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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

[ALBA]

The idea of this topic is to make the most exhaustive list of the BPMs system in all institutes.

Please indicate what your BPM system is as a reply in this topic, and I will include it in the list.

Later, we could do the same kind of list for other systems (emittance monitors, bunch-by-bunch feedback, XBPM, ...), but for the moment let's start with the most wildly used system in storage rings.

ALBA
BPM system:	120 BPMs (Libera Brilliance) in the storage ring 44 BPMs in the booster, 24 of them are equipped with a Libera Brilliance. A few Libra Spark Single Pass for the Linac and transfer lines
References:	Upgrade of BPMs and SRMs for the ALBA Booster to Storage Ring transfer line, DEELS 2017 Commissioning of the ALBA Fast Orbit Feedback system, IBIC2014, WEPD23
Comments:	88 Libera Brilliance among the 120 used for fast orbit feedback to have squared matrix, since we have 88 correctors. Libera Brilliance are doing quite well after ~ 10 years operation but this year (2021) fans started to fail consistently and we decided to perform a full replacement campaign. Testing 2 Libera Brilliance+ and Libera Spark+Pilot-tone in some special BPMs. One BPM (the first after injection) is equipped with a Libera Spark Single pass and we use it for Linac to Booster injection efficiency measurements.
Diamond Light Source
BPM system:	172 BPMs on storage ring (168 orginally); Libera Brilliance + Libera Electron
References:	Performance of the FOFB with DDBA in Diamond Light Source, IPAC2017, TUPIK113 Diamond Light Source Electron Beam Position Feedback: Design, Realization and Performance, ICALEPCS2009, THB003
Comments:	For D-II, number of BPMs on storage ring increases to 252 and we intend to use pilot tone with analog front end in-tunnel and digital signal processing using mTCA platform in the Control and Instrumentation Areas [Diamond-II CDR ].
ESRF
BPM system:	192 Libera Brilliances and 128 Libera Sparks ERXR (iTech) for the Storage Ring 75 Sparks for the Booster
References:	Strongly increased Performance and Functionalities of the ESRF BPMs with the Libera system (ESLS 2010) Complete Test Results of New BPM Electronics for the ESRF New LE-Ring (IBIC2018)
Comments:	SR Fast Orbit Feedback only using the 192 Brilliances (but work in progress to include the 128 Sparks)

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