The OPAL Discussion Forum

["Snuverink Jochem (PSI)" <jochem.snuverink AT psi.ch>]

Dear Huiwen,

 

Thanks for the input file and doing such a detailed comparison.

 

In this case I believe there are some difference in the input beam between SNOP and OPAL.

 

For the space charge the bunch charge is relevant, and I believe this is different.

 

In OPAL the frequency unit is MHz. I believe that you should change the following line:

 

REAL f0             = 37.4179197618764e6;         // Hz

 

to:

 

REAL f0             = 37.4179197618764;         // MHz

 

For 10 mA, the bunch charge is then (Qtot) of 134 pC (instead of 0.134 fC). Note that your frequency is 2*f0).

 

Note that you probably need to change your sigmaZ (0.2 mm) calculation to:

 

REAL sigmaZ  = sigmarf/360/f0/1e6*beta*CLIGHT;

 

With these changes change I get a better agreement with SNOP, but not perfect yet. So there are likely some other differences (z distribution?).

 

Also things to consider, is your frequency 2*f0 or just f0?

 

Hope that helps,

Jochem

 

From: Huiwen Koay <koay AT rcnp.osaka-u.ac.jp>
Sent: Mittwoch, 2. Oktober 2019 07:24
To: Snuverink Jochem (PSI) <jochem.snuverink AT psi.ch>; opal <opal AT lists.psi.ch>
Subject: Space charge in drift using OPAL-t

 

Dear Dr. Jochem Snuverink,

Hi. I am writing regarding the inconsistency of space charge in drift for a low current beam and a high intensity beam using OPAL-t. Hereby I attached with the sample results i obtained for a 40keV proton beam in an 1 m drift tube. I also attached with the input for your further reference. Please let me know if there is any mistake in my setting in the input file.

 

 I truly appreciate your kind attention. 

Thank you very much for your help.

 

Best regards,

Huiwen