The OLYMPUS Collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, R_{2γ}, a direct measure of the contribution of hard two-photon ...exchange to the elastic cross section. In the OLYMPUS measurement, 2.01 GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of ≈20° to 80°. The relative luminosity between the two beam species was monitored using tracking telescopes of interleaved gas electron multiplier and multiwire proportional chamber detectors at 12°, as well as symmetric Møller or Bhabha calorimeters at 1.29°. A total integrated luminosity of 4.5 fb^{-1} was collected. In the extraction of R_{2γ}, radiative effects were taken into account using a Monte Carlo generator to simulate the convolutions of internal bremsstrahlung with experiment-specific conditions such as detector acceptance and reconstruction efficiency. The resulting values of R_{2γ}, presented here for a wide range of virtual photon polarization 0.456<ε<0.978, are smaller than some hadronic two-photon exchange calculations predict, but are in reasonable agreement with a subtracted dispersion model and a phenomenological fit to the form factor data.
A
bstract
A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized ...protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining four single-spin and four double-spin asymmetries allowed in the one-photon-exchange approximation of the semi-inclusive deep-inelastic scattering process for target-polarization orientation perpendicular to the direction of the incoming lepton beam. Among those results, significant non-vanishing cos (
ϕ−ϕ
S
) modulations provide evidence for a sizable worm-gear (II) distribution,
g
1
T
q
x
p
T
2
. Most of the other modulations are found to be consistent with zero with the notable exception of large sin (
ϕ
S
) modulations for charged pions and
K
+
.
Abstract
The Italian Minister for University and Research has recently funded a large program for an Innovative Research Infrastructure on applied Superconductivity (IRIS) in Italy. Based on the LASA ...laboratory in Milan, it is a partnership, in the form of a strongly coordinated work, of existing laboratories of various institutes: INFN (leader, participating with 4 labs: Frascati, Genoa, Milan, Salerno); CNR (SPIN institute in Genoa, Naples and Salerno); five Universities: Genoa, Milan, Naples, Salento and Salerno. IRIS will be an upgrade of existing infrastructures, with new state-of-the-art instruments, reinforcing the capability of Italy in the domain of superconductivity aimed to accelerators. IRIS foresees a strong coordination of the activity of the participating laboratories until 2035, at least, thus enhancing the participation of Italian laboratories to future projects requiring advanced superconducting technology, like FCC or the Muon-Collider, and also for developing societal applications of technologies, pursued for high-energy accelerators, especially for the energy domain and the medical sector. In this paper, we present the two novel demonstrators, part of the initial IRIS program: 1) a green superconducting line, 130 m long and designed for 40 kA current capability at 25 kV; 2) a 1 m long HTS dipole magnet with some characteristics similar to LHC dipoles: 10 T, 50 mm × 80 mm bore, but operating at 20 K rather than 1.9 K.
The Superconducting Ion Gantry (SIG) project is the contribution from INFN (the Italian National Institute for Nuclear Physics) to the international SIGRUM project with the aim of exploring new ...technological solutions for the critical elements of a 430 MeV/u carbon ion gantry. The project includes the design and construction of a cos<inline-formula><tex-math notation="LaTeX">\theta</tex-math></inline-formula> 4 T superconducting dipole demonstrator magnet whose main scope is to prove the feasibility of winding and assembling an accelerator magnet type with a relatively small radius of curvature (1.65 m). In addition to the complexity due to the curvature, the target field ramp rate is 0.4 T/s and the cooling system must not adopt liquid helium. This paper discusses the design activities carried out in the last year on the electromagnetic and thermal domains and reports on the present concepts and infrastructure for the first winding trials.
To meet the milestones set by the High-Luminosity LHC (HL-LHC) project, the integration of new inner triplet magnet circuits is vital for enhancing the focusing of the particle beams at ATLAS and ...CMS. In addition to the Nb 3 Sn quadrupole magnets, high-order Nb-Ti magnets are required for field correction. This comprises self-protected magnets with six, eight, ten, and twelve poles, which also come in skewed variants. The simulation program LEDET was developed as part of the STEAM framework and is now applied to study quench transients in HL-LHC magnets. The electromagnetic and thermal transients occurring after a quench are simulated and validated with experiments at different current levels conducted by LASA (INFN). For the models, the three-dimensional geometry is accurately replicated and for each magnet the conductor parameters of each coil are set according to measurements. After discussing the various assumptions of the model, a simulation study is conducted to investigate the influence of the unknown quench location and inter-filament coupling losses. The developed models of each magnet show satisfactory accuracy and are predictive for different current levels. The models are then used to analyse the simulated hot-spot temperatures and peak voltages-to-ground, which cannot be easily measured. It is concluded that the protection strategy is effective.
Magnets for a Muon Collider Fabbri, S.; Bottura, L.; Quettier, L. ...
Journal of physics. Conference series,
01/2024, Letnik:
2687, Številka:
8
Journal Article
Recenzirano
Odprti dostop
Abstract
The renewed interest for a muon collider has motivated a thorough analysis of the accelerator technology required for this collider option at the energy frontier. Magnets, both normal and ...superconducting, are among the crucial technologies throughout the accelerator complex, from production, through acceleration and collision. In this paper we initiate a catalog of magnet specifications for a muon collider at 10TeV center-of-mass. We take the wealth of work performed within the scope of the US-DOE Muon Accelerator Program as a starting point, update it with present demands for the increased energy reach, and focus on the magnet types and variants with the most demanding performance. These represent well the envelope of issues and challenges to be addressed by future design and development. We finally give a first and indicative selection of suitable magnet technology, taking into account both established practices as well as the perspective evolution in the field of accelerator magnets.
We observe a deuteron beam polarization lifetime near 1000 s in the horizontal plane of a magnetic storage ring (COSY). This long spin coherence time is maintained through a combination of beam ...bunching, electron cooling, sextupole field corrections, and the suppression of collective effects through beam current limits. This record lifetime is required for a storage ring search for an intrinsic electric dipole moment on the deuteron at a statistical sensitivity level approaching 10^{-29} e cm.
Innovative Research Infrastructure on applied Superconductivity (IRIS) is a major project to build a research infrastructure in applied superconductivity, recently approved in Italy and led by INFN. ...As part of this programme, we are currently designing a Green Superconducting Line (GSL), 130 m long and designed to carry 40 kA of current at 25 kV, 1 GW of power, with almost zero dissipation. The article will present the up-to-date conceptual design status for the GSL. The line will eventually be tested in the new facility being prepared by INFN-Salerno and the University of Salerno (Italy).
Canted Cosine Theta layout for accelerator magnets is a very attractive since such magnets can be manufactured and assembled without big tooling, and with a relatively modest number of parts and ...tools. In the frame of European Horizon2020 funds, two collaborations, HITRI plus and I.FAST, are developing a CCT design, of 80 mm free bore, 4 T central dipole field, and 0.4 T/s ramp-rate. This magnet is expected to be the bending element of a gantry, to control the beam delivery in therapy with ions (hadrontherapy). The paper illustrates first a comparison between CCT and more classical cosine theta layout, followed by the comparison between Nb-Ti, Nb 3 Sn, MgB 2 , and HTS tapes coils. Relevant requirement for the magnets of this study is to be operated at low current, to limit the heat generation, in sight of a liquid-free cooling system. The results of the comparison is then applied to the design of two magnet demonstrators. Both adopt a low-losses Nb-Ti rope, consistently with the need for keeping the heat generation as low as possible. The first is a straight combined function dipole-quadrupole, while the second is a curved CCT dipole. The paper concludes with the first manufacturing tests for the CCT formers, for which aluminium -bronze, stainless steel and charged PEEK polymer are being explored as basic material.
A collaboration between CERN, CNAO, INFN, and MedAustron has been formed aiming at designing a light rotating gantry suitable for hadron therapy based on 430 MeV/n carbon ion beams. After a first ...design for a 3 T dipole field, as the backbone of the gantry magnetic system, now the collaboration is looking at an alternative design, for at least 4 T field with a faster ramp rate. The magnet is designed according to the cosθ layout to be wound with Nb-Ti superconducting Rutherford cable. One of the main challenges is the very small curvature radius of 1.65 m with a relatively large aperture, of 70-90 mm. Another challenge is the use of indirect cooling despite the cycling operation of 0.4 T/s. The paper reports the preliminary investigation for a 4.5 T dipole. The design will be followed by the construction of a 1 m long demonstrator to be manufactured and tested at INFN (LASA laboratory) in about three years. The conductor is a Rutherford cable of 2.6 µm Nb-Ti filament size, embedded in a Cu-Mn alloy matrix. The resulting gantry is very compact: the collaboration is working on integration between gantry structure and magnets to allow reducing the rotating weight in the range 50-80 tons, which is a factor 4 to 5 less than the present state-of-the-art.
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