HL-LHC layout for xed-target experiments in ALICE based on crystal-assisted beam halo splitting Marcin Patecki

2025-05-06 0 0 3.37MB 7 页 10玖币

侵权投诉

HL-LHC layout for ﬁxed-target experiments in ALICE based on crystal-assisted beam

halo splitting

Marcin Patecki∗

Warsaw University of Technology, Faculty of Physics, ul. Koszykowa 75, 00-662 Warsaw, Poland.

Alex Fomin, Daniele Mirarchi, and Stefano Redaelli

European Organization for Nuclear Research (CERN), CH-1211 Geneva 23, Switzerland

Cynthia Hadjidakis

Universit´e Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France

Francesca Galluccio

INFN Sezione di Napoli, Complesso Universitario di Monte Sant’Angelo, Via Cintia, 80126 Napoli, Italy

Walter Scandale

Blackett Laboratory, Imperial College, London SW7 2AZ, UK and

INFN Sezione di Roma, Piazzale Aldo Moro 2, 00185 Rome, Italy

(Dated: April 21, 2023)

The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN)

is the world’s largest and most powerful particle accelerator colliding beams of protons and lead

ions at energies up to 7 Z TeV, Z is the atomic number. ALICE is one of the detector experiments

optimised for heavy-ion collisions. A ﬁxed-target experiment in ALICE is being considered to collide

a portion of the beam halo, split using a bent crystal inserted in the transverse hierarchy of the LHC

collimation system, with an internal target placed a few meters upstream of the existing detector.

This study is carried out as a part of the Physics Beyond Collider eﬀort at CERN. Fixed-target

collisions oﬀer many physics opportunities related to hadronic matter and the quark-gluon plasma

to extend the research potential of the CERN accelerator complex. Production of physics events

depends on the particle ﬂux on target. The machine layout for the ﬁxed-target experiment is

developed to provide a ﬂux of particles on the target high enough to exploit the full capabilities of

the ALICE detector acquisition system. This paper summarises the ﬁxed-target layout consisting of

the crystal assembly, the target and downstream absorbers. We discuss the conceptual integration

of these elements within the LHC ring, the impact on ring losses, and expected performance in

terms of particle ﬂux on target.

I. INTRODUCTION

Advancements in the knowledge of fundamental con-

stituents of matter and their interactions are usually

driven by the development of experimental techniques

and facilities, with a signiﬁcant role of particle accel-

erators. The Large Hadron Collider (LHC) [1] at the

European Organization for Nuclear Research (CERN) is

the world’s largest and most powerful particle acceler-

ator colliding opposite beams of protons (p) and lead

ions (Pb), allowing for unprecedentedly high centre-of-

mass energies of up to 14 TeV and 5.5 TeV per nucleon,

respectively. An ALICE ﬁxed-target (ALICE-FT) pro-

gramme [2] is being considered to extend the research

potential of the LHC and the ALICE experiment [3].

The setup of in-beam targets at the LHC is particularly

challenging because of the high-intensity frontier of LHC

beams [4].

Fixed-target collisions in the LHC are designed to

be operated simultaneously with regular head-on colli-

∗Marcin.Patecki@pw.edu.pl

sions without jeopardising the LHC eﬃciency during its

main p-p physics programme. Several unique advan-

tages are oﬀered with the ﬁxed-target mode compared to

the collider mode. With a high density of targets, high

yearly luminosities can be easily achieved, comparable

with luminosities delivered by the LHC (in the collider

mode) and Tevatron [5]. In terms of collision energy,

the ALICE-FT layout would provide the most energetic

beam ever in the ﬁxed-target mode with the centre of

mass energy per nucleon-nucleon of 115 GeV for proton

beams and 72 GeV for lead ion beams [5], in between

the nominal Relativistic Heavy Ion Collider (RHIC) and

Super Proton Synchrotron (SPS) energies. Thanks to

the boost between the colliding-nucleon centre-of-mass

system and the laboratory system, access to far back-

ward regions of rapidity is possible with the ALICE de-

tector, allowing to measure any probe even at far ranges

of the backward phase space, being utterly uncharted

with head-on collisions [5]. Moreover, the possibility of

using various species of the target material extends the

variety of physics cases, especially allowing for unique

neutron studies [5]. The physics potential [2, 5] of such

a ﬁxed-target programme covers an intensive study of

arXiv:2210.13299v3 [physics.acc-ph] 20 Apr 2023

strong interaction processes, quark and gluon distribu-

tions at high momentum fraction (x), sea quark and

heavy-quark content in the nucleon and nucleus and the

implication for cosmic ray physics. The hot medium cre-

ated in ultra-relativistic heavy-ion collisions oﬀers novel

quarkonium and heavy-quark observables in the energy

range between the Super Proton Synchrotron (SPS) and

the Relativistic Heavy Ion Collider (RHIC), where the

QCD phase transition is postulated.

A signiﬁcant innovation of our proposal is to bring

particles of high energy collider to collisions with a

ﬁxed-target by splitting a part of the beam halo using a

bent crystal. Particles entering the crystal with a small

impact angle (≤2.4µrad for silicon crystals and pro-

ton energy of 7 TeV [6]) undergo the channeling process

resulting in a trajectory deﬂection equivalent to the ge-

ometric bending angle of the crystal body [7, 8]. Such

a setup enables an in-beam target at a safe distance

from the circulating beam. This type of advanced beam

manipulation with bent crystals builds on the experi-

ence accumulated in diﬀerent accelerators (see for exam-

ple [9, 10]), and in particular, on the successful results

achieved in the multi-TeV regime for beam collimation

at the LHC [11–13]. The halo-splitting technique allows

proﬁting from the circulating beam halo particles that

are not contributing to the luminosity production and

are typically disposed of by the collimation system.

The problem that we address is to design the machine

layout that provides a number of protons on the target

high enough to exploit the full capabilities of the ALICE

detector acquisition system without aﬀecting the LHC

availability for regular beam-beam collisions. Our pro-

posal of the ALICE-FT layout [14] follows general guide-

lines on technical feasibility and impact on the LHC ac-

celerator of potential ﬁxed-target experiments provided

by the LHC Fixed Target Working Group of the CERN

Physics Beyond Colliders forum [4, 15]. We also proﬁt

from the preliminary designs reported in [16, 17] and from

the design study of an analogous ﬁxed target experiment

at the LHC proposed to measure electric and magnetic

dipole moments of short-lived baryons [18].

In this paper, we summarise the ALICE-FT machine

layout. We report on the conceptual integration of its

elements (crystal and target assemblies, downstream ab-

sorbers), their impact on ring losses, and expected perfor-

mance in terms of particle ﬂux on target. We also discuss

a method of increasing the ﬂux of particles on the tar-

get by setting the crystal at the optimal betatron phase

by applying a local optics modiﬁcation in the insertion

hosting the ALICE experiment (IR2). This method is in-

dependent of the crystal location, allowing for a crystal

installation in a place with good space availability. More-

over, it allows to recover the maximum performance of

the system in case of changes in beam optics in the LHC.

II. MACHINE CONFIGURATION

A potential installation of the ALICE-FT setup will

coincide with a major LHC upgrade in terms of instan-

taneous luminosity, commonly referred to as the High-

Luminosity LHC (HL-LHC) [19], taking place in the Long

Shutdown 3 (2026-2028), to make it ready for the LHC

Run 4 starting in 2029. Some of the expected beam pa-

rameters, having a direct impact on the ALICE-FT ex-

periment performance, are given in Table I. One key

beam parameter to be upgraded is the total beam cur-

rent that will increase nearly by a factor of two, up to

about 1.1 A, leading to about 0.7 GJ of total beam en-

ergy stored in the machine. A highly eﬃcient collimation

TABLE I. Some proton-beam parameters of the future HL-

LHC beams important for the ALICE-FT experiment, re-

ferred to as standard in [19].

Colliding-beam energy E 7 TeV

Bunch population Nb2.2·1011

Maximum number of bunches nb2760

Beam current I 1.09 A

Transverse normalised emittance εn2.5 [µm]

β∗at IP2 10 m

Beam crossing angle at IP2 200 µrad

system is therefore required in the LHC [20] to protect its

elements, especially the superconducting magnets, from

impacts of particles from the beam. The collimation sys-

tem is organised in a precise multi-stage transverse hier-

archy (see Table II) over two dedicated insertions (IRs):

IR3 for momentum cleaning and IR7 for betatron clean-

ing. Each collimation insertion features a three-stage

cleaning based on primary collimators (TCPs), secondary

collimators (TCSGs) and absorbers (TCLAs). In addi-

tion, dedicated collimators are present in speciﬁc loca-

tions of the ring to provide protection of sensitive equip-

ment (e.g. TCTP for the inner triplets), absorption of

physics debris (TCL) and beam injection/dump protec-

tion (TDI/TCDQ-TCSP). The collimation system un-

dergoes an upgrade, as described in [21], to make it

compatible with HL-LHC requirements, but the general

working principle will remain the same. The system is

designed to sustain beam losses up to 1 MJ without dam-

age and with no quench of superconducting magnets.

The halo-splitting scheme relies on placing a crystal

into the transverse hierarchy of the betatron collimation

system, in between the primary and secondary stage of

IR7 collimators, such that the collimation system eﬃ-

ciency is not aﬀected. Placing the splitting crystal closer

to the beam than the primary collimators would not be

possible without designing a downstream system capable

of withstanding the collimation design loss scenarios. Re-

tracting the crystal at larger amplitudes avoids this prob-

lem while still allowing intercepting a signiﬁcant fraction

of the multi-stage halo, as shown below. In this scheme,

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

10 玖币 0人已下载

立即下载

摘要：

HL-LHClayoutforxed-targetexperimentsinALICEbasedoncrystal-assistedbeamhalosplittingMarcinPateckiWarsawUniversityofTechnology,FacultyofPhysics,ul.Koszykowa75,00-662Warsaw,Poland.AlexFomin,DanieleMirarchi,andStefanoRedaelliEuropeanOrganizationforNuclearResearch(CERN),CH-1211Geneva23,SwitzerlandCynth...

展开>> 收起<<

HL-LHC layout for xed-target experiments in ALICE based on crystal-assisted beam halo splitting Marcin Patecki.pdf

共7页,预览2页

还剩页未读，继续阅读

声明：本站为文档C2C交易模式，即用户上传的文档直接被用户下载，本站只是中间服务平台，本站所有文档下载所得的收益归上传人(含作者)所有。玖贝云文库仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对上载内容本身不做任何修改或编辑。若文档所含内容侵犯了您的版权或隐私，请立即通知玖贝云文库，我们立即给予删除！

HL-LHC layout for xed-target experiments in ALICE based on crystal-assisted beam halo splitting Marcin Patecki

相关推荐

开通VIP享超值会员特权

作者详情

相关内容

热门标签

举报选择: