deflection_map of BUMPER

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Zhenbiao
Posts: 5
Joined: 06 Apr 2017, 07:41

deflection_map of BUMPER

Post by Zhenbiao » 20 May 2020, 07:49

Hi everyone:

I'm using element BUMPER to simulate a nonlinear kicker. What do xpFactor and ypFactor in a deflection_map file represent? How can I get xpFactor and ypFactor? What I have is the strength of the magnetic field B that changes with the abscissa x. Can I write a DEFLECTION_MAP file with x and B? Thanks.

Zhenbiao

michael_borland
Posts: 1927
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
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Re: deflection_map of BUMPER

Post by michael_borland » 27 May 2020, 19:20

Zhenbiao,

As stated in the manual, if a deflection map is given, then the kick to a particle in going through a BUMPER element is delta x' = ANGLE*xpFactor(x,y)*W(t)/(1+delta) and delta y' = ypFactor(x,y)*W(t)/(1+delta), where (x, y) are the initial coordinates of the particle, t is the arrival time, W(t) is the kicker time waveform, and delta is the momentum offset of the particle.

Ideally, you should have the integrated Bx and By fields vs (x, y). If you have only By(x), you have several options:
1. If the dominant terms are dipole and sextupole, use the B2 parameter to specify the normalized sextupole term, so that delta x' = ANGLE*(1+B2*(x^2-y^2)). You can use sddspfit to perform the fit of By(x) using orders 0, 2, 4, ... The downside here is that the multipole expansion is only valid out to a radius r=g/2, where g is the full gap of the magnet.
2. Use the MBUMPER element for multipole kickers, or you can use several to synthesize a more complex dependence. Again, the same limitation for multipole expansions applies as for the last option.
3. Extend your table into the y dimension, ideally with measurements for several y values. If you don't have that, you can just assume that the field is uniform in y. Unfortunately, that doesn't conform to Maxwell's equations, but may be useful to get started. An example of the third approach is shown in the attachment.

--Michael
Attachments
bumperVsX.zip
(5.32 KiB) Downloaded 218 times

Saroj_Jena
Posts: 13
Joined: 16 Nov 2020, 08:34

Re: deflection_map of BUMPER

Post by Saroj_Jena » 16 Apr 2021, 01:15

Dear Michael
I am studying the beam injection using a nonlinear kicker (NLK). Is there any provision to input deflection vs x directly. I generate a profile for deflection angle vs x for the NLK in which beam would experience 0.7 mrad kick at -4.9 mm. After going through the previously answered similar query, I have generated B vs x data from the deflection angle data, but could n't succeeded in making a deflection map required in proper format. could you please help me to generate the required deflection map which will have 4 columns x, y, xpFactor and ypFactor which will satisfy my requirement. One more thing, If we are providing the deflection map in BUMPER, what one should define the value of ANGLE.

with best regards
Saroj Jena
Attachments
NLK elegant.rar
(4.99 KiB) Downloaded 151 times

michael_borland
Posts: 1927
Joined: 19 May 2008, 09:33
Location: Argonne National Laboratory
Contact:

Re: deflection_map of BUMPER

Post by michael_borland » 21 Apr 2021, 16:41

Saroj Jena,

Here's a script that creates the type of file that is needed. However, please note that the deflection map constructed in this way does not satisfy Maxwell's equations.

The map is normalized to the range [-1, 1] for xpFactor, so the ANGLE parameter is set to the deflection angle you want for the bunch that sees the maximum deflection.

--Micahel
Attachments
extended.zip
(8.93 KiB) Downloaded 158 times

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