**4. Reaction of particle activation**

1. Nuclear Activation in Reactors:

( ) *n*,γReaction: Radioactive capture: Undergo mostly by thermal neutron

$$\begin{array}{c} \stackrel{59}{29}\text{Co} + \stackrel{1}{0}n \longrightarrow \stackrel{60}{29}\text{Co} + \gamma \qquad\qquad\text{(s=36 b)}\\\\ \stackrel{98}{42}\text{Mo} + \stackrel{1}{0}n \longrightarrow \stackrel{99}{42}\text{Mo} + \gamma \qquad\qquad\text{(s=0.12 b)} \end{array}$$

In such a reaction father and daughter are of the same chemical species so they cannot be separated, reason why the target must have a very high enrichment rate.

(*n*,α) Reaction followed by β- decay

$$^{130}\_{52}Te + ^1\_0n \longrightarrow ^{131}\_{52}Te \xrightarrow{\beta^{-1}} ^{131}\_{53}I + \mathcal{Y}$$

Tellurium and iodine are easily chemical separated (*n*, *p*) Reaction: Neutron Capture

$$\begin{aligned} \,^{32}\_{16}S + \,^{1}\_{0}n &\longrightarrow \,^{32}\_{15}P + \,^{1}\_{1}H \\\\ \,^{58}\_{28}Ni + \,^{1}\_{0}n &\longrightarrow \,^{59}\_{28}Co + \,^{1}\_{1}H \end{aligned}$$

This is similar to the first reaction produced in his cyclotron that be named "neutron capture" despite he was using deuterium as projectile, he observed that neutron stayed inside target nuclear and the remaining mass was expel as a proton.

(*n*,α) Reaction: Light fission

$$\,\_{3}^{6}Li + \,\_{0}^{1}n \xrightarrow{} \,\_{1}^{3}H + \,\_{2}^{4}He$$

2. Activation Equation:

$$\frac{dN\_1}{dt} = \Phi \,\sigma\_{\rm act} N(t)$$

1

Alpha particle Bombardment: Using natural produced alpha particles light elements can be activated, and as far as Pottasium. Such projectile induce the emission of a proton, the liberation of energy and a transmutation, not all the transmutation products are radioactive Neutron Capture: Firstly observed when matter is bombarded with deuteron, which also

Reaction: Radioactive capture: Undergo mostly by thermal neutron

γ

γ

β

<sup>−</sup> <sup>+</sup> ⎯⎯→ ⎯⎯⎯→ +

In such a reaction father and daughter are of the same chemical species so they cannot be

130 1 131 131 52 0 *Te n Te I* <sup>52</sup> <sup>53</sup>

> 32 1 32 1 16 0 15 1 *Sn PH* + ⎯⎯→ +

58 1 59 1 28 0 28 1 *Ni n Co H* + ⎯⎯→ + This is similar to the first reaction produced in his cyclotron that be named "neutron capture" despite he was using deuterium as projectile, he observed that neutron stayed

> 61 34 30 12 *Li n H He* + ⎯⎯→ +

> > = Φσ

*dt*

<sup>1</sup> ( ) *act dN N t*

(s=36 b)

(s=0.12 b)

γ

59 1 60 29 0 29 *Co n Co* + ⎯⎯→ +

98 1 99 42 0 42 *Mo n Mo* + ⎯⎯→ +

separated, reason why the target must have a very high enrichment rate.

�1 � �� �� <sup>⁄</sup> � (14)

� �

involve the emission of a proton, as we will illustrate forward.

With

**3. Methods of particle activation** 

**4. Reaction of particle activation**  1. Nuclear Activation in Reactors:

) Reaction followed by β- decay

(*n*, *p*) Reaction: Neutron Capture

) Reaction: Light fission

Tellurium and iodine are easily chemical separated

inside target nuclear and the remaining mass was expel as a proton.

( ) *n*,γ

(*n*,α

(*n*,α

2. Activation Equation:

Where:

N1 = Atoms of the target

Φ = Neutron flux

σ*act* = Activation cross section

*N t*( ) = Number of atoms activated in a time period elapsed t

So, the number of activated atoms is:

$$N\_1 = \Phi \frac{\sigma\_{act} N(t) (1 - e^{-\lambda t})}{\lambda}$$

And the activity of the sample is:

$$A = \mathcal{X}N\_1 = \Phi \sigma\_{act} N(t)(1 - e^{-\mathcal{X}t})$$

t is the time of irradiation in seconds

A is the activity at the saturation value that is a function of reactor neutron flue at which target has been exposed.

3. Nuclear reaction in cyclotron production

( ) *p*,*n* Reaction

$$\,\_{8}^{18}O + \,\_{1}^{1}H \longrightarrow \xrightarrow{18} \,\_{9}^{18}F + \,\_{0}^{1}n$$

(*d*,α) Reaction:

$$^{20}\_{10}Ne + \longrightarrow \longrightarrow ^{18}\_{9}F + \,\_{2}^{4}He$$

(*p*,α) Reaction

$$\begin{aligned} \, \_{17}^{14}N + \, \_1^1H &\longrightarrow \, \_6^{11}C + \, \_2^4He \\\\ \, \_8^{16}O + \, \_1^1H &\longrightarrow \, \_7^{13}N + \, \_2^4He \end{aligned}$$

(*d n*, ) Reaction

$$\,^{14}\_7N + \,^{2}\_1H \xrightarrow{\,^{15}} \,^{15}\_8O + \,^{1}\_0n$$

(*d n* ,2 ) Reaction

$$\begin{aligned} \,^{68}\_{30}Zn + \,^{2}\_{1}H &\longrightarrow \xrightarrow{65} \,^{65}\_{31}Ga + \,2^{0}\_{1}n \\\\ \,^{124}\_{52}Te + \,^{1}\_{1}H &\longrightarrow \xrightarrow{123} \,^{123}\_{53}I + \,2^{1}\_{0}n \end{aligned}$$

( ) α,2*n* Reaction

But passing thru that dark hour, all the money spend in its development seems to be not

And cyclotron has to compete (and win) against reactors that were redeeming themselves by producing "atoms for the peace" trying to justify the large budget assign to them during

And for a long period of time the guilt drop the balance to reactors side until middle 70's when positron emission tomography arised based in a component containing 18F: 18FDG

This isotope was only produced in cyclotron and the compound could be synthetized in a

This made cyclotrons an Hospital equipment because, due to the short half-life of 18F, it was necessary to stablish the supplier so near to the costumer as it can be, and being a hospital a places were pureness and asepsie is well know, and treat with reverential respect, which other place would be better to activated pure 18F and synthetize the 18FDG in a sterile form

And between 1929 and 1974 lot of things happened to cyclotron to develop its actual characteristic. From Lawrence Cyclotron to Hospital one, until CERN´s a lot of energy has

a) b) c)

Fig. 7. Different cyclotron size: a) Lawrence´s first one, b) Venezuela First one (courtesy of

And size matters, and Cyclotrons win as best hospital candidates due to Reactors are bigger, harder and difficult to be set in a hospital installation. Can you imagine a nuclear reactor inside a health installation? Radiation Protection Program will consume all the budget available. Size, controlled reactions, electrical control, made cyclotrons easy to install, and baby cyclotrons come selfshielded so hospital don´t need to spend money in a extremely large bunker. Now on, we are going to talk about our first experience with the set up of a baby cyclotron for medical uses inside the first PET installation in Latin America. "Baby" means its acceleration "D" diameters are suitable to be set inside a standard hospital room dimensions, with all its needs to be safetly shielded for production transmision and synthetized for human uses for imaging in Nuclear Medicine PET routine. When we ask why Cyclotrons are better than reactors for radioisotopes production to be used in Medicine,

Dorly Coehlo), c) Fermi National Laboratory at CERN.

we also have to have in mind that they has:

1. Less radioactive waste 2. Less harmful debris

that important.

(Fluorodexoxy glucose).

straight forward relative easy way.

to be safe to apply in human.

pass through.

WWII.

$$\mathrm{^{65}\_{29}Cu} + \mathrm{^{4}\_{2}He} \longrightarrow \mathrm{^{67}\_{31}Ga} + \mathrm{2^{1}\_{0}m}$$
