MeV Racetrack Microtron Research Articles

Electron gun with off-axis beam injection for a race-track microtron

A miniature 12 MeV race-track microtron for medical applications is under construction at the Technical University of Catalonia in collaboration with several Spanish centers and companies and the Skobeltsyn Institute of Nuclear Physics of the Moscow State University. As a source of electrons a compact 3D on-axis electron gun with an off-axis cathode has been designed to allow a direct and efficient injection into the accelerating structure. Its prototype has been built and successfully tested. Results of the electron gun design simulations and of the prototype performance are herein described.

Simulation of e– γ– n targets by FLUKA and measurement of neutron flux at various angles for accelerator based neutron source

A 6 MeV Race track Microtron (an electron accelerator) based pulsed neutron source has been designed specifically for the elemental analysis of short lived activation products where the low neutron flux requirement is desirable. The bremsstrahlung radiation emitted by impinging 6 MeV electron on the e– γ primary target, was made to fall on the γ– n secondary target to produce neutrons. The optimisation of bremsstrahlung and neutron producing target along with their spectra were estimated using FLUKA code. The measurement of neutron flux was carried out by activation of vanadium and the measured fluxes were 1.1878 × 10 5, 0.9403 × 10 5, 0.7428 × 10 5, 0.6274 × 10 5, 0.5659 × 10 5, 0.5210 × 10 5 n/cm 2/s at 0°, 30°, 60°, 90°, 115°, 140° respectively. The results indicate that the neutron flux was found to be decreased as increase in the angle and in good agreement with the FLUKA simulation.

A 70 Mev racetrack microtron

We describe here the design, construction, and commissioning of a compact 70 MeV RaceTrack Microtron.

ANKA–Service-Oriented Synchrotron Radiation Facility

ANKA is a 2.5 GeV synchrotron radiation facility under construction at Forschungszentrum Karlsruhe. ANKA is based on a 2.5 GeV electron storage ring injected from a 500 MeV booster synchrotron and a 50 MeV racetrack microtron. Nominal circulating electron current will be 400 mA. The facility is scheduled to become operational in fall 2000. ANKA will deliver photons predominantly in the hard X-ray range but it will also feature both XUV and infrared beamlines. So far, all beamlines will use bending magnets as sources, while provision is made to install appropriate insertion devices later on. ANKA has a novel mission which is characterised by giving preference to providing service to customers while maintaining a significant fraction of research work. ANKA will offer full service in X-ray lithography, mainly for micro- and nanofabrication, and in analysing and investigating non-destructively various structural, mechanical, chemical, electronic, magnetic, and molecular properties of samples and components.

The Eindhoven linac–racetrack microtron combination

The Eindhoven linac–race track microtron (RTM) combination has been designed to serve as injector for an electron storage ring. The linac is a 10 MeV travelling-wave linac (type M.E.L. SL75/10). In the RTM a 5 MeV standing-wave cavity, which is synchronized with the linac, accelerates the electron beam 13 times, such that the extraction energy is 75 MeV. The RTM end magnets are two-sector magnets tilted in their median planes, to provide strong focusing forces for optimal electron-optical properties. Closed-orbit conditions are fulfilled with the help of small correction dipoles located in the RTM drift space; the magnetic-field strengths of these correction dipoles are adjusted on the basis of beam-position measurements. Isochronous acceleration is accomplished by position- and phase-measurements. A low-cost elaborate diagnostic system will be used for efficient commissioning of the combination of the 10 MeV linac and the 10–75 MeV RTM.

A mobile racetrack microtron

Motivated by our need for a light source for our Nitrogen and Carbon Cameras, we have designed and are building a rugged compact 70 MeV RaceTrack Microtron (RTM) with simplified beam optics and tuning, improved beam parameters, and decreased capital and operating costs. The principal innovations that permit this are rare earth permanent bending magnets and a narrow rectangular biperiodic accelerating focusing structure. We describe here our machine as optimized using beam dynamics simulations.

The MAMI source of polarized electrons

The present work describes the source of polarized electrons that is run at the 855 MeV race track microtron MAMI at the Johannes Gutenberg Universität in Mainz. The source is based on photoelectron emission from (III–V)-semiconductors. Presently strained layer InGaP- or GaAsP-cathodes are used, which are processed to negative electron affinity by coverage of the surface with a submonolayer of caesium and oxygen. Electron beams spin-polarized up to a degree of P = 55% at a quantum efficiency of QE = 2% or P = 75% at QE = 0.4%, respectively, are obtained. The well-known but hitherto unsolved problem of limited cathode lifetime has been sidestepped by the attachment of an UHV load lock system to the source electron gun. It allows quick replacement of cathodes without breaking the gun vacuum. Availabilities in excess of 85% are obtained regularly in beamtimes longer than 100h. The source was mainly applied in measurements of nucleon form factors via the reactions 1H(ē, e′ p̄), 2D(ē, e′ p̄), 2D(ē, e′ n̄), and 3H̄e(ē, e′ n). More than 1600 h beamtime have been accomplished in physics experiments with polarized electron beams at MAMI up to now.

The new 1.5 GeV storage ring for synchrotron radiation: MAX II

The MAX laboratory at Lund University, Sweden, today operates an accelerator system consisting of a 100 MeV racetrack microtron and a 550 MeV storage ring (MAX I). At the moment (July 1994) a new storage ring MAX II is near completion and will start first injections within 2 months. This work gives an overview of the MAX II project including the first beamlines and a description of the accelerator system. MAX II is a 1.5 GeV third generation light source optimized for the VUV and soft-x-ray region. It consists of a ten cell double bend achromat lattice forming the 90 m circumference ring. Injection is done at 500 MeV from the existing storage ring MAX I, and ramping up to full energy will take place in MAX II. The straight sections have a length of 3.2 m and eight sections are free to house insertion devices. At start up the ring will be equipped with one 7.5 T superconducting wiggler and one 1.8 T multipole wiggler. Two more undulators are ordered and under construction. To be able to achieve the project a few shortcuts have been made in the design of the storage ring: (1) Nonzero dispersion is allowed in the straight sections, (2) chromaticity correction is built into the quadrupole magnets, and (3) the length of the straight sections is limited to 3.2 m. The project is progressing on time. Extraction of an electron beam from the MAX I storage ring has been achieved and has successfully been transported into the MAX II building. The MAX II ring is under assembly with most of the sections already mounted. First injection is planned to take place in August 1994.

The “TEU-FEL” project

The free-electron laser of the TEU-FEL project will be based on a 6 MeV photo-cathode linac as injector, a 25 MeV race-track microtron as main accelerator and a hybrid, 25 mm period undulator. The project will be carried out in two phases. In phase one only the 6 MeV linac will be used, The FEL will then produce tunable radiation around 200 μm. In phase two the linac will be used as an injector for the microtron. The FEL will then produce tunable radiation around 10 μm. Technical information will be presented on the different subsystems.

Developments of the TEUFEL injector racetrack microtron

In this paper we report on developments of the 25 MeV racetrack microtron (RTM) that will be the electron source for the second phase of the TEUFEL project, to generate radiation of 10 μm in a 2.5 cm period hybrid undulator. The theoretical understanding of this unconventional, azimuthally varying field type of RTM has been extended. A comparison of analytically calculated orbit stability with that based on measured data will be presented; orbit calculations using measured field data show the designed performance. Construction and tuning of the 1300 MHz, 2.2 MV microwave cavity have been completed, and signal level measurements have been performed. The overall assembly of the microtron is nearing completion. At present a vacuum pressure better than 5 × 10 −7 Torr is achieved.

Preclinical evaluation of the reliability of a 50 MeV racetrack microtron

Purpose : A 50 MeV racetrack microtron has been installed and tested at Memorial Sloan-Kettering Cancer Center. It is designed to execute multi-segment conformal therapy automatically under computer control using scanned X ray and electron beams from 10 to 50 MeV. Prior to acceptance of the machine from the manufacturer, formal reliability testing was carried out. Only in this way could confidence be gained in its usefulness for routine 3D computer-controlled conformal therapy. Materials and Methods : To assess reliability, a set of 25 multi-segment test cases, each consisting of 10 to 17 fixed segments, was developed. The field arrangements and modalities for some of the test cases were identical to 3D conformal treatments that were being delivered with multiple static fields on conventional linear accelerators at our institution. Other cases were designed to explore reliability under more complex sets of conditions. These cases were “treated” repeatedly during a total period of 45 hours, over 5 days. During the treatments, ion chambers attached to the head of the machine provided dosimetric data for each field. Data from sensors connected to every set-up parameter (for example, couch positions, gantry angle, collimator leaf positions, etc.) were recorded and verified by an external computer. Results : While preliminary tests indicated an interlock rate of 5%, final reliability test results demonstrated an interlock fault rate of approximately 0.5%. The reproducibility of dosimetric data and geometric setup parameters was within specifications. As an example, leaf position reproducibility in the patient plane was within 0.5 mm for 97% of the setups. The times required to carry out treatments were recorded and compared with the times to carry out identical treatments on a conventional linear accelerator with cerrobend blocks. Areas where additional time savings can be achieved were identified. Conclusion : As an integral part of acceptance testing, the Scanditronix MM50 was rigorously tested for reliability. The machine successfully passed these tests, providing increased confidence in its usefulness for routine 3D conformal therapy.

Status of the “TEU-FEL” project

The free-electron laser of the TEU-FEL project will be realized in two phases. In phase I the FEL will be driven by a 6 MeV photoelectric linac. In phase II the linac will be used as an injector for a 25 MeV race-track microtron. Information is presented on some technical details and the status of the different subsystems.

Numerical design and model measurements for a 1.3 GHz microtron accelerating cavity

As part of the free electron laser project TEUFEL, a 25 MeV racetrack microtron is under construction at the Eindhoven University. The accelerating cavity of this microtron is a standing wave on axis coupled structure. It consists of three accelerating cells and two coupling cells. Numerical field calculations for this cavity were done with the computer codes SUPERFISH, URMEL-T and MAFIA. Not only the accelerating modes but also the dangerous beam breakup modes were calculated with MAFIA. An aluminium, scale 1:1 model of the structure was made in order to measure various cavity properties. Field profiles were measured with the perturbation ball method. An equivalent LC-circuit simulation of the accelerating structure was made, which serves as a model for the interpretation of the results.

Design study of the storage ring EUTERPE

At present the 400 MeV electron storage ring EUTERPE is being constructed at the Eindhoven University of Technology. It is a university project set up for studies of charged particle beam dynamics and applications of synchroton radiation, and for the education of students in these fields. The design of the ring is described in this paper. Considering the requirements of users in different fields, a lattice based on a so-called triple bend achromat structure with a high flexibility has been chosen. With this lattice, different optical options, including the HBSB (high brightness, small beam), the SBL (short bunch length) and the HLF (high light flux) modes can be realized. A small emittance of 7 nm rad and a short bunch length of the order of several mm can be achieved. In the first phase the synchrotron radiation in the UV and XUV region (the critical wavelength is 8.3 nm) will be provided from the regular dipole magnets. Later on, a 10 T wiggler magnet and other special inserters will be added, and other applications and beam dynamics studies will be feasible. Bending magnets are of the parallel faced C configuration. The effective aperture of the vacuum chamber is 2.3 cm (vertical) in the bending magnets and 4.7 cm elsewhere with a working vacuum condition of 10−9 Torr. Collective effects have been studied initially. First calculations indicate that a lifetime of several hours, influenced by the Touschek effect and residual gas scattering will be achievable for a 200 mA beam in the HLF mode for the standard rf parameters. A 70 MeV racetrack microtron will serve as injector for the ring.

Pre-clinical evaluation of the reliability of a 50 MEV racetrack microtron

Pre-clinical evaluation of the reliability of a 50 MEV racetrack microtron

Present development at MAX-lab

The development at the present MAX I ring concerning a new beam position monitor system, enhanced injection efficiency, harmonic generation of coherent radiation, the suppression of longitudinal instabilities and some development work on the 100 MeV race-track microtron to increase the bunch current is presented. The lattice and design philosophy of the 1.5 GeV MAX II third generation synchrotron light source currently being built at MAX-lab are also discussed.

A 28 kV + 0.020% 200 kW DC Power Supply

Design, construction and testing of a prototype HV power supply for the klystrons of the 300 MeV racetrack microtron (MUSL) of the University of Illinois are described. Regulation of 0.02% is achieved with three voltage feedback loops. Two loops to thyristor phase control circuits on the ac primary of a 12-phase rectifier transformer regulate its output to within ± 0.2% (line regulator). A third loop controls a series-connected tetrode to bring the output to within ± 0.02% of the preset value. The voltage drop across the tetrode can be set between 800 V and 1600 V; this setting is maintained by one of the loops to the line regulator. Other unique features are protective circuits that limit the fault current to 150% of the rated current when the klystron and/or the tetrode spark over. Voltage spikes generated by the thyristors are attenuated with LP-filters.

Progress Report on the NBS/LOS Alamos RTM

The NBS-Los Alamos 200 MeV Racetrack Microtron (RTM) is being built under a program aimed at developing the technology needed for high-current intermediateenergy CW electron accelerators. In this report we give an overview of the present status of the project. Recent progress includes: (1) completion of testing of the 100 keV chopper-buncher system demonstrating a normalized emittance well under the design goal of 2.6 π mm mrad at currents exceeding the design goal of 600 μA; (2) operation of the rf structures comprising the 5 MeV injector linac at power levels up to 50 kW/m, resulting in an accelerating gradient at ß=1 of 2 MV/m (compared to a design goal of 1.5 MV/m). The measured shunt impedance is 82.5 Mn/m; (3) construction and installation of the 30 ton end magnets of the RTM. Field mapping of one magnet has been completed and its uniformity exceeds the design goal of ±2 parts in 104; (4) performance tests (with beam) of prototype rf beam monitors which measure current, relative phase, and beam position in both transverse planes. (5) Installation and initial operation of the primary control system.

The 50 MeV racetrack microtron at the royal institute of technology stockholm

The development, construction, and operation of a pulsed 50 MeV two-sector racetrack microtron is described. The machine has internal electron gun injection and uses a biperiodic standing wave linac for the acceleration. Electrons with energies between 3 MeV and 55 MeV can be extracted. Orbital stability is ensured by an inverted magnetic field along the fronts of the main magnets.

Design and Operation of the 100 MeV Aladdin Microtron Injector

At present the Synchrotron Radiation Center (SRC) is nearing completion of its Aladdin project to provide a 1 GeV electron storage ring for the production of synchrotron radiation; the injector for this machine is a 100 MeV racetrack microtron (RTM). The choice of an RTM for this purpose if multifold: monoenergiticity of the output beam; basic simplicity of design; ease of operation; and reasonable cost. It is also for these same reasons that our facility has previously built two conventional (circular orbit) microtrons, used in the same application, at energies of 10 and 45 MeV.