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Frequently asked questiones


Can the same Libera Electron/Brilliance/Brilliance+ unit be used in the storage ring and booster?


Yes, but the software design must be properly installed. In case of Libera instruments produced before year 2011, the instrument should have proper oscillators mounted. Instruments, bought from 2011 on, the reconfiguration is only in software.


Is it possible to use Libera Electron/Brilliance/Brilliance+ in light and collide mode?


Yes, it is possible. But most probably, this will require two different designs, which can be relatively easily exchanged (software only).


How precisely should RF frequency be determined in the Libera Electron/Brilliance/Brilliance+ specification?


Usually, the central RF frequency should be given to us with 1 kHz precision. But the RF frequency may vary in the range of ~20 kHz. Libera is able to follow a variation of +-45 kHz at 500 MHz (+-90 ppm).


What if Libera Electron/Brilliance/Brilliance+ PLL is not locked due to heavy detune (e.g. 499.5 MHz instead of 499.654 MHz)?


The instrument will still be working but one should keep in mind the conditions.


How can I measure first turns with Libera Electron/Brilliance/Brilliance+?


The best and easiest way is to use turn-by-turn data acquired on injection trigger. Certain offset can also be applied in order to retrieve the most interesting part of the event.


What is the typical data bandwidth in Turn-by-Turn mode on Libera Electron/Brilliance/Brilliance+?


It is approximately 0.35 times the revolution frequency.


What is the difference between “internal” and “external” switching source?


The switching frequency (~13 kHz) is obtained only by integer division of the revolution frequency (as Libera sees it). In case one is offset-tuned (detuned) and does not have a fully filled ring, the switching does not exactly follow the actual accelerator revolution frequency. The result is a very low beat frequency in the range of 0 to 20 Hz, depending on the amount of detuning. With CW there is no beating of course. This is called "internal" switching.
On can choose to lock the MC PLL to the externally delivered MC instead. By locking the switching to the MC (with the same division factor) one avoids the beating, since it is always in phase with the filling pattern of the accelerator. This is called "external" switching.


The beam does not arrive on multiple Libera units at the same time. How is it possible to adjust the on-trigger acquisition to see the beam on all units?


The easiest way is to use the Trigger delay, which must be set manually for each unit individually. It is only possible to delay the Trigger (not +/- in time). The setting is done with 1 ADC sample resolution.


What is the meaning of the Machine Time (MT)?


The initial value of the MT (when doing the synchronization) is not important. When one have multiple units synchronized, the MT value must be the same on all units (1 sample difference is allowed). If the MT is not the same on all units, units are not fully synchronized.


Does the System Clock (SC) affect measurements?


No, it does not. It is only used to synchronize multiple Libera units to the same absolute time.


How precise should the operating environment for Liberas be temperature stabilized?


Usually, it is good enough to control the temperature in +/- 1° C range. The airflow should not be applied directly to the instruments. Take into account the RF cables, which are also sensitive to temperature changes.


Can the data between Liberas be exchanged?


Yes. Data exchange (or grouping) is typically done in the fast orbit feedback application. Libera Electron and Brilliance have SFP slots in the front panel (first four from the left), that are used for this application. Libera Brilliance+ can optionally be equipped with FGOFB module, that does the same but with more flexibility than Libera Electron and Brilliance. Software wise, instruments must be equipped with FOFB feature.


Which models of SFP GbE modules can be used for FA data acquisition?


The list of tested SFP modules:
Avago HBCU-5710R
Finisar FCLF-8520/8521-3

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