Elegant users forum

Hi Michael,

In a storage ring using a cavity, particle(electron) going from 155 MeV to 1 GeV energy(two loops, higher and lower energy loops, i.e particle first accelerates, gains energy and in next pass decelerates through the same cavity), it is stable and particle does not get lost. It is possible only when in my elegant file (Elegant_Run_twoDBA.ele) the first two commands are 'on' for '&alter_elements name...' i.e.,

&alter_elements name=B*, type=CSBEND, item=SYNCH_RAD, value=1 &end (commands 'on')
&alter_elements name=B*, type=CSBEND, item=ISR, value=1 &end ('on')
!&alter_elements name=B*, type=CSBEND, item=USE_RAD_DIST, value=1 &end ('off')
!&alter_elements name=B*, type=CSBEND, item=ADD_OPENING_ANGLE, value=1 &end ('off')

when all commands are 'on' in the above set up, particle gets lost after 24 turns. I do not know where is the problem?

However, It works for higher energies, for eg. going from 25 GeV to 25.845 GeV ( same energy gain / loss as in the first case, 845MeV), either first two commands 'on' or all 4 commands 'on'. Particle is stable with a little difference in emittance.

Question: Why it is not working for 155 MeV to 1 GeV case?

For your reference, I have attached elegant and lattice files.

Thank you,
Bhawin

Bhawin,

It appears that your lattice has an integer resonance in the horizontal plane and a (stronger) half-integer resonance in the vertical plane. When you use distribution-based radiation calculations with opening angle included, there are small kicks to x' and y' inside the dipoles. In the presence of a resonance, these end up causing beam loss.

You may want to try moving the tunes to see if that resolves the issue.

--Michael

Hi Michael,

As you suggested, I modified the lattice to avoid those resonances. Now I have two energy loops, each of them having same length (~ 1740 m ). I decided to work with the artificial damping element ( SREFFECT).

For my system, two rings with the same energy (i.e 155 MeV ) with sr effect, particle is stable. But when I use two rings at markedly different energies say 55 MeV and 155 MeV , I have to use two cavities one for accelerating and the other for decelerating. In this case, with the use of sr element, no particle is present after a single pass.I think there may be some thing wrong with cavity set. For your reference, I have attached my elegant and lattice files.
Please give me some suggestions.


Thank you,
Bhawin

Bhawin,

I made some changes to your files to correctly set up the rf cavities. Search for "!!!MB" in the files to see what I changed. There's also a Notebook file with some explanations and plot examples.

There still seems to be an issue with a half-integer resonance in the horizontal plane. --Michael

Hi Michael,

Thank you so much for your suggestion. Now it is more clear for the cavity set up. I really appreciate your help.

Question: A complete system having two rings, one low energy ring (55 MeV) , another high energy ring ( say 155 MeV) ( Both rings have the same lattice design), Does elegant understand and calculate the energy radiated by dipole separately for each ring when passing through the dipole? i.e. does elegant understand and take separate energy for each ring to calculate the radiation energy loss?

This is the new system having two rings connected by a RF cavity to accelerate and decelerate the beam continuously for many turns.

Thank you,
Bhawin,

Bhawin,

If you are just tracking with element-by-element synchrotron radiation, the answer is "yes": elegant does this correctly in your case. However, the radiation-integrals and related calculations in the twiss_output file are not correct. For that, you need to do two separate runs.

--Michael

Hi Michael,

Thank you so much. I really appreciate your help.

Bhawin,