(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Problematic Part of the problem:

Consider a negative ion beam of He- ions. The given beam characteristics are the beam energy (E) and the beam current (I).

An electrostatic chopper is placed on the beam line, which pulses the DC beam with a pulse width of say [tex]t_1[/tex] nanoseconds.

What are the new beam characterisitcs?

2. Relevant equations

Normal Distribution:

[tex]

f(x)= \frac{1}{\sqrt{2 \pi \sigma^2}} e^{-\frac{t^2}{2\sigma^2}}

[/tex]

3. The attempt at a solution

I would have said the new current profile would be, for an incident DC beam of beam current I0

[tex]I(t)=I_0\frac{1}{\sqrt{2 \pi \sigma^2}} e^{-\frac{t^2}{2\sigma^2}}[/tex]

if the beam emerges from the chopper at t=0. Also, since the FWHM of the beam is given to be [tex]t_1[/tex] the standard deviation would be

[tex]\sigma=\frac{t_1}{2.354}[/tex]

(from http://en.wikipedia.org/wiki/Full_width_at_half_maximum)

This seems pretty straightforward, however, this appears to be wrong because according to this, the peak current has changed, and become .046 times its initial value

[tex]I(0)=I_0 f(0)[/tex] where f(x) is the normal distribution...

can anyone tell me what I am doing wrong.

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# Homework Help: Pulsed ion beam

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