Linac4 chopper line commissioning strategy

The report outlines the strategy for beam-based commissioning of the Linac4 3 MeV chopper line as currently scheduled to start in the second half of 2011 in the Test Stand Area. A dedicated temporary diagnostics test bench will complement the measurement devices foreseen for permanent installation in the chopper line. A commissioning procedure is set out as a series of consecutive phases, each one supposed to meet a well- defined milestone in the path to fully characterise the beam-line. Specific set-ups for each stage are defined in terms of beam characteristics, machine settings and diagnostics used. Operational guidelines are given and expected results at the relative points of measurements are shown for simulated scenarios (on the basis of multi-particle tracking studies carried out with the codes PATH and TRACEWin). These are then interpreted in the light of the resolution limits of the available diagnostics instruments to assess the precision reach on individual measurements and the feasibility of techniques aimed at finding working points via particular signatures and signal variations. Where possible different techniques are compared for cross-validation. An attempt is also made to define a time schedule in terms of the number of shifts necessary to accomplish each phase, the baseline assumption being of a single 8hrs shift per day with two main commissioners on duty and dedicated support for all essential systems (diag nostics, RF, power, controls, vacuum, source experts etc.). A 50% allowance for general machine unavailability has been assumed. All hardware commissioning and cold check-out tests are outside the scope of this note and are assumed to have already been completed by the start time of beam commissioning.