1. Weiming Guo Accelerator Physics Group / ASD Advanced Photon Source
The Study of Off-momentum Particle Motion with Independent Component Analysis
Weiming Guo
Accelerator Physics Group / ASD
Advanced Photon Source
I am a software developer, I am going to talk about
My work on software for beam stabilization and
optimization

2. Acknowledgements Katherine Harkay Xiaobiao Huang Michael Borland
Jack Albert
Chunxi Wang
Hairong Shang
orbit stability is #1 user request, in order to improve the orbit
Stability, we enhanced the orbit control and stability software system,
Including DC orbit correction and ID gap feedforward,
the fast dc orbit correction increases
The correction rate from 0.4Hz to 20 Hz and ID gap feedforward gives us the
Benefits of using Insertion Device X-ray BPMs in orbit correction to help better
Control the orbit (as they have “long lever” that permits better control.)
After these improvements, there is no more orbit transient
associated with gap open and close, and the beam stability
has been significantly improved.
Since feedback works only for certain class of optimization, for
General purpose optimization, we developed generic optimizer to perform
Optimizations where feedback is not applicable.

3. What is the mechanism of synchrotron sidebands?
0.206
±0.0083

4. The current theory of dispersion
The transverse motion Hamiltonian
Consider only quadrupoles and dipoles, the first order
dispersion equation
Let
, the equation for the dispersion function
I also worked on software for Experiment Execution to meet the special
Requirements of the accelerator experiments and software testing to improve
The reliability of APS software systems. Currently, I am working on
SaveCompareRestore software, which is a great tool to manage accelerator
Configurations so that we reproduce operating conditions
The boundary condition

5. The physical picture of dispersion
Reference C.O.
δ < 0
δ > 0

6. Analytical solution In vector space
The solution of the homogeneous equation
M(s|0) is the transformation matrix
The solution of the inhomogeneous equation

7. The dispersion functions

8. The ID(s) and function

9. The calculated dispersion function

10. The calculated ID function

11. The meaning of the ID term
Reference C.O.
δ < 0
δ > 0

12. The higher order terms

13. Particle simulation with ELEGANT(I)
Particle on C.O. with 0.4% momentum offset

14. The spectrum of 4000 turns

15. Particle simulation with ELEGANT(II)
Particle on C.O. with 10o phase kick

16. Experiment setup APS storage ring operation parameters
We give the beam a phase shift of 0~14o, with width of 200 ms.
The equilibrium bunch length is about 2.5o . The horizontal dis-
placement is about 0~1.2mm.
There are about 280 BPMs can be used for history data taking.
We analyzed the data with independent component analysis.

17. Temporal pattern of dispersion
Damping time
1188 turns
1300 turns
Synchrotron tune
0.0083
This figure shows the BPMs and correctors in one sector of APS accelerator,
There are 16 rf BPMs and four x-ray bpms, 9 correctors.
These bpms and correctors
Are chosen by our configuration software to use in DC orbit correction

18. The comparison of the dispersion function
This is the configuration application that is used to select bpm and correctors
For orbit correction.
each plane has 640 bpms and 90 correctors.
This application also configures which BPM is non-existent devices or not OK for
Orbit correction. The buttons pointed by the red arrows are not shown up because
These bpms do not exist. The button pointed by the yellow arrows shows that
Bpm is not OK for orbit correction.
the check button for non-existent BPM disappears. The
Check button for “not” ok devices are disabled – prevent user from
selecting this bpm by mistake
thus make sure that orbit correction uses good bpms. The button
Will be enabled when these devices become good and suitable for orbit correction.
After selecting proper bpm and correctors, the configuration can be saved for
Orbit correction.

19. The temporal pattern of second order dispersion
This is not all, we always look for better performances.
The orbit stability has been improved further through one-year hard work of
Accelerator physicists and OAG group. We made following improvements
to increase
The correction speed to make beam more stable. These changes are
Overlap compensation with RTFS, using low-level channel access, ported
Controllaw software to IOC and using sddspvtest to increase testing speed. As
A result, the orbit correction rate is increased from 0.4Hz to 20 Hz.

20. The second order dispersion function
Louis has explained how we did orbit correction, I am not going to repeat here.
I would like to say that we implemented all these complicated aspects in our
Software. And in addition to these complicated designed, we further improved
DC orbit correction through following:
In DC orbit correction software, we implemented all of these complicated
Cases, while in other labs, only SVD is considered. That is why our software
Works much better and is able to provide good quality beam.

21. The coupling Mode
0.205
0.1975

22. The comparison of the ID function
ID gap feedforward allows us to use ID x-ray BPMs in orbit correction,
Providing better orbit stability.
The mixture of x-rays from the ID and other sources changes as the ID gap
Is changed, this introduces gap-dependent offset changes in the x-ray bpms.
If we used the x-ray bpm data as-is, we’d actually move the beam around instead
Of keeping it in place. ID gap feedforward software allows measuring the offset
Changes vs. gap. Automatically changes the offset of x-ray bpms with gap changes.
setting the offset and gain to zero when the gap is too
Large so that the x-ray bpm is automatically taken out of the loop.

23. Phase advance comparison

24. Conclusion
We found the analytical expression of the X-Z coupling term.
The mode is damped in most cases, however we found it in the
experiment under the critical conditions.
Both the amplitude and phase advance agree with prediction.
In the analysis of the experiment data, we also found the first
and second order dispersion function and they all agree
with model value.

25. The effect of the Chromaticity