Sviluppo di uno strumento ad alto livello per diagnostica, controllo e feedback di un acceleratore generico.

Viene descritto il funzionamento di un sistema innovativo di gestione del controllo ad alto livello di macchine acceleratrici, denominato Corolla, sviluppato dal candidato nel corso del lavoro di tesi. Nella tesi vengono esaminate le esigenze più comuni riscontrate nel corso dell'operazione dei moderni acceleratori di particelle e vengono illustrate le soluzioni proposte in Corolla alle problematiche da esse poste. Viene quindi illustrato lo sviluppo all'interno di questo framework di uno strumento di correzione dell'allineamento delle componenti magnetiche di un acceleratore; nel corso di tale trattazione verranno proposte innovazioni sia nella definizione del concetto di matrice di risposta sia nell'impiego della decomposizione SVD per eseguire generiche correzioni. L'insieme degli strumenti proposti viene infine testato su di una simulazione dell'acceleratore DAPHNE dei Laboratori Nazionali di Frascati dimostrando, a differenza degli algortmi più comunemente adoperati, la loro capacità di risalire al disallineamento degli elementi magnetici

Imaging low-energy positron beams in real-time with unprecedented resolution

Particle beams focused to micrometer-sized spots play a crucial role in forefront research using low-energy positrons. Their expedient and wide application, however, requires highly-resolved, fast beam diagnostics. We have developed two different methods to modify a commercial imaging sensor to make it sensitive to low-energy positrons. The first method consists in removing the micro-lens array and Bayer filter from the sensor surface and depositing a phosphor layer in their place. This procedure results in a detector capable of imaging positron beams with energies down to a few tens of eV, or an intensity as low as 35 particles/s/mm2 when the beam energy exceeds 10keV. The second approach omits the phosphor deposition; with the resulting device we succeeded in detecting single positrons with energies upwards of 6 keV and efficiency up to 93%. The achieved spatial resolution of 0.97 micrometers is unprecedented for real-time positron detectors.Comment: 18 pages, 6 figure

Production and excitation of cold Ps for anti-H formation by charge exchange: towards a gravitational measurement on antimatter

The AEgIS experiment pursues the ambitious goal of measuring for the first time the gravitational pull on neutral antimatter. The envisioned method consists in producing a beam of cold anti-hydrogen and measuring the deflection of its free fall by means of a Moiré deflectometer. To do so the pulsed production of abundant cold anti-hydrogen is paramount, therefore the charge exchange production mechanism has been elected as the most promising candidate production method. Performing the charge exchange anti-hydrogen production requires access to an abundant source of cold positronium which can be achieved by the employment of oxide-coated nanochanneled silica plates (NCPs). We spend chapter 1 formulating a classical model of positronium production and thermalisation in NCPs and validating it by testing it against the available experimental data. In chapter 2 we describe the measurement of the energy spectrum of positronium produced by nanochanneled plates using the beam produced by the SURF machine. We then compare the measured energy spectra with the model proposed in chapter 1 showing, in the comparison, the indication of a transition during thermalisation process to a regime where quantum phenomena become significant. We describe in detail in chapter 3 several positronium spectroscopy measurements that we performed during the course of the last three years by employing the positron beam line of the experiment AEgIS. We will the proceed to illustrate an improved version of the detrending technique commonly employed in signal analysis which, applied to the analysis of SSPALS spectra, improves the achievable precision on the experimental results. In chapter 4 we describe an innovative approach that we are currently pursuing to employ the detector FACT, part of the AEgIS apparatus, to confirm the successful production of anti-hydrogen

Monte Carlo simulation of the implantation profile of

The process of implantation and diffusion of positron in nanochanneled silicon crystals has been simulated in detail through the Monte Carlo technique. Our implantation simulations evidenced the fraction of empty volume inside the sample to be the decisive factor in the determination of the shape of the implantation profile, with the specific shape of the nanoscopic structure playing a marginal role for implantation processes with an energy above 3 keV. Moreover we observed that, due to the high density of surfaces inside of the silicon sample, the subsequent diffusion process is highly suppressed and that thermalized positrons reach the surface of a nanoscopic channel close to their implantation depth. Due to this suppression of the diffusion process, 60–80% of the positrons implanted at an energy comprised between 4 and 13 keV will reach, at thermal energy, the surface of a channel without escaping the sample or undergoing annihilation

Experiments with mid-heavy antiprotonic atoms in AEgIS

ments which provide the most precise data on the strong interaction between protons and antiprotons and of the neutron skin of many nuclei thanks to the clean annihilation signal. In most of these experiments, the capture process of low energy antiprotons was done in a dense target leading to a significant suppression of specific transitions between deeply bound levels that are of particular interest. In particular, precise measurements of specific transitions in antiprotonic atoms with Z>2 are sparse. We propose to use the pulsed production scheme developed for antihydrogen and protonium for the formation of cold antiprotonic atoms. This technique has been recently achieved experimentally for the production of antihydrogen at AE$\overline{\rm g}$IS. The proposed experiments will have sub-ns synchronization thanks to an improved control and acquisition system. The formation in vacuum guarantees the absence of Stark mixing or annihilation from high n states and together with the sub-ns synchronization would resolve the previous experimental limitations. It will be possible to access the whole chain of the evolution of the system from its formation until annihilation with significantly improved signal-to-background ratio

DAFNE Consolidation Program and Operation with the KLOE-2 Detector

After a long preparatory phase, including a wide hardware consolidation program, the Italian lepton collider DAFNE, is now systematically delivering data to the KLOE-2 experiment. In approximately 200 days of operation 1 fb-1 has been given to the detector limiting the background to a level compatible with an efficient data acquisition. Instantaneous and maximum daily integrated luminosity measured, so far, are considerably higher with respect to the previous KLOE runs, and are: L(inst) ~ 2.0 1032 cm-2s-1, and L(day) ~ 12.5 pb-1 respectively. A general review concerning refurbishing activities, machine optimization efforts and data taking performances is presented and discussed

Toward a pulsed antihydrogen beam for WEP tests in AEgIS

The AEg̅IS collaboration at CERN’s AD produces antihydrogen atoms in the form of a pulsed, isotropic source with a precisely defined formation time. AEg̅IS has recently undergone major upgrades to fully benefit from the increased number of colder antiprotons provided by the new ELENA decelerator and to move toward forming a horizontal beam to directly investigate the influence of gravity on the H̅ atoms, thereby probing the Weak Equivalence Principle for antimatter. This contribution gives an overview of these upgrades as well as subsequent results from the first beam times with ELENA

Pulsed production of antihydrogen

Antihydrogen atoms with K or sub-K temperature are a powerful tool to precisely probe the validity of fundamental physics laws and the design of highly sensitive experiments needs antihydrogen with controllable and well defined conditions. We present here experimental results on the production of antihydrogen in a pulsed mode in which the time when 90% of the atoms are produced is known with an uncertainty of ~250 ns. The pulsed source is generated by the charge-exchange reaction between Rydberg positronium atoms\u2014produced via the injection of a pulsed positron beam into a nanochanneled Si target, and excited by laser pulses\u2014and antiprotons, trapped, cooled and manipulated in electromagnetic traps. The pulsed production enables the control of the antihydrogen temperature, the tunability of the Rydberg states, their de-excitation by pulsed lasers and the manipulation through electric field gradients. The production of pulsed antihydrogen is a major landmark in the AEgIS experiment to perform direct measurements of the validity of the Weak Equivalence Principle for antimatter

Imaging a positronium cloud in a 1 Tesla

We report on recent developments in positronium work in the frame of antihydrogen production through charge exchange in the AEgIS collaboration [1]. In particular, we present a new technique based on spatially imaging a cloud of positronium by collecting the positrons emitted by photoionization. This background free diagnostic proves to be highly efficient and opens up new opportunities for spectroscopy on antimatter, control and laser manipulation of positronium clouds as well as Doppler velocimetry