### Author Topic: Cyclotron  (Read 396079 times)

#### Zahraa

• Newbie
• • Posts: 11 ##### Re: Cyclotron
« Reply #30 on: November 19, 2010, 02:17:30 am »
You are thinking about a constant acceleration acc acting for a finite time.
However, the acceleration is always perpendicular to the velocity vector.

The magnitude of the velocity will change if the acceleration is in the direction of the velocity.
Because the acceleration is always pendicular to the velocity so it only change the direction of the velocity.

thank you again ..
but is this a general physics rule ??
that
"the acceleration is always pendicular to the velocity so it only change the direction of the velocity"

#### Fu-Kwun Hwang

• Hero Member
•     • • Posts: 3062 ##### Re: Cyclotron
« Reply #31 on: November 19, 2010, 12:37:23 pm »
The acceleration is determined by force \$vec{a}=frac{vec{F}}{m}\$.

The acceleration is in general not necerssary pendicular to the velocity.
The Lorentz's force is \$vec{F_b}=qvec{v}   imesvec{B}\$
For charged particle in uniform magnetic field.
The force \$vec{F_B}\$ is always pendicular to both velocity \$vec{v}\$ and magnetic field \$vec{B}\$.
So the uniform magnetic will only change direction of charged particle (it will not change the speed of charged particle).

#### Zahraa

• Newbie
• • Posts: 11 ##### Re: Cyclotron
« Reply #32 on: December 06, 2010, 01:08:07 pm »
Hello

Am still facing some problems with my simulation for cyclotron ... I have drown 2D module in Open_GL with Java to draw the particle And see its motion  in the Dee and the gap ..

my new problem is with the values of vectors B E ( magnetic  and electric fields  ) ...how can I get A real values for
them to get real simulation and real representation to the cyclotron ?? ...

also the values of mass and charge of the charged particle is so small that I couldn't  represent them in  my simulation ...

#### Fu-Kwun Hwang

• Hero Member
•     • • Posts: 3062 ##### Re: Cyclotron
« Reply #33 on: December 06, 2010, 05:51:14 pm »
Let me know all the parameters you have set for your simulation.
I do not know how to help you if I do not have any information about the simulation from you!

#### Zahraa

• Newbie
• • Posts: 11 ##### Re: Cyclotron
« Reply #34 on: December 07, 2010, 09:22:35 am »
Let me know all the parameters you have set for your simulation.
I do not know how to help you if I do not have any information about the simulation from you!

Am studying the motion in very small period of time and calculate the vector  of velocity and accelerate every moment
then I can calculate the position  of the particle in this moment then I draw it ....

in the Gap I need to know the electric filed to calculate the accelerate  vector acc =  (q.E)/m
and I need the proton mass and  charge ( I know them but they are so small that I couldn't represent them ..

in the Dee I need to know the magnetic filed to calculate the accelerate  vector acc= (q.vB)/m ..

#### Fu-Kwun Hwang

• Hero Member
•     • • Posts: 3062 ##### Re: Cyclotron
« Reply #35 on: December 07, 2010, 12:11:56 pm »
Acceleration \$a=frac{qE}{m}\$
for electron \$q=1.6   imes 10^{-19}\$kg, \$m=9.1   imes 10^{-31}\$
So you can calculate acceleration.
However, the time for the particle to accelerate is very small.
You can not do a real time simulation. However, you can change the time step to small enough number.
e.g. If the velocity is \$v=10^{5}\$m/s , and the gap is 2cm=\$2   imes 10^{-2}\$m, then the time step should be much smaller than \$frac{2   imes 10^{-2}}{10^5}=2   imes 10^{-7}\$s.

\$P=mv= qBr\$, You can use this equation to determine the value of \$B\$.
You need to define what is the maximum energy the charge particle will gain in the cyclotron, which will determine the maximum velocity, and you should be able to find B.
The energy for electron should be much smaller than 511keV (or velocity much small than speed of light),
otherwise, you also need to consider correction due to special relativity effect.

#### lookang

• Hero Member
•     • • Posts: 1772
• http://weelookang.blogspot.com ##### Re: Cyclotron
« Reply #36 on: December 08, 2010, 12:52:13 am »
Hello

Am still facing some problems with my simulation for cyclotron ... I have drown 2D module in Open_GL with Java to draw the particle And see its motion  in the Dee and the gap ..

my new problem is with the values of vectors B E ( magnetic  and electric fields  ) ...how can I get A real values for
them to get real simulation and real representation to the cyclotron ?? ...

also the values of mass and charge of the charged particle is so small that I couldn't  represent them in  my simulation ...
this is my attempt at the assignment given at http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1972.0 for the construction of Cyclotron
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=2021.0
Ejs Open Source Cyclotron Java Applet in 3D
Enjoy!

#### lookang

• Hero Member
•     • • Posts: 1772
• http://weelookang.blogspot.com ##### Re: Cyclotron
« Reply #37 on: December 08, 2010, 04:20:00 pm »

The constancy of the cyclotron frequency led to a device called cyclotron.
This java applet let you play with cyclotron.
<hr>
<center><applet code="cyclotron.class" width=500 height=340 codebase="/java/cyclotron/"><param name="Reset" value="Reset"><param name="Start" value="Start"><param name="Clear" value="Clear"><param name="ratio" value="Frequency ratio"></applet></center>
<hr>

i need to understand why frequency ratio = 1
does not produce the cyclotron effect of shooting particles out of the 2 dees (magnetic field).?

i need to understand is my assumption correct that
frequency ratio = electric field frequency / angular frequency of motion

#### lookang

• Hero Member
•     • • Posts: 1772
• http://weelookang.blogspot.com ##### Re: Cyclotron
« Reply #38 on: December 09, 2010, 08:16:18 pm »
If the gap between the dees is very small , the two frequency is the same.
What if the gap is not small? You will need to adjust the frequency of the electric oscillator.
Enter the value of the frequency ratio (oscillator frequency/cyclotron frequency) into the textfield.
<ul>( Do not forget to hit RETURN button after you change the frequency ratio)</ul>
Click the red dot near the electric oscillator and drag it up/down to change the voltage of the oscillator.

oic.
i finally figure out this cyclotron.
the frequency ratio (oscillator frequency/cyclotron frequency)=1 initially for a few rounds

then the oscillator frequency > cyclotron frequency, i need to adjust it is 1.1?
but the sims did not take new values of frequency ratio, when i key in 1.1 at time >0, the sims reset.
is that correct design of this sim?

#### Fu-Kwun Hwang

• Hero Member
•     • • Posts: 3062 ##### Re: Cyclotron
« Reply #39 on: December 09, 2010, 10:08:12 pm »
Most of the simulation ignore the time for electron to pass the D gap.
I add this time difference into the simulation to remind user for a real device it need some modification.

There are another issue, when there are more than one electron generate at different time.
How to control the device so that more electrons will be focusd?

Welcome to the real world of physics! #### Zahraa

• Newbie
• • Posts: 11 ##### Re: Cyclotron
« Reply #40 on: December 28, 2010, 03:26:06 am »
hello again

I still facing problems in my simulation  my problem is with the very small value of the mass and charge of the proton
charge= 1.602*1e-19
mass =1.673*1e-27

that when I want to calculate the acceleration
acc =  (q.E)/m
I have a very very big number that my application didn't execute it ...
so is there any units that can I apply it in my simulation instead of kg for mass
and coulomb for charge ..
I mean I want to present the  mass and the charge in another units with a different  values ....values that I can apply it in my simulation
i.e : I found that  the mass of the proton is worth 938 Mev/c^2 !!
and this is  a very good number for my application ..
but sure if we want to have a real physics simulation we have to put a right proportion with all units ...
I hope you understand my question ...if you don't tell me to explain more ...

and thank you again for caring about my question ...

#### Fu-Kwun Hwang

• Hero Member
•     • • Posts: 3062 ##### Re: Cyclotron
« Reply #41 on: December 28, 2010, 09:33:15 am »
1. The value range for "float" is 1038, for "double" is 10138 .

There is no problem if you define variable of type "doble" for your case.
You might run into trouble if you use "float" type only.

2.
charge= 1.602*1e-19
mass =1.673*1e-27

for acc=qE/m
I will define a new variable qoverm=1.602/1.673*1e8 without define q or m in the code

#### lookang

• Hero Member
•     • • Posts: 1772
• http://weelookang.blogspot.com ##### Re: Cyclotron
« Reply #42 on: December 28, 2010, 07:26:46 pm »
I also encountered the same issue of very small numbers.
Indeed by using different constant value like what prod Hwang said works.
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1455.0
In this link, is an applet that has very small numbers like
Boltzmann constant and unified mass.
Check it out to see how it is done

#### NagySandorIstvan

• Newbie
• • Posts: 19 ##### Re: Cyclotron
« Reply #43 on: March 28, 2011, 02:45:26 pm »
Hi,
I tried to translate the sim to Hungarian on March 27, 2011. I have downloaded the result but neither the Hungarian nor the English version works. Even the pictures of the formulas are missing from the html.
Best, Sandor

#### Fu-Kwun Hwang

•     •  