also presented. $H$-PMQ accelerating structures following a short radio-frequency quadrupole accelerator can be used both in the front end of ion linacs or in stand-alone applications.

A new extraction system for the Linac4 H−ion sourcea)

Abstract: As part of the CERN accelerator complex upgrade, a new linear accelerator for H− (Linac4) is under construction. The ion source design is based on the non-caesiated DESY RF-driven ion source, with the goal of producing an H− beam of 80 mA beam current, 45 keV beam energy, 0.4 ms pulse length, and 2 Hz repetition rate. The source has been successfully commissioned for an extraction voltage of 35 kV, corresponding to the one used at DESY. Increasing the extraction voltage to 45 kV has resulted in frequent high voltage breakdowns in the extraction region caused by evaporating material from the electron dump, triggering a new design of the extraction and electron dumping system. Results of the ion source commissioning at 35 kV are presented as well as simulations of a new pulsed extraction system for beam extraction at 45 kV.

Photon induced positron annihilation spectroscopy: A nondestructive method for assay of defects in large engineering materials

Abstract: This paper describes a new methodology for volumetric assay of defects in large engineering materials nondestructively. It utilizes high energy photons produced by nuclear reaction to create positrons in situ whose fate is followed using conventional positron spectroscopic techniques. The photon induced positron annihilation (PIPA) spectroscopy system has been set-up using a Folded Tandem Ion Accelerator (FOTIA). Possibility of using prompt γ-rays produced in nuclear reactions 27 Al( 1 H,γ) 28 Si and 19 F( 1 H,αγ) 16 O has been examined. The reaction 19 F( 1 H,αγ) 16 O is seen to provide higher photon flux (and positron yield) and measurements have been carried out in large samples of metals and polymers. We could establish good sensitivity of the technique as well as reproducibility in a number of measurements. This technique has been used to carry out defect studies in cold worked zircaloy-2 plates. The measured S-parameter, indicative of defect concentration, was seen to correlate well with the measured residual stress using X-ray technique. The results were validated by γ-induced positron annihilation lifetime measurements at ELBE LINAC based GiPS facility.

Development of compact linear accelerator in KBSI.

Abstract: The compact linear accelerator using a 28 GHz ECRIS is under construction in KBSI, South Korea. The main capability of this facility is the production of fast neurons for the neutron radiography. The designing of a superconducting magnet, microwave transmission system, beam extraction, and plasma chamber of ECRIS were finished. The nominal axial design fields of the magnets are 3.6 T at injection and 2.2 T at extraction; the nominal radial design field strength at the plasma chamber wall is 2.1 T. We already installed 10 kW, 28 GHz gyrotron, and tested a microwave power from gyrotron using a dummy load. The current status will be discussed in this paper.