The standard proton beams used for irradiations produced by the AGOR cyclotron have primary energies in the range of 40 to 190 MeV. After traversing about 3 m of air the energies at the position of the Device Under Test (DUT) are typically 5-10 MeV lower depending on the scatter system used. Using an energy degrader virtually all energies between 10-184 MeV can be provided.
The energy resolution of the beam when leaving the cyclotron is typically better than 0.25%. However, at the DUT position the resolution is in the order of a few MeV or more due to scatter in air, the scatter system and, when used, the energy degrader.
Both circular and rectangular fields are available. The standard irradiation field has a diameter of 70 mm and homogeneity of better than ±3%. Larger fields (up to 11 to 14 cm) can be realized with homogeneities better than ±10 and 25%, respectively.
Fluxes and fluences: The maximum flux depends on the parameters of the irradiation: field size and energy at DUT. Typical fluxes are in the order of 108 to 109 protons per cm2 per second. Fluences up to 1013 protons per cm2 can be delivered.
Solar proton spectra: Irradiations simulating the effects of a solar proton event can also be conducted. For example, the proton spectrum of the August 1972 flare is approximated using a 10 MeV binning of the energy range between 60 and 184 MeV.
Irradiations with other particles
The AGORFIRM beam line is also used for irradiations with alpha particles and carbon ions. For carbon ions with an energy of 90 MeV/u a standard field of 30 mm diameter (homogeneity ±10%) has been developed.
The AGORFIRM beam line is situated in a dedicated irradiation cell of about 10x7 m2.
All beam line components are fixed with universal mounting plates on breadboard tables. This allows all components to be rapidly placed on any position in the beam line with an accuracy of ± 0.25 mm. Components can be moved with a 5 mm stepping interval in and 25 mm perpendicular to the beam direction.
Beam line components
The initial narrow particle beam from the accelerator is broadened and flattened by using scatter foils. Our standard setup uses the dual foil technique in which the particles are scattered by a homogeneous Pb-foil and an inhomogeneous W-foil. When very large fields are needed other, thicker foils can be used. However, often one has to make a trade off between field size, homogeneity and attainable flux.
The initial beam energy can be degraded to lower energies by a compact ensemble of 9 aluminum plates of various thicknesses. These plates can be placed in the path of the beam by a remotely controlled pneumatic system. Energies can be selected between 10 and 184 MeV for protons and between 10-90 MeV/u for alphas. Possibilities for lower energies and other particles exist but are not standard at the moment.
Downstream of the scatter system there are various collimators in the beam line to stop protons that have been scattered to such large angles that they will not end up in the intended irradiation field. The final shape of the irradiation field is defined by a field collimator. A large choice of field collimators is provided. Customized formats can be made by the KVI workshop according to specification of the client. A remotely controlled dual collimator system is available to allow for fast changes in field shape.
Available standard field collimators:
Rectangular (mm x mm)
10 x (1, 2, 3, 4, 7.5, 12, 16,19)
100 x (2, 4, 8, 20, 40, 50, 100)
Circular (∅ mm)
0, 2, 5, 30, 50, 60, 70, 80, 100
XY table and sample mounting
The XY table contains a large mounting rack that allows movement of samples through the beam with a range of 600 mm in the horizontal and 300 mm in the vertical direction with a relative accuracy of 0.01 mm. Special predrilled plates for sample mounting are used that can be quickly fitted to the mounting rack.
Laser positioning system
Samples and beam line components are positioned using a 3D laser positioning system.
To minimize dose variations over a 3D target a spread-out Bragg peak (SOBP) is needed. Modulation Wheels (MWs) are available to produce SOBP's starting with primary beams of 150 MeV protons (aluminum wheel) and 90 MeV/u 12C6+ (plastic wheel). The MWs were designed on basis of measured and calculated pristine Bragg peaks.
|Laatst gewijzigd:||02 maart 2018 12:34|