Compact Linear Accelerator Research Articles

Absolute energy calibration of the Telescope Array fluorescence detector with an electron linear accelerator

The Electron Light Source(ELS) is a new light source for the absolute energy calibration of cosmic ray Fluorescence Detector(FD) telescopes. The ELS is a compact electron linear accelerator with a typical output of 109 electrons per pulse at 40 MeV. We fire the electron beam vertically into the air 100 m in front of the telescope. The electron beam excites the gases of the atmosphere in the same way as the charged particles of the cosmic ray induced extensive air shower. The gases give off the same light with the same wavelength dependence. The light passes through a small amount of atmosphere and is collected by the same mirror and camera with their wavelength dependence. In this way we can use the electron beam from ELS to make an end-to-end calibration of the telescope. In September 2010, we began operation of the ELS and the FD telescopes observed the fluorescence photons from the air shower which was generated by the electron beam. In this article, we will reort the status of analysis of the absolute energy calibration with data which was taken in September 2010, and beam monitor study in November 2011.

Development of compact linear accelerator in KBSI

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.

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

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.

X-band linac technology for a high repetition rate light source

Traditionally, the pulse-to-pulse charging and switching time for a thyratron-switched line-type modulator has limited the repetition rate of normal-conducting high-energy linacs; however the recent development of solid-state modulators employing IGBT switches has allowed the repetition rate of a high-power modulator to be increased by an order of magnitude. When combined with the high accelerating gradients that can be achieved in an X-band accelerating structure, this enables a relatively compact linear accelerator to be constructed that can operate with a pulse repetition rate in excess of 1 kHz. A study has been undertaken on the issues arising from the operation of an X-band linac in this mode, including a survey of availability and limitations of modulators, klystrons and structures. Close attention has been paid to the dissipation of power in critical parts of the high-power RF chain, both on average and transiently during the high-power RF pulse.

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

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.

EBIS/T charge breeding for intense rare isotope beams at MSU

Experiments with reaccelerated beams are an essential component of the science program of existing and future rare isotope beam facilities. NSCL is currently constructing ReA3, a reaccelerator for rare isotopes that have been produced by projectile fragmentation and in-flight fission and that have been thermalized in a gas stopper. The resulting low-energy beam will be brought to an Electron Beam Ion Source/Trap (EBIS/T) in order to obtain highly charged ions at an energy of 12 keV/u. This charge breeder is followed by a compact linear accelerator with a maximum beam energy of 3 MeV/u for 238U and higher energies for lighter isotopes. Next-generation rare isotope beam facilities like the Facility for Rare Isotope Beams FRIB, but also existing Isotope Separator On-line (ISOL) facilities are expected to provide rare-isotope beam rates in the order of 1011 particles per second for reacceleration. At present the most promising scheme to efficiently start the reacceleration of these intense beams is the use of a next-generation high-current charge-breeder based on an EBIS/T. MSU has formed a collaboration to develop an EBIT for this purpose. A new high-current EBIS/T breeder will be developed and constructed at MSU, where also first tests on achievable beam rate capability will be performed. The EBIT is planned to be installed at the Isotope Separator and Accelerator facility ISAC at TRIUMF laboratory for on-line tests with rare isotope beams and to provide intense energetic reaccelerated radioactive beams. The status of the ReA3-EBIS/T in the NSCL reaccelerator project is given with a brief summary of results, followed by a discussion of plans for the future high-intensity EBIS/T charge breeder.

Transient Effects in an X-Band Magnicon Amplifier

The Naval Research Laboratory X-band magnicon is a frequency-doubling amplifier for accelerator applications at 11.4 GHz, with high power (10-20 MW), adjustable pulsewidth (200 ns-1 μs), stable gain (> 50 dB), and a modest tuning range (~0.1%) but a narrow bandwidth (a few megahertz). The magnicon is the heart of a facility to study dielectric-loaded accelerating structures, and to drive a compact linear accelerator. In these applications, frequency control is important. However, it was recently observed that in short pulse (~200 ns) operation, the output frequency does not match twice the drive frequency. This paper presents a brief description and analysis of this phenomenon as well as other transient effects that are observed in longer pulses.

X-ray source based on a compact electron linear accelerator with a thin anode

An experiment confirming the possibility of extracting a narrow energy band from a wide spectrum produced by a compact electron linear accelerator with a thin transmission anode is described. A flat crystal of pyrolytic graphite was used as a monochromator.

Demonstrating gain in a dielectric Cherenkov maser with a rod slow-wave system

We report the first results of experiments that demonstrate the amplification of megawatt nanosecond microwave pulses in a Cherenkov maser with a dielectric rod and moderately relativistic annular electric beam generated in a compact linear induction accelerator module. The input signal was generated by a resonant microwave compressor operating in a 3-cm wavelength range. A maximum gain of ∼12.5 dB and a maximum output power of ∼16 MW for a pulse duration of ∼4 ns at a frequency of 9.388 GHz were obtained with a quartz rod. The dependence of the gain on the compressor power was determined for various values of the accelerating voltage and beam current.

The NSCL electron beam ion trap for the reacceleration of rare isotopes coming to life: First extraction tests with a high-current electron gun

NSCL is currently constructing the ReA3 reaccelerator, which will accelerate rare isotopes obtained from gas stopping of fast-fragment beams to energies of up to 3 MeV/u for uranium and higher for lighter ions. A high-current charge breeder, based on an electron beam ion trap (EBIT), has been chosen as the first step in the acceleration process, as it has the potential to efficiently produce highly charged ions in a single charge state. These ions are fed into a compact linear accelerator consisting of a radio frequency quadrupole structure and superconducting cavities. The NSCL EBIT has been fully designed with most of the parts constructed. The design concept of the EBIT and results from initial commissioning tests of the electron gun and collector with a temporary 0.4 T magnet are presented.

Image-Guided Robotic Radiosurgery as Salvage Therapy for Locally Recurrent Prostate Cancer after External Beam Irradiation: Retrospective Feasibility Study on Six Cases

Technological advances in treatment planning and execution are providing new potential opportunities in the treatment of recurrent prostate cancer. This study was conducted to evaluate the feasibility and safety of reirradiation with image-guided radiosurgery using CyberKnife, a robotic arm-driven compact linear accelerator, for intraprostatic recurrence after external beam radiotherapy (EBRT). Between September 2007 and May 2008, 6 patients diagnosed with locally recurrent prostate cancer after EBRT were treated using the CyberKnife system. The total reirradiation dose was 30 Gy in five fractions. Prior to radiosurgery four patients were treated with androgen-deprivation therapy. Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer criteria and the Houston-Phoenix definition (PSA nadir + 2 ng/mL) were used for toxicity and biochemical failure evaluation, respectively. After a median follow-up of 11.2 months (range, 9.6-18.6 months), all patients are alive with no evidence of severe urinary or rectal acute morbidity. Local control cannot be exactly determined due to the short follow-up and the bias of the use of androgen ablation. Four patients had biochemical failure, three of them with clinical failure evidence (lymph node, bone and lung metastasis, respectively): none of these patients had clinical evidence of tumor persistence in the prostate. Salvage radiosurgery with CyberKnife after irradiation is feasible with low urinary and rectal morbidity. A longer follow-up and a larger number of patients are necessary to evaluate its effectiveness and optimal patient selection criteria.

X-ray imaging with laser-Compton scattering X-ray at AIST

An X-ray facility with a compact electron linear accelerator via laser-Compton scattering (LCS X-ray) is recently installed at AIST. The LCS X-ray facility in approximately 8–m square consists of a 40–MeV linac, a femtosecond terawatt laser and an X-ray beamline. The LCS X-ray facility produces quasi-monochromatic X-rays with energy in the range of 12 ∼ 40 keV which are commonly used in many studies currently carried out at synchrotron radiation facilities. The LCS X-ray is suitable for phase-contrast imaging such as in-line method, diffraction-enhanced imaging method, X-ray interferometry method, because of the quasi-monochoromaticity and the small source size. These advantages produce much clearer image of weakly absorbing specimens in the radiography of clinical and industrial application. Here we report on the feasibility study of the in-line phase-contrast imaging of biological samples using the LCS X-ray. Our experimental arrangement is widely used in the in-line method. The weakly absorbing parts of the samples are successfully imaged under the phase-contrast condition.

End-to-end absolute energy calibration of atmospheric fluorescence telescopes by an electron linear accelerator

The Telescope Array (TA) is a hybrid detector composed of atmospheric fluorescence telescopes and a ground array of particle detectors for the precise energy measurement of ultra high-energy cosmic rays. We propose an end-to-end absolute energy calibration of fluorescence telescopes by using air showers induced by electron beams from a linear accelerator, which will be installed at the site of the TA experiment and will have a well-measured beam energy. We have simulated electron beam dynamics and interaction of electrons in air to evaluate the accuracy of the beam energy determination, beam currents, air showers, and detector response using a beam simulation code (PARMELA) and GEANT4. We found that the systematic error of energy measurement estimated for the TA fluorescence telescopes can be reduced from 23% to 17% by this end-to-end energy calibration. We are developing and constructing a compact linear accelerator with a maximum electron energy of 40 MeV and an intensity of 6.4 mJ/pulse. In this article, we describe the method of absolute energy calibration and the design of the accelerator.

Compact linear electron accelerator for radiation technologies

A prototype of a commercial compact continuous-beam linear electron accelerator has been designed and constructed. With its energy of 600 keV and a beam with 30 kW maximum power, the accelerator can be used in various radiation technologies. Its compact size, easy operation, reliability, wide adjustment range for the main parameters, and possible local shielding allow it to be integrated into the majority of radiation technology processes.

An electron beam ion trap for the NSCL reaccelerator

The reacceleration of stopped fast-fragment beams or low-energy ISOL beams to the energy range of 0.3–12MeV/nucleon allows for experiments such as low-energy Coulomb excitation and transfer reaction studies and for the precise study of astrophysical reactions. The coupling of a reaccelerator to a gas stopper at a fragmentation facility will provide rare isotope beams of nuclides not available at ISOL facilities in this energy regime. The implementation of charge breeding is a key to obtain a compact and cost-efficient reaccelerator and it is foreseen in the development of a reaccelerator at the NSCL at MSU. An Electron Beam Ion Trap (EBIT) will be used for charge-breeding as it has the potential to rapidly and efficiently output highly charged ions in a single charge state. The system will provide highly charged ions at an energy of 12keV/nucleon to a compact linear accelerator for further acceleration.

MO‐E‐AUD‐03: Study of Total Positioning Accuracy of a Newly Developed Image‐Guided Radiotherapy System

Purpose: The aim of this study was to evaluate system accuracy of our newly developed image‐guided radiotherapy (IGRT) system. Method and Materials: The system has the following structural characteristics; (1) C‐band compact linear accelerator (LINAC), (2) O‐ring shaped gantry, (3) Gimbals mechanism at X‐ray head, and (4) Imaging subsystem. The whole X‐ray head with the LINAC and a MLC is equipped on gimbals mechanism to correct beam direction to isocenter. The imaging subsystem mounted on the O‐ring gantry consists of two sets of a kV X‐ray tube with an image detector, and can obtain either X‐ray images or cone‐beam CT (CBCT) images. By using Electronic Portal Imaging Device, the IGRT system also provides an automatic daily QA tool for total positioning accuracy, which means beam accuracy towards isocenter combined with image‐guiding accuracy. The daily QA requires only 3 minutes. Firstly in this study, to evaluate the image‐guiding accuracy, a spherical metal ball with a diameter of 10 mm was set at given positions within 20 mm from isocenter. X‐ray images or CBCT images were obtained to measure the ball position, and the difference between true and measured position was calculated. Secondly, Mechanical accuracy of beam direction to isocenter was measured in various gantry angles with CCD camera attached to MLC frame. Finally, the combined accuracy was verified by using the daily QA tool. Results: The difference between true and measured position was 0.34 mm in SD and 0.9 mm at the maximum for X‐ray image, then 0.17mm in SD and 0.4 mm at the maximum for CBCT, respectively. Mechanical beam accuracy was within 0.1mm. The combined accuracy was better than 0.5 mm. Conclusion: The IGRT system has suitable accuracy for image‐guided stereotactic irradiation. Conflict of Interest: Research sponsored by New Energy and Industrial Technology Development Organization, Japan.

The REX-ISOLDE charge breeder as an operational machine

The charge breeding system of radioactive beam experiment at ISOLDE (REX-ISOLDE), consisting of a large Penning trap in combination with an electron-beam ion source (EBIS), is now a mature concept after having delivered radioactive beams for postacceleration to a number of experiments for three years. The system, preparing ions prior to injection into a compact linear accelerator, has shown to be versatile in terms of the ion species and energies that can be delivered. During the experimental periods 2004 and 2005 a significant part of the ISOLDE beam time was dedicated to REX-ISOLDE experiments. Ion masses in the range between A=7 and 153 have been handled with record efficiencies. High-intensity as well as very-short-lived isotope beams were proven to be feasible. Continuous injection into the EBIS has also been successfully tested. Two means of suppressing unwanted beam contaminations were tested and are now in use. In addition, the experience gained from the trap-EBIS concept from a machine operational point of view will be discussed and the limitations described.

Preliminary Study of Dynamic Tumor Tracking and Shooting Capability Using a Compact Linear Accelerator Installed on Gimbals in Gantry Head of an Image-Guided Radiotherapy System

Purpose/Objective: We have been investigating a new type of image-guided radiotherapy (IGRT) system aiming at precise initial setup, and dynamic tumor tracking and shooting of a moving target. In this paper fundamental characteristics of dose distribution in a dynamic phantom using a prototype IGRT system are reported.

Recent highlights from ISOLDE@CERN

The ISOLDE online mass separator located at CERN provides a large variety of radioactive ion beams for research on nuclear physics, nuclear astrophysics, fundamental interactions, atomic physics, radiochemistry, nuclear medicine, condensed matter science, life sciences and others. The recently operational REX-ISOLDE post-accelerator is capable of accelerating the isotopes produced at ISOLDE to energies of up to 3.0MeV/u by using an ion trap and charge breeder and a compact linear accelerator structure. The post-accelerator is complemented by a highly segmented Ge array in conjunction with a compact silicon strip detector at one of the secondary target positions, while a general spectroscopy setup occupies a second station. REX-ISOLDE has opened up the possibility of nuclear spectroscopy studies by means of transfer reactions and Coulomb excitation of exotic nuclei. The facility maintains an extensive physics-driven target and ion source development program, which has helped ISOLDE keep its international status for more than 35 years. Some recent experimental highlights and technical developments are discussed.

Robotic whole body stereotactic radiosurgery: clinical advantages of the Cyberknife® integrated system

Radiosurgery is defined as the delivery of high doses of ionising radiation, in mono- or hypo- fractionated treatments, to destroy tumours or focal areas of pathology. The clinical requirements of designing a radiosurgical treatment system include providing: a) a highly precise beam delivery to targets located throughout the body, b) a highly conformal dose distribution, c) the ability to irradiate both small and/or large complex-shaped lesions while minimising the dose to adjacent radiosensitive tissues and d) the ability to interactively track lesion motion due to normal patient motion. To accomplish this, the CyberKnife radiosurgery system has pioneered in this area by taking advantage of the inherent geometrical targeting precision of a commercial arm-based robotic system carrying a compact X-band linear accelerator and integrated with X-ray imaging and visualisation feedback systems. The arm-mounted linear accelerator, equipped with patient specific anatomical models, registered to the patient in real-time with image guidance, dynamically and safely delivers conformal and homogeneous radiation for therapeutic benefit. This paper details the components of the CyberKnife system and their integration in the clinical workflow of radiosurgery.