• Register
PhysicsOverflow is a next-generation academic platform for physicists and astronomers, including a community peer review system and a postgraduate-level discussion forum analogous to MathOverflow.

Welcome to PhysicsOverflow! PhysicsOverflow is an open platform for community peer review and graduate-level Physics discussion.

Please help promote PhysicsOverflow ads elsewhere if you like it.


New printer friendly PO pages!

Migration to Bielefeld University was successful!

Please vote for this year's PhysicsOverflow ads!

Please do help out in categorising submissions. Submit a paper to PhysicsOverflow!

... see more

Tools for paper authors

Submit paper
Claim Paper Authorship

Tools for SE users

Search User
Reclaim SE Account
Request Account Merger
Nativise imported posts
Claim post (deleted users)
Import SE post

Users whose questions have been imported from Physics Stack Exchange, Theoretical Physics Stack Exchange, or any other Stack Exchange site are kindly requested to reclaim their account and not to register as a new user.

Public \(\beta\) tools

Report a bug with a feature
Request a new functionality
404 page design
Send feedback


(propose a free ad)

Site Statistics

203 submissions , 161 unreviewed
5,006 questions , 2,162 unanswered
5,341 answers , 22,655 comments
1,470 users with positive rep
815 active unimported users
More ...

  When can a beam of protons can show an inverse parabola characteristic?

+ 0 like - 0 dislike

We have proton beam line consists of a quadruple and a drift space. At the end of the drift, we are projecting the beam to a camera and examining the photograph with quadruple scan techniques.

However, in one of the irradiations, when we examined the data, in the y-axis, the standard deviations of distribution of the beam has the characteristic of an inverse parabola, such as (y axis shows the sigma square in metre, and x axis shows minus the quadrapole strength in 1/m^2)


Note that, the quadruple was focusing in x-axis, and defocusing in y-axis, and the data of x-axis as the characteristic of a normal $x^2$ parabola.

However, as you might know, in the normal conditions, both y and x axis of the beam has to have a characteristic of a normal parabola when they are plotted against the quadruple strength, which is not the case in the y-axis of the beam. I have done a lot reading about beam optics; however, there is no explanation about such a behaviour.


What might be causing such a behaviour in the beam ? is it because maybe our beam do not have a ellipse shape in the phase space, since most of the formalism on beam optics done on this assumption ? 

Disclaimer:  This question is cross-posted in https://physics.stackexchange.com/questions/415676/when-can-a-beam-of-protons-can-show-an-inverse-parabola-characteristic

asked Jul 8, 2018 in Experimental Physics by Leth (0 points) [ revision history ]

Several parameters contributing to the current ( and the camera ! ) are not controlled. Did you read this one ? not about protons but it is with the same technics.

Your answer

Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead.
To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL.
Please consult the FAQ for as to how to format your post.
This is the answer box; if you want to write a comment instead, please use the 'add comment' button.
Live preview (may slow down editor)   Preview
Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:
Then drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds).
To avoid this verification in future, please log in or register.

user contributions licensed under cc by-sa 3.0 with attribution required

Your rights