WP 3 Magnets for Insertion Regions Roberto Kersevan

WP 3 – Magnets for Insertion Regions Roberto Kersevan TE-VSC-IVM (Some material taken from recent presentations by G. Arduini, E. Todesco, R. Jones) The Hi. Lumi LHC Design Study is included in the High Luminosity LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.

Agenda: 3/9/2021 While reviewing the present situation… … will point out some open issues… … suggest some changes (mainly to apertures)… … and make remarks and hint at future developments. WP 3 – Magnets for Insertion Regions 2

BPMs White bands: allowed BPM installation areas E. Todesco Current BPM locations WP 3 – Magnets for Insertion Regions 3/9/2021 R. Jones HL-LHC PLC Jan 2013 Proposed BPM locations 3

Interconnects: margins on no W shielding length of BS 3/9/2021 • 260+178 = 438 mm seems the bare minimum • Taper: 15 degrees slant? WP 3 – Magnets for Insertion Regions 4

Baseline At Q 1 -Q 2 -Q 3 -CP-D 1: 1. He gap: 1 mm 1. 5 mm 2. Cold bore: ID 138 mm 137 mm 3. Tungsten absorbers (6 mm thickness) Annular gap: 0. 5 mm 1. 5 mm 4. Sliding rings ~ 0. 5 mm (included in 4) 5. 2 mm thickness octagonal BS. ID (inscribed circle): 121 mm 118 mm Question: Is that compatible with optics? 3/9/2021 L. Esposito WP 3 – Magnets for Insertion Regions 5

Vacuum Issues for the Hi. Lumi Triplets – R. Kersevan – CERN – TE/VSC/IVM – 4 Sept 2012 REF. 7. Engineering/Integration Issues: COLD BORE OD/ID Solid W absorber (4 x) Proposal: in order to guarantee a precise fitting of the external CB surface to the ID of the SC coils, a 159 mm tube with 11 mm wall thickness is needed, to be rectified until OD is reduced to 2 x 73. 5=147 mm Remaining wall thickness is 5 mm (+/- tolerance) Question: what margin on minimum thickness ? (minus tolerance on ID compatible with structural requirements) (NOT to scale) • • ISO standard for seamless tubing for the CB dictates fabrication tolerances: +/- 0. 5% on OD +/-10% on thickness For the case of an 8. 8 mm-thick 160 mm OD tube the combined tolerances on the OD of the cold bore are +/- 0. 889 +/- 0. 88 => +/- 1. 77 mm @ LHC Phase 1 Upgrade? 3/9/2021 ISSUE #1: Is this compatible with the design of the Q 1, Q 2, Q 3 and D 1 cold masses and coils? WP 3 – Magnets for Insertion Regions 6

What if increased shielding at Q 1? L. Esposito Reduction of the beam screen diameter at Q 1 proposed by S. Fartoukh with corresponding increase of the W shielding to reduce radiation dose. WP 3 – Magnets for Insertion Regions 3/9/2021 Need to simulate losses with longitudinal gaps for BPMs and sliding joints (a. k. a. plug-in modules… see next talk) 7

What if increased shielding at Q 1? L. Esposito 101 mm – midplane aperture Remark by G. Arduini: “some issues to be addressed concerning the pumping slots” I see no issue, other than a reduced area to machine the slots. The specific conductance of the slots is 677 l/s/m for H 2 at T=15 ⁰K WP 3 – Magnets for Insertion Regions 8 3/9/2021 98 mm (OK? ) (with 1. 5 mm He gap, 1. 5 mm annular gap for tolerance and sliding rings, as per slide 5)

Questions for us (G. Arduini’s) and my reply… • Is the reduction in aperture at Q 1 acceptable? Even for ultimate optics like 10 cm or flat? Aperture is reduced even more when tolerances are taken into account! OK? • What is the required tapering in the transition Q 1/Q 2 A. (present value is 15 degrees, ~ 1 : 4 (radial/long. ) ratio: OK? ) WP 3 – Magnets for Insertion Regions 3/9/2021 • Any issue from impedance/e-cloud from smaller aperture at Q 1? We should evaluate that before we make any decision on Q 1 BS aperture and therefore on D 1 aperture. WP 2. 4 • impedance impact (longitudinal welding at BS can double its impedance? ? ? . . . As per Ph. D student… true? ) • e-cloud heat load (leave that to the experts)

BS prototype design and fabrication: In order to launch the fabrication of a meaningful cold bore/beamscreen prototype the following issues should be settled (aiming at presenting a proposal at 5 th HL-PLC, 2 nd July 2013): 1. Finalize beam-stay-clear area 2. Set number and position of BPMs 3. Set number and position of plug-in modules (default is one at each cryostat interconnection) 4. Define thickness of W shielding bars, and possibly their brazing/fixation technique 5. Define insertion sequence and position of CB inside magnets’ coils: vertical vs horizontal. Impact on magnet assembly sequence 6. LHe gap: 1. 5 mm? Vis a vis of possible sagging of the cold bore (with ~60 kg/m for BS and W shielding) what’s the minimum radial gap allowed? 3/9/2021 7. Define minimum length of prototype (8 m, like Q 1/Q 3? ) WP 2 - Task Leaders' Meeting 10

Thanks for your attention: any questions? 3/9/2021 (With many thanks to P. Cruikshank and N. Koos for fruitful discussions) WP 2 - Task Leaders' Meeting 11