CNA

Centro Nacional de Aceleradores

18/9 MeV Cyclotron Accelerator

The cyclotron is a circular particle accelerator which, by the combined application of an oscillating electric field and a magnetic field, accelerates the ions by spinning them in increasing radio or energy orbits
 
The Cyclotron was the second particle accelerator installed at CNA (year 2004). In this accelerator, ions are accelerated through the combined application of an electric and a magnetic field. It was manufactured by IBA (Belgium) and it accelerates protons and deuterons to 18 and 9 MeV, respectively. The extracted maximum beam intensities in the internal target ports are 80 μA ± 10% for protons and 35 μA ± 10% for deuterons.
 
The Cyclone 18/9 allows the simultaneous bombardment with the same particle of one or two targets that are located in opposite positions (Dual Beam Mode). Seven out of the eight targets are devoted to the production of positron emitters. Thus, CNA offers the possibility to produce the most frequent radioisotopes employed in the imaging modality Positron Emission Tomography (PET).
 
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This is the description of the available targets at the CNA Cyclotron:
 
1.- Large-volume target (2 ml) filled with 18O-enriched water ([18O]-H2O, purity > 95% in 18O). It is used for the production of 18F as [18F]-Fluoride through the 18O(p,n)18F nuclear reaction.
 
2-3.- Two large-volume targets (2 ml) with the cavities made of niobium and filled with 18O-enriched water ([18O]-H2O, purity > 95% in 18O). They are utilized for the production of 18F as [18F]-Fluoride through the 18O(p,n)18F nuclear reaction.
 
4.- 1.7 ml target filled with an ethanol-water mixture for the in-target production of 13N in the form of [13N]-Ammonia using the 16O(p,α)13N nuclear reaction.
 
5.- 60 ml target containing 18O2 gas used to produce 18F as [18F]-F2 by protons bombardment.
 
6.- 60 ml target, where a nitrogen-oxygen mixture is bombarded with protons, obtaining 11C as [11C]-CO2 through the 14N(p,α)11C nuclear reaction.
 
7.- 60 ml target filled with a nitrogen-oxygen mixture and used to produce 15O as [15O]-O2 by means of the 14N(d,n)15O nuclear reaction.
 
8.- Finally, there is an exit line (Experimental Beam Line) in the last target port which transports the beam line to a second vault. A reaction chamber devoted to the irradiation of technological materials is located in this second room.
 
Cyclotron external beam line
The research which requires the use of protons and deuterons, with energies above 6 MeV, must be carried out in the Cyclotron beam transport line. Until 2010, it had worked in vacuum coupling the portable irradiation and implantation line. This line can be fixed to both, the 3 MV Tandem Accelerator and the Cyclotron. At 2010, it had been a number of changes in the line leading to expand the versatility of this accelerator. Regarding the energy of the particles, the compact Cyclotron is limited to supply 18 MeV protons and deuterons of 9 MeV. In 2010, a “true” external beam line has been installed, as the particle beam goes to the air before impacting on the target.
 
From the analytical standpoint, this presents some advantages over the use of a vacuum chamber, such as the low background X-Ray spectra obtained by PIXE technique. On the other hand, the assembly of some irradiation experiments is simplified, the temperature reached in the target is lower than working in vacuum, and the size of the samples to be irradiated is not limited by the chamber dimensions. However, it is difficult to monitor the beam current density and in many cases is necessary to do indirect measurements through calibration. When working with particles fluxes around microamps, a direct reading of current in different graphite collimators and/or the target itself is done. To measure very low fluxes, particle or scintillation detectors are used.
 
The line is elementary and versatile; it can be modified with the necessary elements for each investigation without much complexity. This is now coupled to the fixed line of the Cyclotron and there are various sizes collimators available, where can be adapted different materials windows according to the study concerned. This is very interesting, since the many applications imply very different experimental needs (energy, flux, beam size ...) involving the use of various devices for the beam degradation and/or diagnosis. Although there is not possibility of scanning, it allows for a diverse range of irradiation areas by playing with the material of the exit window and the target distance.

 

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