Showing papers on "Linear particle accelerator published in 2011"

Phase velocity and particle injection in a self-modulated proton-driven plasma wakefield accelerator.

Abstract: It is demonstrated that the performance of the self-modulated proton driver plasma wakefield accelerator is strongly affected by the reduced phase velocity of the plasma wave. Using analytical theory and particle-in-cell simulations, we show that the reduction is largest during the linear stage of self-modulation. As the instability nonlinearly saturates, the phase velocity approaches that of the driver. The deleterious effects of the wake's dynamics on the maximum energy gain of accelerated electrons can be avoided using side-injections of electrons, or by controlling the wake's phase velocity by smooth plasma density gradients.

Magnetic control of particle injection in plasma based accelerators.

Abstract: The use of an external transverse magnetic field to trigger and to control electron self-injection in laser- and particle-beam driven wakefield accelerators is examined analytically and through full-scale particle-in-cell simulations A magnetic field can relax the injection threshold and can be used to control main output beam features such as charge, energy, and transverse dynamics in the ion channel associated with the plasma blowout It is shown that this mechanism could be studied using state-of-the-art magnetic fields in next generation plasma accelerator experiments

A low emittance and high efficiency visible light photocathode for high brightness accelerator-based X-ray light sources

Abstract: Free-electron lasers and energy recovery linacs represent a new generation of ultra-high brightness electron accelerator based x-ray sources. Photocathodes are a critical performance-limiting component of these systems. Here, we describe the development of photocathodes based on potassium-cesium-antimonide that satisfy many of the key requirements of future light sources, such as robustness, high quantum efficiency when excited with visible light, and low transverse emittance.

Towards MRI-guided linear accelerator control: gating on an MRI accelerator.

Abstract: To boost the possibilities of image guidance in radiotherapy by providing images with superior soft-tissue contrast during treatment, we pursue diagnostic quality MRI functionality integrated with a linear accelerator. Large respiration-induced semi-periodic target excursions hamper treatment of cancer of the abdominal organs. Methods to compensate in real time for such motion are gating and tracking. These strategies are most effective in cases where anatomic motion can be visualized directly, which supports the use of an integrated MRI accelerator. We establish here an infrastructure needed to realize gated radiation delivery based on MR feedback and demonstrate its potential as a first step towards more advanced image guidance techniques. The position of a phantom subjected to one-dimensional periodic translation is tracked with the MR scanner. Real-time communication with the MR scanner and control of the radiation beam are established. Based on the time-resolved position of the phantom, gated radiation delivery to the phantom is realized. Dose distributions for dynamic delivery conditions with varying gating windows are recorded on gafchromic film. The similarity between dynamically and statically obtained dose profiles gradually increases as the gating window is decreased. With gating windows of 5 mm, we obtain sharp dose profiles. We validate our gating implementation by comparing measured dose profiles to theoretical profiles calculated using the knowledge of the imposed motion pattern. Excellent correspondence is observed. At the same time, we show that real-time on-line reconstruction of the accumulated dose can be performed using time-resolved target position information. This facilitates plan adaptation not only on a fraction-to-fraction scale but also during one fraction, which is especially valuable in highly accelerated treatment strategies. With the currently established framework and upcoming improvements to our prototype-integrated MRI accelerator, we will realize more intricate MRI-guided linear accelerator control in the near future.

Monte Carlo linear accelerator simulation of megavoltage photon beams: Independent determination of initial beam parameters

Abstract: Purpose: To individually benchmark the incident electron parameters in a Monte Carlo model of an Elekta linear accelerator operating at 6 and 15 MV. The main objective is to establish a simplified but still precise benchmarking procedure that allows accurate dose calculations of advanced treatment techniques. Methods: The EGSnrc Monte Carlo user codes BEAMnrc and DOSXYZnrc are used for photon beam simulations and dose calculations, respectively. A 5 x 5 cm{sup 2} field is used to determine both the incident electron energy and the electron radial intensity. First, the electron energy is adjusted to match the calculated depth dose to the measured one. Second, the electron radial intensity is adjusted to make the calculated dose profile in the penumbrae region match the penumbrae measured by GafChromic EBT film. Finally, the mean angular spread of the incident electron beam is determined by matching calculated and measured cross-field profiles of large fields. The beam parameters are verified for various field sizes and shapes. Results: The penumbrae measurements revealed a non-circular electron radial intensity distribution for the 6 MV beam, while a circular electron radial intensity distribution could best describe the 15 MV beam. These electron radial intensity distributions, given as the standardmore » deviation of a Gaussian distribution, were found to be 0.25 mm (in-plane) and 1.0 mm (cross-plane) for the 6 MV beam and 0.5 mm (both in-plane and cross-plane) for the 15 MV beam. Introducing a small mean angular spread of the incident electron beam has a considerable impact on the lateral dose profiles of large fields. The mean angular spread was found to be 0.7 deg. and 0.5 deg. for the 6 and 15 MV beams, respectively. Conclusions: The incident electron beam parameters in a Monte Carlo model of a linear accelerator could be precisely and independently determined by the benchmarking procedure proposed. As the dose distribution in the penumbra region is insensitive to moderate changes in electron energy and angular spread, accurate penumbra measurements is feasible for benchmarking the electron radial intensity distribution. This parameter is particularly important for accurate dosimetry of mlc-shaped fields and small fields.« less

A compact post-acceleration scheme for laser-generated protons

Abstract: Protons generated by irradiating a thin metal foil with a high-intensitylaser have shown to posses interesting characteristics in terms of energy, emittance, current, and pulse duration. Therefore, in the near future, they might become a competitive source with respect to conventional proton sources. Previous theoretical, numerical, and experimental studies have already demonstrated efficient coupling between laser-accelerated proton beams with traditional radio frequency (RF)-based particle accelerators. These hybrid proton accelerators benefit from both the excellent properties of the laser-based source and the flexibility, reliability, and know-how of beam handling as provided by RF-based accelerator structures. In this paper, state of the art experimental results of laser-accelerated proton beams are used as input for a numerical study using compact and innovative conventional accelerator structures designed for medical applications. Results show that this compact hybrid accelerator allows even more efficient capture and acceleration of the laser-generated proton beam.

An overview of design for CSNS/RCS and beam transport

Abstract: The China Spallation Neutron Source(CSNS) is the first accelerator-based pulsed neutron source in China.Its accelerators are made up of an 80 MeV H~- linac,a Rapid Cycling Synchrotron(RCS) and two beam transport lines.RCS accumulates and accelerates protons to the design energy of 1.6 GeV,and ext...

Generation, transport, and detection of linear accelerator based femtosecond-terahertz pulses.

Abstract: The generation and detection of intense terahertz (THz) radiation has drawn a great attention recently. The dramatically enhanced energy and peak electric field of the coherent THz radiation can be generated by coherent superposition of radiated fields emitted by ultrafast electron bunches. The femtosecond (fs)-THz beamline construction at the Pohang Accelerator Laboratory (PAL) was completed in the end of 2009. The fs-THz beamline at PAL can supply ultrafast and intense fs-THz radiation from a 75 MeV linear accelerator. The radiation is expected to have frequency up to 3 THz (∼100 cm(-1)) and the pulse width of <200 fs with pulse energy up to 10 μJ. This intense THz source has great potential for applications in nonlinear optical phenomena and fields such as material science, biomedical science, chemistry, and physics, etc.

KEK digital accelerator

Abstract: The High Energy Accelerator Research Organization KEK digital accelerator (KEK-DA) is a renovation of the KEK 500 MeV booster proton synchrotron, which was shut down in 2006. The existing 40 MeV drift tube linac and rf cavities have been replaced by an electron cyclotron resonance (ECR) ion source embedded in a 200 kV high-voltage terminal and induction acceleration cells, respectively. A DA is, in principle, capable of accelerating any species of ion in all possible charge states. The KEK-DA is characterized by specific accelerator components such as a permanent magnet X-band ECR ion source, a low-energy transport line, an electrostatic injection kicker, an extraction septum magnet operated in air, combined-function main magnets, and an induction acceleration system. The induction acceleration method, integrating modern pulse power technology and state-of-art digital control, is crucial for the rapid-cycle KEK-DA. The key issues of beam dynamics associated with low-energy injection of heavy ions are beam loss caused by electron capture and stripping as results of the interaction with residual gas molecules and the closed orbit distortion resulting from relatively high remanent fields in the bending magnets. Attractive applications of this accelerator in materials and biological sciences are discussed.

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

Abstract: The disclosure relates to systems and methods for interleaving operation of a standing wave linear accelerator (LINAC) for use in providing electrons of at least two different energy ranges, which can be contacted with x-ray targets to generate x-rays of at least two different energy ranges. The LINAC can be operated to output electrons at different energies by varying the power of the electromagnetic wave input to the LINAC, or by using a detunable side cavity which includes an activatable window.

The myrrha linear accelerator

Abstract: Accelerator Driven Systems (ADS) are promising tools for the efficient transmutation of nuclear waste products in dedicated industrial installations, called transmuters. The Myrrha project at Mol, Belgium, placed itself on the path towards these applications with a multipurpose and versatile system based on a liquid Pb-Bi (LBE) cooled fast reactor (70 MWth) which may be operated in both critical and subcritical modes. In the latter case the core is fed by spallation neutrons obtained from a 600 MeV proton beam hitting the LBE coolant/target. The accelerator providing this beam is a high intensity CW superconducting linac which is laid out for the highest achievable reliability. The combination of a parallel redundant and of a fault tolerant scheme should allow obtaining an MTBF value in excess of 250 hours that is required for optimal integrity and successful operation of the ADS. Myrrha is expected to be operational in 2023. The forthcoming 4-year period is fully dedicated to R&D activities, and in the field of the accelerator they are strongly focused on the reliability as pects and on the proper shaping of the beam trip spectrum.

Drift-tube linear accelerator

Abstract: A drift-tube linear accelerator that passes an injected particle beam through inside a plurality of cylindrical drift-tube electrodes arranged in a cylindrical cavity in a particle beam traveling direction and accelerates the particle beam by a radio-frequency electric field generated between the plurality of cylindrical drift-tube electrodes, wherein at least part of a focusing device for focusing the particle beam is disposed inside an end drift-tube electrode that is arranged nearest the injection side of the cylindrical cavity among the plurality of cylindrical drift-tube electrodes, with the focusing device being positionally adjustable independently of the end drift-tube electrode.

Lattice design of a rapid cycling medical synchrotron for carbon/proton therapy*

Abstract: We present a design of the ion Rapid Cycling Medical Synchrotron (iRCMS) for carbon/proton cancer therapy facility. The facility design, produced at Brookhaven National Laboratory (BNL) at the Collider Accelerator Department (CAD), with BEST Medical International, Inc., will be able to treat the cancer patients with carbon, lighter ions and protons. The low energy injector system accelerates ions and protons to the kinetic energy of 8 MeV/u. It consists of a laser driven ion source (for either fully stripped carbon ions or protons), matching solenoid, Radio-Frequency Quadrupole (RFQ) and linac. The 8 MeV beam is injected into a fast cycling synchrotron (iRCMA). The lattice design is a racetrack, with zero dispersion with two parallel straight sections. There are 24 combined function magnets in the two arcs with a bending radius of ~5 meters and maximum magnetic field of Bmax~1.3 T. The acceleration is performed with a frequency of 30 Hz up to required energy for the treatment with a maximum depth of 27 cm with the spot scanning technique. The maximum energy for carbon ions is 400 MeV/u. Ions are extracted in a single turn and fed to different beam lines for patient treatment.

The First Atomic and Molecular Experiments at the Linac Coherent Light Source X-Ray Free Electron Laser

Abstract: The Stanford Linac Coherent Light Source (LCLS) located at the SLAC National Accelerator Laboratory in Menlo Park, California, began operation in the Fall of 2009. The LCLS is a true x-ray laser, approximately one billion times brighter than any previous laboratory source of x-ray radiation. Here we review some of the first atomic, molecular, and optical experiments that probe the fundamental interactions of such uniquely bright and short x-ray pulses with atoms and molecules, summarize some of the theory leading up to these experiments and conclude with some ideas on future avenues of investigation.

Estimation of neutron production from accelerator head assembly of 15 MV medical LINAC using FLUKA simulations

Abstract: For the production of a clinical 15 MeV photon beam, the design of accelerator head assembly has been optimized using Monte Carlo based FLUKA code. The accelerator head assembly consists of e–γ target, flattening filter, primary collimator and an adjustable rectangular secondary collimator. The accelerators used for radiation therapy generate continuous energy gamma rays called Bremsstrahlung (BR) by impinging high energy electrons on high Z materials. The electron accelerators operating above 10 MeV can result in the production of neutrons, mainly due to photo nuclear reaction (γ, n) induced by high energy photons in the accelerator head materials. These neutrons contaminate the therapeutic beam and give a non-negligible contribution to patient dose. The gamma dose and neutron dose equivalent at the patient plane (SSD = 100 cm) were obtained at different field sizes of 0 × 0, 10 × 10, 20 × 20, 30 × 30 and 40 × 40 cm 2 , respectively. The maximum neutron dose equivalent is observed near the central axis of 30 × 30 cm 2 field size. This is 0.71% of the central axis photon dose rate of 0.34 Gy/min at 1 μA electron beam current.

Charged particle beam generator, charged particle irradiation system, method for operating charged particle beam generator and method for operating charged particle irradiation system

Abstract: A charged particle beam generator, a charged particle irradiation system, a method for operating the charged particle beam generator and a method for operating the charged particle irradiation system, which allow a charged particle beam to be injected into a circular accelerator at an arbitrary timing and can reduce an irradiation time and a time for a therapy, are provided while maintaining the lower limit of an operation cycle of a linear accelerator. An accelerator control device controls an operation of a synchrotron on the basis of a beam extraction request signal transmitted from a beam utilization system control device. A control device generates a timing signal notifying the linear accelerator of an injection timing of a next operation cycle of the synchrotron after completion of an extraction process performed by the synchrotron, changes an operation timing of the linear accelerator so that the operation timing of the linear accelerator matches the injection timing.

A dual-energy linac cargo inspection system

Abstract: X-ray inspection systems for cargo containers, capable of performing Z analysis, are an actively evolving type of equipment for cargo inspections [1–3]. A linear electron accelerator with fast energy tuning, operating in the mode of interlacing low- and high-energy electron pulses, has been developed for use in such a system. The output electron energy in this accelerator can vary in the range of 3–15 MeV under software control. An X-ray radiographic image of a container is obtained in a monoenergetic mode with a beam energy of 9 MeV. Pulses with energies of 4 and 9 MeV are used to recognize materials inside a container (i.e., perform Z analysis). The standing-wave linear electron accelerator operates at a frequency of 2856 MHz, its pulse repetition frequency with different energies is 240 Hz, the pulse duration is 10 μs, and the beam energy in each pulse is >10 J.

Injector Layout and Beam Injection into Solaris

Abstract: The Solaris synchrotron radiation storage ring to be built in Krakow, Poland is based on the MAX IV 1.5 GeV design. The injector will be a linear accelerator and its components identical to those for the MAX IV project, however, injection is not at full energy and the injector layout is different. The linac and transfer line layout, optics and injection scheme into the storage ring is presented and an analysis of accumulation before energy ramping is discussed.

Design of hybrid electron linac with standing wave buncher and traveling wave structure

Abstract: A disk-loaded waveguide (DLW) is the most common structure for compact linear accelerators working in a traveling wave (TW) regime. Among its advantages are high shunt impedance and manufacturing simplicity. The other popular structure is an on-axis coupled bi-periodical accelerating structure (BAS) that works in standing wave (SW) regime. Both the standing and the traveling wave regimes have their own advantages and disadvantages. The design of the hybrid accelerator with SW buncher and TW accelerating section presented in this paper unites the advantages of both regimes. For example, the buncher in the hybrid accelerator is shorter than in a pure TW accelerator, and it requires no solenoid; this structure is more technologically convenient as it does not require a circulator. The other way to combine the advantages of DLW and BAS is to design a magnetic coupled disk-loaded waveguide (DLW-M). This paper also presents the results of a survey study that analyzed the electrodynamical parameters of such a structure and compared them with those of DLW. The experimental data is also presented. Higher order modes, multipacting discharge and thermal simulations show that DLW-M structure is more preferable to classical DLW.

ReA3 - the Rare Isotope Re-accelerator at MSU

Abstract: Rare isotope beam (RIB) accelerator facilities provide rich research opportunities in nuclear physics in particular for nuclear structure physics, nuclear astrophysics and applied physics. The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) is constructing a RIB facility, called ‘ReA3‘. The facility will provide unique low-energy rare isotope beams by stopping RIBs produced in-flight and reaccelerating them in a compact linac. ReA3 comprises gas stopper systems, an Electron Beam Ion Trap (EBIT) charge state booster, a room temperature radio frequency quadrupole (RFQ), a linac using superconducting quarter wave resonators (QWRs) and an achromatic beam transport and distribution line to the new experimental area. Beams from ReA3 will range from 3 MeV/u for heavy ions to about 6 MeV/u for light ions, as the charge state of the ions can be adjusted by the EBIT. ReA3 will initially use beams from NSCL‘s Coupled Cyclotron Facility (CCF). Later ReA3 will provide reacceleration capability for the Facility for Rare Isotope Beams (FRIB), a new national user facility funded by the Department of Energy (DOE) that will be hosted at MSU. The ReA3 concept and status of ReA3 will be presented, with emphasis on the commissioning of the facility, which is underway.

The medium energy beam transport line (mebt) of ifmif/eveda lipac ∗

Abstract: The IFMIF-EVEDA [1] Linear IFMIF Prototype Accelerator (LIPAc)will be a 9 MeV, 125 mA CW deuteron accelerator which aims to validate the technology that will be used in the future IFMIF accelerator. The acceleration of the beam will be carried out in two stages. An RFQ will increase the energy up to 5 MeV before a Superconducting RF (SRF) linac made of a chain of eight Half Wave Resonators bring the particles to the final energy. Between both stages, a Medium Energy Beam Transport line (MEBT) is in charge of transporting and matching the beam between the RFQ and the SRF. The transverse focusing of the beam is controlled by five quadrupole magnets with integrated steerers, grouped in one triplet and one doublet. Two buncher cavities surrounding the doublet handle the longitudinal dynamics. Two movable collimators are also included to purify the beam optics coming out the RFQ and avoid losses in the SRF. From the inputs of the beam dynamics group, CIEMAT is in charge of designing, manufacturing and integrating all the components of the beamline. In this contribution, the MEBT subsystem will be described and the main objectives and issues for each component will be discussed.

A Next Generation Light Source Facility at LBNL

Abstract: The Next Generation Light Source (NGLS) is a design concept, under development at LBNL, for a multibeamline soft x-ray FEL array powered by a ~;;2 GeV superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. The CW superconducting linear accelerator is supplied by a high-brightness, highrepetition- 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 EEHG, HGHG, SASE, or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format, with pulse durations ranging from sub-femtoseconds to hundreds of femtoseconds.

Experimental verification of an APF linac for a proton therapy facility

Abstract: Alternating phase focusing (APF) is known as a beam focusing method; it was applied to an interdigital H-mode structure and successfully accelerated high current proton beams up to the desired energy for a medical synchrotron injector. A high-current APF linac was achieved by the optimal design of the cavity and the drift tubes themselves, as well as drift tube arrangement based on the co-iteration of a precise electromagnetic field and space charge beam dynamics. A proton injector for a medical accelerator complex was fabricated with the newly developed APF linac. The injector consists of an electron cyclotron resonance ion source, a radio-frequency quadrupole linac and the APF linac. The experimental results showed that over 10 mA proton beams were accelerated up to 7.4 MeV.

Two-beam interdigital-H-type radio frequency quadrupole linac with direct plasma injection for high intensity heavy ion acceleration

Abstract: We developed a two-beam interdigital-H-type radio frequency quadrupole (IH-RFQ) linac as a prototype of a multibeam IH-RFQ for high intensity heavy ion acceleration in the low energy region. This linac has two sets of RFQ electrodes within an IH-type resonant frequency cavity that is a power-efficient structure for low energy beam acceleration. The linac can accelerate two beams in parallel in one cavity with a reduction in the coulomb repulsive force (the space charge effect) between the accelerated heavy ion particles. The resonance frequency and the Q factor of the linac were found to be 47 MHz and 5900, respectively. We also developed a two-beam laser ion source with a direct plasma injection scheme as an injection system for the two-beam IH-RFQ linac and built a system to demonstrate the use of the two-beam IH-RFQ linac. Using this linac system, we were able to accelerate carbon ions from 5 to 60 keV/u and generate an output beam current of about 108 mA (2×54 mA/channel). A coherency between the two beams, derived from the imbalance of the beam loading, was observed in the acceleration test with carbon ions.

ESS-Bilbao light-ion linear accelerator and neutron source: design and applications

Abstract: The baseline design for the ESS-Bilbao light-ion linear accelerator and neutron source has been completed and the normal conducting section of the linac is at present under construction. The machine has been designed to be compliant with ESS specifications following the international guidelines of such project as described in Ref. [1]. The new accelerator facility in Bilbao will serve as a base for support of activities on accelerator physics carried out in Spain and southern Europe in the frame of different ongoing international collaborations. Also, a number of applications have been envisaged in the new Bilbao facility for the outgoing light ion beams as well as from fast neutrons produced by low-energy neutron-capture targets, which are briefly described.

Beam dynamics simulation for the Compact Linear Collider drive-beam accelerator

Abstract: In the Compact Linear Collider (CLIC) now being studied at CERN, the rf power which accelerates the main beam is provided by decelerating a high current drive beam. The drive-beam linac has to accelerate a 4.2 A electron beam up to 2.4 GeV in almost fully loaded structures. The pulse contains about 70 000 bunches, one in every second rf bucket, and has a length of $140\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$. The beam stability along the beam line is of concern for such a high current and pulse length. We present different options for the lattice of the linac based on FODO, triplet, and doublet cells and compare the transverse instability for each lattice including the effects of beam jitter, alignment, and beam-based correction.

Development of a coherent THz radiation source based on the ultra-short electron beam and its applications

Abstract: At the National Institute of Advanced Industrial Science and Technology (AIST), a coherent terahertz (THz) radiation source has been developed based on an ultra-short electron beam using an S-band compact electron linac. The designed THz pulse has a high peak power of more than 1 kW in the frequency range 0.1–2 THz. The entire system is located in one research room of about 10 m square. The linac consists of a laser photocathode rf gun (BNL type) with a Cs 2 Te photocathode load-lock system and two 1.5-m-long S-band accelerator tubes. The electron beam can be accelerated up to approximately 42 MeV. The electron bunch was compressed to less than 1 ps (rms) with a magnetic bunch compressor. The coherent synchrotron radiation (CSR) of the THz region was generated from the ultra-short electron bunch at the 90° bending magnet, and it was extracted from a z-cut quartz window for THz applications. In this work, the THz scanning transmission imaging was successfully demonstrated for measuring the freshness of a vegetable leaf over a period of time.