The OPAL Discussion Forum

[Huiwen Koay <koay AT rcnp.osaka-u.ac.jp>]

Dear Dr Jochem, 

For your information, I managed to reproduce SNOP results for the one without space charge effect. However, for the one with SC, I still find some deviations. I am still investigating the possible reasons. Hereby I attached with the comparison for your reference. Please do not hesitate to let me know if you had any idea of the possible reason.

Again, thank you very much for your great help!

Goodnight. 

Best regards,

Huiwen

On Wed, Oct 2, 2019 at 8:27 PM Huiwen Koay <koay AT rcnp.osaka-u.ac.jp> wrote:

Dear Dr Jochem,

Thank you very much for your prompt response.

It was really helpful and I managed to proceed after this.

Thanks again for your help.

Best regards,

Huiwen

On Wed, Oct 2, 2019 at 5:58 PM Snuverink Jochem (PSI) <jochem.snuverink AT psi.ch> wrote:

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

Attachment: OPALvsSNOP.pdf
Description: Adobe PDF document