LATTICE and CALCULATE INPUT MATCHED BEAM [SOLVED]

[wtam]

Hi Colleagues,

When I use "lattice" and "set_adv" to "calculate input matched beam", can I set constraints to the resulting twiss parameters? For example, if I want the resulting input beam to be a round beam.

Best regards,
Wai-Ming

[Didier]

Dear Wai-Ming,

I don't see any way to do that except to average the results.

Regards,

Didier

[wtam]

Dear Didier,

Is it possible to start with a known input beam and use "adjust" on a few quadrupoles to match the beam at the beginning of a "lattice"?

Best regards,
Wai-Ming

[Didier]

Dear Wai-Ming,

I think that yes, it is necessary to put diagnostics of type "DIAG_DSIZE2" in the first lattice (at least, 5 I think) so as to force the matching. By the way, this is the way we calculate the beam to inject in the SPIRAL2 accelerator. Experimentally validated method.

Regards,

Didier

[wtam]

Dear Didier,

Could you please show me how to use "DIAG_DSIZE2" on Q1 and Q2 in the example project (attached) to match the input beam calculated by "LATTICE" at the beginning of the lattice itself?

Best regards,
Wai-Ming

[Didier]

Dear Wia-Ming,

Below is an example of how to use the DIAG_DSIZE2 diagnostics. Now starting with a round beam it is virtually impossible to get a perfect matching in your channel.
Another point, while working on your example I noticed a bug in the GAP element, which I corrected in the latest online version.

Regards,

Didier

match.cal

(77 Bytes) Downloaded 165 times

match.dat

(791 Bytes) Downloaded 180 times

match.ini

(43.77 KiB) Downloaded 187 times

[wtam]

Dear Didier,

It is great! Thanks!
Two follow up questions:
(1) Does a "DIAG" statement count as an element? It seems it does but it does not affect the lattice periodicity.
(2) See attached. I keep commenting out the "DIAG_DSIZE2" statement one by one but the matching still works fine. I don't think I understand how it work.

Best regards,
Wai-Ming

[Didier]

Dear Wia-Ming,

1) Yes DIAG are element but they are not counted in the periodicity for convenience
2) As long as there are at least 2 DIAG_DSIZE2, the adaptation is theoretically always feasible, but most of the time more are needed to ensure continuity of the focus channel, it depends very much on the machine.

Regards,

Didier