Creation of NV centers in diamond under 155 MeV electron irradiation

Single-crystal diamond substrates presenting a high concentration of negatively charged nitrogen-vacancy centers (NV-) are on high demand for the development of optically pumped solid-state sensors such as magnetometers, thermometers or electrometers. While nitrogen impurities can be easily incorporated during crystal growth, the creation of vacancies requires further treatment. Electron irradiation and annealing is often chosen in this context, offering advantages with respect to irradiation by heavier particles that negatively affect the crystal lattice structure and consequently the NV- optical and spin properties. A thorough investigation of electron irradiation possibilities is needed to optimize the process and improve the sensitivity of NV-based sensors. In this work we examine the effect of electron irradiation in a previously unexplored regime: extremely high energy electrons, at 155 MeV. We develop a simulation model to estimate the concentration of created vacancies and experimentally demonstrate an increase of NV- concentration by more than 3 orders of magnitude following irradiation of a nitrogen-rich HPHT diamond over a very large sample volume, which translates into an important gain in sensitivity. Moreover, we discuss the impact of electron irradiation in this peculiar regime on other figures of merits relevant for NV sensing, i.e. charge state conversion efficiency and spin relaxation time. Finally, the effect of extremely high energy irradiation is compared with the more conventional low energy irradiation process, employing 200 keV electrons from a transmission electron microscope, for different substrates and irradiation fluences, evidencing sixty-fold higher yield of vacancy creation per electron at 155 MeV

First Steps Toward an Autonomous Accelerator, a Common Project Between DESY and KIT

Reinforcement Learning algorithms have risen in popularity in recent years in the accelerator physics community, showing potential in beam control and in the optimization and automation of tasks in accelerator operation. The Helmholtz AI project "Machine Learning toward Autonomous Accelerators" is a collaboration between DESY and KIT that works on investigating and developing RL applications for the automatic start-up of electron linear accelerators. The work is carried out in parallel at two similar research accelerators: ARES at DESY and FLUTE at KIT, giving the unique opportunity of transfer learning between facilities. One of the first steps of this project is the establishment of a common interface between the simulations and the machine, in order to test and apply various optimization approaches interchangeably between the two accelerators. In this paper we present the first results on the common interface and its application to beam focusing in ARES, and the idea of laser shaping with spatial light modulators at FLUTE

Review of \u3ci\u3eUrochloa\u3c/i\u3e Breeder’s Toolbox with the Theory of Change and Stage Gate System Approach

Livestock production in the global south is at crossroads as there is a demand to increase Animal Source Foods to address hunger and pressure to lighten the environmental footprint often associated with livestock production. To satisfy both needs, the use of technologies that improve animal performance, while reducing land use and net Greenhouse Gas emissions produced by animals is essential. One of such technologies are Urochloa forage grasses. Urochloa forage grasses are well known for their rusticity and their ability to grow in soils of low fertility and high aluminum content. These characteristics allow Urochloa to grow in areas temporally or spatially less suitable for crop production, but also have made ruminants production profitable in areas that would not be otherwise. However, productivity and sustainability of ruminant production in these areas is likely to fall within the next decade due to climate change unless action is taken. Despite these known benefits of Urochloa forage species, breeding programs have long delayed initiation due to apomixes and differences in ploidy. In the mid-1980s, the development of suitable sexual germplasm allowed crossings, and therefore favoured the emergence of breeding programs. In recent decades, several advances in biology, molecular biology, phenotyping, population genetics, genomics and transcriptomics have generated a plethora of information that ought to be integrated for its use in a single breeding toolbox. We use the Theory of Change and Stage-Gate systems approach to review these advances in research and the utility of the current and future available tools. Further, we address the remaining lack of information, thus bridging the knowledge gap and enabling us to maximize the genetic gain in the different Urochloa breeding programs. In this way, we identify breeding bottlenecks and help to pinpoint priorities for Urochloa research and development

End-of-fill study on collimator tight settings

In 2010 and 2011 the collimation system has been operated with relaxed settings, i.e. with retractions between different collimator families larger than the nominal settings that provide optimum cleaning. This configuration ensured a sufficient cleaning performance at 3.5 TeV while allowing larger tolerances on orbit control. Tighter collimator settings were proposed to push the cleaning performance and to allow larger orbit margins between TCDQ dump protection and tertiary collimators. With the same margins as with the relaxed settings, the β∗ could be reduced. After having verified with beam that the cleaning is improved as expected, the feasibility of tighter collimator settings must be addressed with high stored intensity. For this purpose, an end-of-fill study was proposed after a standard physics fill with 1380 bunches nominal bunches at 3.5 TeV, for a total stored energy of 95 MJ. During this test, primary and secondary collimators were moved to tight settings after about 8 hours of stable physics conditions in all experiments. This note summarises the operational procedure followed and the results of beam measurements during this study.peer-reviewe

Collimation dependent beam lifetime and loss rates in the LHC

The four primary collimators in each LHC beam define the smallest aperture. Particles with high betatron amplitudes or momentum offsets will therefore hit first a primary collimator. The instantaneous particle loss rate at primary collimators measured by precise beam loss monitors (BLM) is an important measure for the global lifetime of the beams and a major ingredient to identify collimation induced performance limitations in the LHC. These loss rates have been measured during a number of LHC fills, featuring both "good" fills with high luminosity and "bad" fills with beam instabilities. The beam lifetime at the collimators was then calculated from these data for different cases. The results are presented and interpreted within this paper.Ministerio de Ciencia e Innovacion - Gobierno de Espana,Ayuntamiento de San Sebastian,Gobierno Vasco,Diputacion Foral de Gipuzkoa,San Sebastian Turismo - Convention Bureau.peer-reviewe

Halo scrapings with collimators in the LHC

Understanding the population and the shape of the beam halo is important to predict possible intensity limitations due to collimation at 7 TeV. Therefore the population of the beam halo has been measured in horizontal, vertical and skew plane, using the primary collimators of the LHC collimation system. In addition these measurements were used to calibrate the beam loss monitor signals to a particle loss rate at the primary collimators. Within this paper the halo scraping method, the measured halo distribution and the calibration factors are presented and discussed.Ministerio de Ciencia e Innovacion - Gobierno de Espana,Ayuntamiento de San Sebastian,Gobierno Vasco,Diputacion Foral de Gipuzkoa,San Sebastian Turismo - Convention Bureau.peer-reviewe

Learning to Do or Learning While Doing: Reinforcement Learning and Bayesian Optimisation for Online Continuous Tuning

Online tuning of real-world plants is a complex optimisation problem that continues to require manual intervention by experienced human operators. Autonomous tuning is a rapidly expanding field of research, where learning-based methods, such as Reinforcement Learning-trained Optimisation (RLO) and Bayesian optimisation (BO), hold great promise for achieving outstanding plant performance and reducing tuning times. Which algorithm to choose in different scenarios, however, remains an open question. Here we present a comparative study using a routine task in a real particle accelerator as an example, showing that RLO generally outperforms BO, but is not always the best choice. Based on the study's results, we provide a clear set of criteria to guide the choice of algorithm for a given tuning task. These can ease the adoption of learning-based autonomous tuning solutions to the operation of complex real-world plants, ultimately improving the availability and pushing the limits of operability of these facilities, thereby enabling scientific and engineering advancements.Comment: 17 pages, 8 figures, 2 table

Comparison of LHC collimation setups with manual and semi-automatic collimator alignment

The LHC collimation system beam-based alignment procedure has recently been upgraded to a semi-automatic process in order to increase its efficiency. In this paper, we describe the parameters used to measure the accuracy, stability and performance of the beam-based alignment of the LHC collimation system. This is followed by a comparison of the results at 450 GeV and 3.5 TeV with (1) a manual alignment and (2) with the results for semi-automatic alignment.peer-reviewe

Electron beam test facilities for novel applications

Delivering and tailoring high brightness electron beams for a wide range of novel applications is a challenging task in single pass accelerator test facilities. This paper will review beam dynamics challenges at single pass accelerator test facilities in Europe to generate, transport and tailor low- to medium-energy high brightness electron beams for a range of novel applications