Small-angle approximation in the description of radiative collective effects within an ultrarelativistic electron bunch

The problem of the evaluation of radiative collective effects accompanying accelerated motion of a short ultrarelativistic electron bunch in vacuum is considered within the framework of the small-angle approximation; second order expansion in the transverse velocity of electrons is performed in order to obtain an analytical expression for energy spread within the bunch. Comparison with earlier results by other authors shows good agreement

An Irradiation Production Unit for Polymer Research

Electron irradiation is a well known method in polymer research for studying polymer structure changes. Using an existing 6 MeV linear accelerator a general irradiation facility has been built which is especially suited for this purpose. The monitored dose is variable between 5 and 300 kGy and may be evenly distributed over the sample, with a typical size of 10x10x0.5 cm3. The linac macro pulse frequency is in the range of 1 to 50 Hz and the maximum irradiation duration is in the order of minutes. Regarding sample conditions: the temperature can be controlled between 20 and 300 oC in an environment of pure nitrogen. The control system has been modernised using a PLC controller together with a visualisation program (Intouchâ). Distributing the dose over the sample is realised either by sweeping the beam in the vertical direction using a bending magnet and moving the sample in the horizontal direction, or with the help of a permanent quadrupole magnet, inserted in the beam guiding system

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

Proposal for a race-track microtron with high peak current

In order to obtain high gain in a free electron laser a high-quality electron beam with high peak current is required. It is well-known that a microtron is able to produce a high-quality beam having low emittance and small energy spread (1%). Because a circular microtron has a limited high-current capability a race-track design is adopted for providing flexibility, better beam quality and of course higher peak current in the microbunch. Space charge problems may be severe in a microtron. It can be shown that bunching on certain specific subharmonic frequencies will lead to a strong reduction of the space charge problems. The general layout of our microtron design will be presented. The characteristics are: energy 25 MeV, micropulse 10° of the rf frequency of 3 GHz. Our aim is to come beyond the present state of the art with the following characteristics: relative energy spread 0.001, emittance 3 mm mrad, current in the micropulse 100 A, macropulse length 50 μs and subharmonic bunching at 1:64

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

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

Design of a Double Focusing Beam Transport System for the 25 MeV Electron Beam

At the University of Twente in collaboration with the Technical University of Eindhoven a Free Electron Laser is being realised with a set-up of two accelerators. The injector is a 6 MeV photo cathode linac producing a high brightness beam. The second accelerator is a Race-Track-Microtron. For the Free Electron Laser project TUEFEL fase II a system was designed to transport the electron beam with an energy of 25 MeV from the racetrack microtron to the undulator. The constructive features of the undulator and resonator demand a detailed matching between electron beam and undulator. The relative small length of the resonator requires a compact injection part of the transport system. Matching of the electron beam is performed in two steps general fixed focusing is done with quadrupoles in a dispersive section. Fine tuned focusing is done in the dispersion free part of the transport line. Dynamic 3-D simulations with space charge were done to obtain the design parameters of the beam transport system. Optimal matching of the electron beam at the undulator’s entrance is obtained

Design and Performance of a Permanent Magnetic Quadrupole for a Low Energy Linear Accelerator Beam Line

Permanent magnets which show the highest magnetic flux density, have been used in constructing an insertable Permanent Magnetic Quadrupole (PMQ). The PMQ is part of an electron irradiation facility for polymer research at the Eindhoven University of Technology. For polymer irradiation that requires a homogeneous dose distribution, the PMQ is inserted and the expanded electron beam will irradiate the target completely. Design criteria of the quadrupole are discussed. The quadrupole geometry has been optimised using CEDRAT finite element software. The influence of mechanical alignment errors (0.15 mm) and variations in permanent magnet properties (0.5%) on the magnetic field have been simulated. Sixteen NdFeB magnets (42x42x10 mm3) have been used to produce a quadrupole with an aperture radius of 50 mm. Before insertion, the magnetic flux density of all magnets has been determined versus magnetic field and temperature. After construction the lens strength of the quadrupole has been determined using the floating wire technique. The flux density has been measured using a Hall probe. Results show a magnetic field gradient that varies less than 0.5% within a radius of 25 mm. Alignment errors have been determined comparing simulation and measurement