MD on Injection Quality – Longitudinal and Transverse Parameters

Losses at injection depend on the beam quality in the longitudinal and transverse plane in the injectors. During the MD on the 30th of June to 1st of July, 2011, many parameters in the injectors were de-tuned on purpose to see the effect on injection losses and hence bring some understanding to recurring problems with injection quality during LHC filling. The effect of the 800 MHz in the SPS, radial steering, larger momentum spread at the SPS extraction and many other longitudinal parameters were studied during the MD. The MD showed however that the injection losses are dominated by far by the transverse size of the particle population. If the SPS scrapers are correctly positioned, injection losses are low even at the presence of quality issues in the longitudinal plane. To be able to inject brighter 50 ns beams or eventually 25 ns beams, injection losses with nominal emittances (3.5 m) must still be acceptable. This MD showed that nominal emittances can be injected with similar loss levels as the typical 2 – 2.5 m emittances of the single batch 50 ns beams, provided the scraping in the SPS is well under control. The sensitivity of injection losses to transfer line steering could not be addressed in the MD due to lack of time.