This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI proto-collaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial large-scale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more km-scale detectors, which will be operational in the mid-2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions.

We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies.

A new design for the use of photovoltaic and thermal (PV/T) technology with thermal storage is reported in this work. In the new design, a phase change material (PCM) tank is added to the backside of the photovoltaic panel. The advantages of this design are the storage of thermal energy and the efficiency improvement of the photovoltaic (PV) panel as a result of the temperature control of the PV cell during the phase change process. In addition, a perimeter with a black surface surrounds the PV panel to increase the absorption of thermal energy. The thermal energy is then transferred to the backside of the PCM tank by heat pipes. One prototype with lauric acid as PCM was tested under two different operating configurations and resulted in an overall daily efficiency of 50% coulding be improve by controlling the PCM temperature during the day.

Excess molar enthalpies, HmE, at 298.15K and atmospheric pressure, have been measured, over the entire mole fraction range, by means of a Tian–Calvet microcalorimeter, for the systems: dipropylamine (DPA), or dibutylamine (DBA)+2-propanone,+2-butanone,+2-pentanone, or+2-heptanone. These data, together with those available in the literature for aniline or N-methylaniline+2-alkanone systems, or for 2-alkanone, or amine+heptane mixtures have been used to determine ΔHNCO, the enthalpy of the amine–ketone interactions. For solutions with a given aromatic amine, ΔHNCO values are large and decrease with the increasing of the ketone size. The corresponding HmE values are large and negative. Mixtures with DPA or DBA are characterized by much weaker interactions between unlike molecules and ΔHNCO is nearly independent of the ketone. The HmE values are positive and decrease when the chain length of the 2-alkanone is increased, which has been ascribed to a decreasing positive contribution to HmE from the disruption of the ketone–ketone interactions upon mixing. Excess molar internal energies at constant volume, UVmE, have been obtained from HmE data using our previous volumetric measurements for the studied mixtures. Similar trends that for HmE are observed. Differences between UVmE and HmE are about 15% for DPA or DBA solutions and are ranged between 35% and 45% for mixtures with aromatic amines. The excess molar volume, VmE, changes in line with HmE and both magnitudes are usually of the same sign, which reveals that the main contribution to the former is the interactional one. In systems including linear secondary amines, structural effects increase with the chain length of the ketone. Amine+2-alkanone systems have been also investigated in terms of the DISQUAC, UNIFAC and ERAS models. DISQUAC and ERAS interaction parameters are reported. As in other many applications, the quasichemical interchange coefficients for l=1 (Gibbs energy), 3 (heat capacity) remain constant along each homologous series considered. DISQUAC improves meaningfully ERAS results on HmE, while UNIFAC results are slightly better. This suggests that physical interactions are more relevant than those related to association/solvation effects.

Liquid + liquid equilibrium (LLE) temperatures have been determined for the N-methylaniline + tetradecane, or + hexadecane systems by the method of the critical opalescence using a laser scattering technique. The coexistence curves have an upper critical solution temperature (UCST) and, due to size effects, are skewed towards high mole fractions of the amine. Excess molar enthalpies, H-m(E), at 298.15 K and atmospheric pressure, have been also measured over the entire mole fraction range, using a Tian-Calvet microcalorimeter, for the mixtures N-methylamine + heptane, + octane, + decane, + cyclohexane, or + toluene. The H-m(E) curves of alkane solutions are characterized by a large maximum and a rather flattened top, which are typical features of systems at temperature close to the UCST. N-methylamine + alkane, + benzene, + toluene or + 1-alkanol mixtures have been investigated in terms of the DISQUAC and ERAS models. The corresponding interaction parameters are reported. From the analysis of the experimental data and of the theoretical results, it is shown that: (i) H-m(E) of the studied N-methylamine solutions is mainly determined by the disruption, upon mixing, of the interactions between like molecules; (ii) interactions between isomeric aromatic amines become weaker in the sequence: primary > secondary > tertiary; (iii) for isomeric molecules, interactions between aromatic amines are stronger than between linear amines; (iv) in aromatic amine + aromatic hydrocarbon or + 1-alcohol systems, amine-solvent interactions are stronger in the order tertiary < secondary < primary; (v) physical interactions play a dominant role in the investigated mixtures; (vi) DISQUAC and ERAS models provide similar H-m(E) results for systems including alkanes. In the case of mixtures with aromatic hydrocarbons or 1-alkanols, where interactions between unlike molecules are relevant, H-m(E) is better described by DISQUAC; and (vii) the quasichemical interchange coefficients (l = 1,3) for the contacts amine/aliphatic; amine/aromatic; amine/cyclic and amine/hydroxyl are the same for systems with aniline, 2-methylaniline, N-methylaniline, or N,N-dimethylaniline. (C) 2012 Elsevier Ltd. All rights reserved.

Molar excess enthalpies, H-m(E), measured by means of a Tian-Calvet microcalorimeter, for the ternary system {1-propanol + N,N,N-triethylamine (TEA) + 2-butanone} at T = 298.15 K are reported. Values of H-m(E) for the constituent binaries are available in the literature. The data are interpreted in terms of different interactional contributions to H-m(E). The coefficients of the corresponding fittings of binary and ternary H-m(E) values have been used to determine the partial molar excess enthalpies of each component. It is concluded that 1-propanol and TEA molecules can participate in interactions between unlike molecules, and that 2-butanone is mainly a breaker of interactions between like molecules. The DISQUAC model is applied, using binary parameters only, for the H-m(E) prediction of the ternary mixture investigated. Large differences between experimental values and theoretical results show the existence of ternary interactions. (C) 2013 Elsevier Ltd. All rights reserved.

Molar excess enthalpies, H-m(E), at 298.15 K and 0.1 MPa have been measured using a Tian-Calvet microcalorimeter for N,N,N-triethylamine (TEA) + 2-alkanone mixtures. These data have been used to determine Delta HN-CO, the enthalpy of the amine-ketone interaction, which is practically independent of the ketone size. This allows explain the observed H-m(E) decrease when the ketone size is increased in terms of a lower positive contribution to H-m(E) from the breaking of the alkanone-alkanone interactions. Inspection of molar excess volumes and of molar excess internal energies at constant volume (determined in this work) reveals the existence of structural effects, which are more important for mixtures with 2-heptanone. Tertiary alkyl amine + 2-alkanone, and amino-ketone + n-alkane mixtures have been treated in terms of DISQUAC. The interaction parameters for the carbonyl/amine contacts are reported. It is shown that such contacts are essentially dispersive. Proximity effects in amino-ketone mixtures lead to increased dispersive parameters in comparison to those of amine + ketone solutions. Steric effects related to the length of the alkyl chains attached to the N atom lead to decreased dispersive parameters. DISQUAC describes accurately vapour-liquid equilibria (VLE) and H-m(E) of the investigated mixtures, which have been also treated using UNIFAC (Dortmund version). UNIFAC predictions compare well with DISQUAC results for TEA mixtures. For amino-ketone systems, UNIFAC calculations largely differ from the experimental results. This reveals that interactions parameters must be modified to take into account proximity effects. (C) 2013 Elsevier B.V. All rights reserved.

A vibrating tube densimeter and sound analyzer Anton Paar model DSA-5000 has been used for the measurement of densities, rho, and speeds of sound, c, of N-methyl-phenylamine (N-methylaniline) + heptane, or + cyclohexane, or + toluene mixtures at (293.15 to 303.15) K and atmospheric pressure. From these data, we have obtained excess molar volumes, V-m(E), at the three temperatures and excess functions for c and the isentropic compressibility, K-s at 298.15 K. V-m(E) results reveal the existence of structural effects in alkane solutions and of interactions between unlike molecules in systems with toluene. N-Methylaniline + hydrocarbon mixtures have been characterized in terms of the ERAS model. The theory provides a good representation of excess molar enthalpies, H-m(E), and describes correctly the relative variation of V-m(E). ERAS calculations show the importance of the physical interactions in the studied systems, which is consistent with the experimental H-m(E), and V-m(E) data.

Linear alkanone or cyclohexanone + aromatic hydrocarbon mixtures have been studied using DISQUAC and the Kirkwood-Buff formalism. The aromatic compounds considered are: benzene, toluene, 1,4-dimethylbenzene, 1,2,4-trimethylbenzene and ethylbenzene. Vapour-liquid equilibria (VLE), molar excess Gibbs energies, G(m)(E), molar excess enthalpies, H-m(E), and isobaric molar excess heat capacities, C-pm(E), of the binary systems studied are well represented by DISQUAC. There is a good agreement between experimental H-m(E) of related ternary mixtures, and DISQUAC predictions obtained by means of binary interaction parameters only DISQUAC improves very meaningfully UNIFAC results on H-m(E), C-pm(E), properties which are closely related to the molecular structure of the mixture components. The enthalpy (H-int(CO-S)) of the ketone-aromatic hydrocarbon interactions has been evaluated. These interactions become weaker when the alkanone size increases in mixtures with a given aromatic hydrocarbon, or when the aliphatic surface of the alkylbenzene is increased in systems with a given ketone. Steric effects are more relevant in 1,4-dimethylbenzene mixtures than in those with ethylbenzene. The application of the Kirkwood-Buff formalism to mixtures including toluene or ethylbenzene shows that orientational effects, related to ketone-ketone interactions, exist in solutions with the shorter 2-alkanones. Such effects are weakened when the chain length of the 2-alkanone increases. The opposite behaviour is observed when increasing the aliphatic surface of the alkylbenzene in systems with a given 2-alkanone. The cyclohexanone + benzene mixture shows a structure close to random mixing. (C) 2012 Elsevier B.V. All rights reserved.

Densities, ρ, and speeds of sound, u, of 2-pentanone+aniline, +N-methylaniline, or +pyridine systems have been measured at (293.15, 298.15 and 303.15) K and atmospheric pressure using a vibrating tube densimeter and sound analyzer Anton Paar model DSA-5000. The ρ and u values were used to calculate excess molar volumes, VmE, and the excess functions at 298.15K for the speed of sound, uE, the thermal expansion coefficient, αPE, and for the isentropic compressibility, κSE at 298.15K. VmE and κSEare both negative magnitudes and increase in the same sequence: aniline<N-methylaniline<pyridine, while uE is positive and increases in the opposite way. The similar trends are observed for mixtures including the same aromatic amines and propanone, 2-butanone or 2-heptanone. The data have been interpreted assuming strong ketone–amine interactions, which become weaker when the chain length of the 2-alkanone is increased in solutions with a given aromatic amine. Ketone–amine interactions are more easily created in mixtures with aniline. Interactions between unlike molecules are stronger than in 2-alkanone+dipropylamine, or +dibutylamine, or +triethylamine systems. These findings are confirmed by the results obtained from internal pressures and molecular interaction parameters for the investigated mixtures.

The Flory model has been applied to linear or cyclic ether+benzene, or +toluene mixtures. In addition, the relative variation of the molar excess enthalpy, HmE, along homologous series of the considered systems, has been discussed taking into account the contributions to HmE from the ether–ether, aromatic–aromatic and ether–aromatic interactions. It has been shown that in CH3(CH2)u−1O(CH2CH2O)v(CH2)u−1CH3+benzene mixtures, the u increase (v fixed) leads to a weakening of interactions between unlike molecules, and that proximity effects also weaken this type of interactions. In contrast, the v increase (u fixed) or cyclization lead to stronger interactions between unlike molecules. From the application of the model, it is concluded that the random mixing hypothesis may be considered to be valid to a large extent for many of the investigated solutions. Erroneously, strong orientational effects are predicted for 1,3-dioxolane, or 1,4-dioxane+benzene systems, but this has been attributed to the model can not describe asymmetric HmE curves when the mixture compounds show close values for Vi (molar volume) and for Vi* (reduction parameter for volume). Previous calculations on the basis of the Kirkwood–Buff integrals formalism confirm that the mixture structure is close to random mixing. Flory results on the excess molar volumes have been discussed taking into account the so-called curvature and P* contributions to this excess function.

Densities, ρ, and speeds of sound, u, of {2-heptanone+dipropylamine (DPA), +dibutylamine (DBA), or +triethylamine (TEA)} systems have been measured at (293.15, 298.15, and 303.15)K and atmospheric pressure using a vibrating tube densimeter and sound analyzer Anton Paar model DSA-5000. The ρ and u values were used to calculate excess molar volumes, VmE, and the excess functions at 298.15K for the speed of sound, uE, the thermal expansion coefficient, αPE, and for the isentropic compressibility, κSE. Structural effects increase with the ketone size in mixtures with a fixed amine. VmE, κSE, and αPE increase when DPA is replaced by DBA in systems with a given ketone as: (i) interactions between unlike molecules are more easily created in solutions containing the shorter amines; (ii) this effect predominates over that related to the disruption of the amine–amine interactions. Contributions to VmE from the creation of interactions between unlike molecules and from the breaking of the amine–amine interactions are both lower in absolute value for TEA systems when are compared to those of DPA solutions. The increasing positive VmE values observed when DPA is replaced by TEA in solutions with propanone or 2-butanone reveal that the former contribution is less relevant, and more important for the DPA mixtures. The opposite behavior for 2-heptanone systems is attributed to the existence of structural effects when this ketone is mixed with TEA. These general trends are confirmed by the treatment of the mixtures using the PFP theory, and the internal pressure concept.

Molar excess enthalpies, H-m(E), at 298.15 K and atmospheric pressure have been determined over the entire mole fraction range, using a Tian-Calvet microcalorimeter, for the systems: propanone, 2-butanone, 2-pentanone, or 2-heptanone + aniline or + N-methylaniline. The negative H-m(E), values obtained for all of the mixtures reveal that interactions between unlike molecules are prevalent. Aniline solutions show more negative H-m(E) due to stronger amine-ketone interactions compared to those in N-methylaniline solutions. In addition, H-m(E), increases with the size of the alkanone, which may be interpreted in terms of a weakening of interactions between unlike molecules. H-m(E) somewhat differently in N-methylaniline solutions, probably due to the positive contribution to H-m(E), is here more important. Molar excess internal energies at constant volume, U-Vm(E), have been determined from the present H-m(E) using our previous measurements on molar excess volumes, compressibilities, and isothermal expansion coefficients. U-Vm(E) behaves similarly to H-m(E). U-Vm(E) values are much higher than those of HEmE, which remarks the importance of the contribution of the equation of state term to H-m(E).

Densities, ρ, and speeds of sound, u, of 2-heptanone + aniline + N-methylaniline or + pyridine systems have been measured at (293.15, 298.15 and 303.15) K and atmospheric pressure using a vibrating tube densimeter and sound analyzer. The ρ and u values were used to calculate excess molar volumes, V E, and the excess functions at 298.15 K for the speed of sound, u E, the thermal expansion coefficient, \(\alpha_{p}^{\mathrm{E}}\), and for the isentropic compressibility, \(\kappa_{\mathrm{S}}^{\mathrm{E}}\). V E and \(\kappa_{\mathrm{S}}^{\mathrm{E}}\) are both negative and increase in the sequence: aniline <N-methylaniline < pyridine. In contrast, u E is positive and changes in the opposite way. The data suggest the existence of interactions between unlike molecules, which are much weaker in the pyridine solution. Aromatic amine–alkanone interactions are stronger in mixtures with acetone. The linear dependence of Rao’s constant with concentration reveals that there is no complex formation in the investigated systems.

The coexistence curves of the liquid-liquid equilibria (LLE) for (epsilon-caprolactam + heptane), (epsilon-caprolactam + octane), (epsilon-caprolactam + nonane), (epsilon-caprolactam + decane), and (epsilon-caprolactam + 2,2,4-trimethylpentane) have been determined by critical opalescence with a laser scattering technique. All the curves show an upper critical solution temperature (UCST) and have a rather horizontal top, and their symmetry depends on the size of the alkane. The UCST increases almost linearly with the chain length of the alkane. For the octane mixture, the UCST is lower than for the solution including 2,2,4-trimethylpentane.

Densities, ρ, and speeds of sound, u, of 2-propanone+dipropylamine, + dibutylamine or + triethylamine systems have been measured at (293.15, 298.15 and 303.15) K and atmospheric pressure using a vibrating tube densimeter and sound analyser Anton Paar model DSA-5000. The ρ and u values were used to calculate excess molar volumes, VE, and the excess functions at 298.15K for the thermal expansion coefficient, αPE, and for the isentropic compressibility, KSE at 298.15K. VE, KSE and αPE are positive magnitudes. When replacing dipropylamine by dibutylamine or triethylamine in the studied mixtures, the excess functions increase. This may be ascribed to the interactions between unlike molecules which are more important in the former solutions. From the comparison with similar data obtained for 2-propanone+aniline, + N-methylaniline, or + pyridine systems, it is concluded that interactions between unlike molecules are stronger in mixtures containing aromatic amines. Free volume effects are present in solutions with dipropyl or dibutylamine as the VE curves are shifted towards higher mole fractions of 2-propanone.