How Do I Calculate Fluence, Flux, and Dose for a TiH Beam?

[sportcardinal90]

Homework Statement

I want to calculate the flux, fluence,and dose and I know several things:

Beam energy = 40 keV
Current = 10 nAmps
Irradiated area = 10 mm^2
Time irradiated = 15 minutes
Beam is made up of TiH with a charge state of -1

The material being irradiated is TiO2.

Homework Equations

What equations can I use here? I want to calculate flux, fluence, and dose. I have many problems like this. If someone could show me how to work through the solution for one of these, that would be very helpful.
Do I use a combination of the beam energy, current, and electron charge to get ions passing through? I have my irradiated area, and the length of deposition. How can I determine the number of ions/cm^2/s?

The Attempt at a Solution

[/B]
I imagine I need to start with multiplying the current by 1.602-19?
Honestly, I am very lost. I just want to calculate the fluence but have no idea where to begin/how to do this.

 

[kuruman]

I imagine I need to start with multiplying the current by 1.602-19?

Nope. The current is Coulombs per second. How do you convert that so that it becomes ions per second? Once you find that, how do you find (ions per second) per cm²?

 

[sportcardinal90]

Nope. The current is Coulombs per second. How do you convert that so that it becomes ions per second? Once you find that, how do you find (ions per second) per cm²?

Since the current is C/s and I have a charge state of -1, wouldn't C/s be identical to ions/s? Then I divide by area to get ions/s/cm^2?

 

[kuruman]

... charge state of -1 ...

-1 what? Apples, bananas, oranges ... ?

 

[sportcardinal90]

-1 what? Apples, bananas, oranges ... ?

The charge state of TiH is -1. The charge state of the ion beam

 

[kuruman]

The charge state of TiH is -1.

What kind of information does that convey to you when you read it?

 

[sportcardinal90]

I don't know. I just know that is the "charge state" I am very lost, and why I am asking here

 

[kuruman]

The charge state of -1 indicates to me that the ion has gained an extra electron's worth of charge. Can you answer the question now?

I don't know. I just know that is the "charge state" I am very lost, and why I am asking here

For future reference, it is best that you first understand the meaning of the information that a problem gives you and then ask about how to solve it.

 

[sportcardinal90]

The charge state of -1 indicates to me that the ion has gained an extra electron's worth of charge. Can you answer the question now?

For future reference, it is best that you first understand the meaning of the information that a problem gives you and then ask about how to solve it.

Fair enough, do you think you can help me with this?

 

[kuruman]

Fair enough, do you think you can help me with this?

I already have. Please read again post #2. Do you understand what it suggests that you do?

 

[sportcardinal90]

I gave my answer and then you just asked another question, so I am not sure where to go from here. You did not say if I was right or wrong.

 

[kuruman]

Since the current is C/s and I have a charge state of -1, wouldn't C/s be identical to ions/s?

This part of your answer is incorrect. Coulombs per second is not the same as ions per second. Read post #8 and then see if you can figure out how you go from Coulombs per second to ions per second.

Then I divide by area to get ions/s/cm^2?

This part of your answer is correct, but you need to get the first part first.

 

[sportcardinal90]

Do I divide by 1.6e-19, the elementary charge?

 

[kuruman]

Yes.

 

[sportcardinal90]

So the number of ions is 10 nAmps/1.6e-19? So 10 nAmps = 10x10^-9 Amps. Then divide by 1.602e-19 and I get:

6.24e10 ions/second?

 

[kuruman]

That's what it is.

 

[sportcardinal90]

So I have 6.24e10 ions/second. Then I can calculate the fluence (ions/cm^2/second) by just dividing by the area right? Since I have area is 10 mm^2, convert to cm^2 and I get 6.24e13 ions/cm^2/s. Am I still correct so far?

 

[sportcardinal90]

My mistake, so its 6.24e11 ions/cm^2/s right?

 

[sportcardinal90]

Sorry, I mean 6.24e11 ion/cm^2/s. Good so far?

 

[kuruman]

That is correct.

 

[sportcardinal90]

So now that I have all of that, how do I calculate the dose?

 

[sportcardinal90]

actually, before i get to that, what if my charge state were different? Instead of -1, what if it were say, +3? Would my answer be what I just got but times 3?

 

[kuruman]

Would my answer be what I just got but times 3?

Divide or multiply by 3? You can answer that yourself. If the current remains the same (same coulombs per second) but each ion carries 3 times the charge, does your beam have more or fewer ions going by per second?

So now that I have all of that, how do I calculate the dose?

That is beyond my expertise but maybe I can help you. Somewhere you must have information about how the dose is related to the fluence and the other given quantities. What is that relation?

 

[sportcardinal90]

It would have fewer ions since they each have more charge. So I would divide by 3, right?

 

[kuruman]

So I would divide by 3

Correct.

 

[PSRB191921]

Hi,
To calculate the dose used the stopping power.
For my part it is not clear what particles is your beam (protons ?)

 

[sportcardinal90]

The beam is TiH