Collimation method studies for next-generation hadron colliders

Abstract

In order to handle extremely-high stored energy in future proton-proton colliders, an extremely high-efficiency collimation system is required for safe operation. At LHC, the major limiting locations in terms of particle losses on superconducting (SC) magnets are the dispersion suppressors (DS) downstream of the transverse collimation insertion. These losses are due to the protons experiencing single diffractive interactions in the primary collimators. How to solve this problem is very important for future proton-proton colliders, such as the FCC-hh and SPPC. In this article, a novel method is proposed, which arranges both the transverse and momentum collimation in the same long straight section. In this way, the momentum collimation system can clean those particles related to the single diffractive effect. The effectiveness of the method has been confirmed by multi-particle simulations. In addition, SC quadrupoles with special designs such as enlarged aperture and good shielding are adopted to enhance the phase advance in the transverse collimation section, so that tertiary collimators can be arranged to clean off the tertiary halo which emerges from the secondary collimators and improve the collimation efficiency. With one more collimation stage in the transverse collimation, the beam losses in both the momentum collimation section and the experimental regions can be largely reduced. Multi-particle simulation results with the MERLIN code confirm the effectiveness of the collimation method. At last, we provide a protection scheme of the SC magnets in the collimation section. The FLUKA simulations show that by adding some special protective collimators in front of the magnets, the maximum power deposition in the SC coils is reduced dramatically, which is proven to be valid for protecting the SC magnets from quenching.

Design Concept for a Future Super Proton-Proton Collider

“…Figure 5 shows the schematic for such a five-stage collimation system, where four stages are in a dedicated collimation section and the fifth is at the IPs to protect the detectors. To avoid the critical SDE which becomes more important at higher energy, we developed a novel concept by combining the betatron collimation and momentum collimation in a same long straight section [41]. In this way, the particles from the SDE at the betatron primary collimators can be cleaned by the momentum collimation system, and we can avoid warm collimators in the downstream DS sections.…”

“…These cold quadrupoles are very different from those in the arcs, and they will be designed with enlarged apertures and lower pole strength (not higher than 8 T) with strong radiation shielding, somewhat comparable to the triplet quadrupoles used in the experiment insertions at the LHC. Simulations show that with all the measures taken the radiation is manageable [41]. To further reduce the particle losses in magnets from the SDE, some protective or passive collimators are also used.…”

Merlin++, a flexible and feature-rich accelerator physics and particle tracking library

“…Over the years, Merlin++ has been extended and applied to a variety of use-cases, such as ILC beamline and damping rings studies [15,16,17], NLC depolarisation/spintracking [18], and LHC collimation [19,20,21,22,23,24]. Currently, Merlin++ remains under active development and use for HL-LHC, FCC [25] and SppC collimation studies [26]. As a result, the code base has grown to become one of the most feature-rich and functionally capable tracking codes available.…”

Axions: From Magnetars and Neutron Star Mergers to Beam Dumps and BECs

“…Particles collided Center-of-mass energy [TeV] Integrated L [ab −1 ] HL-LHC [386] pp 14 3 HE-LHC [387] pp 27 10 SPPC [383,396] pp 75, 100 3 FCC-hh [387] pp 100 30 FCC-ee [381] e + e − 0.091, 0.161, 0.24, 0.34 -0.365 145, 120, 50, 15 ILC [382] e + e − 0.25 2 CEPC [383] e + e − 0.25 5 CLIC [384,385] e + e − 0.35 (and 0.35), 1.5, 3.0 1, 2.5, 3 LHeC [388] e − p 1.3 (Ee = 0.05, Ep = 6.5) 1 FCC-he [388,397] e − p 4.8 (Ee = 0.06, Ep = 20), 12 (Ee = 0.06, Ep = 50) 3, 3 on the plane of (m a , g aγγ ) in the channel Z → a + γ with Br(a → γ + γ) = 1, and assuming 3,000 fb −1 of pp collision data at the LHC. The authors calculate the relevant cross-sections and determine the signal significance by requiring a minimum signal yield of 100 events, and find that g aγγ ∼ 5 × 10 −6 GeV −1 can be probed for m a ∼ 1 − 100 GeV.…”