First Operation of the High Duty Cycle Saclay Electron Linac (A.L.S.)

Tests in CSF laboratories have given evidence for the excellent quality of the bunching in the first section. Tests on the site starting in january 1968 were performed during all the year. Operations with both electron and positron beams give many results, namely maximum electron energy 640 MeV with zero current and 540 MeV with 40 mA peak current and an energy distribution with FWHM 3 to 4/1000. The maximum peak current obtained was 60 mA and no beam break-up does appear. Operations were performed at duty cycles of 1 % and 2 % with electron beam power of the order of 100 kW during many shifts of 30 hours ; energy stability was better than 1 % for 30 hours. Special devices helping to handle the beam inside and outside the linac at such a power level are described. First measurements of e+/e- conversion efficiency give an intensity ratio of positron beam relatively to electron beam, above 400 MeV positron energy, of the order of 10-3 and improvements are expected.