Comportamento di gallerie in versanti in frana

Il lavoro esamina i fattori geometrici e meccanici che influenzano i meccanismi di interazione frana-galleria, in cui si presuppone un meccanismo plastico con mobilizzazione delle resistenze nel terreno. Definite le grandezze adimensionali che governano il fenomeno utilizzando i principi dell’analisi dimensionale e del teorema di Buckingham, si è avviato uno studio parametrico di cui sono presentati alcuni risultati

Effetti dei movimenti di versante sui rivestimenti di una galleria

The research concerns the effects of landslides on linings tunnel. The monitoring data elaboration of a real case defined the distinctive elements that characterize the behavior of the tunnel linings, highlighting differences with those not involved in landslides. The problem of interaction has been generalized and numerical studies provided correlation between the landslide movements and mechanical response of the tunnel lining

Misure di convergenza di una galleria realizzata in un versante in frana

In questa nota sono illustrati i dati di monitoraggio di una galleria che attraversa un versante in frana, al fine di stimare gli effetti del movimento gravitativo sull’opera. I dati si riferiscono all’imbocco sud della galleria Val di Sambro, opera della nuova autostrada A1 (MI-NA) nel tratto di attraversamento dell’appennino Tosco Emiliano. L’elaborazione e la rappresentazione delle misure di convergenza della galleria, unite alle misure inclinometriche realizzate sul versante in frana, permettono di formulare alcune ipotesi sull’interazione frana-galleria

Septum shadowing by means of a bent crystal to reduce slow extraction beam loss

The flux of high-energy protons slow-extracted from the CERN Super Proton Synchrotron (SPS) is limited by the induced radioactivity caused by the beam loss intrinsic to the extraction process. Methods to substantially increase the efficiency of the extraction process are of great interest to fulfill requests for an increasing flux of 400 GeV protons to the present experiments, located in the North Area of the SPS, and also for potential future experiments with very high demanded protons on target. A crystal shadowing technique to significantly reduce the beam scattered and lost on the electrostatic extraction septum during the third-integer resonant slow extraction process has been developed and a prototype system tested with beam. The technique is based on the use of a thin, bent silicon crystal to coherently channel or volume reflect the portion of beam that would otherwise impinge the wire array of the electrostatic septum and instead eject it into the transfer line toward the production targets of the experiments. In this paper, the concept is described and applied to the SPS machine in order to specify the requirements of the prototype crystal shadowing system. Beam dynamics simulations of the prototype system are compared and benchmarked to the results obtained through beam tests, before being exploited to understand the characteristics of the present system and the potential performance reach of an optimized, future operational configuration. The remaining challenges faced to bring the system into operation, the optimization possibilities and other potential applications are discussed

Angular asymmetry of the nuclear interaction probability of high energy particles in short bent crystals

The rate of inelastic nuclear interactions in a short bent silicon crystal was precisely measured for the first time using a 180 GeV/c positive hadron beam produced in the North Experimental Area of the CERN SPS. An angular asymmetry dependence on the crystal orientation in the vicinity of the planar channeling minimum has been observed. For the inspected crystal, this probability is about $$\sim 20\%$$ larger than in the amorphous case because of the atomic density increase along the particle trajectories in the angular range of volume reflection, whose dimension is determined by the crystal bending angle. Instead, for the opposite angular orientation with respect to the planar channeling, there is a smaller probability excess of $$\sim 4\%$$

SPS slow extraction losses and activation: update on recent improvements

Annual high intensity requests of over $1 \times 10^{19}$ protons on target (POT) from the CERN Super Proton Synchrotron (SPS) Fixed Target (FT) physics program continue, with the prospect of requests for even higher, unprecedented levels in the coming decade. A concerted and multifaceted R&D; effort has been launched to understand and reduce the slow extraction induced radioactivation of the SPS and to anticipate future experimental proposals, such as SHiP [1] at the SPS Beam Dump Facility (BDF) [2], which will request an additional $4 \times 10^{19}$ POT per year. In this contribution, we report on operational improvements and recent advances that have been made to significantly reduce the slow extraction losses, by up to a factor of 3, with the deployment of new extraction concepts, including passive and active (thin, bent crystal) diffusers and extraction on the third-integer resonance with octupoles. In light of the successful tests of the prototype extraction loss reduction schemes, an outlook and implications for future SPS FT operation will be presented

Improvements to the SPS Slow Extraction for High Intensity Operation

Slow extraction using the third-integer resonance and thin electrostatic septa as used in the SPS to serve the North Area is a process with inherent beam loss. For high-flux 400 GeV protons, the beam losses result in high machine activation, reduced component lifetime and severe limitations on personnel access and maintenance. The instantaneous and integrated loss levels are strong limitations on the annual attainable POT for present operation and for the much higher fluxes requested by SHiP at the proposed BDF facility. In this report the present constraints and potential improvements to the slow extraction system in the SPS are described along with the recent theoretical studies and practical implementation of prospective operational improvements. Machine results of testing of new extraction loss reduction techniques and hardware are presented in the context of SHiP POT requests, SPS BDF and the PBC project and the potential extraction loss reduction factor is evaluated with an outlook to future high intensity operation. The prospects of deployment on the present operational beams and the resulting improvement factors are discussed

Demonstration of loss reduction using a thin bent crystal to shadow an electrostatic septum during resonant slow extraction

A proof-of-principle experiment demonstrating the feasibility of using a thin, bent crystal aligned upstream of an extraction septum (ES) to increase the efficiency of the third-integer resonant slow extraction process has been carried out at the CERN Super Proton Synchrotron (SPS). With the primary aim of reducing the beam loss and induced radio-activation of the SPS, the crystal was aligned to both the beam and the septum to reduce by up to 40% the beam intensity impinging the ES and increase the intensity entering the external transfer line. In this contribution, we introduce the concept and the prototype system that was installed in 2018 before reporting in detail on the dedicated program of machine development studies carried out to characterise its performance and demonstrate operational feasibility. The performance reach and compatibility with other loss reduction techniques proposed to further increase the extraction efficiency, such as phase space folding with octupoles, is discussed in view of future high intensity operation

Crystal for slow extraction loss-reduction of the SPS electrostatic septum

International audienceThe use of a bent crystal was investigated in order to reduce the losses at the CERN Super Proton Synchrotron (SPS) electrostatic septum (ZS) during the slow extraction of 400 GeV/c protons toward the North Area. The crystal, installed a few meters upstream of the ZS, bends protons that would otherwise impinge on the ZS wires. Since particle deflection with good efficiency is achieved only when the crystal lattice is aligned within 10 μrad to the trajectory of the incoming particles (at p = 400 GeV/c), a compact goniometer was built to allow the correct angular alignment of the crystal with a precision of a few μrad. In this paper, we report on the crystal features measured during a dedicated beam test by the UA9 experimental installation in the CERN H8 beam line. Details of the goniometer and its installation are also reported. The first results achieved during dedicated Machine Development (MD) sessions are finally presented