Optimisation of storage rings and RF accelerators via advanced fibre-based detectors

In particle accelerators, diverse causes may lead to the unwanted deviation of the beam particles from the nominal beam orbit and their loss in the machine. To protect from dangerous beam losses and provide valuable information on the accelerator operation, Beam Loss Monitors (BLMs) are being employed. Conventional BLMs are localised detectors, with a wide range of characteristics, depending on which the appropriate monitor for each application is selected. The optical fibre BLM is an alternative type of detector, used and examined in various facilities for its ability to cover and effectively protect long parts (of the order of 100m) of an accelerator. The Compact Linear Collider (CLIC) is a proposal for a future electron-positron collider, based on the simultaneous operation of two parallel beam lines, aiming to reach a 3 TeV center of mass energy at approximately 48km of machine length. In the present work an optical fibre based detector was developed, consisting of a quartz optical fibre coupled with a Silicon PhotonMultiplier (SiPM), to be studied as a beam loss monitor for RF accelerators, such as CLIC, and storage rings. A dedicated housing was fabricated for the photosensor and the related electronics, which optimised the system in terms of sensitivity, low noise and robustness. Instead of the most commonly used, for such detectors, Photo Multiplier Tubes (PMTs), this study made use of the SiPMs taking advantage of their insensitivity to magnetic fields and their efficiency in terms of cost and required power. The developed system was characterised for its capabilities as a BLM in the CLIC Test Facility 3 (CTF3) and in the Australian Synchrotron Light Source (ASLS). An intrinsic time resolution of 260 ps was measured, and a discrimination in beam losses with a 25cm spacing between them was demonstrated for single bunch beams. For 350 ns long electron beams, in order to distinguish simultaneous beam losses on different locations, a distance of 3m between them was required. The ability of the detector to monitor steady state losses was validated, and a method to assess all beam loss locations utilising only one initially identified, was demonstrated. The limitations introduced to BLMs from the beam loss crosstalk effect in parallel beam lines was investigated, while the sensitivity limitations induced by the RF cavity electron field emission background were estimated as not significant. The optical fibre based detector, combined with appropriate localised detectors at high risk locations, was proven a promising system for the monitoring of beam losses, for both linear accelerators and storage rings. Finally, a modified, highly sensitive version of the detector was introduced as an advanced RF cavity diagnostics tool. This was proven able of monitoring RF breakdowns and field emitted electrons along with estimating the Fowler-Nordheim field enhancement factor. Additionally, both measurements and simulations confirmed the presence of high energy electrons in the radiation environment of accelerating structures due to electron field emission

Measurement of beam losses at the australian synchrotron

The unprecedented requirements that new machines are setting on their diagnostic systems is leading to the development of new generation of devices with large dynamic range, sensitivity and time resolution. Beam loss detection is particularly challenging due to the large extension of new facilities that need to be covered with localized detector. Candidates to mitigate this problem consist of systems in which the sensitive part of the radiation detectors can be extended over long distance of beam lines. In this document we study the feasibility of a BLM system based on optical f ber as an active detector for an electron storage ring. The Australian Synchrotron (AS) comprises a 216 m ring that stores electrons up to 3 GeV. The Accelerator has recently claimed the world record ultra low transverse emittance (below pm rad) and its surroundings are rich in synchrotron radiation. Therefore, the AS provides beam conditions very similar to those expected in the CLIC/ILC damping rings. A qualitative benchmark of beam losses in a damping ring-like environment is presented here. A wide range of beam loss rates can be achieved by modifying three beam parameters strongly correlated to the beam lifetime: bunch charge (with a variation range between 1 uA and 10 mA), horizontal/vertical coupling and of dynamic aperture. The controlled beam losses are observed by means of the Cherenkov light produced in a 365 μ m core Silica f ber. The output light is coupled to different type of photo sensors namely: Metal Semiconductor Metal (MSM), Multi Pixel Photon Counters (MPPCs), standard PhotoMulTiplier (PMT) tubes, Avalanche Photo- Diodes (APD) and PIN diodes. A detailed comparison of the sensitivities and time resolution obtained with the different read-outs are discussed in this contribution

A distributed beam loss monitor for the Australian Synchrotron

© 2018 Elsevier B.V. A distributed beam loss monitoring system, named the optical fibre Beam Loss Monitor, has been installed at the Australian Synchrotron. Relativistic charged particles produced in beam loss events generate photons via the Cherenkov mechanism in four silica fibres that run parallel to the beam pipe and cover the majority of the accelerator's length. These photons are then guided by the fibres to detectors located outside of the accelerator tunnel. By measuring the time of flight of these photons, the locations of beam losses can be reconstructed. Based on this method a calibration was produced, mapping the time of flight to a position along the accelerator. This calibration was applied to loss signals collected on the first pass of the beam through the accelerator and the locations of prominent losses were determined. Using this system it was possible to investigate the effect, on the location and intensity of losses, in response to changes in the lattice parameters on a shot-by-shot basis. This system is now used in routine operations and has resulted in a 40 % increase in the capture efficiency of the booster ring

The Compact Linear Collider (CLIC) - 2018 Summary Report

The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^-$ collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively. CLIC uses a two-beam acceleration scheme, in which 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in an increased energy efficiency (power around 170 MW) for the 380 GeV stage, together with a reduced cost estimate at the level of 6 billion CHF. The detector concept has been refined using improved software tools. Significant progress has been made on detector technology developments for the tracking and calorimetry systems. A wide range of CLIC physics studies has been conducted, both through full detector simulations and parametric studies, together providing a broad overview of the CLIC physics potential. Each of the three energy stages adds cornerstones of the full CLIC physics programme, such as Higgs width and couplings, top-quark properties, Higgs self-coupling, direct searches, and many precision electroweak measurements. The interpretation of the combined results gives crucial and accurate insight into new physics, largely complementary to LHC and HL-LHC. The construction of the first CLIC energy stage could start by 2026. First beams would be available by 2035, marking the beginning of a broad CLIC physics programme spanning 25-30 years

Study of MicroMegas Detector in neutron and photon field with the simulation toolkit Geant4

119 σ.Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Φυσική και Τεχνολογικές Εφαρμογές”Οι ανιχνευτές αερίου, βασισμένοι στην τεχνολογία του MicroMegas, χρησιμοποιούνται ευρέως σε διάφορα πειράματα ατομικής, πυρηνικής και σωματιδιακής φυσικής. Επιπλέον έχουν ιδιαίτερα χαμηλό κόστος κατασκευής, παρουσιάζουν ανθεκτικότητα σε περιβάλλον υψηλής ακτινοβολίας, ενώ συνδυάζουν ικανότητες σκανδαλισμού και προσδιορισμού τροχιάς. Οι παραπάνω ιδιότητες τους καθιστούν ιδανικούς υπ[οψήφιους για την αναβάθμιση του συστήματος ανίχνευσης μιονίων, ως αντικαταστάτες των ανιχνευτών Cathode Strip Chabmers(CSC), του πειράματος ATLAS. Στο πείραμα αυτό συγκρούονται δέσμες πρωτονίων με αποτέλεσμα την παραγωγή καταιγισμό σωματιδίων, συμπεριλαμβανομένων νετρονίων. Για τον λόγο αυτό είναι απραίτητη η μελέτη της συμπεριφοράς του MicroMegas σε περιβάλλον νετρονίων έτσι ώστε να προβλεφθεί η απόκριση του ανιχνευτή στον σωματιδιακό θόρυβο, δεδομένου ότι το ενδιαφέρον εστιάζεται στην ανίχνευση μιονίων. Για τις ανάγκες της μελέτης χρησιμοποιήθηκε το πακέτο προσομοίωσης Monte Carlo, Geant4 με το οποίο μελετήθηκε η εναπόθεση ενέργειας νετρονίων 5.5MeV σε δύο διαφορετικούς τύπους ανιχνευτή microMegas, σε διαφορετικές αναλογίες αερίου και σε διαφορετικές κατευθύνσεις. Επίσης πραγματοποιήθηκε εικονικό πείραμα με φωτόνια χαμηλών ενεργειών, προκειμένου να μελετηθεί η λειτουργία του ανιχνευτή σε τέτοια πεδία καθώς και η σημαντική συμβολή των υλικών κατασκευής του.Gaseous detectors based on the Micromegas principle have already been used in several atomic, nuclear and particle physics experiments. Moreover, they have low construction cost and are resistant to high levels of radiation. They also succeed in combining triggering and tracking properties. Consequently, they provide an excellent candidate for replacing the Cathode Strip Chambers (CSC) of the ATLAS muon spectrometer in the very forward/backward region. In the ATLAS experiment, two proton beams collide, producing article showers, including neutrons. Therefore it is vital that the performance of the detectors in a neutron radiation field be studied, in order to redict the response of the detector to the particle "noise", taking into consideration the fact that the purpose of the detector is to detect muons. To meet this end, the MonteCarlo simulation toolkit Geant4 has been utilized in the present work, in order to study the energy eposition of 5.5 MeV neutrons on two different types of Micromegas detectors, with different proportion of gases and at different direction. n addition to that, a virtual experiment with low energy photons has been held, in order to study the function of the detector in such fields as well as the significant contribution of its construction materials.Μαρία Μ. Καστριώτο