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The Super-FRS is an electromagnetic separator and spectrometer designed for the production and selection of highly energetic and intense exotic heavy-ion beams. It is part of the Facility for Antiproton and Ion Research (FAIR) particle accelerator currently under construction at GSI, Darmstadt, Germany. The Super-FRS will feature in total 63 superconducting magnet cryostats: 27 dipoles, 35 multiplets (7 short and 28 long), and the GLAD experiment magnet. The Super-FRS Local Cryogenics will distribute and feed cold helium from the central cryogenic plant “CRYO2” to the magnet cryostats. Daisy-chain like arrays of feed and end boxes are connected via transfer line pieces. Each single magnet cryostat is supplied by one feed box via a jumper connection. The dipole, short- and long multiplets require different helium mass streams at different operation modes. Moreover, the Local Cryogenics system must follow the Super-FRS curvature and irregular pattern of cryostat locations. In order to simplify the production process, lower the risk of technical mistakes, and increase the flexibility of the installation sequence during the conceptual design project phase an effort was made to develop a uniform construction of the feed boxes for all cryostat types. The paper provides the description of the Super-FRS Local Cryogenics system and the process requirements for all cryostat types in all possible operation modes. The Super-FRS feed box flow scheme and features that allow for unification of its design for all cryostat types are also presented.

Physics letters / B 763, 16 - 19 (2016). doi:10.1016/j.physletb.2016.10.015, Published by North-Holland Publ., Amsterdam

The superconducting synchrotron SIS100 of the FAIR accelerator project will provide heavy ion beams of highest intensities. SIS100 is the first synchrotron with a special design, optimized for the control of ionization beam loss. Ionization beam loss is the most pronounced loss mechanism at operation with high-intensity, intermediate charge state heavy ions. The new synchrotron layout comprises an ion catcher system, which in combination with a charge separator lattice shall suppress dynamic vacuum effects.A prototype cryogenic ion catcher, including a dedicated cryostat has been designed, manufactured, and tested under realistic conditions with beams from the heavy-ion synchrotron SIS18 at GSI. The gas desorption induced by the impact of heavy ions on this cryocatcher has been measured. For the very first time, a rise of desorption yield with increasing beam energy has been observed. However, measurements at room temperature have confirmed the known decrease of the pressure rise in the investigated energy regime. A transition temperature of 18 K, underneath hydrogen is adsorbed, could be verified several times. The results are significant and used to predict the ionization beam loss at operation of SIS100 at full-beam intensity.

A novel method for measuring nuclear reactions in inverse kinematics with stored ion beams was successfully used to extract the nuclear-matter radius of $^{58}\mathrm{Ni}$. The experiment was performed at the experimental heavy-ion storage ring at the GSI facility using a stored $^{58}\mathrm{Ni}$ beam at energies of 100 and 150 MeV/u and an internal helium gas-jet target. Elastically scattered $\ensuremath{\alpha}$-recoils at low momentum transfers were measured with an in-ring detector system compatible with ultrahigh vacuum. Experimental angular distributions were fitted using density-dependent optical model potentials within the eikonal approximation. This permitted the extraction of the point-matter root-mean-square radius of $^{58}\mathrm{Ni}$ with an average value of 3.70(7) fm. Results from this work are in good agreement with several experiments performed in the past in normal kinematics. This pioneering experiment demonstrates a major breakthrough towards future investigations with far-from-stability stored beams using the present technique.

The presented work focuses on the development of a differential pumping system using double-sided silicon-strip detectors to separate the ultra-high vacuum of a storage ring from subsequent detectors and outgassing components placed in an auxiliary vacuum. Such a technical concept will give the opportunity to use telescope-like detector systems in an ultra-high vacuum environment, such as a storage ring, without enclosing the entire system in a pocket. Therefore, it will enable the detection of recoil particles with the smallest possible energy due to the use of the innermost strip detector as an active window. Our results prove that such an assembly is feasible without having an effect, within experimental errors, on the performance of the strip detector. Vacuum separation better than six orders of magnitude was achieved with the ultra-high vacuum side reaching down to the 10(-10) mbar pressure region. (C) 2011 Elsevier B.V. All rights reserved.

This paper describes new experiments on the heavy ion desorption yield measurements with 5 MeV/u Ar8+ and summarizes all results of experiments with 5 MeV/u Ar8+ performed at The Svedberg Laborator ...

Non-evaporable getter (NEG) coatings are widely used in large vacuum systems such as particle accelerators. Since NEG coatings produced at the GSI Helmholtzzentrum fur Schwerionenforschung have a finite thickness of typically 1 μm, ion beam analysis techniques such as ERDA and RBS are the methods of choice to study element and depth-resolved evolution of the getter film during gas pumping. The film thickness and stoichiometry can be determined by RBS while ERDA is sensitive to lighter elements such as carbon, nitrogen and oxygen, the main residual gas components of a vacuum environment. In this work we first present exsitu and insitu measurements of NEG thin films using ERDA. For the investigation of the pumping speed and capability of the getter films, we have used a vacuum test chamber where getter coated samples can be activated and saturated in a very controlled way. Afterwards, depth distributions of the pumped gas components have been measured using ERDA. To study the gas components in NEG coatings online, i.e., during activation or pumping, we have set up an ERDA system working at vacuum pressures down to 10 - 11 mbar . A special target heater system allows to activate the getter coatings insitu at typical temperatures between 180 and 300 °C in a UHV environment with tolerable influence to the total and partial gas pressure. With this UHV-ERDA setup, a temperature dependent diffusion process of gas components into the getter material could be analyzed for the first time.

Particle accelerators have, during operation with heavy ion beams, shown a significant pressure rise when the intensity of the beam is increased. This pressure rise is due to ion induced desorption, which is the result of beam ions colliding with residual gas atoms in the beam pipe, where they undergo charge exchange. This causes them to hit the vacuum chamber after the next dipole magnet and gas to be released. For the upgrade of the SIS18 synchrotron at GSI the intensity has to be a few orders of magnitude higher than it is today at the injection energy of 10 MeV/u. The aim of this experiment is to measure desorption yields, η , (released molecules per incident ion) from materials commonly used in accelerators: 316LN stainless steel, Cu, etched Cu, gold coated Cu and Ta, using an Ar beam at impact energies in the range of 5–17.7 MeV/u for perpendicular incidence. The measured initial desorption yields vary for the same material from sample to sample: up to 4.5 times for stainless steel and up to 3 times for etched Cu. Therefore more samples should be studied to have better statistics. Beam conditioning at lower energy does not significantly reduce the desorption yield at higher energy. There is a significant difference of up to a few times in desorption yield between flat and tubular samples. The desorption yield from a Cu sample at grazing incident angle of 125 mrad was an order of magnitude larger than at normal incident angle. It was found that the total number of positively and negatively charged secondary particles, emitted from the surface bombarded with heavy ions, does not exceed ∼40 secondary particles per impact heavy ion. The current of negatively charged particles was about 2.3 times larger than the current for positively charged particles. The impact from secondary particles on dynamic gas pressure was not possible to investigate.

TiZrV nonevaporable getter (NEG) coated vacuum chambers is a new vacuum technology which is already used in many particle accelerators worldwide. This coating is also of interest for heavy-ion accelerator vacuum chambers. Heavy-ion desorption yields from an activated as well as a CO saturated NEG coated tube have been measured with 5MeV∕u Ar8+ beam. The sticking probability of the NEG film was obtained by using the partial pressure ratios on two sides of the NEG coated tube. These ratios were compared to results of modeling of the experimental setup with test particle Monte Carlo and angular coefficient methods. The partial pressures inside the saturated NEG coated tube bombarded with heavy ions were up to 20 times larger than those inside the activated one. However, the partial pressure of methane remained the same. The value of the total desorption yield from the activated NEG coated tube is 2600molecules/ion. The desorption yields after saturation for CH4, H2, and CO2 were found to be very close to the...

In several experiments at CERN, GSI and BNL it has been found that the lifetime of highly energetic heavy ions in synchrotrons decreases with increasing number of injected ions. This phenomenon occ ...

For the future project the Facility for Antiproton and Ion Research (FAIR) at GSI, an accelerator system with a base pressure of 10−10 Pa is required. The low pressure is needed to reduce the charge exchange rate between the accelerated ions and the residual gas molecules and therefore to increase the ion beam lifetime. Among the different measures undertaken to upgrade the existing UHV system, the installation of non-evaporable getter (NEG)-coated dipole and quadrupole chambers is foreseen. For this purpose a licence agreement for the non-evaporable thin film getters was signed between GSI and CERN in the end of June 2005. A new dedicated magnetron sputtering facility was designed and commissioned at GSI to perform the Ti–Zr–V coating on the dipole chambers of the heavy-ion synchrotron (SIS 18). Those pipes, made from stainless steel, have an elliptical cross section, are 3 m long, and are characterised by a wall thickness of 0.3 mm and a 15° bending angle. The characterisation of the thin films produced has been carried out by Rutherford backscattering spectroscopy (RBS), energy dispersive X-ray spectroscopy (EDX) and elastic recoil detection analysis (ERDA) for the chemical composition, scanning electron microscopy (SEM) for the morphology, and X-ray photoelectron spectroscopy (XPS) for the activation behaviour. The coating facility, its operating mode, and the first results obtained on the NEG characterisation by means of the different techniques will be described.

Ion–beam-loss induced desorption is a well known intensity limitation for high current, low charge state heavy ion accelerators like the heavy ion synchrotron SIS18 at GSI. Therefore dedicated measurements of desorption yields has been made, e.g., at CERN and at GSI in the last few years. In this work we will present studies performed at GSI starting from purely phenomenological pressure rise experiments to highly sophisticated ion beam analysis techniques like UHV-ERDA.

First results on swift heavy ion induced electron emission from solids obtained with a reaction microscope are presented. This advanced technique, which is successfully used since quite some time to study electron ejection in ion–atom collisions, combines the measurement of the time-of-flight of electrons with imaging techniques. A combination of electric and magnetic fields guides the ejected electrons onto a position sensitive detector, which is capable to accept multiple hits. From position and time-of-flight measurement the full differential emission characteristics of up to 10 electrons per single incoming ion can be extracted. As a first example, we show energy spectra, angular distributions and the multiplicity distribution of electrons from impact of Au24+ (11 MeV/u) on a thin carbon foil (28 μg/cm2).

We have measured the nuclear-matter distribution of the doubly-magic N = Z nucleus Ni-56 by investigating elastic proton scattering in inverse kinematics. The radioactive beam of Ni-56 was injected and stored in the experimental storage ring (ESR, GSI) and interacted with an internal hydrogen gas-jet target. The high revolution frequency of the ions in the ring enabled a high luminosity, despite the low density of the target being used. This way, measurements at very low momentum transfers became possible. By measuring the energy and the scattering angle of the recoiling protons, we were able to separate the elastic reaction channel from inelastic scattering to the first excited 2(+) state of Ni-56 and deduced the differential cross section of Ni-56 (p, p)(56) Ni. The data were analyzed within the framework of the Glauber multiple-scattering theory in order to extract the nuclear-matter radius and radial matter distribution of Ni-56. Parameterizing the matter distribution with the phenomenological Symmetrized Fermi distribution, a preliminary value of 3.5 fm for the rms matter radius was deduced. This experiment was part of an EXL (EXotic nuclei studied in Light-ion induced reactions at storage rings) campaign at GSI in 2012 and was the first successful investigation of nuclear reactions with a stored radioactive beam ever.

Highly differential cross sections have been obtained for dissociative single ionization of H2 by 6 MeV proton impact by measuring the momentum vectors of the electron and the H+ fragment in coincidence. The investigation of the momentum balance of the fragments along the projectile beam provided detailed insight into the four-particle dynamics, even though the H atom is not detected. Within the axial recoil approximation, molecular-frame angular distributions of emitted electrons have been determined for molecules oriented perpendicular to the projectile beam. They are compared with the predictions of a CDW-EIS calculation.

The planning revision of the cryogenic system for the Facility of Antiproton and Ion Research (FAIR, Darmstadt, Germany) resulted in the choice of a single universal plant, which should provide a wide range of cryogenic operation modes, as refrigeration capacity at 4.4K, liquefaction or intermediate temperature levels. The adaptation to the FAIR specific requirements will be done later by adding a second plant. One major demand for the plant is the short term adaptation to variations in the load requirements in the system. An exemplary integration into the overall FAIR system will be shown with the experiments in the Compressed Baryonic Matter (CBM) cave. The CBM cave will house an already existing magnet, HADES, and a new magnet for the CBM experiment, which is still under design. The scheduling of the different operation modes related to the operation of the main consumers as SIS100 or SuperFRS is shown.

The investigation of light-ion induced direct reactions using stored and cooled radioactive beams, interacting with internal targets of storage rings, can lead to substantial advantages over external target experiments, in particular for direct reaction experiments in inverse kinematics at very low momentum transfer, q. This new and challenging experimental technique enables high-resolution measurements down to very low q and provides a gain in luminosity from accumulation and recirculation of the stored beams. For performing first experiments of this kind a dedicated experimental setup housing several DSSD (Double-sided Silicon Strip Detector) and Si(Li) detectors for recoil particles, well suited for meeting the demanding UHV (Ultra High Vacuum) conditions of a storage ring, was recently designed, constructed and installed at the internal target of the ESR storage ring at GSI. From the interaction of a stored 56Ni beam with an internal H2 target, good quality differential cross section data for elastic proton scattering, measured with the aim to determine the radial shape of the nuclear matter distribution of 56Ni, were obtained. Preliminary results are presented. Being the first reaction experiment ever performed with a stored radioactive beam on a world-wide scale, this experiment can be considered as a breakthrough for nuclear structure and astrophysics studies, and, in addition, as a successful proof-of-principle of the new experimental concept. In addition, preliminary results from a feasibility study on inelastic α-scattering from 58Ni in inverse kinematics, where it was demonstrated that the Isoscalar Giant Monopole Resonance in 58Ni can be investigated by the present technique down to CM angles below 1 degree, are discussed. Such an experiment, performed in the future with the doubly magic 56Ni, would provide important information on the EOS of nuclear matter.

The European physical journal / Web of Conferences 66, 03093 (2014). doi:10.1051/epjconf/20146603093, Published by EDP Sciences, Les Ulis

We have performed a kinematically complete experiment and calculations on single ionization in 100 MeV/amu C6+ + He collisions. For electrons ejected into the scattering plane (defined by the initial and final projectile momentum vectors) our first- and higher-order calculations are in good agreement with the data. In the plane perpendicular to the scattering plane and containing the initial projectile axis a strong forward-backward asymmetry is observed. In this plane both the first-order and the higher-order calculations do not provide good agreement neither with the data nor amongst each other.

For the GSI future project Facility for Antiproton and Ion Research a beam intensity of 1012U28+ions∕s is planned to be extracted from the GSI heavy ion synchrotron SIS18. Measurements performed in 2001 showed that the beam lifetime of the ions in the synchrotron is decreasing with increasing number of injected particles due to vacuum instabilities caused by ion-induced desorption. The injection energy for the SIS18 is about 10MeV∕u and U28+ ions are accelerated to 200MeV∕u limited by the magnetic rigidity for the low charge state. The aim of this work was to measure the desorption yield as a function of the impact energy from injection to extraction of SIS18 at GSI. Low energy yields at 5.0, 9.7, and 17.7MeV∕u were measured at the Cyclotron of The Svedberg Laboratory in Uppsala. High energy yields at 40, 80, and 100MeV∕u were measured at SIS18 of GSI in a different setup. It was found that the desorption yield scales with the electronic energy loss (dE∕dx)eln, with n between 2 and 3, decreasing for incre...

Single and multiple ionization of neon and argon atoms by 3.6 MeV/u Au{sup 53+} impact has been explored in kinematically complete experiments. Doubly differential cross sections for low-energy electron emission have been obtained for a defined charge state of the recoiling target ion and the receding projectile. Observed target specific structures in the electron continuum are attributable to the nodal structure of the initial bound state momentum distribution. The experimental data are in excellent accord with continuum-distorted-wave eikonal-initial-state single ionization calculations if multiple ionization is considered appropriately. (c) 1999 The American Physical Society.

The momentum vectors of the recoil ion and up to three electrons were measured in coincidence with the projectiles which did not change charge state for 3.6 MeV amu-1 Au53+ Ne collisions. New techniques were applied to obtain differential energy-loss spectra for multiple-target ionization as a function of the recoil-ion charge state. A resolution unprecedented for this energy regime was achieved. The data are in good agreement with a classical trajectory Monte Carlo calculation. Our studies represent a first step for a method of modelling stopping powers on a microscopic level and are relevant for plasma applications.

A central issue in modem atomic physics is the understanding of the role of static and dynamic electron-electron correlation in multi-electron transitions. In this respect the investigation of double ionization of helium induced in collisions with projectiles is fundamental since it presents the simplest particle impact induced three body break-up and it is the first step in order to understand multiple ionization processes. Experiments aim to obtain fully differential cross sections since they provide the most stringent tests for theory and to give an understanding of the mechanisms involved for a large range of incident energies and of the final state momentum space. For double ionization of helium by electron impact very few experimental results are available and besides the present study only one kinematically complete experiment using conventional electron spectrometry was performed by (1998).

Double ionization of helium in the perturbative regime has been explored in a kinematically complete collision experiment using 100 MeV/u C 6+ ions. Different ionization mechanisms are identified by inspecting the angular distribution of the electrons as a function of the momentum transfer q to the target by the projectile. For q 1 :2 au, the faster electron resulting from a binary encounter with the projectile is emitted along the direction of momentum transfer, while the other electron is distributed uniformly. Experimental data are compared with various model calculations based on the Bethe-Born approximation with shake-off. Surprisingly, the effect of the final state interaction is found to depend decisively on the choice of the initial state wavefunction.

Single and double ionization of helium by 1GeV/nucleon U{sup 92+} impact was explored in a kinematically complete experiment. The relativistic ion generates a subattosecond (10{sup {minus}18} s ) superintense (I{gt}10{sup 19} W/cm {sup 2} ) electromagnetic pulse, which is interpreted as a field of equivalent photons (Weizs{umlt a}cker-Williams method). Cross sections, the emission characteristics of ions and electrons as well as momentum balances, are quantitatively discussed in terms of photoionization of the atom in this broadband, ultrashort virtual photon field. {copyright} {ital 1997} {ital The American Physical Society}

The collision dynamics of He single ionization by 3.6MeV/uSe{sup 28+} impact was explored using the reaction microscope of the Gesellschaft f{umlt u}r Schwerionenforschung, a high-resolution integrated multielectron recoil-ion momentum spectrometer. The complete three-particle final-state momentum distribution (nine Cartesian components p{sub i}) was imaged with a resolution of {Delta}p{sub i}{approx}{plus_minus}0.1a.u. by measuring the three momentum components of the emitted electron and the recoiling target ion in coincidence. The projectile energy loss has been determined on a level of {Delta}E{sub p}/E{sub p}{approx}10{sup {minus}7} and projectile scattering angles as small as {Delta}{var_theta}{approx}10{sup {minus}7}rad became accessible. The experimental data which are compared with results of classical trajectory Monte Carlo calculations reveal an unprecedented insight into the details of the electron emission and the collision dynamics for ionization of helium by fast heavy-ion impact. {copyright} {ital 1997} {ital The American Physical Society}

Electrons emerging form ionizing collisions of any projectiles (ions, photons, electrons) with the particles in a supersonic jet target (atoms, clusters, molecules) are projected onto three large-area, multi-hit capable position sensitive detectors applying well controlled electric and solenoidal magnetic fields. Up to three electrons with an energy bandwidth for each between 0 eV ≤ Ee ≤ 1 keV are detected simultaneously with a solid angle close to 4π. Each momentum vector (three spatial components pei) is calculated from the measured hitting positions and time-of-flights with a resolution of Δ pei < 2 × 10−2 a.u.. Thus, the complete final many-electron momentum space (up to 9 momentum components) is visualized. The theoretical limits in resolution achievable with such a method is in the neV-regime. In addition, the recoil-ion momentum vector is determined simultaneously applying “conventional” recoil-ion momentum spectroscopy.

Double ionization of He and Ne by charged particle impact was explored in kinematically complete experiments measuring the final momenta of the two emerging electrons ({ital P}{sub {ital e}1}{sup {ital f}},{ital P}{sub {ital e}2}{sup {ital f}}) and of the recoiling target ion {ital P}{sup {ital f}}{sub {ital R}}. The momentum transfer from the 3.6 MeV/{ital u} Se{sup 28+} projectile to the electrons is found to be negligibly small. Thus distinct patterns observed in the {ital P}{sub {ital e}1}{sup {ital f}}-versus-{ital P}{sub {ital e}2}{sup {ital f}} spectra sensitively reflect the details of the electrons{close_quote} correlated motion. Classical calculations reasonably describe the data only when the ({ital e}{minus}{ital e}) interaction during the ionization reaction is included. {copyright} {ital 1996 The American Physical Society.}

21st International School on Nuclear Physics and Applications & the International Symposium on Exotic Nuclei, Varna, Bulgaria, 7 Sep 2015 - 12 Sep 2015; Journal of physics / Conference Series Conference Series 724(1), 012026 - (2016). doi:10.1088/1742-6596/724/1/012026, The EXL project aims to study nuclear structure by direct reactions in inverse kinematics at the storage rings of the future FAIR facility. In this contribution, we present the status of the project: the technical implementation at the ESR at GSI and preliminary results of the EXL campaign in 2012, the first using also a radioactive beam., Published by IOP Publ., Bristol

We have implemented a forward electron spectrometer in the supersonic jet target region of the ESR for Rydberg- and projectile continuum electron spectroscopy of few-electron highly charged ions; a first result from commissioning is presented.

In order to test the fast-ramped superconducting magnets for FAIR (Facility for Antiproton and Ion Research), a cryogenic test facility with an equivalent overall capacity of 1.5 kW at 4.4 Kelvin was designed and commissioned at GSI Helmholzzentrum fur Schwerionenforschung GmbH.For efficient testing of the 108 dipole magnets the cryogenic infrastructure consists of a refrigeration system and four main test benches. Due to the different operating modes and load fluctuations a dedicated process and control concept was developed which allows an independent operation of each test bench and ensures highest efficiency over the whole operating range. The system is designed in a way that one magnet can be cooled down to its operating temperature while simultaneously another magnet is kept at cold state for the measurements. The third and fourth test benches serve for warming up and exchanging the magnets respectively.The high flexibility of the set-up moreover allows the testing of other FAIR magnets like the SIS100 quadrupole modules or the operation of a string configuration.The project was executed in a close collaboration between GSI and Linde Kryotechnik AG. The paper will show the key solutions of the refrigeration system and the test benches and highlight some commissioning results.

The ion-induced desorption experiment, installed in the CERN Heavy-Ion Accelerator LINAC 3, has been used to study the dynamic outgassing of cryogenic surfaces. Two different targets, bare and gold-coated copper, were bombarded under perpendicular impact with 4.2 MeV/u Pb^{54+} ions. Partial pressure rises of H_{2}, CH_{4}, CO, and CO_{2} and effective desorption yields were measured at 300, 77, and 6.3 K using single shot and continuous ion bombardment techniques. We find that the heavy-ion-induced desorption yield is temperature dependent and investigate the influence of CO gas cryosorbed at 6.3 K. The gain in desorption yield reduction at cryogenic temperature vanishes after several monolayers of CO are cryosorbed on both targets. In this paper we describe the new cryogenic target assembly, the temperature-dependent pressure rise, desorption yield, and gas adsorption measurements.

Electron emission from multi-electronic target atoms by 3.6 MeV/uAu53+ ion impact is explored in kinematically complete experiments. DDCS as a function of the longitudinal and transverse component of the emitted electron momentum are in very good agreement with calculations using the CDW-EIS model. A study of the electron emission from specific sub-states shows that the initial state momentum distribution is mapped onto low lying continuum states with characteristic features which depend on the initial state wave- function.

A kinematically complete experiment for double ionization of He by 3.6 Mev/u Au53+ impact has been performed using a high-resolution integrated multi-electron recoil-ion momentum spectrometer. Nine out of twelve momentum components of the outgoing fragments were measured. The electrons sum-momentum is found to be in the forward direction and the recoil ion almost compensates the electrons being ejected into the backward hemisphere. The momentum change of the projectile is found to be small compared to the momenta of the ejected reaction products, which reveals similarity with photoionization. The strongest interaction among the collision partners is found to exist between the recoil ion and the electrons.

The ion induced desorption is a severe luminosity limitation for low charge state heavy ion accelerators. Therefore it was intensively investigated in dedicated experiments during the last years. Several experimental results were obtained providing numerous desorption yields for different ion beam parameters and different materials as well as surface treatments. The heavy ion induced desorption was identified as a pure surface effect. Nevertheless it was shown that the yields have a strong link to the irradiated material. Furthermore it was observed that the ion beam is cleaning the sample. After desorbing a number of gas molecules corresponding to one monolayer of gas under the beam spot the sample is cleaned and the ion induced desorption is minimized. With the geometrical cross section of a projectile ion a desorption yield of several hundred molecules per ion from a monolayer is hard to explain. Therefore we have expanded the inelastic Thermal Spike Model to describe the process as thermal desorption from a microscopic heated region. The obtained results of this new model represent very well the numbers from many experimental studies.

As a first step of the EXL project scheduled for the New Experimental Storage Ring at FAIR a precursor experiment (E105) was performed at the ESR at GSI. For this experiment, an innovative differential pumping concept, originally proposed for the EXL recoil detector ESPA, was successfully applied. The implementation and essential features of this novel technical concept will be discussed, as well as details on the detectors and the infrastructure around the internal gas-jet target. With Ni-56(p, p)Ni-56 elastic scattering at 400 MeV u(-1), a nuclear reaction experiment with stored radioactive beams was realized for the first time. Finally, perspectives for a next-generation EXL-type setup are briefly discussed.

During heavy-ion operation in several particle accelerators worldwide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion-induced gas desorption scales with the electronic energy loss (dE{sub e}/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.

A dedicated cold‐bore ion desorption experiment was performed in August 2004 at CERN’s Heavy Ion Accelerator LINAC 3. The dynamic outgassing of 4.2 MeV/u Pb53+ ions, impacting under 89.2° grazing incidence onto a copper tube, was studied as a function of the target temperature. Partial pressure rises of H2, CH4, CO, CO2, H2O, and O2 were measured at 300 K, 77 K, and 15 K using continuous lead ion bombardment. The new experimental setup is described and first pressure rise measurements are presented.A dedicated cold‐bore ion desorption experiment was performed in August 2004 at CERN’s Heavy Ion Accelerator LINAC 3. The dynamic outgassing of 4.2 MeV/u Pb53+ ions, impacting under 89.2° grazing incidence onto a copper tube, was studied as a function of the target temperature. Partial pressure rises of H2, CH4, CO, CO2, H2O, and O2 were measured at 300 K, 77 K, and 15 K using continuous lead ion bombardment. The new experimental setup is described and first pressure rise measurements are presented.

Ion‐beam loss induced desorption is a well known intensity limitation for low charge state heavy ion accelerators. Therefore dedicated measurements were performed, e.g., at CERN and at GSI in the last few years. In this work we will summarize results obtained at GSI with a focus on a observed scaling of the desorption yield with the electronic energy loss of the incident ion in the target material.

Dissociative as well as nondissociative single ionization of ${\mathrm{H}}_{2}$ by 6 MeV proton impact has been studied in a kinematically complete experiment by measuring the momentum vectors of the electron and the ${\mathrm{H}}^{+}$ fragment or the $\mathrm{H}_{2}{}^{+}$ target ion, respectively. For the two ionization pathways, the electron spectra reveal the role of autoionization of the doubly and singly excited states of ${\mathrm{H}}_{2}$. The latter explicitly involve the coupling between the electronic and the nuclear motion of the molecule. This is a clear manifestation of a breakdown of the Born-Oppenheimer approximation.

Dissociative as well as nondissociative single ionization of H2 by 6 MeV proton impact has been studied in a kinematically complete experiment by measuring the momentum vectors of the electron and the H+ fragment or the H+2 target ion, respectively. For the two ionization pathways, the electron spectra reveal the role of autoionization of the doubly and singly excited states of H2. The latter explicitly involve the coupling between the electronic and the nuclear motion of the molecule. This is a clear manifestation of a breakdown of the Born-Oppenheimer approximation.

Double ionization of helium by 6 MeV proton impact has been explored in a kinematically complete experiment using a "reaction microscope." For the first time, fully differential cross sections for positively charged projectiles have been obtained and compared with data from 2 keV electron impact. The significant differences observed in the angular distribution of the ejected electrons are attributed to the charge sign of the projectile, resulting in different dynamics of the four-particle Coulomb system, which is not considered in the first Born approximation.

The rapid and still ongoing development of recoil-ion momentum spectroscopy (RIMS) during the last ten years can undoubtedly be viewed as an experimental breakthrough for the investigation of any kind of atomic reaction dynamics. Whenever atoms or simple molecules interact with electrons, ions or photons, the concept of high—resolution recoil-ion measurements resulted in additional and complementary information compared to the traditional electron spectroscopy methods, and in some cases even kinematically complete data sets could be collected for the very first time. State—of—the—art high-resolution recoil-ion momentum spectrometers evolved through numerous technical developments like, e.g., the implementation of cold supersonicjet targets, the use of well defined electric extraction fields for recoil ions as well as for electrons and the rapid progress in charged particle detection techniques. Among them the use of supersonic jets to produce well localized and internally cold targets (COLd Target Recoil-Ion Momentum Spectroscopy COLTRIMS) can be viewed as the most important ingredient. They allowed one to achieve a recoil-ion momentum resolution far below 1 a.u. (atomic unit) that would be impossible with room-temperature targets due to the thermal motion (the momentum spread of room-temperature helium atoms is about 3.7 a. u.). Another decisive development was the invention of completely novel and extremely efficient electron—imaging concepts.

Double ionization of helium in collisions with 6 MeV protons (vP = 15.5 a.u.) has been explored in a kinematically complete experiment using a so‐called “reaction microscope”. For the first time fully differential cross sections for positively charged particle impact have been obtained and compared to previous (e,3e) results with 2 keV electrons (vP = 12 a.u.). Differences have been found in the angular distribution of the two emitted electrons, which originate from projectile charge effects that are not considered in the first Born approximation.

To understand the physical processes that occur in nature we need to obtain a solid concept about the ‘fundamental’ forces acting between pairs of elementary particles. It is also necessary to describe the temporal and spatial evolution of many mutually interacting particles under the influence of these forces. This latter step, known as the few-body problem, remains an important unsolved problem in physics. Experiments involving atomic collisions represent a useful testing ground for studying the few-body problem. For the single ionization of a helium atom by charged particle impact, kinematically complete experiments have been performed1,2,3,4,5,6 since 1969 (ref. 7). The theoretical analysis of such experiments was thought to yield a complete picture of the basic features of the collision process, at least for large collision energies8,9,10,11,12,13,14. These conclusions are, however, almost exclusively based on studies of restricted electron-emission geometries1,2,3. Here, we report three-dimensional images of the complete electron emission pattern for the single ionization of helium by the impact of C6+ ions of energy 100 MeV per a.m.u. (a four-body system) and observe features that have not been predicted by any published theoretical model. We propose a higher-order ionization mechanism, involving the interaction between the projectile and the target nucleus, to explain these features.

A kinematically complete experiment for simultaneous ionization of a projectile and target has been performed for 3.6 MeV/u C2+ on He collisions measuring the final vector momenta of the He1+ recoil ion and of two electrons (projectile, target) in coincidence with the emerging C3+ projectile. The feasibility of an event-by-event separation of the various reaction channels, among them the ionization of C2+ by the interaction with a quasifree target electron, is demonstrated in agreement with six-body classical trajectory Monte Carlo calculations, paving the way to kinematically complete electron-ion scattering experiments.