1. Study Group for slow extraction assisted by bent crystals in the SPS B.Goddard, W.Scandale 23/7/15

3. Investigation topics 1.Loss reduction: Bent crystals could be used to intercept separatix particles that otherwise would hit the wires of ES, deflecting them into the extraction channel, well inside ES aperture. The local beam loss and debris produced by ES wires will be thus reduced, and shifted in a safer area of the accelerator. 2.ZS replacement: Bent crystals may intercept the totality of the particles to be extracted, deflecting them into the extraction channel by a similar angle as the ES, thus allowing resonant extraction without ES. 3.Noise-driven extraction: An electromagnetic (EM) device could induce random deflections in the circulating beam and enhance halo diffusion. By shaping of the EM noise, it should be possible to produce a constant. As in 2., a bent crystal could intercept the totality of the beam halo, in a non-resonant extraction process without ES

4. Motivation The possibility of shifting the beam loss from the ES to a safer accelerator area, inherent in 1 and 2, may bring immediate benefits for daily SPS operation and for future extractions scenarios at higher intensity such as the proposed SHiP experiment. The possibility of suppressing the ES septum in the extraction channel, inherent in 2 and 3, may drastically reduce the complexity and cost of the extraction, resulting in much easier integration for beam extraction at very high energy, for example for multi-TeV fixed-target beams for the FCC era The possibility of using non-resonant slow extraction and reduced length extraction channel for the suppression of the ES, inherent in 3, is a very elegant scenario for integrating extraction in an accelerator with reduced mechanical aperture.

5. Study objectives The study should comprise theoretical and experimental parts, and should be concluded by end 2018. The main objectives are: 1.Investigate and develop a concept for crystal-assisted loss mitigation in SPS for 450 GeV p+ slow extraction, aiming at a factor of 3 or more reduction at ES. 2.Investigate the feasibility of crystals to replace ES as the initial beam intercepting element in a slow extraction system, at 450 GeV in the SPS; 3.Simulate and specify the EM excitation needed for non-resonant slow extraction in SPS. 4.Define and implement baseline experiments to test slow-extraction assisted by bent crystals into one of the SPS extraction channel. The test should be initially performed using stored beams at 270 GeV, and could later be extended to 450 GeV with pulsed cycles. The new hardware required for the experiments, comprising crystals, goniomenters and detectors, should be defined by the initial study phase and first be characterized with tests in the laboratory and later in the H8 beam-line in the SPS North Area.

6. Study Group Brennan Goddard (Chair, TE/ABT) Matthew Fraser (TE/ABT) Stefano Redaelli (Collimation Project Leader) Walter Scandale (UA9 Spokesperson) Simone Montesano (UA9 Technical Coordinator) Karel Cornelis (BE/OP-SPS) Francesca Galluccio (UA9 INFN) Federica Andrisani (UA9, EN/STI Group) Yu Gavrikov (UA9-PNPI) Roberto Rossi (UA9, Collimation Team) Alexander Taratin (UA9-JINR) Francesco Velotti (ABT) Verena Kain (BE/OP-SPS) Gianluca Cavoto (UA9 INFN) Achille Stocchi (UA9 LAL) Veronique Puill (UA9 LAL) Iouri Ivanov (UA9 PNPI) Alessandro Masi (EN/STI)

7. Study Group scope The Study Group will define or review: layout of the experiment; simulation tools; list of the hardware component (including the beam instrumentation); key performance indicators; integration needs; costs; beam time for each experiment; experimental procedures, including the front-end and the application software.

8. Upcoming topics Concept for demonstration of crystal-assisted extraction and new SPS installation needed Future post-LS2 configuration of UA9 system in LSS5 in view of internal beam dump system relocation Concept for loss reduction for high intensity extraction and proof of principle experiment Concept for controlled halo diffusion replacing 3 rd integer resonance and design of proof of principle experiment

9. Practicalities Interface with Francesca’s UA9-SE Working Group UA9-SE WG to continue actively on the detailed investigations Scope of SPS-SEBC limited to SPS and defined topics SPS-SEBC to interface with ATS management where needed Meeting frequency and time Approximately monthly Next agenda UA9 needs post LS2 and LSS5 layout implications? Overview of actions needed for progress on the different objectives? Tentative planning?