Recent posts

General Discussion / BeamDiag forum is shutting dow...
Last post by Benoît Roche - July 09, 2024, 04:28:54 PM
Dear all,

I would like to thank you all for subscribing to the BeamDiag forum and for the exchanges there had been here.

However, since there is no more message posted here for more than one year, I think it is not worth continuing to subscribe for the web storage required to maintain this forum alive.

As a consequence, the Internet service will stop on the 31th of August. This forum will not work anymore after this date.

Thank you all again for your contribution. Please let me know if you have any comment or suggestion.

General Discussion / Simulation Help: effect of the...
Last post by cozkan - August 11, 2022, 06:54:15 PM
Does anyone have any experience simulating the effect of the thermal heatload on the surface of a monochromator crystal?
We would like to couple this with focusing xray optics to simulate its impact. This could be with SHADOW, for example.
Thank you.
General Discussion / Re: Back-end for longitudinal ...
Last post by Benoît Roche - July 19, 2022, 05:05:49 PM
Hello Nashat,

At ESRF we used to have (in the previous machine) a longitudinal feedback with a QPSK modulator as backend. It was an home-made system, and I'll be honest it was a bit complicated and it was not very easy to adjust the different delays etc..

A few months before the end of the previous machine we tried to simplify a lot the backend. We wanted to have something very easy to maintain and install in case we need it for our new machine. If I remember well we just used a mixer with a LO at 4 times the master source frequency, and a bandpass filter from Mini-Circuit. We did only a few tests and it seems that working well. The comparison with the QPSK modulator was quite satisfying.

Then we installed our new machine and it was decided to not have a longitudinal feedback anymore. Today it is not required at all.

So it seems to me that a very simple, home-made backend can be used. However I don't have a lot of experience with it, so maybe there are some performance issue that I am not aware of.

General Discussion / Back-end for longitudinal feed...
Last post by Nashat1985 - July 02, 2022, 02:32:20 PM
Dear Experts,
This Nashat Sawai from SESAME synchrotron, it is first time posting here  :D
Currently, we are working on the design and implementing longitudinal feedback for our storage ring,  we run a 500 MHZ RF system.

we already have some components for feedback and still missing the other components such as the Backend and cavity kicker,   we intend to use the i-Tech Libera bunch-by-bunch processer,   does anybody have used Libera electronics for longitudinal feedback  ?! what is the typical setup for modulator/backend? should we use DSB  or do I need QPSK modulator?
Your comments and feedback are greatly appreciated
General Discussion / Re: Do you have fast magnet (b...
Last post by Benoît Roche - May 16, 2022, 05:25:19 PM
Thanks a lot for your answer, the links are very interesting.

In fact my question was more about the use of such a magnet not as a kicker to inject or extract beam, but more as a correction magnet or for machine physics studies. We also have kicker magnets for the injection scheme, and in fact the design is very similar to our shaker. For the kickers we also use a core made of the material called 8C11, and to be honest I don't know how it compares to the Magnetic alloy you mention.
General Discussion / Re: Do you have fast magnet (b...
Last post by Ji-Gwang Hwang - May 12, 2022, 10:14:38 AM
MHz-bandwidth magnets are widely used in Hadron machines as well as therapy machines for a fast switching (for machine projection) and a fast kicker magnet. This is also necessary to inject or extract beams to/from a ring. But these kickers are using a ferrite core since this can achieve the field requirement.
   M.J. Barnes:

Recent progress in material research, particularly on Magnetic Alloy, allows accessing that bandwidth (a few MHz) for the core, which is used for a magnetic-alloy-loaded cavity.
   C. Ohmori:

General Discussion / Do you have fast magnet (bandw...
Last post by Benoît Roche - May 10, 2022, 03:15:59 PM
At the ESRF we use what we call "magnetic shakers". It is more or less a special magnet with a high bandwidth (a few MHz). To have such a high bandwidth we need a ceramic vacuum chamber with titanium coating in order to reduce the eddy currents. This is the same kind of vacuum chamber used for the injection kickers. The magnet itself is a coil with just a few loops.

My question to everyone is: do you have a similar device in your ring? If yes, what do you do with it? And how do you call it?

Of course you may have strip-line kickers (for a bunch-by-bunch feedback), which have a much higher bandwidth (of the order of 1 GHz). So you may ask what is the purpose of a fast magnet with a lower bandwidth. The main advantage of this fast magnet (or shaker as we call it) is that it is roughly 10 time more powerful than a strip-line kicker for the same amplifier power in the DC -> few MHz regime.

We use this device mostly for 3 purposes:

  • Transverse betatron excitation for tune measurement and beam emittance blow-up (high amplitudes are required for beam dynamics studies),
  • Compensate the perturbations induced by the injection kickers during refills,
  • Protect the machine when a interlock occurs: before killing the beam, we increase the vertical beam profile as much as possible by resonant betatron excitation to protect the vacuum chamber and collimators from the energy deposition due to electrons hitting these elements.

I would be happy to know if similar devices exists in other institutes. Thanks
Need help? / Re: Strange vertical 50Hz nois...
Last post by Laura - May 09, 2022, 11:26:09 AM
Good idea, I will try next week (shutdown)!
Need help? / Re: Strange vertical 50Hz nois...
Last post by Benoît Roche - May 09, 2022, 11:05:19 AM
Just an idea: maybe it could be an "impurity" which is in the vaccum chamber between the button and the vaccum chamber a create a non-infinite resistance. Sometimes the impurity creates the short-circut, sometime it does not.

It does not explain everything (why the perturbation is only in the vertical plane? why 50 Hz?), but it is easy to check with only a multimeter (without beam).
Need help? / Re: Strange vertical 50Hz nois...
Last post by Laura - May 05, 2022, 11:34:25 AM
Well, the step I observe with BPMs is 4 um so I should be able to see it with accelerometers!
Also, sometime it is a jump: it does not go back to the previous location...
I will keep you updated!