arXiv subjects
Publications and source records attributed to M. Zobov.
The DA{\Phi}NE operations during the last year have been devoted to deliver a statistically significant data sample to perform the first-ever measurement of kaonic deuterium X-ray transitions to the fundamental level. Operations for the SIDDHARTA-2 detector using a deuterium gas target started officially on the second half of May 2023, and have been organized in several runs here described.
The FCC-ee impedance model is being constantly updated closely following the vacuum chamber design and parameters evolution. In particular, at present, a thicker NEG coating of 150 nm (instead of previous 100 nm) has been suggested by the vacuum experts, and a more realistic impedance model of the bellows has been investigated. Moreover, also the transverse impedance has been updated by considering the same sources as for the longitudinal case. Therefore, the FCC-ee impedance database is getting more complete and the impedance model is being refined. In this paper we describe the presently available machine coupling impedance in both longitudinal and transverse planes, and study the impedance-driven single bunch instabilities (with and without beam-beam interaction) for the new FCC-ee parameter set with 4 interaction points (IPs). The results are compared with the previously obtained ones and a further possible mitigation of the beam-beam head-tail instability (X-Z instability) is proposed.
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.
The CERN FCC-ee top-up booster synchrotron will accelerate electrons and positrons from an injection energy of 20 GeV up to an extraction energy between 45.6 GeV and 182.5 GeV depending on the operation mode. These accelerated beams will be used for the initial filling of the high-luminosity FCC-ee collider and for keeping the beam current constant over time using continuous top-up injection. Due to the high-intensities of the circulating beams, collective effects may represent a limitation in the top-up booster. In this work we present a first evaluation of the impedance model and the effects on beam dynamics. Methods to mitigate possible instabilities will be also discussed.
In this paper a review of some important impedance-induced instabilities are briefly described for both the longitudinal and transverse planes. The main tools used nowadays to predict these instabilities and some considerations about possible mitigation techniques are also presented.
Chapter 2 in High-Luminosity Large Hadron Collider (HL-LHC) : Preliminary Design Report. The Large Hadron Collider (LHC) is one of the largest scientific instruments ever built. Since opening up a new energy frontier for exploration in 2010, it has gathered a global user community of about 7,000 scientists working in fundamental particle physics and the physics of hadronic matter at extreme temperature and density. To sustain and extend its discovery potential, the LHC will need a major upgrade in the 2020s. This will increase its luminosity (rate of collisions) by a factor of five beyond the original design value and the integrated luminosity (total collisions created) by a factor ten. The LHC is already a highly complex and exquisitely optimised machine so this upgrade must be carefully conceived and will require about ten years to implement. The new configuration, known as High Luminosity LHC (HL-LHC), will rely on a number of key innovations that push accelerator technology beyond its present limits. Among these are cutting-edge 11-12 tesla superconducting magnets, compact superconducting cavities for beam rotation with ultra-precise phase control, new technology and physical processes for beam collimation and 300 metre-long high-power superconducting links with negligible energy dissipation. The present document describes the technologies and components that will be used to realise the project and is intended to serve as the basis for the detailed engineering design of HL-LHC.
Current bearing wire compensators were successfully used in the 2005-2006 run of the DAΦNE collider to mitigate the detrimental effects of parasitic beam-beam interactions. A marked improvement of the positron beam lifetime was observed in machine operation with the KLOE detector. In view of the possible application of wire beam-beam compensators for the High Luminosity LHC upgrade, we revisit the DAΦNE experiments. We use an improved model of the accelerator with the goal to validate the modern simulation tools and provide valuable input for the LHC upgrade project.
Gamma sources with high flux and spectral densities are the main requirements for new nuclear physics experiments to be performed in several worldwide laboratories and envisaged in the ELI-NP (Extreme Light Infrastructure-Nuclear Physics) project or in the IRIDE (Interdisciplinary Research Infrastructure with Dual Electron Linacs) proposals. The paper is focalized on an experiment of gamma photons production using Compton collisions between the DAΦNE electron beam and a high average power laser pulse, amplified in a Fabry-Pérot optical resonator. The calculations show that the resulting gamma beam source has extremely interesting properties in terms of spectral density, energy spread and gamma flux comparable (and even better) with the last generation gamma sources. The energy of the gamma beam depends on the adopted laser wavelength and can be tuned changing the energy of the electron ring. In particular we have analyzed the case of a gamma factory tunable in the 2-9 MeV range. The main parameters of this new facility are presented and the perturbation on the transverse and longitudinal electron beam dynamics is discussed. A preliminary accelerator layout to allow experiments with the gamma beam is presented with a first design of the accelerator optics.
The discovery by the ATLAS and CMS experiments of a new boson with mass around 125 GeV and with measured properties compatible with those of a Standard-Model Higgs boson, coupled with the absence of discoveries of phenomena beyond the Standard Model at the TeV scale, has triggered interest in ideas for future Higgs factories. A new circular e+e- collider hosted in a 80 to 100 km tunnel, TLEP, is among the most attractive solutions proposed so far. It has a clean experimental environment, produces high luminosity for top-quark, Higgs boson, W and Z studies, accommodates multiple detectors, and can reach energies up to the t-tbar threshold and beyond. It will enable measurements of the Higgs boson properties and of Electroweak Symmetry-Breaking (EWSB) parameters with unequalled precision, offering exploration of physics beyond the Standard Model in the multi-TeV range. Moreover, being the natural precursor of the VHE-LHC, a 100 TeV hadron machine in the same tunnel, it builds up a long-term vision for particle physics. Altogether, the combination of TLEP and the VHE-LHC offers, for a great cost effectiveness, the best precision and the best search reach of all options presently on the market. This paper presents a first appraisal of the salient features of the TLEP physics potential, to serve as a baseline for a more extensive design study.
During the current run of an electron-positron collider DAFNE special electrodes for electron cloud suppression have been inserted in all dipole and wiggler magnets of the positron ring. In this paper we discuss the impact of these electrodes on beam dynamics and overall collider performance. In particular we report results of measurements such as e-cloud instabilities growth rate, transverse beam size variation, tune shifts along the bunch train etc. with the electrodes switched on and off that clearly indicate the effectiveness of the electrodes for e-cloud suppression.
The SuperB international team continues to optimize the design of an electron-positron collider, which will allow the enhanced study of the origins of flavor physics. The project combines the best features of a linear collider (high single-collision luminosity) and a storage-ring collider (high repetition rate), bringing together all accelerator physics aspects to make a very high luminosity of 10$^{36}$ cm$^{-2}$ sec$^{-1}$. This asymmetric-energy collider with a polarized electron beam will produce hundreds of millions of B-mesons at the $Υ$(4S) resonance. The present design is based on extremely low emittance beams colliding at a large Piwinski angle to allow very low $β_y^\star$ without the need for ultra short bunches. Use of crab-waist sextupoles will enhance the luminosity, suppressing dangerous resonances and allowing for a higher beam-beam parameter. The project has flexible beam parameters, improved dynamic aperture, and spin-rotators in the Low Energy Ring for longitudinal polarization of the electron beam at the Interaction Point. Optimized for best colliding-beam performance, the facility may also provide high-brightness photon beams for synchrotron radiation applications.
In DAΦNE, the Frascati e+/e- collider, the crab waist collision scheme has been successfully implemented in 2008 and 2009. During the collision operations for Siddharta experiment, an unusual synchrotron damping effect has been observed. Indeed, with the longitudinal feedback switched off, the positron beam becomes unstable with beam currents in the order of 200-300 mA. The longitudinal instability is damped by bringing the positron beam in collision with a high current electron beam (~2A). Besides, we have observed a shift of \approx 600Hz in the residual synchrotron sidebands. Precise measurements have been performed by using both a commercial spectrum analyzer and the diagnostics capabilities of the DAΦNE longitudinal bunch-by-bunch feedback. This damping effect has been observed in DAΦNE for the first time during collisions with the crab waist scheme. Our explanation is that beam collisions with a large crossing angle produce a longitudinal tune shift and a longitudinal tune spread, providing Landau damping of synchrotron oscillations.
Recently the peak luminosity achieved on the DAΦNE collider has been improved by almost a factor three by implementing a novel collision scheme based on large Piwinski angle and Crab-Waist. This encouraging result opened new perspectives for physics research and a new run with the KLOE-2 detector has been scheduled to start by spring 2010. The KLOE-2 installation is a complex operation requiring a careful design effort and a several months long shutdown. The high luminosity interaction region has been deeply revised in order to take into account the effect on the beam caused by the solenoidal field of the experimental detector and to ensure background rejection. The shutdown has been also used to implement several other modifications aimed at improving beam dynamics: the wiggler poles have been displaced from the magnet axis in order to cancel high order terms in the field, the feedback systems have been equipped with stronger power supplies and more efficient kickers and electrodes have been inserted inside the wiggler and the dipole vacuum chambers, in the positron ring, to avoid the e-cloud formation. A low level RF feedback has been added to the cavity control in both rings.
The Phi-factory DAFNE was upgraded in the second half of 2007 in order to implement a recently proposed scheme of crab waist collisions aimed at substantial luminosity increase. Commissioning of the modified collider started in November 2007. In this paper we briefly describe the crab waist collision concept and discuss in detail the DAFNE hardware upgrade and obtained experimental results.
Since several years the DAFNE Team has been discussing ideas and performing experimental activities aimed at the collider luminosity increase. In this paper we briefly describe the proposed ideas and discuss results of the most relevant beam dynamics experimental studies that have been carried at DAFNE. We also introduce the concept of crab waist collisions that is the base of the undergoing DAFNE upgrade.
Long-range beam-beam interactions (parasitic crossings) were one of the main luminosity performance limitations for the lepton F-factory DAFNE in its original configuration. In particular, the parasitic crossings led to a substantial lifetime reduction of both beams in collision. This puts a limit on the maximum storable current and, as a consequence, on the achievable peak and integrated luminosity. In order to mitigate the problem, numerical and experimental studies of the parasitic crossings compensation by current-carrying wires have been done. During the operation for the KLOE experiment two such wires have been installed at both ends of the interaction region. They produced a relevant improvement in the lifetime of the weak beam (positrons) at the maximum current of the strong one (electrons) without luminosity loss, in agreement with the numerical predictions. The same compensating mechanism has been adopted during the run for the FINUDA experiment as well, with less evident benefits than in the previous case. The interplay between nonlinearities originating from the beam-beam interaction and the ring lattice has been studied by theoretical simulation and experimental measurements. Compensation procedures have been set up relying on the electromagnetic octupoles installed on both rings and used in addition to wire compensation. In this paper the parasitic crossings effects in the DAFNE interaction regions and their compensation by wires and octupoles are described. A detailed theoretical analysis of the interplay about different non-linearities is presented; eventually experimental measurements and observations are discussed.
Numerical simulations have shown that the recently proposed "crab waist" scheme of beam-beam collisions can substantially boost the luminosity of existing and future electron-positron colliders. In this paper we describe the crab waist concept and discuss potential advantages that such a scheme can provide. We also present the results of beam-beam simulations for the two currently proposed projects based on the crab waist scheme: the DAFNE upgrade and the Super B-factory project.
The Frascati Phi-factory DAFNE has successfully completed experimental runs for the three main detectors, KLOE, FINUDA and DEAR. The best peak luminosity achieved so far is 1.6x10^32 cm-2s-1, while the best daily integrated luminosity is 10 pb-1. At present the DAFNE team is preparing an upgrade of the collider based on the novel crab waist collision scheme. The upgrade is aimed at pushing the luminosity towards 10^33 cm-2s-1. In this paper we describe present collider performance and discuss ongoing preparatory work for the upgrade.