Corrector at exit method

Use n_compensating cavities around the failure to shape the beam and propagate it without losses. Rephase downstream cavities to keep the beam as intact as possible. Give an ultimate energy boost to the beam with the last n_correctors cavities.

This method is very similar to the one used at SNS [SP22]. In this paper however, there are no compensating cavities around the failure.

Important

This method was designed to work with:

1. reference_phase_policy = "phi_s". This way, cavities downstream of a failure are rephased to preserve synchronous phase and hence acceptance.

2. strategy = "corrector at exit". This tells the failed_and_compensating() called at initialization of FaultScenario to add n_correctors cavities at the end of the linac to retrieve energy.

LightWin will not verify that these keys are properly set.

Todo

Automatically check validity of reference_phase_policy and consistency of strategy/objective_preset.

Warning

Setting n_compensating = 0 in the [wtf] section of the TOML configuration file will raise an error, as LightWin currently does not handle optimization problem without compensating elements.

Todo

Handle optimization problems without compensating cavities.

• Skip creation of associated Fault?

• Other solution?

Entry	Type	Description	Mandatory?	Allowed values
tie_politics	str	How to select the compensating elements when several are equidistant to the failure.	❌	(‘upstream first’, ‘downstream first’)
shift	int	Distance increase for downstream elements (shift < 0) or upstream elements (shift > 0). Used to have a window of compensating cavities which is not centered around the failed elements.	❌
n_compensating	int	Number of compensating cavities around every failure. They are used to shape the beam without retrieving nominal energy, so that it can propagate up to the `` correctors `` without losses. Currently, you must set at least 1 compensating cavity to avoid errors.	✅
n_correctors	int	Number of compensating cavities at the exit of the linac. They are used to retrieve nominal energy. Not affected by the `` shift `` keyword.	✅