The OPAL Discussion Forum

["Adelmann Andreas (PSI)" <andreas.adelmann AT psi.ch>]

Hello Malek yes the mentioned paper nicely explained these things. 

On top of that do not forget that you are integrating in time, hence part

of the beam is already in the quadrupole and the other part in the drift. This is

different when using maps. However you can add a monitor and record the particles

at a given location and then calculate the emittances, projected and total. I have root scripts

that are doing this if you need them I am more than happy to share them with you. 

A FODO channel +  focussing asymmetries paired with heavy space charge

can develop non-linearities, and this means it is not a priori clear that the projected 

emittance must be conserved. 

I hope that helps, cheers Andreas 

On 10 Sep 2015, at 03:37, Haj Tahar, Malek <mhajtahar AT bnl.gov> wrote:

I believe that the answer lies in the definition of the trace space emittance.
I found a nice paper comparing the development of the normalized emittance and the normalized trace space emittance.

http://journals.aps.org/prstab/pdf/10.1103/PhysRevSTAB.6.034202

Best regards,

Malek 

---

From: Haj Tahar, Malek
Sent: Wednesday, September 09, 2015 2:11 PM
To: opal AT lists.psi.ch
Subject: normalized emittance OPAL

Dear all,

I have little experience with OPAL and I would like to know if anyone has already encountered this problem: I track a KV beam distribution in an injection line and compute the x-rms emittance which is expected to be constant (since this is a KV beam). Instead, I obtain a strange behavior: when space charge is off, the x-normalized emittance is constant, however, once space charge is on, I have an overshoot in certain locations, specifically at the entrance and exit of some quadrupoles (attached).

I wonder if anyone has an experience with this problem.

Thank you in advance for your help!

Malek Haj Tahar UJF/BNL
PhD student / ADS-R Group

Brookhaven National Laboratory
Collider Accelerator Department
35 Lawrence Drive, Bldg. 911B, Off. 211
11973 UPTON, NY, USA

Phone: +1 (631)-344-5573
Email: mhajtahar AT bnl.gov