How to use diag_denergy

[wtam]

Colleagues,

What does the 2nd argument for the element DIAG_DENERGY means? It says "Wanted Delta Energy (MeV)" in the manual. I expected it means "change in energy of the synchronous particle". I am not getting what I expected.

Best regards,
Wai-Ming

[Didier]

Dear Wai-Ming,

No, it is the difference between the energy of the synchronous particles and the energy of the beam. This therefore assumes that some errors affecting the beam energy are present.

Regards,

Didier

[npichoff]

Dear Wai-Ming,

If I understand correctly, "wanted" means that it is a requirement that has to be fullfiled by adjusting some components (controled by ADJUST command).
Here, one wants to adjust the beam energy to an offset with respect to the synchronous particle.

Usual condition :
- A linac with errors : wrong energy of the beam at this position,
- DIAG_ENERGY X 0 : Field amplitude and phase of some cavities are adjusted in order to recover the good (synchronous) energy (DeltaE=0) at the position of the diagnostic.

I hope I'm clear.

Best regards.

Nicolas.

[wtam]

Dear Nicolas, Didier,

Thank you for your reply.

I thought the "energy of the beam" is by definition the "energy of the synchronous particle". If they could be different, what is the "energy of the beam"?

I understand the element DIAG_ENERGY. But I don't understand DIAG_DENERGY. What is the difference?

Best regards,
Wai-Ming

[Didier]

Dear Waig-ming,

Beam energy is the energy of a particle representing the centre of gravity of the input distribution which is transported into a machine where the cavities don't have exactly the right field or RF phase. Also including errors such as source voltage errors.
So normally in a perfect machine without any impections and with a very small input emittance, the energy of the beam must be equal to the synchone particle.

Typically in envelope, if you hadn't defined errors in your machine, DENERGY = 0

Regards,

Didier

[wtam]

Dear Didier,

If you open Charts -> Structure Charts -> Energy, there are two curves: Beam and Linac. Does the Linac energy curve represent the energy of the synchronous particle with the designed field strength and phase, assuming no error? Also, what does the Beam energy curve represent?

Thanks,
Wai-Ming

[Didier]

Dear Wing-ming,

Yes, most of charts show perfect machine, 'Linac" and th e imparfait machine with errors, "Beam". Exmple below show beam in 2 DTL tank with 4% error about the entrance beam energy. Here, the error is so large that the beam is not even accelerated when it reaches the second DTL tank.

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