Beam Diagnostics EXamples from High Energy Colliders

Beam Diagnostic Requirements: an Overview

Beam diagnostics and instrumentation are an essential part of any kind of accelerator. There is a large variety of parameters to be measured for observation of particle beams with the precision required to tune, operate, and improve the machine. In the first part, the basic mechanisms of information transfer from the beam particles to the detector are described in order to derive suitable performance characteristics for the beam properties. However, depending on the type of accelerator, for the same parameter, the working principle of a monitor may strongly differ, and related to it also the r…

Advancing Superconducting Magnet Diagnostics for Future Colliders

Future colliders will operate at increasingly high magnetic fields pushing limits of electromagnetic and mechanical stress on the conductor [1]. Understanding factors affecting superconducting (SC) magnet performance in challenging conditions of high mechanical stress and cryogenic temperatures is only possible with the use of advanced magnet diagnostics. Diagnostics provide a unique observation window into mechanical and electromagnetic processes associated with magnet operation, and give essential feedback to magnet design, simulations and material research activities. Development of novel d…

Formulae of luminosity and beam-beam tune shifts for flat-beam asymmetric colliders

This note outline the formulae of luminosity and beam-beam tune shifts applicable to flat-beam asymmetric colliders. The formulae are tested with the machine parameters of SuperKEKB.

Challenges in Accelerator Beam Instrumentation

The challenges in beam instrumentation and diagnostics for present and future particle accelerator projects are presented. A few examples for advanced hadron and lepton beam diagnostics are given.

Beam energy determination in experiments at electron-positron colliders

The review of using of compton backscattering method for determination of the beam energy in collider experiments is given.

Feedback and control systems for future linear colliders: White Paper for Snowmass 2021 Topical Group AF07-RF

Particle accelerators for high energy physics will generate TeV-scale particle beams in large, multi-Km size machines colliding high brightness beams at the interaction point [1-4]. The high luminosity in such machines is achieved by producing very small asymmetric beam size at the interaction point, with short durations to minimize beam-beam effects. Tuning energy, timing and position of the beam for optimal performance will require high-precision controls of amplitude and phase of high-frequency electromagnetic fields and real-time processing of complex algorithms. The stability of the colli…

Crossing angle at the photon collider

For removal of disrupted beams at the ILC linear e+e- collider it is desirable to collide beams at some crossing angle. An especially large crossing angle, of about 25 mrad, is necessary for the photon collider, where disrupted beams are softer and wider than in the e+e- case. Some complications arise due to the solenoidal magnetic field of the detector. Radiation of particles in this field can increase the vertical beam size, leading to a loss of the luminosity. In addition, in the presence of a detector magnetic field the beam trajectories are not flat. Moreover, in the case of e-e- beams, t…

Electron-Ion Collider with Quasi-Ordered Ion Beam

The possibility of using in an electron-ion collider the so-called quasi-ordered ion beam deep cooled by electron cooling is considered. The properties of the ordered and quasi-ordered beams are described. The advantages of using the quasi-ordered beam are discussed

Comment on "Physics considerations for laser-plasma linear colliders" and on "Beamstrahlung considerations in laser-plasma-accelerator-based linear colliders"

C. B. Schroeder, E. Esarey, C. Benedetti, and W. P. Leemans {Phys. Rev. ST Accel. Beams 13, 101301 (2010) and 15, 051301 (2012)} have proposed a set of parameters for a TeV-scale collider based on plasma wake field accelerator principles. In particular, it is suggested that the luminosities greater than 10^34 cm-2s-1 are attainable for an electron-positron collider. In this comment we dispute this set of parameters on the basis of first principles. The interactions of accelerating beam with plasma impose fundamental limitations on beam properties and, thus, on attainable luminosity values.

Summary of the Working Group on 'Beam-Beam Experience in Hadron Colliders'

There were four presentations given during the session 'Beam-beam experience in hadron colliders', reporting the beam-beam observations in SPS [1], Tevatron [2], RHIC [3] and HERA [4]. Presentations were followed by discussions. Below we summarize the major observations, findings and results.

Luminosity of a collider with asymmetric beams

A formula for the collider luminosity is derived for a head-on collision of two beams with different parameters. Three particular cases are presented: the collision of two identical axially symmetric bunches, the collision of a bunch with a coasting beam, and the collision of two coasting beams. The colliding beams have coinciding longitudinal axes. The formula is valid for colliding both counter propagating and co-propagating ("merging") beams.

$\mathrm{e}^+$$\mathrm{e}^-$ Beam-beam Parameter Study for a TeV-scale PWFA Linear Collider

We perform a beam-beam parameter study for a TeV-scale PWFA (particle-driven plasma wakefield acceleration) $\mathrm{e}^+$$\mathrm{e}^-$ linear collider using GUINEA-PIG simulations. The study shows that the total luminosity follows the $1/\sqrt{σ_z}$-scaling predicted by beamstrahlung theory, where $σ_z$ is the rms beam length, which is advantageous for PWFA, as short beam lengths are preferred. We also derive a parameter set for a 3 TeV PWFA linear collider with main beam parameters optimised for luminosity and luminosity spread introduced by beamstrahlung. Lastly, the study also compare the…

Chasing beams and muon colliders

A possible alternative way of producing muons (or other unstable particles) for colliders is proposed. It consists in colliding beams in a "chasing beam" configuration, i.e. collisions of two beams having the same direction but with different energies. This would produce muons with a good collimation, having already a high energy from the beginning, and then a longer life.

Beam-Beam Effects in the SPS Proton-Anti Proton Collider

During the proton-anti proton collider run several experiments were carried out in order to understand the effect of the beam-beam interaction on backgrounds and lifetimes. In this talk a selection of these experiments will be presented. From these experiments, the importance of relative beam sizes and tune ripple could be demonstrated.

Luminosity and beam-beam tune shifts with crossing angle and hourglass effects in e$^+$-e$^-$ colliders

We develop theoretical expressions for the luminosity and beam-beam tune shifts in the presence of both a crossing angle and hourglass effects for the present and next generation of symmetric e$^+$-e$^-$ colliders. The theory is applied to the design of the Fermilab site filler Higgs factory and to the FCC-ee collider.

Beam-beam Effects of 'Gear-changing' in Ring-Ring Colliders

In ring-ring colliders, the collision frequency determines the bunch structures, e.g. the time between the bunches in both rings should be identical. Because of relatively low relativistic speed of the hadron beam in sub-TeV hadron-hadron- and electron-ions-colliders, scanning the hadron beam's energy would require either a change in the circumference of one of the rings, or a switching of the bunch (harmonic) number in a ring. The later would cause so-called 'gear-changing', i.e. the change of the colliding bunches turn by turn. In this article, we study the difficulties in beam dynamics in t…

$γγ$ Beam-beam Parameter Study for a 3 TeV PWFA Linear Collider

Our beam-beam parameter study using beam-beam simulations and PWFA (particle-driven plasma acceleration) beam parameters indicates that at 3 TeV, for examined electron beam lengths ${2~μ\mathrm{m}\leqσ_z\leq 10~μ\mathrm{m}}$, the total luminosity, as well as the sharpness of the luminosity spectrum for a $γγ$ collider are independent of the beam length of the electron beams used to scatter the photons, given that the hourglass effect is avoided. The total luminosity can consequently be maximised by minimising the horizontal and vertical beta functions $β_{x,y}^*$ at the interaction point. Furt…

Model to study interplay between Beamstrahlung and coupling impedance in future lepton colliders

A semi-analytical model has been developed to study a combined effect of Beamstrahlung due to beam-beam interaction and beam coupling impedance in the future lepton colliders CEPC and FCCee. This model allows evaluating an impact of the coupling impedance on the bunch length and energy spread in collision. The model is benchmarked against numerical simulations. Analytical estimates for the supercolliders are presented.

Specific instrumentation and diagnostics for high-intensity hadron beams

An overview of various typical instruments used for high-intensity hadron beams is given. In addition, a few important diagnostic methods are discussed which are quite special for these kinds of beams.

Transition radiation based transverse beam diagnostics for non relativistic ion beams

The usage of optical transition radiation for profile monitoring of relativistic electron beams is well known. This report presents the case for beam diagnostic application of optical transition radiation for non-relativistic ion beams. The angular distribution of the transition radiation emitted from few target materials for ion beam irradiation is shown. In addition to expected linearly polarized transition radiation in the plane of observation, a large amount (roughly factor 20) of unpolarized radiation is observed towards grazing angles. The unpolarized radiation has the characteristics of…

Beam-beam effects investigation and parameters optimization for a circular e+e- collider TLEP to study the Higgs boson

Several proposals exist for future circular electron-positron colliders designed for precise measurements of the Higgs boson characteristics and electroweak processes. At very high energies, synchrotron radiation of the particles in a strong electromagnetic field of the oncoming bunch (beamstrahlung) becomes extremely important, because of degradation of the beam lifetime and luminosity. We present theoretical calculations of beamstrahlung (including the beam lifetime reduction and the energy spread increase) which are benchmarked against quasi strong-strong computer simulation. Calculation re…

CLIC Drive Beam and LHC Based Fel-Nucleus Collider

The feasibility of a CLIC-LHC based FEL-nucleus collider is investigated. It is shown that the proposed scheme satisfies all requirements of an ideal photon source for the Nuclear Resonance Fluorescence method. The physics potential of the proposed collider is illustrated for a beam of Pb nuclei.

Polarized Beams in a Muon Collider

This paper presents a first overview on how to obtain and maintain polarized beams in a muon-collider

Weak-Strong Simulation of Beam-Beam Effects in Super Proton-Proton Collider

A Super Proton-Proton Collider (SPPC) that aims to explore new physics beyond the standard model will be built in China. Here we focus on the impact of beam-beam interactions in the SPPC. Simulations show that with the current optics and nominal tunes, the dynamic aperture (DA) with all the beam-beam interactions is less than 6σ, the dominant cause being the long-range interactions. First, we show the results of a tune scan done to maximize the DA. Next, we discuss the compensation of the long-range interactions by increasing the crossing angle and also by using current carrying wires.

A system of beam energy measurement based on the Compton backscattered laser photons for the VEPP-2000 electron-positron collider

The beam energy measurement system for the VEPP-2000 electron-positron collider is described. The method of Compton backscattering of $CO$ laser photons on the electron beam is used. The relative systematic uncertainty of the beam energy determination is estimated as 6\cdot10^{-5}. It was obtained through comparison of the results of the beam energy measurements using the Compton backscattering and resonance depolarization methods.

Feasibility of backward diffraction radiation for non-destructive diagnostics of relativistic charged particle beams

The characteristics of backward diffraction radiation (BDR), i.e. radiation of the charged particle passing through a slit in the tilted screen, has been considered. The technique for non-destructive beam diagnostics based on the measurements of BDR yield for different tilted angles (theta-scan) is suggested.

Analytical Estimation of the Beam-Beam Interaction Limited Dynamic Apertures and Lifetimes in e^+e^- Circular Colliders

Physically speaking, the delta function like beam-beam nonlinear forces at interaction points (IPs) act as a sum of delta function nonlinear multipoles. By applying the general theory established in ref. 1, in this paper we investigate analytically the beam-beam interaction limited dynamic apertures and the corresponding beam lifetimes for both the round and the flat beams. Relations between the beam-beam limited beam lifetimes and the beam-beam tune shifts are established, which show clearly why experimentally one has always a maximum beam-beam tune shift, ξ_{y, max}, around 0.045 for e-^+e$^…

Coherent Beamstrahlung at the International Linear Collider

Although we believe most of the results presented here are correct, they are correct only in the limit of negligible beam disruption, which is not the ILC case. Also, the paper needs a convincing treatment of beam pipe shielding effects, though we believe that these effects will be proven to be small eventually.

Diagnostics needs for beam-beam studies and optimization

During the recent years of LHC operation, we analysed the situation of beam instrumentation and the need to optimize it for beam-beam studies. The most important beam instrumentation devices will be highlighted and modifications or optimizations will be suggested. A complete wish list will be presented to make sure we will be ready after LS1 (Long Shutdown 1) to study the beam-beam effect in a more complete way.

Achievable Luminosities at the THERA and LinacXLHC Based ep Colliders: 1. Round Beams

Different limitations on luminosity of linac-ring type colliders coming from beam dynamics issues are considered for the examples of the $ep$ options of the THERA and LinacXLHC proposals. It is shown that $L=1.3\times 10^{31}$ for THERA and $L=2.7\times 10^{32}$ for LinacXLHC can be achieved for round beams case. Corresponding sets of parameters are given with the explanations.

Mitigating performance limitations of single beam-pipe circular e+e- colliders

Renewed interest in circular e+e- colliders has spurred designs of single beam-pipe machines, like the CEPC in China, and double beam pipe ones, such as the FCC-ee effort at CERN. Single beam-pipe designs profit from lower costs but are limited by the number of bunches that can be accommodated in the machine. We analyse these performance limitations and propose a solution that can accommodate O(1000) bunches while keeping more than 90% of the ring with a single beam pipe.

RF Bucket Reduction as an Experimental Tool for Beam Diagnostics and Manipulation

A technique using RF bucket reduction for acquiring information about the particle distribution in longitudinal phase space has been applied in the Fermilab Booster. Data sets were obtained at six important time intervals of a Booster cycle for three different beam intensities. Controlled RF bucket reduction also provides other opportunities for beam manipulation.

A concept of the photon collider beam dump

Photon beams at photon colliders are very narrow, powerful (10--15 MW) and cannot be spread by fast magnets (because photons are neutral). No material can withstand such energy density. For the ILC-based photon collider, we suggest using a 150 m long, pressurized (P ~ 4 atm) argon gas target in front of a water absorber which solves the overheating and mechanical stress problems. The neutron background at the interaction point is estimated and additionally suppressed using a 20 m long hydrogen gas target in front of the argon.

Renormalization Group Approach to the Beam-Beam Interaction in Circular Colliders

Building on the Renormalization Group (RG) method the beam-beam interaction in circular colliders is studied. A regularized symplectic RG beam-beam map, that describes successfully the long-time asymptotic behavior of the original system has been obtained. The integral of motion possessed by the regularized RG map has been used to construct the invariant phase space density (stationary distribution function), and a coupled set of nonlinear integral equations for the distributions of the two colliding beams has been derived.

相对论重离子对撞机中大发射率比离子束的束内散射研究及其对电子-离子对撞机的影响

Intrabeam scattering studies with large-emittance-ratio ion beams in the Relativistic Heavy Ion Collider, and implications for the Electron-Ion Collider

在RHIC中成功产生并加速了发射率比为11:1的金离子束，测量并建模了束内散射效应，为EIC的平束碰撞设计提供参考。

Particle Beam Diagnostics

This lecture gives an overview about beam diagnostics techniques for the characterization of electron bunches obtained with plasma accelerators. Due to the limited space, the lecture does not aim to go into the specifics of the single measurements but rather to offer an overview of the present techniques (including ongoing developments) highlighting advantages and disadvantages of each of them. The linked references provide on the other side a more in depth discussion about the technical aspects.

Long-range beam-beam experiments in the relativistic heavy ion collider

Long-range beam-beam effects are a potential limit to the LHC performance with the nominal design parameters, and certain upgrade scenarios under discussion. To mitigate long-range effects, current carrying wires parallel to the beam were proposed and space is reserved in the LHC for such wires. Two current carrying wires were installed in RHIC to study the effect of strong long-range beam-beam effects in a collider, as well as test the compensation of a single long-range interaction. The experimental data were used to benchmark simulations. We summarize this work.

Luminosity Performance Studies of Linear Colliders with Intra-train Feedback Systems

The design luminosity for the future linear colliders is very demanding and challenging. Beam-based feedback systems will be required to achieve the necessary beam-beam stability and steer the two beams into collision. In particular we have studied the luminosity performance improvement by intra-train beam-based feedback systems for position and angle corrections at the interaction point. We have set up a simulation model which introduces different machine imperfections and can be applied to both the International Linear Collider (ILC) and the Compact Linear Collider (CLIC).

Beam-based mapping of pulsed septum stray field at VEPP-2000 collider

Various beam-based methods are widely used for machine study and accurate tuning. Beam closed orbit (CO) responses are routinely used worldwide for magnetic elements alignment and lattice correction. The paper presents the beam-based field mapping technique, applied for measurement of pulsed septum magnet stray field at VEPP-2000 electron-positron collider. Relatively slow pulse of weak leakage field disturbs the CO allowing detecting field longitudinal integral. While scanning with transverse coordinate in wide range one can measure the field map of the localized perturbation at machine in si…

基于机器学习的加速器束流成像诊断感兴趣区域分割

Machine Learning Based ROI Segmentation for Beam Imaging Diagnostics at Accelerators

针对传统束流感兴趣区域检测方法在非理想束流轮廓下可靠性不足的问题，开发机器学习方法实现像素级ROI识别，提升了挑战性条件下的鲁棒性与准确性，可应用于各类加速器的束流成像诊断。

Diffusion due to the Beam-Beam Interaction and Fluctuating Fields in Hadron Colliders

Random fluctuations in the tune, beam offsets and beam size in the presence of the beam-beam interaction are shown to lead to significant particle diffusion and emittance growth in hadron colliders. We find that far from resonances high frequency noise causes the most diffusion while near resonances low frequency noise is responsible for the large emittance growth observed. Comparison of different fluctuations shows that offset fluctuations between the beams causes the largest diffusion for particles in the beam core.

Fermilab PXIE Beam Diagnostics Development and Testing at the HINS Beam Facility

Fermilab is planning the construction of a prototype front end of the Project X linac. The Project X Injector Experiment (PXIE) is expected to accelerate 1 mA cw H- beam up to 30 MeV. Some of the major goals of the project are to test a cw RFQ and H- source, a broadband bunch-by-bunch beam chopper and a low-energy superconducting linac. The successful characterization and operation of such an accelerator places stringent requirements on beam line diagnostics. These crucial beam measurements include bunch currents, beam orbit, beam phase, bunch length, transverse profile and emittance, beam hal…

Physics Design Considerations of Diagnostic X Beam Transport System

Diagnostic X (D-X) transport system would extract the beam from the downstream transport line of the second- axis of the Dual Axis Radiographic Hydrodynamic Test facility (DARHT-II) and transport this beam to the D-X firing point via four branches of the beamline in order to provide four lines of sight for x-ray radiography. The design goal is to generate four DARHT-II-like x-ray pulses on each line of sight. In this paper, we discuss several potential beam quality degradation processes in the passive magnet lattice beamline and indicate how they constrain the D-X beamline design parameters, s…

Investigation of beam self-polarization in the future $e^{+}e^{-}$ circular collider

The use of resonant depolarization has been suggested for precise beam energy measurements (better than 100 keV) in the $e^{+}e^{-}$ Future Circular Collider (FCC-$e^{+}e^{-}$) for Z and WW physics at 45 and 80 GeV beam energy respectively. Longitudinal beam polarization would benefit the Z peak physics program; however it is not essential and therefore it will be not investigated here. In this paper the possibility of self-polarized leptons is considered. Preliminary results of simulations in presence of quadrupole misalignments and beam position monitors (BPMs) errors for a simplified FCC-$e…

The charged beam dumps for the international linear collider

The baseline configuration of the International Linear Collider requires 2 beam dumps per interaction region, each rated to 18MW of beam power, together with additional beam dumps for tuning purposes and machine protection. The baseline design uses high pressure moving water dumps, first developed for the SLC and used in the TESLA design, although a gas based dump is also being considered. In this paper we discuss the progress made by the international community on both physics and engineering studies for the beam dumps.

e$^+$e$^-$对撞机中的束流-尘埃相互作用

Beam-dust interactions in an e$^+$e$^-$ collider

针对低发射度高电流正负电子对撞机中束流与管内残余尘埃作用形成等离子体、进而导致束流发射度增长的问题，通过数值模拟研究了尘埃诱导等离子体对束流的影响。

Beam Blow Up due to Beamstrahlung in Circular $e^+e^-$ Colliders

After the discovery of the Higgs boson at the Large Hadron Collider in 2012, several possible future circular colliders -- Higgs factories are proposed, such as FCC-ee and CEPC. At these highest-energy $e^+e^-$ colliders, beamstrahlung, namely the synchrotron radiation emitted in the field of the opposing beam, can greatly affect the equilibrium bunch length and energy spread. If the dispersion function at the collision point is not zero, beamstrahlung will also increase the transverse emittances. In this letter, we first show that, for circular Higgs factories, a classical description of the …

10 TeV尾场对撞机的束流源

Beam Sources for 10 TeV Wakefield Collider

针对10 TeV尾场对撞机设计需求，评估现有和新兴粒子产生技术，重点关注可达到的亮度。

高能电子-正子对撞机中束辐射的解析近似

Analytical Approximations for Beamstrahlung at Very High Energy Electron-Positron Colliders

本文提出在高能电子-正子对撞机中，通过大量子参数极限下的解析近似，简化束辐射描述，为高能束束相互作用研究提供工具。

Equilibrium Distribution and Tune Shift of Beams in a Linear Collider

The evolution of two colliding beams in a linear accelerator can be described by two coupled Vlasov equations. In PEP-NOTE-325 by S. Kheifets and A. W. Chao the case without external focusing was considered. In this paper we derive the equilibrium distribution and the tune shift in the presence of external focusing. Motion is considered only in the vertical direction and the beams are presumed to be one-dimensional.

用于束流发散度诊断的切伦科夫衍射辐射干涉测量法

Cherenkov Diffraction Radiation Interferometry for Beam Divergence Diagnostics

该研究结合切伦科夫辐射与同步辐射干涉测量技术，提出基于切伦科夫辐射的干涉法，实现带电束流发散度的精准诊断。

Beam Diagnostics

As soon as the first particles emerge from an ion source, the source characteristics need to be determined. The total beam intensity, the transverse particle distributions, the beam divergence and emittance as well as the longitudinal parameters of the beam must be measured. This chapter provides an overview of typical measurement methods and the instruments used, and shows the results obtained.

Beam Measurements and Machine Learning at the CERN Large Hadron Collider

This paper presents a review of the recent Machine Learning activities carried out on beam measurements performed at the CERN Large Hadron Collider. This paper has been accepted for publication in IEEE Instrumentation and Measurement Magazine and in the published version no abstract is provided.

Diagnostics Examples from CTF3

After a short introduction of CLIC, the Compact Linear Collider, and its test facility CTF3 (CLIC Test Facility 3), this paper gives an overview and some examples of the diagnostics used at CTF3.