SLOW EXTRACTION AT THE SPS: EXTRACTION EFFICIENCY AND LOSS REDUCTION STUDIES

Authors

  • M. A. Fraser et al.

DOI:

https://doi.org/10.23727/CERN-Proceedings-2017-002.87

Abstract

Elevated activation levels in LSS2 were first reported during an intervention on the SPS extraction septum (ZS) in September 2015. The increase was attributed to higher intensity Fixed Target (FT) operation and poorer extraction efficiency, and reported to the IEFC [1]. Since this event the awareness of the impact of slow extraction losses on the operation and maintenance of the SPS has been heightened This is particularly pertinent in light of tightening limits on dose to personnel and recent requests for increased intensities, as well as ambitious future experimental proposals in the North Area (NA), such as the SPS Beam Dump Facility BDF) [2]. To follow up these issues the SPS Losses and Activation Working Group (SLAWG) was formed. The MD programme for 2016 was originally foreseen to test the faster spill on a 1.2 second flat-top for the BDF and benchmark simulations of the extraction process, but this was not possible due to the restrictions imposed by the TIDVG Nevertheless, during operational set-up and re-alignment of the electrostatic septum (ZS) the extraction efficiency could be studied parasitically. The first re-alignment of the ZS actually took place during dedicated MD time in May before moving to physics time. The application of bent crystals used in different configurations and modes of operation for slow extraction is being studied [3, 4]. Bent crystals offer promising solutions for reducing the activation of the SPS LSS2 extraction region that is induced by the small fraction of beam that unavoid ably impinges the ZS during the conventional resonant slow extraction process. In 2016, the slow extraction of a low intensity coasting 270 GeV proton beam into the TT20 extraction line towards the NA of the SPS was demonstrated in dedicated MDs using the extraction septa in LSS2 and a bent crystal, provided by the UA9 collaboration as part of their experimental installation in LSS5.

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Published

2017-12-12