MD1388: A tiv e Halo Con trol using narro w band ex itation at inje tion Morales 1 , 2 He tor Gar ia Bru e 2 Redaelli 2 tino 2 Ro derik , Sefano , Gianlu a V alen , h 2 agner 2 Xu 2 Daniel V alu , Jos hk a W , C. LHC Collimation T eam 1 Ro y al Hollo w a y Univ ersit y of London, Egham, UK 2 CERN, Genev a, Switzerland August 2, 2016
Motiv ation T esting a new te hnique for the depletion of o v erp opulated b eam tails with presen t hardw are. The study of the metho d ould b e v ery b ene� ial for HL-LHC to a v oid spurious b eam dumps b y pro viding an a tiv e halo on trol. Narro w band ex itation Apply a narro w band ex itation using the transv erse dump er (ADT) for di�eren t frequen ies to ex ite the desired amplitude.
Pro edure Previous attempts Gained exp erien e from previous MDs arried out in 2015. These tests w ere not fully on lusiv e. One promising ase to b e done again in this MD. Inje t 4 nominal bun hes and sta y at inje tion. ( 2 σ Blo w up one of the bun hes. ) Measure pro�le with wire s anners. ADT ex itation. Measure pro�le with wire s anners. Get rid of all but blo wn up bun h. S rap e do wn the remaining bun h to get a more a urate pro�le of the b eam tails. Diamond dete tor to distinguish bun h b y bun h losses. Reinje t and measure again.
Bun h s heme 4 nominal bun hes ( × 2 Referen e bun h ): Outside the ADT windo w. Blo wn up bun h: Inside ADT windo w, fat tails bun h to in rease monitoring signal. Witness bun h: Inside ADT windo w, nominal bun h to sho w that the ore is not a�e ted.
MD o v erview time: ∼ 5 T otal h (in luding w aiting time) (Start 8:00, Finish: 13:00). In parallel with rystal MD. Three measuremen ts arried out.
Preliminary results frequen y: Q ADT = 0 . 295 ≈ 5 . 5 σ x Fixed ADT = (0 . 2908 → s an: Q F requen y 0 . 2986) ≈ (4 . 5 σ x → 6 σ x ) One measuremen t with s an in ADT ADT = 0 . 2908 → 0 . 2986 frequen y Q . T w o measuremen ts at �xed ADT ADT = 0 . 295 2% frequen y: Q (5 min). in tensit y loss for the ex ited ( < 0 . 2% ) bun h. Small de rease in W e ould repro du e what w e in tensit y for witness bun h. T o b e observ ed in previous MDs. analyzed o�ine. 1% in tensit y de rease for the ex ited bun h while other remained unp erturb ed. No emittan e in rease observ ed.
Con lusions The MD w as arried out in parallel with the rystal ollimator MD. W e tested again the a tiv e halo on trol using resonan t ADT ex itation. Similar s heme as the one used in previous MDs. 2 nominal witness bun hes not a�e ted b y the ADT ex itation and 2 nominal bun hes under the ADT ( 2 ε ) e�e ts, one of the blo wn up W e rep eated the same ase as in the 2015 MD that ga v e promising results. ( Q x = 0 . 295 Fixed frequen y ) and ADT amplitude 0.03. y 1% In this ase the in tensit y w as de reased b while emittan e sta y ed onstan t and the other bun hes w ere not a�e ted. Detailed o�ine analysis is ongoing in luding diamond dete tors data, but w e obtained promising results using this metho d for tail depletion. The e�e tiv eness of this metho d dep ends on the remaining halo p opulation after the ex itation whi h has to b e analyzed o�ine from the s raping data.
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