Trapping of gold anions in a linear Paul trap

In order to demonstrate laser cooling on negatively charged ions, it is necessary to confine the ions in a region free of strong magnetic fields. In the course of this thesis, the pre-existing design of a linear Paul trap was modified and taken into operation. The new design possesses two additional end cap electrodes whose shape provides effective axial confinement without blocking optical access to the trapped particles. The influence of these end cap electrodes on the trapping potential was simulated and compared to experimental results. Measurements with AU- ions show that the trap allows storage of ions for multiple hours. Analysis ofthe storage time suggests that the loading process heats up the trapped ions. The lifetime τHot of the hot ions was determined to be 23(3) min. After thermalization, the lifetime increases to 75(2) min. Measurements of the ion cloud’s radius provide an estimation of the equilibrium temperature T∞ ≈5000 K. The experimentally determined time constant of the cooling process is τcool = 41:6(4) s

Win-win? CDM hydropower projects and their implications for climate justice

The current discussion about global warming and the possibility to reduce greenhouse gas emissions through hydropower has given a new turn to the debate about dams, resulting in the re-evaluation of this otherwise disputed technology. This trend materializes in the massive financial support that the United Nation’s carbon offsetting scheme Clean Development Mechanism (CDM) mobilizes for the construction of new hydropower plants in developing countries. As defined in the Kyoto Protocol, CDM projects are supposed to avoid greenhouse gas emissions while simultaneously contributing to sustainable development. The objective of this chapter is to analyze to what extent carbon-offsetting-dams are able to live up to this ‘win-win’ expectation. By identifying considerable challenges and constraints it is argued that the contribution of large hydropower projects to climate protection as well as their sustainability impact is in many cases highly doubtful. Given the controversial effects large dams may have on the local level it is discussed in which respect carbon-offsetting-dams constitute a form of ‘carbon colonialism’ that results in the exacerbation of one of the most problematic aspects of global warming: the asymmetries of problem causation and burdensharing

Strategies and policies to reach a land-degradation neutral world

Despite the difficulties in quantifying the extent and degree of land degradation or restoration, evidence shows that continued land degradation will be an impediment to meeting several SDGs. The United Nations states that it aims for land degradation neutrality (LDN) which in 2015 became firmly established as an agreed-upon objective in the realm of international environmental politics. First, as part of the SDGs whose Target 15.3 calls to “combat desertification, restore degraded land and soil, including land affected by desertification, drought and floods, and strive to achieve a land degradationneutral world” by 2030 (UNGA, 2015). The Conference of Parties (COP) of the United Nations Convention to Combat Desertification (UNCCD) took the decision to align the implementation of the Convention with SDG 15.3 and invited its Parties to set voluntary LDN targets (UNCCD, 2015). From that point onwards, the key question is how to implement these global aspirations at the national level and what is needed to operationalize the LDN concept and translate it into concrete strategies to meet LDN at scale..

Ultra-thin polymer foil cryogenic window for antiproton deceleration and storage

We present the design and characterization of a cryogenic window based on an ultra-thin aluminized biaxially oriented polyethylene terephthalate foil at T < 10 K, which can withstand a pressure difference larger than 1 bar at a leak rate < 1 × 1 0 − 9 mbar l/s. Its thickness of ∼1.7 μm makes it transparent to various types of particles over a broad energy range. To optimize the transfer of 100 keV antiprotons through the window, we tested the degrading properties of different aluminum coated polymer foils of thicknesses between 900 and 2160 nm, concluding that 1760 nm foil decelerates antiprotons to an average energy of 5 keV. We have also explicitly studied the permeation as a function of coating thickness and temperature and have performed extensive thermal and mechanical endurance and stress tests. Our final design integrated into the experiment has an effective open surface consisting of seven holes with a diameter of 1 mm and will transmit up to 2.5% of the injected 100 keV antiproton beam delivered by the Antiproton Decelerator and Extra Low ENergy Antiproton ring facility of CERN

Trap-integrated fluorescence detection based on silicon photomultipliers in a cryogenic Penning trap

We present a fluorescence-detection system for laser-cooled 9Be+ ions based on silicon photomultipliers (SiPM) operated at 4 K and integrated into our cryogenic 1.9 T multi-Penning-trap system. Our approach enables fluorescence detection in a hermetically-sealed cryogenic Penning-trap chamber with limited optical access, where state-of-the-art detection using a telescope and photomultipliers at room temperature would be extremely difficult. We characterize the properties of the SiPM in a cryocooler at 4 K, where we measure a dark count rate below 1/s and a detection efficiency of 2.5(3) %. We further discuss the design of our cryogenic fluorescence-detection trap, and analyze the performance of our detection system by fluorescence spectroscopy of 9Be+ ion clouds during several runs of our experiment.Comment: 12 pages, 11 figure

Testing CPT Invariance by High-Precision Comparisons of Fundamental Properties of Protons and Antiprotons at BASE

The BASE collaboration at the Antiproton Decelerator facility of CERN compares the fundamental properties of protons and antiprotons using advanced Penning-trap systems. In previous measurement campaigns, we measured the magnetic moments of the proton and the antiproton, reaching (sub-)parts-in-a-billion fractional uncertainty. In the latest campaign, we have compared the proton and antiproton charge-to-mass ratios with a fractional uncertainty of 16 parts in a trillion. In this contribution, we give an overview of the measurement campaign, and detail how its results are used to constrain nine spin-independent coefficients of the Standard-Model Extension in the proton and electron sector

A 16 Parts per Trillion Comparison of the Antiproton-to-Proton q/m Ratios

The Standard Model (SM) of particle physics is both incredibly successful and glaringly incomplete. Among the questions left open is the striking imbalance of matter and antimatter in the observable universe which inspires experiments to compare the fundamental properties of matter/antimatter conjugates with high precision. Our experiments deal with direct investigations of the fundamental properties of protons and antiprotons, performing spectroscopy in advanced cryogenic Penning-trap systems. For instance, we compared the proton/antiproton magnetic moments with 1.5 ppb fractional precision, which improved upon previous best measurements by a factor of >3000. Here we report on a new comparison of the proton/antiproton charge-to-mass ratios with a fractional uncertainty of 16ppt. Our result is based on the combination of four independent long term studies, recorded in a total time span of 1.5 years. We use different measurement methods and experimental setups incorporating different systematic effects. The final result, $-(q/m)_{\mathrm{p}}/(q/m)_{\bar{\mathrm{p}}}$ = $1.000\,000\,000\,003 (16)$, is consistent with the fundamental charge-parity-time (CPT) reversal invariance, and improves the precision of our previous best measurement by a factor of 4.3. The measurement tests the SM at an energy scale of $1.96\cdot10^{-27}\,$GeV (C$.$L$.$ 0.68), and improves 10 coefficients of the Standard Model Extension (SME). Our cyclotron-clock-study also constrains hypothetical interactions mediating violations of the clock weak equivalence principle (WEP$_\text{cc}$) for antimatter to a level of $|\alpha_{g}-1| < 1.8 \cdot 10^{-7}$, and enables the first differential test of the WEP$_\text{cc}$ using antiprotons \cite{hughes1991constraints}. From this interpretation we constrain the differential WEP$_\text{cc}$-violating coefficient to $|\alpha_{g,D}-1|<0.030$

Ultra thin polymer foil cryogenic window for antiproton deceleration and storage

We present the design and characterisation of a cryogenic window based on an ultra-thin aluminised PET foil at T < 10K, which can withstand a pressure difference larger than 1bar at a leak rate < $1\times 10^{-9}$ mbar$\cdot$ l/s. Its thickness of approximately 1.7 $\mu$m makes it transparent to various types of particles over a broad energy range. To optimise the transfer of 100keV antiprotons through the window, we tested the degrading properties of different aluminium coated PET foils of thicknesses between 900nm and 2160nm, concluding that 1760nm foil decelerates antiprotons to an average energy of 5 keV. We have also explicitly studied the permeation as a function of coating thickness and temperature, and have performed extensive thermal and mechanical endurance and stress tests. Our final design integrated into the experiment has an effective open surface consisting of 7 holes with 1 mm diameter and will transmit up to 2.5% of the injected 100keV antiproton beam delivered by the AD/ELENA-facility of CERN

BASE-STEP: A transportable antiproton reservoir for fundamental interaction studies

Currently, the only worldwide source of low-energy antiprotons is the AD/ELENA facility located at CERN. To date, all precision measurements on single antiprotons have been conducted at this facility and provide stringent tests of the fundamental interactions and their symmetries. However, the magnetic field fluctuations from the facility operation limit the precision of upcoming measurements. To overcome this limitation, we have designed the transportable antiproton trap system BASE-STEP to relocate antiprotons to laboratories with a calm magnetic environment. We anticipate that the transportable antiproton trap will facilitate enhanced tests of CPT invariance with antiprotons, and provide new experimental possibilities of using transported antiprotons and other accelerator-produced exotic ions. We present here the technical design of the transportable trap system. This includes the transportable superconducting magnet, the cryogenic inlay consisting of the trap stack and the detection systems, and the differential pumping section to suppress the residual gas flow into the cryogenic trap chamber.Comment: To be submitted to Rev. Sci. Instrument

Land in balance: the scientific conceptual framework for land degradation neutrality

The health and productivity of global land resources are declining, while demand for those resources is increasing. The aim of land degradation neutrality (LDN) is to maintain or enhance land-based natural capital and its associated ecosystem services. The Scientific Conceptual Framework for Land Degradation Neutrality has been developed to provide a scientific approach to planning, implementing and monitoring LDN. The Science-Policy Interface of the United Nations Convention to Combat Desertification (UNCCD) led the development of the conceptual framework, drawing in expertise from a diverse range of disciplines. The LDN conceptual framework focuses on the supporting processes required to deliver LDN, including biophysical and socio-economic aspects, and their interactions. Neutrality implies no net loss of the land-based natural capital relative to a reference state, or baseline. Planning for neutrality involves projecting the likely cumulative impacts of land use and land management decisions, then counterbalancing anticipated losses with measures to achieve equivalent gains. Counterbalancing should occur only within individual land types, distinguished by land potential, to ensure “like for like” exchanges. Actions to achieve LDN include sustainable land management (SLM) practices that avoid or reduce degradation, coupled with efforts to reverse degradation through restoration or rehabilitation of degraded land. The response hierarchy of Avoid > Reduce > Reverse land degradation articulates the priorities in planning LDN interventions. The implementation of LDN is managed at the landscape level through integrated land use planning, while achievement is assessed at national level. Monitoring LDN status involves quantifying the balance between the area of gains (significant positive changes in LDN indicators) and area of losses (significant negative changes in LDN indicators), within each land type across the landscape. The LDN indicators (and associated metrics) are land cover (physical land cover class), land productivity (net primary productivity, NPP) and carbon stocks (soil organic carbon (SOC) stocks). The LDN conceptual framework comprises five modules: A: Vision of LDN describes the intended outcome of LDN; B: Frame of Reference clarifies the LDN baseline; C: Mechanism for Neutrality explains the counterbalancing mechanism; D: Achieving Neutrality presents the theory of change (logic model) articulating the impact pathway; and E: Monitoring Neutrality presents the LDN indicators. Principles that govern application of the framework provide flexibility while reducing risk of unintended outcomes.Annette L. Cowie, Barron J. Orr, Victor M. Castillo Sanchez, Pamela Chasek, Neville D. Crossman, Alexander Erlewein, Geertrui Louwagie, Martine Maron, Graciela I. Metternicht, Sara Minelli, Anna E. Tengberg, Sven Walter, Shelley Welto