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Aria is a plant hosting a$${350}\,\hbox {m}$$350mcryogenic isotopic distillation column, the tallest ever built, which is being installed in a mine shaft at Carbosulcis S.p.A., Nuraxi-Figus (SU), Italy. Aria is one of the pillars of the argon dark-matter search experimental program, lead by the Global Argon Dark Matter Collaboration. It was designed to reduce the isotopic abundance of$${^{39}\hbox {Ar}}$$39Arin argon extracted from underground sources, called Underground Argon (UAr), which is used for dark-matter searches. Indeed,$${^{39}\hbox {Ar}}$$39Aris a$$\beta $$β-emitter of cosmogenic origin, whose activity poses background and pile-up concerns in the detectors. In this paper, we discuss the requirements, design, construction, tests, and projected performance of the plant for the isotopic cryogenic distillation of argon. We also present the successful results of the isotopic cryogenic distillation of nitrogen with a prototype plant.

Electronic sputtering of organic species being mixed to water ice by residual-gas condensation is analyzed by secondary ion time-of-flight mass spectrometry. The ice samples were prepared at 15 K by deposition from a H2O gas-flow and irradiated by 1.5 MeV N2+ ions while the temperature was raised up to 216 K. Desorption ion yields of positive H2O specific ions as of some organic ion species are measured as a function of temperature. Remarkably high desorption yield variations, mainly of the CnHm ions, were observed during the enrichment of organics hiding the emission of (H2O)nH3O+ cluster ions.

Ion cluster desorption yields from LiF were measured at PUC-Rio with ≈0.1 MeV/u N q+ (q = 2,4,5,6) ion beams by means of a time-of-fight (TOF) mass spectrometer. A 252Cf source mounted in the irradiation chamber allows immediate comparison of cluster emissions induced by ≈65 MeV fission fragments (FF). Emission of (LiF) n Li+ clusters are observed for both the N beams and the 252Cf fission fragments. The observed cluster size n varies from 1 to 6 for N q+ projectiles and from 1 to ≈40 for the 252Cf-FF. The size dependence of the Y(n) distributions suggests two cluster formation regimes: (i) recombination process in the outgoing gas phase after impact and (ii) emission of pre-formed clusters from the periphery of the impact site. The corresponding distribution of ejected negative cluster ions (LiF) n F− closely resembles that of the positive secondary (LiF) n Li+ ions. The desorption yields of positive ions scale as Y(n) ∼ q 5. A calculation with the CASP code shows that this corresponds to a cubic scaling ∼S 3 with the electronic stopping power S e , as predicted by collective shock wave models for sputtering and models involving multiple excitons (Frenkel pair sputtering). We discuss possible interpretations of the functional dependence of the evolution of the cluster emission yield Y(n) with cluster size n, fitted by a number of statistical distributions.

Secondary ion emission from vapor-deposited water ice has been investigated in exploring the influence of phase transitions on the desorption yield of H2O ions, particularly, the hydronium H3O+ and the cluster ions (H2O)nH3O+. For 1.5 MeV N2+ ion bombardment on water ice at a temperature of ∼80 K, the sum of the yields of H3O+ and of the cluster ions represents 80% of the positive ion yield (i.e., 0.23 ions/impact) and 0.33% of the total H2O molecular sputtering yield. When the beam energy of N2+ is varied between 0.5 and 1.7 MeV, the shape of the cluster mass distributions does not change and the total cluster ion yield scales with the third power of the electronic energy loss. Time-of-flight mass spectra were taken during the warming up of the ice from 10 to 216 K. Up to 30 K, the cluster ion yields are approximately constant, whereas between 30 and 75 K, they decrease gradually by a factor 6.5 and remain constant until 130 K. This is in analogy with modifications in the ice structure: in the 38–78 K re...

The effect of solar wind on cometary ice was studied by using oxygen ions with energy near to that corresponding to their maximum abundance in space for bombarding CO ice. This gas was condensed on a CsI substrate at 14 K and irradiated by 28 keV 18O6+ ions up to a final fluence of 1.3 × 1016 cm−2. We have used a methodology in which the sputtering yields, the destruction rate of CO, and the rate of formation of new molecular species are determined by Fourier transform infrared spectroscopy (FTIR). In the current experiment, the condensation of a thin water ice film has prevented the CO sputtering. Quantities such as the dissociation yield, Yd (the number of ice molecules destroyed or dissociated per projectile impact), and the formation yield, Yf (the number of daughter molecules of a given species formed per projectile) are found to be more appropriate and useful than using an integrated or average cross section, since the projectiles are slowing down in the ice from their initial energy until zero velocity (implantation).

Water, carbon oxide, carbon dioxide, and ammonia ices are known to be pervasive constituents of the solar system and the interstellar medium. These ices and ice-covered surfaces are exposed to bombardment by energetic projectiles like photons, electrons, and ions. Laboratory experiments have been carried out to study the effects of such irradiation. However, there is a clear lack of information about the interaction of heavy ion components of solar/stellar wind and galactic cosmic rays (e.g. Fe) with ices in the keV to GeV energy range. The objective of this work is to study the effects produced in astrophysical ices by highly charged nickel ions at relatively high energy (∼50–500 MeV) in the electronic energy loss regime, and to compare them with those produced by protons, photons, and electrons. Our results for CO 2 and CO indicate that sputtering induced by heavy ions can be an important mechanism to desorb molecules in astrophysical environments.

Two ices, O2 and a mixture of O2 and N2, are bombarded by 252Cf fission fragments (FF) (approximately 65 MeV at target surface); the emitted positive and negative secondary ions are analyzed by time-of-flight mass spectrometry (TOF-SIMS). These studies shall enlighten sputtering from planetary and interstellar ices. Three temperature regions in the 28-42-K range are analyzed: (1) before N2 sublimation, in which hybrid chemical species are formed, (2) before O2 sublimation, in which the TOF mass spectrum is dominated by low-mass (O2)p cluster ions and (3) after O2 sublimation, in which (N2)p or (O2)p cluster ions are practically inexistent. In the first region, four hybrid ion series are observed: NOn-1+, N2On-2(+/-), and N4On-4(-). In the second region, two positive and negative ion series are identified: (O2)pO(+/-) and (O2)pO2(+/-). Their yield distributions are fitted by the sum of two decreasing exponentials, whose decay constants are the same for all series. It is observed that the cluster ion desorption from solid oxygen is very similar to that of other frozen gases, but its yield distribution oscillates with a three- or six-atom periodicity, suggesting O3 or 3O2 units in the cluster structure, respectively.

Condensed CO and CO2 are bombarded by approximately 65 MeV 252Cf fission fragments and the desorbed ions are analyzed by time-of-flight mass spectrometry as a function of target temperature, in the ranges 25-33 K and 75-91 K, respectively. Absolute desorption yields are measured up to complete ice sublimation. The mass spectra of both ice targets reveal the emission of: (1) low mass ions, produced by direct Coulomb interaction of the highly charged projectiles and delta-electrons with CO and CO2, and (2) pronounced series of cluster ions. The basic ice cluster structures (CO)n and (CO2)n are present in the emitted cluster series such as (CO)nCO+, (CO2)nCO2+, or (CO2)nCO3-. In the case of CO ice, however, the intense production of the series Cn+, Cn-, and (CO)mCn+ shows that Cn is the main cluster structure, consequence of a higher concentration of free carbon atoms in the nuclear track plasma of CO ice than in that of CO2 ice. Ion cluster abundance is observed to decrease exponentially with cluster mass. The decay constant is k(n) congruent with 0.13, about the same for series based on (CO)n and (CO2)n, but a factor 3.3 higher for the Cn series. The Cn clusters are formed by gas-phase condensation, but the (CO)n and (CO2)n clusters are produced by fracturing of the highly excited solid around the nuclear track. A dramatic reduction of the ion desorption yield is observed near T = 29 K for CO and near T = 85 K for CO2, when fast sublimation occurs and ice thickness vanishes. Close to sublimation temperature, the decay constant of the (CO)2Cn+ series increases due to a decreasing formation probability of large Cn clusters.

Experimental results on fast ion collision with icy surfaces having astrophysical interest are presented. 252Cf fission fragments projectiles were used to induce ejection of ionized material from H2O, CO2, CO, NH3, N2, O2 and Ar ices; the secondary ions were identified by time-of-flight mass spectrometry. It is observed that all the bombarded frozen gas targets emit cluster ions which have the structure XnR±, where X is the neutral ice molecule and R± is either an atomic or a molecular ion. The shape of the positive or negative ion mass spectra is characterized by a decreasing yield as the emitted ion mass increases and is generally described by the sum of two exponential functions. The positive ion water ice spectrum is dominated by the series (H2O)nH3O+ and the negative ion spectrum by the series (H2O)nOH− and (H2O)nO−. The positive ion CO2 ice spectrum is characterized by R+ = C+, O+, CO+, O2+ or CO2+ and the negative one by R− = CO3−. The dominant series for ammonia ice correspond to R+ = NH4+ and to R− = NH2−. The oxygen series are better described by (O3)nOm+ secondary ions where m = 1, 2 or 3. Two positive ion series exist for N2 ice: (N2)nN2+ and (N2)nN+. For argon positive secondary ions, only the (Ar)nAr+ series was observed. Most of the detected molecular ions were formed by one-step reactions. Ice temperature was varied from ∼20 K to complete sublimation.

Nitrogen (0.13–0.85 MeV) and 252Cf fission fragments (∼65 MeV) beams are employed to sputter positive and negative secondary ions from frozen water. Desorption yields are measured for different ice temperatures and projectile energies. Target surface is continuously refreshed by condensed water while the target temperature varies and ice thickness changes. In both projectile energy ranges, the preferentially ejected ions are H+, H 2 + and (H2O)nH+-cluster ions. The yields of the corresponding negative ions H− and (H2O)nO− or (H2O)nOH− are 1–2 orders of magnitude lower. The (H2O)nH+ desorption yields decrease exponentially as the cluster size, n, increases. In the low energy range, the desorption of positive ion clusters may occur in a two-step process: first, desorption of preformed H2O clusters and, then, ionization by H+ or H3O+ capture. For 0.81 MeV N+ projectile ions, the cluster ion emission contributes with 0.05% to the total H2O desorbed yield. There are indications that emission of the (H2O)nH+ disappears for an electronic energy loss lower than 20 eV/A. For the high energy range, desorption of small ion clusters is particularly enhanced, revealing that a fragmentation process also exists.

Secondary ion emission from polycrystalline CsI irradiated by pulsed-UV laser (337 nm) is analyzed by time-of-flight (TOF) mass spectrometry. Measurements were performed for different laser intensities and for several delayed extraction times (0–200 ns). The TOF peak shape is characterized by a Gaussian-like structure (fast component), followed by a tail (slow component) that is more pronounced when the extraction field is delayed. A thermal-sputtering uni-dimensional model is employed to describe the solid surface and plasma temperatures as a function of time. Heat diffusion, vapor photo-ionization, radiative emission and plume expansion are considered. Within the approximations used, the model predicts reasonable drift velocities of the plume (≈1.4 km s−1) but very high plasma temperatures (≈105 K). The width of the TOF peak fast component allows determination of the plume temperature during its expansion.

The combination of the time-of-flight (TOF) technique with two-dimensional position-sensitive (XY) ion detection is employed for tracking projectile-gas collisions. The main goal is to determine the detailed distribution of local electric fields, which accelerate the gas ions produced in the collisions. A low-pressure target gas spectrometer for this goal is described and all necessary XY- TOF expressions concerning the ion dynamics are presented. Experimental results of a 150 keV neutral H beam colliding with a He–Ne–Ar mixture are compared with the calculations. The new method can also be used for mapping magnetic fields or in large collision gas cells, e.g., to increase resolution in mass spectrometry and to perform initial momentum measurements of the produced ions.

Electronic sputtering of lithium fluoride by swift heavy ions was studied as a function of electronic energy loss (dE/dx) e . The single crystal targets were irradiated with swift heavy ion beams (166Z P 692; 46E P /M P (MeV/u) 611). This allowed varying the deposited energy by a factor of 20 (1.86dE/dx (keV/nm) 632). The sputtered secondary ions were measured from well controlled LiF targets without surface contaminations, by means of the time-of-flight technique (TOF-SIMS). The mass spectrum reveals an important contribution of clusters (over single ions), which increases with (dE/dx) e . Another observation for the strongest perturbation at high dE/dx (>8 keV/nm) is that the secondary ion yields saturate: Y(dE/dx) = constant. In contrast, at lower dE/dx (

In this work, we report a joint experimental-theoretical investigation on interaction of vacuum-ultraviolet radiation with trimethylphosphate (TMP) molecule (C(3)H(9)O(4)P) in gas phase. This species together with tetrahydrofuran (THF) are model compounds of deoxyribose nucleic acids (DNA)/ribose nucleic acids (RNA) backbone. Absolute photoabsorption cross sections (σ(a)) and ionization yields (η) are measured using the double-ion-chamber technique in the 11.0-21.45 eV energy range. Photoionization (σ(i)) and neutral-decay (σ(n)) cross sections in absolute scale are also derived. Moreover, theoretical photoabsorption cross sections are calculated using the time-dependent density functional theory from the excitation threshold up to 16 eV. Good agreement between the present calculated and experimental photoabsorption cross sections in the 11.0-14.5 eV range is encouraging. Also, the present measured data of σ(a) and σ(i) for TMP are about 1.3 and 1.5 times of those of THF, respectively. Thus, the experimental evidences that the majority of strand breaks being located at sugar rings in the irradiated DNA/RNA backbone moiety may be induced by a possible migration of the hole, initially created at phosphate group, to the linked sugar groups. Finally, absolute partial photoionization cross sections are derived from the experimental time-of-flight mass spectra.

A combination of imaging techniques (XY) and time-of-flight (TOF) spectroscopy was used to measure the complete velocity vector of sputtered positive secondary ions in collisions of Kr33+ (10.1 MeV/u) with well-prepared LiF single crystals in the electronic stopping regime. The energy distributions N(E) of the cluster ions (LiF) n Li+ (n ≥ 0) depend on the size of the ejecta: the maximum is slightly shifted towards lower energy with increasing cluster size n. The measured energy distributions of emitted cluster ions can be fitted by a Maxwell-Boltzmann function N(E) = AEexp(−βE). This could be an indication that the processes generating the sputtering are compatible with a thermal origin.

A combination of imaging techniques (XY) and time-of-flight (TOF) spectroscopy was used to measure the complete velocity vector of sputtered positive secondary ions in collisions of Kr33+ (10.1 MeV/u) with well prepared LiF single crystals in the electronic stopping regime. The angular distributions of (LiF) n Li+ clusters become broader with increasing cluster size n. This could be an indication of contributions from different ejection mechanisms. The experimental secondary ion angular distributions can be fitted by a simple cosine function of the type N(θ) = A cos m (θ), but it does not reproduce the shape of the jet-like structure observed for the emission of neutral LiF particles perpendicular to the ion beam. Therefore, the cluster emission hypothesis does not explain in a simple way the observed narrow jet.

Sputtering occurs as a result of deposition of kinetic or potential energy in solids irradiated with swift particles. We studied ejection of secondary ions from LiF induced by swift heavy ion impact. A new UHV system allows measuring the mass distributions and the velocity vectors of each emitted secondary ion by means of time-of-flight and imaging techniques (XY-TOF-SIMS) with controlled target surfaces. We present results performed at GANIL (Caen) with Ca beams at 7.6 and 9 MeV/u (electronic stopping regime). Under UHV conditions, particles emitted from cleaved LiF monocrystals include the omnipresent hydrogen, and the two isotopes of natural LiF (6Li+ and 7Li+). Two groups of clusters, namely Li n + and (LiF)nLi+ appear. The cluster size (n) dependence of the cluster ion yields Y(n) can be described by an exponential function. LiF emission as ionic clusters (LiF)nLi+ with n ⩾ 2 is dominant over emission as monomers LiFLi+.

Icy grain mantles consist of small molecules containing hydrogen, carbon, oxygen and nitrogen atoms (e.g. H2O, CO, CO2, NH3). Such ices, present in different astrophysical environments (giant planets satellites, comets, dense clouds, and protoplanetary disks), are subjected to irradiation of different energetic particles: UV radiation, ion bombardment (solar and stellar wind as well as galactic cosmic rays), and secondary electrons due to cosmic ray ionization of H2. The interaction of these particles with astrophysical ice analogs has been the object of research over the last decades. However, there is a lack of information on the effects induced by the heavy ion component of cosmic rays in the electronic energy loss regime. The aim of the present work is to simulate of the astrophysical environment where ice mantles are exposed to the heavy ion cosmic ray irradiation.Sample ice films at 13K were irradiated by nickel ions with energies in the 1-10 MeV/u range and analyzed by means of FTIR spectrometry. Nickel ions were used because their energy deposition is similar to that deposited by iron ions, which are particularly abundant cosmic rays amongst the heaviest ones.In this work the effects caused by nickel ions on condensed gases are studied (destruction and production of molecules as well as associated cross sections, sputtering yields) and compared with respective values for light ions and UV photons.

In the present paper the emission of intact insulin quasi-molecular ion [M+H]+ during laser ablation (MALDI) is studied. It was observed in particular that the insulin TOF molecular peak increases as the laser power increases. The DE-Vestal method for the initial velocity measurements was improved theoretically including the distance (d0) until the free expansion regime can be considered. According to the present analysis, the v0 parameter given by the DE-Vestal method is interpreted as the initial velocity that the desorbed ion would have if no collision occurs in the plasma. The improved method interprets v0 as the "final" initial velocity, i.e., as the velocity that the desorbed ions have when the plasma free expansion starts and, effectively, collisions no longer occur. The new method allows also the determination of d0, the distance to the solid when the free expansion starts. The data fitting shows that the distance (d0) has a linear dependence on the laser's intensity. Extrapolation of these values gives I = 0.69 G W cm-2 as the minimum energy density necessary to produce high density plasma during the insulin ions desorption when using alphaCHCA matrix.

In order to simulate the effects of the heavy ion component of cosmic rays on ices in astrophysical environments, the CO and CO2 ices were irradiated with swift nickel ions in the electronic energy loss regime. The ices were prepared by condensing gas onto a CsI substrate at a temperature of 14 K and analyzed by means of infrared (FTIR) spectroscopy. The physical process of deposition by Ni ions is similar to more important and abundant heavy cosmic rays such as Fe ions. Dissociation of the ice molecules, and formation of new molecules were observed. Also, sputtering (leading to desorption of molecules from the solid surface to the gas phase) was observed. It was found that the sputtering yield due to heavy ions cannot be neglected with respect to desorption induced by weakly ionizing particles such as UV photons and protons.

In this work, we report an experimental investigation into the interaction of vacuum-ultraviolet radiation with tetrahydrofuran molecules in the gas phase. More specifically, absolute photoabsorption cross sections and photoionization quantum yields are measured and reported in the (11.11–21.45) eV energy range. In addition, photoionization and neutral-decay cross sections in absolute scale are derived and reported. The measurements were performed using the double-ion-chamber technique. The comparison between our measured data and the existing experimental results is encouraging.

A model based on the nuclear track potential is described and used to predict trajectories and the energy distribution of secondary ions emitted by insulating targets. In this model, the electric field generated by each track pushes away the secondary ions formed on the target surface. The effects on the potential due to target thickness, track charge density, projectile incidence angle and secondary ion mass are analyzed. Predictions are compared with experimental data existing in the literature. It is found that the proposed model describes partially the behavior observed in the angular distribution of the emitted ions and new processes are proposed to be included in the model.