Cyclotrons are particle accelerators that use magnetic and electric fields to accelerate charged particles in a circular path. They are commonly used to produce short-lived radionuclides for positron emission tomography by bombarding target materials with protons or deuterons. Key components of a cyclotron include ion sources, dees, magnetic fields, radiofrequency systems, and targets.

1. Radionuclide production methods Cyclotron Nuclear reactor Radionuclide generator

2. CYCLOTRON Pawitra Masa-at 4937092 SIRS/M January 31, 2007

3. Basics of PET Tracer Production

4. Generates high-energy particles Generate PET radionuclide Generates TRACER

5. Particle Accelerators CYCLOTRON One of the earliest types of particle accelerators Cyclotron are source of a large number of high-energy (MeV) range charged particle .

6. CTI RDS-Eclipse shelf-shielding cyclotron Accelerations proton to 11 MeV . MINI trace (GE) shelf-shielding cyclotron Accelerate protons to 9.6 MeV Cyclone 18/9 PET trace (GE) 16.5 MeV negative ion cyclotron Six target proton and deuteron

7. Physics of cyclotron A device invented by E . O . Lawrence and M . S . Livingston at Berkeley in 1931 that is used to accelerate charged particles by means of a magnetic field . A particle of mass (m ) and charge (q ) moving with a velocity ( v ) will interact with a magnetic field of strength ( B ) whose direction is perpendicular to the plane of its travel with force

8. The force of the magnetic field The force of the electric field Charged Particle in an EM Field Lorentz force

10. Centripetal force on particle in an orbit The force of the magnetic field is perpendicular to the particle's direction, resulting in a circular path inside the cyclotron. Equating F with a centripetal force gives

11. Homogeneous magnetic field in which case, So Where then T (time) can be written as

12. RF oscillator frequency For particle of constant mass , the frequency does not depend upon the radius of the particle’s orbit.

13. As the beam spirals out, its frequency does not decrease, and must continue to accelerate, as it travelling more distance in the same time.

14. As mentioned earlier, this is a constant frequency orbital accelerator, but one in which the orbit radius increases. Frequency given by …………… .

15. Max KE achievable: ………… ..

16. Cyclotron Component Major Exterior Component Shielding Major Interior Component Vacuum system Ion Source Magnetic system Radiofrequency system Dees Beam extraction Targets

17. Vacuum System High vacuum (10 -6 , 10-8) needed to reduce interaction of accelerated particles with air molecules. prevents the creation of other unwanted nuclides. Electrical insulation of the DEEs. All material needs to be compatible with level of vacuum .

18. Ion Source Provide the source of ions (proton or deuteron) that that will be accelerated Introduce the ion into magnetic field The input to the ion source is 99.9995% pure hydrogen. mounted in the centre of the cyclotron. p+ e- e-

19. Ion source system (cont) Ion Source

20. Magnetic System Provide the magnetic field Makes the ion travel in circular orbit Keeps the beam of ions focused and compact.

21. Charged Particle in an EM Field

22. Radiofrequency System (RF) Pulls the ions out of the ion source. The RF oscillates about the two Des at high frequency and voltage. Push and Pull particles around the cyclotron Accelerates the ions to the specified energy prior to its bombardment.

23. RF System (cont) Flaps Fine tuning RF frequency Stem Supplying RF power to Dee’s

24. Dees Electrode inside the cyclotron. Pulse with fluctuating negative and positive charges. to “push” and “pull” the ions through the circular acceleration.

25. DEEs Ion Source

26. Particle acceleration

27. Beam Extraction Thin carbon foil placed at the extraction radius Electron are tripped off Ion become Positron. Remove the “-” e - in the case of F-18 production No beam losses here.

29. Beam Extraction (cont) H - Ion source Creates the ion Orbits controlled by magnet field RF System Accelerates the ion Carbon foil H + Extraction System Changes polarity of ions 16.5 MeV p+ e- e- p+ e- e- p+ e- e-

30. Target Targets are located outside the cyclotron The high energy particle beam of protons hit the nucleus (of the target material) & cause a nuclear reaction. The target material can be a gas, liquid or solid.

31. Radionuclide Production Reactions with different particles  need to accelerate different particles Different reaction thresholds  need to accelerate to different energies

32. Uses of Cyclotrons Multi-particle, multi-energy cyclotrons: very flexible, but complex machines often positive ion cyclotrons Dedicated cyclotron: usually 2 types of particles (p and d) and 1 fixed energy for each particle typical for negative ion cyclotrons

33. Advantage of Cyclotron Produce atom has different charge. High specific activity / short half-life. Biochemical atoms.

34. Cyclotron Radioisotope For PET studying Nuclide T 1/2 Production Carbon-11 20.4 min 10 B(d,n) 11 C Nitrogen-13 9.96 min 12 C(d,n) 13 N Oxygen-15 2.05 min 14 N(d,n) 15 O 16 O(p,pn) 15 O Fluorine-18 110 min 18 O(p,n) 18 F

35. Cyclotron Radioisotope other Nuclide T 1/2 Cobalt-57 272 d  marker for in-vitro kits. Gallium-67 78 h  tumour imaging & localization of infection Indium-131 2.8 d  diagnostic studies ; brain, infection, colon transit studies Iodine-123 13 h  diagnostic of thyroid function Rubidium-82 65 h  myocardial perfusion imaging Strontium-92 25 d  parent of Rb-82 in generator Thallium-201 73 h  dianostic of heart condition etc.

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