Authorization and Inspection of Cyclotron Facilities Cyclotron Accelerators: Operation and Components

Authorization and Inspection of Cyclotron Facilities Objectives Become familiar with the basic principles of operation of cyclotrons and auxiliary systems. Identify the different types of accelerators, particle energies and currents. Targets: Types, preparation and recovery

Authorization and Inspection of Cyclotron Facilities 1) History; 2) Operating basics; 3) Ion sources; 4) Magnetic field; 5) Radiofrequency; 6) Beam extraction systems;

Authorization and Inspection of Cyclotron Facilities 7) Beam delivery systems; 8) Target holders; 9) Vacuum systems; 10) Cooling Systems; 11) Uses of cyclotrons.

Authorization and Inspection of Cyclotron Facilities In the 30s, Ernest Lawrence built the first circular accelerator named cyclotron.

Authorization and Inspection of Cyclotron Facilities

246 (2002) 262 (39 IAEA Members) 350 (in the world)

Authorization and Inspection of Cyclotron Facilities Some modern accelerators IBA cyclotron

Authorization and Inspection of Cyclotron Facilities ACSI cyclotron

Authorization and Inspection of Cyclotron Facilities GE cyclotron

Authorization and Inspection of Cyclotron Facilities Siemens cyclotron

Authorization and Inspection of Cyclotron Facilities A cyclotron is a compact device for accelerating charged particles to high energies. Motion of charged particles in an electromagnetic field:

Authorization and Inspection of Cyclotron Facilities Electromagnet producing the constant magnetic field. The correct choice of electric and magnetic fields results in a semicircular movement of charged particles. The electric field accelerates the particles at every turn.

Authorization and Inspection of Cyclotron Facilities 2 Dees connected to an RF generator producing the electric field. The charged particles rotate in the plane perpendicular to the magnetic field.

Authorization and Inspection of Cyclotron Facilities

Acceleration in a circular trajectory Electric field Charged particle Magnetic field Alternative to provide an acceleration on every moment.

Authorization and Inspection of Cyclotron Facilities The ion beam is injected into the center of the cyclotron, accelerated by an electric field, when it crosses the space between the Dee's. Under the action of a magnetic field, the beam is deflected until it reaches the other side of the Dee's and it is accelerated again. The process is repeated until the particle reaches the expected energy value, where it is directed to the target to be bombarded, through a device called stripper.

Authorization and Inspection of Cyclotron Facilities DEE’s Central region

Authorization and Inspection of Cyclotron Facilities DEE’s

Authorization and Inspection of Cyclotron Facilities 18 F - 15 O 11 C 18 F H-H- D-D- Ion Source H+H+ H-H- H-H- Carbon (stripper) foils e-e- Beam delivery system-extractor (negative ion)

Authorization and Inspection of Cyclotron Facilities Dee

Authorization and Inspection of Cyclotron Facilities

r Half-turn -  x r Time- t

Authorization and Inspection of Cyclotron Facilities Independent of the radius

Authorization and Inspection of Cyclotron Facilities

A real cyclotron requires more than: –RF (electric field) –Magnetic Field It is necessary: –Vacuum –Ion Source For radionuclides production is necessary: –Extraction –Targets

Authorization and Inspection of Cyclotron Facilities The ion source that generates the particles; The vacuum system to avoid collisions; The magnet field (B) to provide the circular path; The RF system that accelerates the particles; The extraction system that extracts the particles; Targets, where radioisotopes are produced.

Authorization and Inspection of Cyclotron Facilities There are several types of ion sources with different performance characteristics. The sources most commonly used today are: Hot cathode; Cold cathode; External source, and Internal source. External Ion Source

Authorization and Inspection of Cyclotron Facilities Positive Ions Based on the ionization of a gas; A hot filament produces free electrons in the magnetic field; An electric field accelerates the electrons through the gas - there is production of plasma therein; Positive ions from the plasma are extracted through a slit.

Authorization and Inspection of Cyclotron Facilities Gas Inlet Vacuum shutter Electrical connections Cooling (water) Ion Sources – Positive Ions

Authorization and Inspection of Cyclotron Facilities Commercial compact cyclotrons Negative Ions H2H2 H-H- Plasma is created between two cathodes. The magnetic field maintains the arc confined. The entire system is maintained in a closed volume to avoid the gases to influence the cyclotron vacuum.

Authorization and Inspection of Cyclotron Facilities Chimney: copper-tungsten alloy Cathodes: tantalum

Authorization and Inspection of Cyclotron Facilities Internal Ion Source – PIG type

Authorization and Inspection of Cyclotron Facilities  To produce the circular path;  To contain the plasma in the ion source;  Is generated by two coils (top and bottom);  Big electromagnet (20 tons).

Authorization and Inspection of Cyclotron Facilities Coils Yoke Poles

Authorization and Inspection of Cyclotron Facilities The generated magnetic field allows the acceleration of protons and negative ions.

Authorization and Inspection of Cyclotron Facilities

 The function of the RF system is to direct the ions from the ion source, in order to produce their acceleration, giving the conditions for achieving the required energy for the nuclear reaction. Creation of the field E

Authorization and Inspection of Cyclotron Facilities Valley: almost-straight trajectory Hill: curved trajectory- 90º Dee Gap: acceleration Trajectory in a field with azimuthally variation

Authorization and Inspection of Cyclotron Facilities Ion source Poles yoke Dees

Authorization and Inspection of Cyclotron Facilities  The method of extraction of the beam into the cyclotron depends on the sign of the charge particles. Positive particles: deflector. Negative particles: extraction foils (strippers).

Authorization and Inspection of Cyclotron Facilities Inside view of a cyclotron - 2 deflectors Electrostatic device used to remove particles from the magnetic field.

Authorization and Inspection of Cyclotron Facilities  Beam losses in the deflector ( %);  Difficulties with cooling the deflector;  Increased activation of components;  Need for high electrostatic fields (100 kV / cm).

Authorization and Inspection of Cyclotron Facilities Beam delivery system– stripper stripper 2 e - H+ => to the target

Authorization and Inspection of Cyclotron Facilities Thin carbon foil placed in the extraction radius.

Authorization and Inspection of Cyclotron Facilities  Ions have their electrons removed and become positive;  The direction of rotation is inverted suddenly and ions are extracted from the magnetic field;  Almost no losses in the stripper foil, therefore there is little activation and possibility of higher currents;  Each stripper position corresponds to a single beam position  limited energy possibilities (frequently one for each type of particle).

Authorization and Inspection of Cyclotron Facilities

 Increased autonomy to develop target holders and transfer systems.

Authorization and Inspection of Cyclotron Facilities

 Bipolar Coils;  Quadrupole coils;  Pressure Sensors;  Collimators.

Authorization and Inspection of Cyclotron Facilities  Targets can be:  solid  liquid or  gas

Authorization and Inspection of Cyclotron Facilities  18 O(p,n) 18 F

Authorization and Inspection of Cyclotron Facilities Beam Beam power ~ 1800 Watts –Volume: 3 ml –Pressure: 40 bars

Authorization and Inspection of Cyclotron Facilities  124 Te(p,n) 124 I Heat dissipation

Authorization and Inspection of Cyclotron Facilities 14 N(d,n) 15 O 14 N(p,α) 11 C  Gases

Authorization and Inspection of Cyclotron Facilities  Vacuum pumps:  High vacuum is required to reduce the interaction of the accelerated particles with air molecules.  Typical vacuum: 10-6 mbar for positive ion cyclotrons, 10-8 mbar for negative ions.  All materials (connectors, flanges, shutters,...) must be compatible with the vacuum level.

Authorization and Inspection of Cyclotron Facilities  2 phases;  40 or 80 m³/h;  Atm -> to mbar.  3 phases;  to mbar.

Authorization and Inspection of Cyclotron Facilities

 Generally based on two subsystems:  Primary, outside the cyclotron;  Secondary, deionized water, supplying water to all subsystems of the equipment.

Authorization and Inspection of Cyclotron Facilities  Helium Refrigeration Units  Cooling of the targets.

Authorization and Inspection of Cyclotron Facilities Uses of cyclotrons Radionuclide production For use in medicine, research and industry High energy charged particles introduce changes in the nucleus of the atoms being irradiated Typically threshold reactions, hence minimal energy of particles necessary

Authorization and Inspection of Cyclotron Facilities Uses of cyclotrons (cont) Radionuclide production:  -emitters Radio nuclide UseReaction 77 BrIn vitro studies and optim. of chemistry 77 As( ,2n) 77 Br 201 TlScintigraphy of the heart 203 Tl(p,3n) 201 Pb  201 Tl 111 InLabelling of monoclonal anti-bodies 112 Cd(p,2n) 111 In 56 CoCalibration source 56 Fe(p,n) 56 Co 57 CoHaematological studies 58 Ni(p,pn) 57 Ni  57 Co 58 CoPositron annihilation studies 59 Co(p,pn) 58 Co 67 GaLabelling of monoclonal anti-bodies 68 Zn(p,2n) 67 Ga

Authorization and Inspection of Cyclotron Facilities Uses of cyclotrons (cont) Radionuclide production: Positron emitters Radio nuclide UseReaction 11 C Labelling of molecules for PET studies 14 N(p,  ) 11 C 13 N 16 O(p,  ) 13 N 15 O 14 N(d,n) 15 O 18 F 18 O(p,n) 18 F 16 O( ,pn) 18 F 75 Br 75 As( 3 He,3n) 75 Br 76 Br 75 As( ,3n) 76 Br 62 Cu 63 Zn(p,pn) 62 Zn  62 Cu

Authorization and Inspection of Cyclotron Facilities Uses of cyclotrons (cont) Radionuclide production Reactions with different particles  need to accelerate different particles Different reaction thresholds  need to accelerate to different energies Multi-particle, multi-energy cyclotrons: very flexible, but complex machines, often positive ion cyclotrons Dedicated accelerators: usually 2 types of particles (p and d) and 1 fixed energy for each particle, typical for negative ion cyclotrons

Authorization and Inspection of Cyclotron Facilities Uses of cyclotrons (cont) Simulation of radiation damage Often associated with fusion research: 2 H + 3 H  4 He + n Materials exposed to intense beams of  -particles and neutrons  -particles: implantation of He gas Neutrons: displacement of atoms in crystal lattice

Authorization and Inspection of Cyclotron Facilities Uses of cyclotrons (cont) Fast neutron activation analysis (FNAA) Fast secondary neutrons used to activate samples Determination of activation products reveals information on atomic composition of samples Need for a well-characterised multi-energy neutron source Proton induced X-ray Emission (PIXE) Excitation of K/L-electrons by protons followed by emission of characteristic X-ray for determination of atomic composition Need for low energy proton beams of low intensity (1nA)

Authorization and Inspection of Cyclotron Facilities Uses of cyclotrons (cont) Proton therapy Delivering high doses to malignant tissue using proton beams in stead of electron or photon beams Bragg peak: tissue sparing effect is much larger and sharp dose gradients are possible Patient and tumour positioning are crucial