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Timing for the Libera |
To provide beam-synchronous timing for the Libera pilot project, the standard CODD timing system has been extended with two extra modules. One of these provides Base Line Restoration pulses (BLR), and the other produces gate signals. These signals are standard ECL and expect to be terminated into 50Ω to -2V. A real-time program, 'libera', has been added to the controlling DSC. This program communicates with a user application via a UDP socket.
The user application program gives control over the parameters of the timing system without interfering with the normal operation of CODD. A Linux executable is available on AFS under ~jeroen/public/libera. It requires the presence of the GTK+ widget shared library.
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| Timing control application window |
The figure shown here is the main timing control window of the application. The effective PLS user line can be selected from the PLS menu. If the application is used from an operator console, this will usually be set automatically from the current context. The chosen user line here is 'SFTPRO'.
The top-most control allows to set the harmonic number, i.e., the number of RF periods fitting in one revolution period. This figure should match the actual harmonic number of the machine.
Just below that is a group of controls that affects the Gate signal. Gate pulses can be positioned on any bunch from 1 up to the value of the harmonic number. Gate pulses can be generated for multiple consecutive turns by checking the multi-turn button. By checking the multi-bunch button, gates will be produced for every RF bucket. The bunch number selection does not work for multi-bunch operation. The Delay control specifies the number of revolution periods between injection and the first gate pulse. The maximum Delay is 65534. In case of multi-turn operation, the number of Gate pulses produced will be 65535-Delay.
To optimally align the Gate pulses with the beam, the Phase control allows the pulse to be positioned within one RF period. The resolution of this is 1/16th of an RF period. The pulse Length can be set with the same resolution, using the Length control. Although the Length setting will go up to 64, corresponding to 4 RF periods, choosing the length such that successive pulses would overlap will not generally be useful. The Enable check button will turn the generation of pulses on or off.
The Phase, Length and Enable controls for the BLR signal are the same
as for the Gate.
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