SR loss per turn with momentum offset

[amal]

I want to compute the SR loss per turn in an electron storage ring with fractional offset in the momentum. For this, I defined an element of type "malign" and then "vary_element" with item as dp, followed by "twiss_output". However, it did not work. How I can obtain this loss as a function of momentum offset? Can I save the results in a file for plotting?

[michael_borland]

The twiss_output command can't do this computation at present. I'll add it in a future version.

Meanwhile, I've attached some files that show how to do it using element-by-element radiation, which is more accurate in any case. In this example, I used the closed_orbit command to first find the off-momentum closed orbit, so the calculation is appropriate to a particle that circulates for a while at some momentum deviation. The result is not the same as the E^4 scaling that you'll get if you scale the magnets and beam energy together.

--Michael

[amal]

Thanks for sharing the examples.

[amal]

I obtained SR loss per turn with energy off-set using Elegant, as you described. The files .lte and .ele are attached here for your reference. I also computed same function using analytical formula up to second order in energy off-set. There is a discrepancy in both the results, which I could not understand. The results with the derived formula are also attached in the word file for your kind review...

Amal ...

[michael_borland]

Amal,

I think issue may be that in the tracking simulation, you include synchrotron radiation in the quadrupoles

Code: Select all

&alter_elements name=*[QS]*, type=K*, item=SYNCH_RAD, value=1 &end

If I comment out that statement, the nonlinearity (judging by the second-order term in a fit) is reduced an order of magnitude.

--Michael

[amal]

Michael,

Thanks for clarifying the doubt. By commenting the statement, results from the code and formulation are closer. In fact, now output from the code has slightly lesser nonlinear effect (not much different) compared to the formulation.

Thanks again,

Amal.