Scraping for LHC and collimation tests in the CERN SPS

Scraping of the SPS beam prior to extraction towards the LHC will be important in order to remove the beam tails and ensure clean injection conditions. Scrapers recuperated from the ISR were installed in the SPS for this purpose. The scrapers are associated with a two stage collimation system using collimators previously installed in LEP to reduce the irradiated area in the SPS. Tests have been performed to demonstrate that with the help of these collimators, it is possible to scrape with very little contamination outside the scraping area. Another issue was whether enough time is left for ejection towards the LHC after scraping, before repopulation of the removed tails. This was investigated with the SPS rest gas profile monitor and synchrotron radiation telescope. Scraping tests down to 1% of SPS beams accelerated to 450 GeV have been performed. The repopulation time constant was measured to be longer than 1 second, long enough to ensure clean extraction conditions towards the LHC. It appears that the radiation induced by the scraping is concentrated at the scraper and collimator locations, without irradiating other parts of the accelerator