Focusing of high energy electron beam using crystal lenses for applications in radiotherapy

The two dominant radiotherapy methods are either simplified in terms of beam generation and handling, which compromises the energy deposition curve in tissues (photon therapy), or require extensive accelerator facilities and complex beam delivery systems to provide a favorable shape of the energy deposition curve (hadron therapy). The advantages of both of these methods, such as the low cost of the apparatus, ease of beam generation, and a suitable shape of the energy deposition curve in tissues, can potentially be achieved by using a very high-energy electron beam (beam energy in the order of a few hundreds of MeV) focused on the area of the tumor lesion. However, focusing of the beam is usually done with the use of quadrupole magnets which makes the beam delivery system complex and challenging from the engineering point of view. In this thesis, the feasibility of an alternative solution is explored, where focusing is performed by a bent silicon crystal with an appropriate shape of its exit face. Such a crystal lens can be a very light object (mass in the order of grams), allowing for much simpler beam delivery systems of radiotherapy facilities. As a result of this feasibility study, a simulation of a bent silicon crystal with profiled exit was prepared in Geant4. The outcome obtained from the simulation proved the focusing ability of such profiled crystal. However, the focusing strength of the crystal is not strong enough. Technical requirements needed to enable an improvement in focusing efficiency were identified and understood. Moreover, alternative solutions providing stronger focusing while using profiled crystals were proposed.Comment: Master's thesi

HL-LHC layout for fixed-target experiments in ALICE based on crystal-assisted beam halo splitting

The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) is the world's largest and most powerful particle accelerator colliding beams of protons and lead ions at energies up to 7 ZTeV, Z is the atomic number. ALICE is one of the detector experiments optimised for heavy-ion collisions. A fixed-target experiment in ALICE is being considered to collide a portion of the beam halo, split using a bent crystal inserted in the transverse hierarchy of the LHC collimation system, with an internal target placed a few meters upstream of the existing detector. This study is carried out as a part of the Physics Beyond Collider effort at CERN. Fixed-target collisions offer many physics opportunities related to hadronic matter and the quark-gluon plasma to extend the research potential of the CERN accelerator complex. Production of physics events depends on the particle flux on target. The machine layout for the fixed-target experiment is developed to provide a flux of particles on the target high enough to exploit the full capabilities of the ALICE detector acquisition system. This paper summarises the fixed-target layout consisting of the crystal assembly, the target and downstream absorbers. We discuss the conceptual integration of these elements within the LHC ring, the impact on ring losses, and expected performance in terms of particle flux on target

Experimental Verification Towards Feed-Forward Ground Motion Mitigation at ATF2

International audienceWithout counter measures, ground motion effects would deteriorate the performance of future linear colliders to an unacceptable level. An envisioned new ground motion mitigation method (based on feed-forward control) has the potential to improve the performance and to reduce the system cost compared to other proposed methods. For the experimental verification of this feed-forward scheme, a dedicated measurement setup has been installed at ATF2 at KEK. In this paper, the progress on this experimental verification is described. An important part of the feed-forward scheme could be already demonstrated, namely the prediction of the orbit jitter due to ground motion measurements

Beam losses, lifetime and collimator hierarchy

The aim of the LHC collimation system is to ensure a safe machine operation; it provides the LHC with passive protection and minimises the risk of magnet quenches induced by beam losses. In 2017, the LHC collimation system confirmed its excellent performance, with no magnet quenches due to losses from circulating beams while accommodating changes in machine configurations. The system availability in 2017 was also very good. The present work reviews key elements of the 2017 operation, from initial commissioning with beam to beam losses, lifetime and collimator hierarchypeer-reviewe

In situ measurements of atmospheric O2 and CO2 reveal an unexpected O2 signal over the tropical Atlantic Ocean

We present the first meridional transects of atmospheric O2 and CO2 over the Atlantic Ocean. We combine these measurements into the tracer atmospheric potential oxygen (APO), which is a measure of the oceanic contribution to atmospheric O2 variations. Our new in situ measurement system, deployed on board a commercial container ship during 2015, performs as well as or better than existing similar measurement systems. The data show small short-term variability (hours to days), a step-change corresponding to the position of the Intertropical Convergence Zone (ITCZ), and seasonal cycles that vary with latitude. In contrast to data from the Pacific Ocean and to previous modeling studies, our Atlantic Ocean APO data show no significant bulge in the tropics. This difference cannot be accounted for by interannual variability in the position of the ITCZ or the Atlantic Meridional Mode Index and appears to be a persistent feature of the Atlantic Ocean system. Modeled APO using the TM3 atmospheric transport model does exhibit a significant bulge over the Atlantic and overestimates the interhemispheric gradient in APO over the Atlantic Ocean. These results indicate that either there are inaccuracies in the oceanic flux data products in the equatorial Atlantic Ocean region, or that there are atmospheric transport inaccuracies in the model, or a combination of both. Our shipboard O2 and CO2 measurements are ongoing and will reveal the long-term nature of equatorial APO outgassing over the Atlantic as more data become available

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

Background: The EMPA KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population. Methods: EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110. Findings: Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5–2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62–0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16–1·59), representing a 50% (42–58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1). Interpretation: In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease. Funding: Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council

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

Analysis of LHC Beam Gas Ionization monitor data and simulation of the Electron transport in the detector

Since July 2012 I had an honor to work in the European Organization for Nuclear Researc\n(CERN) as a member of the Technical Student Programme. This thesis presents the research concerning the electron transport in the Beam Gas Ionization (BGI) monitor in order to study the effects of the electrons interaction with a high energy particle beam.\nIn the first chapter the Beam Gas Ionization monitor is described together with its operating \nprinciple to give an overview of the analyzed detector. Chapter 2 contains the introduction to the \ntransverse beam dynamics in the particle accelerator which is the theoretical background for the \nemittance measurements. The analyzed BGI data are presented in chapter 3. As the research was based on the computer simulations, its description together with the results are given in the chapter 4. \nFinally the chapter 5 contains the investigation of the magnetic field threshold in the BGI \nelectron dynamics. In very short words the Beam Gas Ionization monitors installed in the CERN LHC make use of the ionization of a small volume of the injected neon gas by the circulating beam. The electrons produced are guided towards the readout system using a combination of electric and magnetic fields. In the presence of the beam field their tracks are modified and the resulting profile is distorted. The Geant4 particle simulation package is used to simulate the ionization process, while the CERN developed PyECLOUD code is used for tracking of the resulting ionized particles.\nIt turned out that the space charge effects of the beam strongly affect the electron distribution \nof the liberated electrons. The profile broadening and distortion therefore occur which causes the \nwrong indications of the BGI monitors. Those effects strongly depend on the beam density which is defined by the bunch intensity and the beam size. It is important to mention that those phenomena occur only for proton beam which is more intense than the ion beam.\nBy running the simulations it was found that the stronger magnetic field dumps the space charge \neffects. The simulations have shown that a magnetic field of 1 T is enough to reproduce the beam \nprofile correctly and obtain right value of the beam emittance. The further investiga- tion of this \nissue resulted in obtaining the empirical formula for magnetic field threshold needed to keep the \nspace charge effects at the expected level.\nThe performed research is a justification for possible BGI magnet exchange in order to\nensure the correct operation also for a proton beam