Laserwire Emittance Scanner at CERN Linac 4

SUMMARY AND OUTLOOK The laserwire system capable of measuring the H beamattwocommissioningstagesofLinac4hasbeensuccessfully 6 4 2 0 2 4 6 8Vertical laser focus / slit position (mm)-6-4-20246Divergence (mrad)-6-4-20246Divergence (mrad)0.00.10.20.30.40.50.60.70.80.9Intensity (arb. units)0.00.10.20.30.40.50.60.70.80.91.0Intensity (arb. units)Figure 4: Vertical transverse phase space of the 12 MeVH beam measured by the laserwire (top) and conventionalslit and grid (bottom) methods.demonstrated. The main advantages of described system arethe use of low power, commercially available laser sourceand delivery of the laser pulses to the IP through the exi-ble optical bre. Obtained results from laserwire scannerdemonstrate very good agreement with conventional slitand grid diagnostic both for 3 MeV and 12 MeV H beam.These encouraging results represent the rst step towardsthe design of a laserwire system for the Linac 4 top energy.For the nal system it is foreseen to install two indepen-dent laserwire stations. Both shall be able to measure thephase space and, consequently, the emittance and prole ofthe beam in vertical and horizontal plane. The design of thethelaseropticsanddiagnosticwillremainsimilarwithsomeminor modications. For example, due to high radiationlevel the laser source will be relocated to a hutch on topof the accelerator tunnel. Additional optical path will berequired in order to perform the scan in the horizontal plane.A longer bre (  20 m) will be required to deliver the laserpulses to the IP. As for the detection system, the diamonddetector is still considered as a primary instrument for thenal system. The resolution of the detector can be improvedby increasing the number of readout channels. To measureprole of the H beam another possibility with detection ofthe stripped electrons is considered.