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Linac4 is the negative hydrogen ion (H-) injector of the CERN accelerator complex. Modelling of the beam formation is essential for optimizing the current and emittance of the H- ion source. We exploited the 3D PIC-Monte Carlo ONIX (Orsay Negative Ion eXtraction) code for studying H- beam formation processes in caesiated negative ion sources. The various geometries of the IS03 prototypes have been implemented into ONIX. The code, designed for neutral injector multi-aperture sources for fusion has been adapted to match the single-aperture extraction region of the Linac4 H- source. A plasma electrode designed to ensure radial metallic boundary conditions was produced and tested. The simulation results of the beam formation region at low plasma density to validate the functionality of the modified ONIX version are presented.

Linac4 is a 160 MeV linear H − accelerator at CERN. It is an essential part of the beam luminosity upgrade of the Large Hadron Collider (LHC) and will be the primary injector into the chain of circular accelerators. It aims at increasing the beam brightness by a factor of 2, when compared to the currently used 50 MeV linear proton accelerator, Linac2. Linac4’s ion source is a cesiated RF-plasma H − ion source. Several beam extraction systems were designed for H − beams of 45 keV energy, 50 mA intensity and an electron to H − ratio smaller than 5. The goal was to extract a beam with an rms-emittance of 0 . 25 π mm mrad. One of the main challenges in designing an H − extraction system is dumping of the co-extracted electrons. Separating the electrons from the negative ions as early as possible reduces space-charge induced emittance-growth. However, a strong magnetic field close to the extraction might cause unnecessary strong deflection in a region of low beam energy. For this purpose a novel magnetic configuration was designed using a magnetic shield between the magnetic fields of the source and the electron dump, which conserves the filter field strength to keep the electron to H − ratio low and effectively dumps the co-extracted electrons. Magnetic configuration and beam trajectories were calculated using the TOSCA Opera 3D code and IBSimu, respectively. Three extraction systems will be discussed in terms of electron dumping efficiency, emittance and transport through the extraction system and LEBT to the RFQ and compared to the simulations. An improved emittance conservation through the extraction system and LEBT is predicted and further design improvements are proposed. Measurements show that the novel electron dump successfully traps the co-extracted electrons.

Linac4 is radio frequency (RF) driven type negative hydrogen H− ion source. In the RF system, it is required to match the impedance between the RF-system and plasma loading. In order to match the impedance, it is essential to analyze the plasma impedance. In this study, we analyze the plasma impedance by using the Electro-Magnetic Particle in Cell model. As a result, plasma impedance calculated by the Electro-Magnetic Particle in Cell model agrees qualitatively with one calculated by fluid model model in the steady state. On the other hand, plasma impedance calculated by the numerical simulation code is significantly different from one calculated by the zero dimensional equivalent circuit model during plasma ignition. The results show that the kinetic effects are necessary especially during plasma ignition. It is useful to propose more efficiency power transfer.

Negative hydrogen ion source extraction system development is dependent on accurate and fast simulation methods for modelling the behaviour of ion and electron beams. Traditionally this type of work has been done using ray-tracing extraction codes, such as IBSimu. The plasma extraction model in IBSimu has been observed to under-estimate the charge density near the plasma sheath, leading to incorrect prediction of the current at which the system produces the optimum emittance. It is suspected that this deviation results from the approximations made by the model, neglecting the magnetic field and collisional effects near the sheath region. Results and comparisons to simulations are presented for three ion sources, for which two show similar variation and one is more accurately modelled. Conclusions with the currently available data can not be made and therefore further experimental and simulation campaigns to study the effect are suggested. peerReviewed

Negative hydrogen (H −) ion sources have a wide range of applications. The general requirement for these H − ion sources is to produce intense H − ion beams with good beam optics. The purpose of this paper is to clarify the effects of the beam extraction voltage on the beam divergence angle by three-dimensional Particle-in-Cell (PIC) modeling. Perveance matching has been studied for a wide range of the extraction voltage with the model geometry of a Linac4 H − ion source. The extracted H − beam divergence angle is evaluated for extraction voltages ranging from 7 to 14 kV by using the Keio-BFX PIC code. The results show divergence minima in the range of 9.2–11.5 kV for the case without surface H − production, which correspond to experimental results. The dependence of divergence on the extraction voltage is explained by the change of the shape of the meniscus. In particular, a flat meniscus corresponds to low beam divergence, and particles extracted through the center of the meniscus have a lower divergence than particles extracted near the Plasma Electrode.

A filament driven multi-cusp negative ion source has been developed for proton cyclotron applications. In this study, numerical analysis of the H− volume production in the negative ion source has been conducted by the KEIO-MARC code and zero dimensional rate equations. The code calculate the Electron Energy Distribution Function (EEDF) in multi-cusp arc discharge sources from the following main input parameters: 1) 3D geometry of the source chamber and filaments, 2) 3D magnetic configuration, 3) arc voltage, 4) arc current and 5) gas pressure. Using the EEDF, we can also estimate the resultant amount of the H- volume production by the 0D rate equations. In this paper, we focus on the dependency of the H− production on the filter magnetic field and the arc-discharge voltage. It is shown that KEIO-MARC code reproduces the magnetic filter effect, i.e., the electron temperature and density are reduced across the filter region. Also, the 0D analysis shows that the amount of H-production increases with the arc-...

Linac4 is a 160 MeV H− linear accelerator part of the upgrade of the LHC injector chain. Its cesiated surface H− source is designed to provide a beam intensity of 40-50mA. It is operated with periodical Cs-injection at typically 30 days intervals [1] and this implies that the beam parameters will slowly evolve during operation.Autopilot is a control software package extending CERN developed Inspector framework. The aim of Autopilot is to automatize the mandatory optimization and cesiation processes and to derive performance indicators, thus keeping human intervention minimal.Autopilot has been developed by capitalizing on the experience from manually operating the source. It comprises various algorithms running in real-time, which have been devised to: • Optimize the ion source performance by regulation of H2 injection, RF power and frequency. • Describe the performance of the source with performance indicators, which can be easily understood by operators. • Identify failures, try to recover the nominal operation and send warning in case of deviation from nominal operation. • Make the performance indicators remotely available through Web pages. Autopilot is at the same level of hierarchy as an operator, in the CERN infrastructure. This allows the combination of all ion source devices, providing the required flexibility. Autopilot is executed in a dedicated server, ensuring unique and centralized control, yet allowing multiple operators to interact at runtime, always coordinating between them. Autopilot aims at flexibility, adaptability, portability and scalability, and can be extended to other components of CERN’s accelerators. In this paper, a detailed description of the Autopilot algorithms is presented, along with first results of operating the Linac4 H− Ion Source with Autopilot.

In order to understand the H− extraction mechanism and investigate the effect of the extraction voltage applied by the puller-electrode on the H− extraction in the Linac4 negative ion source, we are developing a 2D3V-PIC (two dimensions in the real space and three dimensions in the velocity space, Particle in Cell) model with volume produced H− ions. It is shown that how to take the magnetic filter field direction is important for the 2D modeling to take into account the important 3D effect of electron E×B drift. It is also shown that the meniscus formation is not symmetric due to the electron E×B drift in the extraction region and the divergence of the H− beam is asymmetric. In order to make more quantitative comparison of the extracted H− and electron currents with the experiments and 3D modeling, further improvements, especially the electron loss along the magnetic filter field line will be needed.

The power requirements of RF heated sources for negative hydrogen ions in fusion are substantial, which poses strong demands on the generators and components of the RF circuit. Consequently, an increase of the RF coupling efficiency would be highly beneficial. Fundamental investigations of the RF efficiency in inductively coupled hydrogen and deuterium discharges in cylindrical symmetry are conducted at the lab experiment CHARLIE. The experiment is equipped with several diagnostics including optical emission spectroscopy and a movable floating double probe to monitor the plasma parameters. The presented investigations are performed in hydrogen at a varying pressure between 0.3 and 10 Pa, utilizing a conventional helical ICP coil driven at a frequency of 1MHz and a fixed power of 520W for plasma generation. The coupling efficiency is strongly affected by the variation in pressure, reaching up to 85% between 1 and 3 Pa while dropping down to only 50% at 0.3 Pa, which is the relevant operating pressure for negative hydrogen ion sources for fusion. Due to the lower power coupling, also the measured electron density at 0.3 Pa is only 5 . 10(16) m(-3), while it reaches up to 2.5 . 10(17) m(-3) with increasing coupling efficiency. In order to gain information on the spatially resolved aspects of RF coupling and plasma heating which are not diagnostically accessible, first simulations of the discharge by an electromagnetic Particle-In-Cell Monte Carlo collision method have been conducted and are compared to the measurement data. At 1 Pa, the simulated data corresponds well to the results of both axially resolved probe measurements and radially resolved emission profiles obtained via OES. Thereby, information regarding the radial distribution of the electron density and mean energy is provided, revealing a radial distribution of the electron density which is well described by a Bessel profile.

Linac4 cesiated surface H− sources are routinely operated for the commissioning of the CERN’s Linac4 and on an ion source test stand. Stable current of 40-50 mA are achieved but the transmission through the LEBT of 80% was below expectations and triggered additional beam simulation and characterization. The H− beam profile is not Gaussian and emittance measurements are larger than simulation. The status of ongoing development work is described; 36 mA H− and 20 mA D− beams were produced with a 5.5 mm aperture cesiated surface ion source. The emittances measured at the test stand are presented. During a preliminary test, the Linac4 proton source delivered a total beam intensity of 70 mA (p, H2+, H3+). peerReviewed

CERN ’s new particle accelerator Linac4 is part of the upgrade of the LHC accelerator chain. Linac4 is required to deliver 160 MeV H− beam to improve the beam brightness and luminosity in the Large Hadron Collider (LHC). The Linac4 H− source must deliver 40-50 mA, 45 keV H− beam in the RFQ acceptance. Since the RF power coupled to the H− source plasma is one of the important parameters that determines the quality of the H− beam, the experimental investigation of the dependence of the load impedance on the operational parameters is mandatory. In this study, we have measured the impedance of the H− source plasma varying the RF power coupled to the plasma and the condition of the hydrogen gas. Also, optical emission spectroscopy (OES) measurements have been carried out simultaneously with the impedance measurement in order to determine the plasma parameters. The determination of the plasma parameters allows us to compare the experimental results with the analytic model of the plasma parameters, which is useful to discuss the results from a physical point of view.CERN ’s new particle accelerator Linac4 is part of the upgrade of the LHC accelerator chain. Linac4 is required to deliver 160 MeV H− beam to improve the beam brightness and luminosity in the Large Hadron Collider (LHC). The Linac4 H− source must deliver 40-50 mA, 45 keV H− beam in the RFQ acceptance. Since the RF power coupled to the H− source plasma is one of the important parameters that determines the quality of the H− beam, the experimental investigation of the dependence of the load impedance on the operational parameters is mandatory. In this study, we have measured the impedance of the H− source plasma varying the RF power coupled to the plasma and the condition of the hydrogen gas. Also, optical emission spectroscopy (OES) measurements have been carried out simultaneously with the impedance measurement in order to determine the plasma parameters. The determination of the plasma parameters allows us to compare the experimental results with the analytic model of the plasma parameters, which is usef...

When the H− ion source of CERN’s Linac4 is operated in volume mode, a maximum of the extracted current is obtained at varying RF power. The power required for this maximum and its absolute value is strongly influenced by the cusp magnets installed at the source for electron confinement: without magnets, 15−20 mA are typically obtained at 20 kW whereas with magnets a factor of two more power is needed and 25−30 mA are achieved. In order to access the reasons behind the peaked performance with varying RF power and for determining the influence of the cusp field on the discharge, optical emission spectroscopy (OES) measurements of the atomic Balmer series and of the molecular Fulcher transition have been carried out. In all investigated cases, the gas temperature of the discharge has been virtually equal to the ambient temperature as the short discharge pulse length of 500 µs is not long enough for considerable heavy particle heating. When no cusp magnets are installed, the plasma parameters evaluated with the collisional radiative models Yacora H and Yacora H2 show a minimum in the electron temperature of 3.25 eV and a maximum in the electron density of 4×1019 m−3 and also in the vibrational excitation of the hydrogen molecule at 20 kW. Assessing the relevant production and destruction processes demonstrates that the H− yield is maximal at this point thereby explaining the optimum ion source performance. When the cusp magnets are applied, the same general trends are observed but the required RF power is a factor of two higher. The OES results indicate an optimum performance around 30 kW whereas the highest H− current is actually achieved around 40 kW. Furthermore, a higher H− yield is indicated without cusp magnets but a better ion source performance is observed with magnets. These differences can most likely be attributed to changing gradients in the plasma parameters which are not accessible by OES. Nevertheless, the obtained plasma parameters can be used as benchmark for RF coupling codes simulating the Linac4 ion source.

Recently, a filament driven multi-cusp negative ion source has been developed for proton cyclotrons in medical applications. In this study, numerical modeling of the filament arc-discharge source plasma has been done with kinetic modeling of electrons in the ion source plasmas by the multi-cusp arc-discharge code and zero dimensional rate equations for hydrogen molecules and negative ions. In this paper, main focus is placed on the effects of the arc-discharge power on the electron energy distribution function and the resultant H(-) production. The modelling results reasonably explains the dependence of the H(-) extraction current on the arc-discharge power in the experiments.

To understand the Electron Energy Distribution Function (EEDF) in the Radio Frequency Inductively Coupled Plasmas (RF-ICPs) in hydrogen negative ion sources, the detailed analysis of the EEDFs using numerical simulation and the theoretical approach based on Boltzmann equation has been performed. It is shown that the EEDF of RF-ICPs consists of two parts, one is the low energy part which obeys Maxwellian distribution and the other is high energy part deviated from Maxwellian distribution. These simulation results have been confirmed to be reasonable by the analytical approach. The results suggest that it is possible to enhance the dissociation of molecules and the resultant H(-) negative ion production by reducing the gas pressure.

A new target and ion source unit has been developed at CERN-ISOLDE with the aim of delivering isobarically clean beams of short lived neutron-rich Cd and Zn. A quartz insert in the transfer line allows the retention and the decay of alkali contaminants by controlling its temperature from 308 °C to 792 °C. This paper presents the design of this transfer line. New alkali suppression factors are deduced from 80Rb, 8Li, 46K and 126,142Cs yield measurements. The enthalpy of adsorption for Rb and Cs is calculated from 80Rb and 126Cs suppression factors. The yield of 77Ga and 96Sr are presented.

A new target and ion source unit has been developed at CERN-ISOLDE with the aim of delivering isobarically clean beams of short lived neutron-rich Cd and Zn. A quartz insert in the transfer line allows the trapping and the decay of alkali contaminants. This paper presents the design of the quartz transfer line. Alkali suppression is demonstrated with 80Rb and 114Cs. The yield of 8Li, 46K, 77Ga and 75Zn is presented.

Linac4 is a new 160 MeV linear accelerator designed to improve by a factor of 2 the beam brightness out of the LHC injection chain for the needs of the LHC luminosity upgrade. The project started in 2008 and beam commissioning takes place in 2014–2015. The new linac accelerates H− ions that are then stripped at injection into the PS Booster; production of the H− beam takes place in a state-of-the-art ion source of the RF-driven caesiated surface type. Acceleration is provided by four different accelerating sections matched to the increasing beam velocity, including two of novel designs, and focusing is provided by a combination of permanent-magnet and electromagnetic quadrupoles.

In the framework of the EURISOL project, the production of neutron-rich isotopes of rubidium and cesium has been studied. The intensities of mass-separated beams of rubidium and cesium isotopes generated from a thick 238 UC x target connected to a surface ionizer have been measured. The release properties of 140 Cs and 91 Rb have been investigated. The obtained results allowed us to determine the relative fission yields of rubidium and cesium isotopes with high accuracy.

The production of light noble gas radioisotopes with high ionization potentials has been hampered by modest ionization efficiencies for standard plasma ion-sources. However, the decay losses are minimal as the lingering time of light noble gases within plasma ion-sources is negligible when compared to its diffusion out of the target material. Previous singly charged ECRIS have shown a higher efficiency but also a lingering time of the order of 1 s and a total weight that prevents remote handling by the ISOLDE robot. The compact MINIMONO efficiently addressed the lingering time and weight issues. In addition, the MINIMONO maintained the high off-line ionization efficiency for light noble gases. This paper describes a standard ISOLDE target unit equipped with a MINIMONO ion-source and the first tests. The ion-source has been tested off-line and equipped with a CaO target for on-line tests. Valuable information was gained about high current (100-500 muA) transport through the ISOLDE mass separators designed for

A new high-spin isomer in 215Bi, with a half-life of 36.9(6) s, has been identified at the PSB-ISOLDE on-line mass separator using the pulsed-release technique combined with the element selective RILIS source. A decay scheme of $^{215{\rm m}}$ Bi was constructed and complemented with the low-spinstructure observed in $^{215{\rm g}}$ Bi decay. The population of a cascade on top of the $\left( \nu g_{9/2} \right)^5_{9/2+}$ level in 215Poprovides evidence for Gamow-Teller $\beta$ -decay of the high-spin 215Bi isomer.

A liquid metal target is one of the options for the pion production target of a ν-factory. The interaction between a liquid metal and a proton beam were observed with static mercury as well as with a free mercury jet and up to 4×1012 protons/bunch. The experimental method for investigating the magneto-fluid-dynamic effects of a high-velocity liquid metal in a high magnetic field magnet has been validated by recording the behaviour of a 15 m/s mercury burst entering the gradient of a 13 T solenoid at GHMFL Grenoble. The paper includes the description of the optical read-out system as well as numerical results of the mercury drop velocities.

The discharge process of a radiofrequency (RF) inductively coupled plasma (ICP) has been modeled by an ElectroMagnetic Particle-in-Cell Monte Carlo Collision method (EM PIC-MCC). Although the simulation had been performed by our previous model to investigate the discharge mode transition of the RF ICP from a kinetic point of view, the model neglected the collision processes of ions (H+ and H2+) with neutral particles. In this study, the RF ICP discharge process has been investigated by the latest version of the model which takes the ion-neutral collision processes into account. The basic characteristics of the discharge mode transition provided by the previous model have been verified by the comparison between the previous and present results. As for the H-mode discharge regime, on the other hand, the ion-neutral collisions play an important role in evaluating the growth of the plasma. Also, the effect of the ion-neutral collisions on the kinetic feature of the plasma has been investigated, which has high...

We present a study of the global event shape variables thrust and heavy jet mass, of energy-energy correlations and of jet multiplicities based on 250 000 hadronic Z 0 decays. The data are compared to new QCD calculations including resummation of leading and next-to-leading logarithms to all orders. We determine the strong coupling constant α s (91.2 GeV) = 0.125±0.003 (exp) ± 0.008 (theor). The first error is the experimental uncertainty. The second error is due to hadronization uncertainties and approximations in the calculations of the higher order corrections.

The development of the Linac 4 and its integration into CERN’s acceleration complex is part of the foreseen luminosity upgrade of the Large Hadron Collider (LHC). The goal is to inject a 160 MeV H− beam into the CERN PS Booster (PSB) in order to increase the beam brightness by a factor of 2 compared to the 50 MeV proton linac, Linac 2, that is currently in operation.The requirements for the ion source are a 45 keV H− beam of 80 mA intensity, 2 Hz repetition rate and 0.5 ms pulse length within a normalized rms-emittance of 0.25 mm· mrad.The previously installed beam extraction system has been designed for an H− ion beam intensity of 20 mA produced by an RF-volume source with an electron to H− ratio of up to 50.For the required intensity upgrades of the Linac4 ion source, a new beam extraction system is being produced and tested; it is optimized for a cesiated surface RF-source with a nominal beam current of 40 mA and an electron to H− ratio of 4. The simulations, based on the IBSIMU code, are presented.At ...

Time structure of Balmer Hα line intensity in Linac4 RF plasma has been analyzed by the combined simulation model of atomic transport and Collisional-Radiative models. As a preliminary result, time variation of the line intensity in the ignition phase of RF plasma is calculated and compared with the experimental results by photometry. For the comparison, spatial distribution of the local Hα photon emission rate at each time is calculated from the numerical model. The contribution of the local photon emission rates to the observed line intensity via optical viewing port is also investigated by application of the mock-up of the optical viewing port and the known light source. It has been clarified from the analyses that the higher and the lower peaks of the Hα line intensity observed during 1 RF cycle is mainly due to the different spatial distributions in the electron energy distribution function and the resultant local photon emission rate. These results support previous suggestion that the existence of the capacitive electric field in axial direction leads to the higher/lower peaks of the line intensity.

Two volume sources equipped with DESY and CERN plasma generators and a low voltage electron dump were operated at 45 kV in the Linac4 tunnel and on a dedicated test stand. These volume sources delivered approximately 20 mA and ensured the commissioning of the Radio Frequency Quadrupole accelerator and of the first section of the Drift Tube Linac. CERN’s prototype of a cesiated surface source equipped with this electron dump was operated continuously from November 2013 to April 2014 on the ion source test stand and is being commissioned in the Linac4 tunnel. Before cesiation, the prototype conditioned in volume mode provided up to 30 mA H− beam. Short cesiations, of the order of 10 mg effectively reduced the intensity of co-extracted electrons down to 2 - 8 times the H− current; this cesiated surface operation mode delivered up to 60 mA H− beam. An H− beam of the order of 40 mA was sustained up to four weeks operation with 500 μs pulses at 1.2s spacing. A new extraction was designed to match these beam pro...

In order to evaluate Electron Energy Distribution Function (EEDF) more correctly for radio frequency inductively coupled plasma (RF-ICP) in hydrogen negative ion sources, the Electromagnetic Particle-In-Cell (EM-PIC) simulation code has been improved by taking into account electron-electron Coulomb collision. Binary collision model is employed to model Coulomb collision process and we have successfully modeled it. The preliminary calculation including Coulomb collision has been done and it is shown that Coulomb collision doesn’t have significant effects under the condition: electron density ne ∼ 1018 m−3 and high gas pressure pH2 = 3 Pa, while it is necessary to include Coulomb collision under high electron density and low gas pressure conditions.

The H− source for the Linac4 accelerator at CERN uses an RF driven plasma for the production of H−. The RF is supplied by a 2 MHz RF tube amplifier with a maximum power output of 100 kW and a pulse duration of up to 2 ms. The low-level RF signal generation and measurement system has been developed using standard CERN controls electronics in the VME form factor. The RF frequency and amplitude reference signals are generated using separate arbitrary waveform generator channels. The frequency and amplitude are both freely programmable over the duration of the RF pulse, which allows fine-tuning of the excitation. Measurements of the forward and reverse RF power signals are performed via directional couplers using high-speed digitizers, and permit the estimation of the plasma impedance and deposited power via an equivalent circuit model. The low-level RF hardware and software implementations are described, and experimental results obtained with the Linac4 ion sources in the test stand are presented.

Linac4, a 160 MeV normal-conducting H(-) linear accelerator, is the first step in the upgrade of the beam intensity available from the LHC proton injectors at CERN. The Linac4 Low Energy Beam Transport (LEBT) line from the pulsed 2 MHz RF driven ion source, to the 352 MHz RFQ (Radiofrequency Quadrupole) has been built and installed at a test stand, and has been used to transport and match to the RFQ a pulsed 14 mA H(-) beam at 45 keV. A temporary slit-and-grid emittance measurement system has been put in place to characterize the beam delivered to the RFQ. In this paper a description of the LEBT and its beam diagnostics is given, and the results of beam emittance measurements and beam transmission measurements through the RFQ are compared with the expectation from simulations.

We have measured the partial widths of the Z 0 into lepton pairs, and the forward-backward charge asymmetry for the process e + e − → μ + μ − using the L3 detector at LEP. We obtain an average Γ ll of 83.0±2.1±1.1 MeV.From this result and the asymmetry measurement, we extract the values of the vector and axial vector couplings of the Z 0 to leptons: g rmv =−0.066 −0.027 +0.046 and g rmA = −0.495 −0.007 +0.007 .

A chemically selective laser ion source has been used in a β-decay study of heavy Ag isotopes into even-even Cd nuclides. Gamma-spectroscopic techniques in time-resolving event-by-event and multiscaling modes have permitted the identification of the first 2+ and 4+ levels in 126Cd78, 128Cd80, and tentatively the 2+ state in 130Cd82. From a comparison of these new states in 48Cd with the E(2+) and E(4+)/E(2+) level systematics of 46Pd and 52Te isotopes and several recent model predictions, possible evidence for a weakening of the spherical N = 82 neutron-shell below double-magic 132Sn is obtained.

High-resolution measurements of low-energy conversion electrons have been performed in odd and odd–odd nuclei with masses around A=182. The experimental setup, a magnetic spectrograph coupled to a specific tape transport system, is described. Three experiments have been performed and the main results are presented.

Laser spectroscopy measurements have been carried out on very neutron-deficient isotopes of Au, Pt and Ir, produced as daughter elements from a Hg ISOLDE beam. For these transitional region nuclides, the hyperfine structure (HFS) and isotope shift (IS) were measured by Resonance Ionization Spectroscopy (RIS). Magnetic moments μ, spectroscopic quadrupole moments Qs and changes of the nuclear mean square charge radius δ〈rc 2〉along isotopic series have been extracted. For some results, a detailed comparison with theoretical predictions is presented.

Resonance ionization laser ion source (RILIS) technique has been used in the β-decay studies of 59Mn and 58Zn. The importance of the RILIS for production of these elements is discussed. The properties of the low-lying levels of the studied nuclei are discussed.

The latest results of the research and development program Production d'Atomes Radioactifs Riches en Neutrons (PARRNe) at Institut de Physique Nucleaire (IPN) Orsay are presented. The production of neutron rich isotopes by fast neutron induced fission in a liquid depleted uranium target was measured. A comparison of the production rates with a uranium carbide (UCx) target is given.

The 7Be(p,γ)8B capture reaction is of major importance to the physics of the sun and the issues of the “solar neutrino puzzle”. We report here on a new determination of the absolute cross section of this reaction, using a novel method which overcomes some of the major experimental uncertainties of previous measurements. We utilize a 7Be target implanted into a Cu substrate and a uniformly scanned particle beam larger than the target spot, eliminating issues of target homogeneity and backscattering loss of 8B reaction products. The target was produced using a beam of 1.8·1010/s 7Be nuclei extracted at ISOLDE (CERN) from a graphite target bombarded by 1 GeV protons in a two-step resonant laser ionization source. The 7Be nuclei were directly implanted into a copper substrate to obtain a target of 2 mm diameter with a total of 3.1015 atoms. The measurement of the 8B production cross section was carried out at the Van de Graaff laboratory of the Weizmann Institute of Science. We obtain for the S factor of the reaction: S17(Ecm = 1.09 MeV) = 22.7(1.2) eV. barn and S17(Ecm = 1.29 MeV) = 23.8(1.5) eV. barn, somewhat higher than other recent measurements. The present results can serve as a benchmark for further measurements of this cross section.

The use of chemically selective laser ionization combined with beta-delayed neutron counting at CERN/ISOLDE has permitted identification and half-life measurements for 623-ms Mn-61 up through 14-ms Mn-69. The measured half-lives are found to be significantly longer near N=40 than the values calculated with a QRPA shell model using ground-state deformations from the FRDM and ETFSI models. Gamma-ray singles and coincidence spectroscopy has been performed for Mn-64 and Mn-66 decays to levels of Fe-64 and Fe-66, revealing a significant drop in the energy of the first 2+ state in these nuclides that suggests an unanticipated increase in collectivity near N=40., Latex-file with 4 figures, 5 pages, Phys. Rev. Lett., in print

A new method to reduce the isobaric contamination problem for the production of neutron rich Bi, Pb and Tl nuclei at on-line mass separators, based on the pulsed release of these radioactive species, is presented. The results of a feasibility study are reported.

The ISOLDE on-line mass separator facility is operating on a Personal Computer based control system since spring 1992. Front End Computers accessing the hardware are controlled from consoles running Microsoft Windows™ through a Novell NetWare4™ local area network. The control system is transparently integrated in the CERN wide office network and makes heavy use of the CERN standard office application programs to control and to document the running of the ISOLDE isotope separators. This paper recalls the architecture of the control system, shows its recent developments and gives some examples of its graphical user interface.

Radioactive ion-beams produced from various uranium and thorium targets at the ISOLDE mass separator facility are presented. The targets are bombarded with 1 GeV protons delivered by the PS-Booster at CERN. The target materials are uranium carbide and thorium carbide, both prepared from the oxides or diphtalocyanines of uranium and thorium. Due to the pulsed structure of the PS-Booster, release can be measured as a function of time for a number of elements. Beam intensities and delay time distributions of the alkali-metals, the earth-alkalis, the boron group and the noble gases measured from the described targets are discussed. Comparisons are made between the target materials and with ISOLDE beam intensities produced by 600 MeV protons from the CERN synchrocyclotron.

The linear accelerator is the first vital stage of the LHC injector complex. The Linac4 is an H− linear accelerator intended to replace Linac2 as injector into the CERN accelerator complex. It is a machine 90 m long and it will accelerate H− ions up to 160 MeV. The Linac4 represent a crucial step for the LHC high luminosity program since it will allow improving brightness and reducing beam losses. The new linear accelerator is now under construction. A long reliability run will start during 2014.

A very compact Electron Cyclotron Resonance Ion Source (ECRIS) for singly charged radioactive gases has been developed at ISOLDE/CERN. The radioisotopes are produced by fission, spallation, and fragmentation reactions induced via high-energy protons impacting on a thick target. The often short-lived radioactive elements required for ISOLDE physics diffuse out of the target, effuse through a transfer tube, and eventually reach the ionizing volume. An efficient ionization process is mandatory in view of the very small production cross sections of radioactive elements far from stability and fast ionization is desired to minimize decay losses. The MECRIS (Mono ECR ISOLDE) is intended for light noble gases (He, Ne, Ar, and Kr), which have low ionization efficiency in ordinary plasma ion sources, but also for gaseous molecular compounds of C, N, and O isotopes. We will report on the design and construction of the device, including magnetic field calculations and rf simulations. Results of the first tests performed with stable ion beams are presented.

The resonance ionization laser ion source (RILIS) of the ISOLDE on-line isotope separation facility is based on the method of laser stepwise resonance ionization of atoms in a hot metal cavity. The atomic selectivity of the RILIS compliments the mass selection process of the ISOLDE separator magnets to provide beams of a chosen isotope with greatly reduced isobaric contamination. Using a system of dye lasers pumped by copper vapor lasers, ion beams of 22 elements have been generated at ISOLDE with ionization efficiencies in the range of 0.5%–30%. As part of the ongoing RILIS development, recent off-line resonance ionization spectroscopy studies have determined the optimal three-step ionization schemes for yttrium, scandium, and antimony.

Linac4 is a 160 MeV linear accelerator which will inject negative hydrogen ions (H−) into CERN’s Proton Synchrotron Booster, a required upgrade to improve the beam brightness in the LHC injector chain. A volume production RF ion source, based on the design of the DESY RF source was implemented, but showed considerable electron dump ablation during operation at 45 keV beam energy. To reduce the electron beam power density in the dump, a magnetized Einzel lens is designed that reduces the beam energy to 10 keV before permanentmagnets dump the electrons on a tungsten surface. Presented in this paper are simulations of the design using IBSimu, the tunable range of parameters depending on the extracted H− and electron current, as well as details of the implementation, the choice of pulsed power converters and the electrode alignment system. In addition, simulations of proton extraction from this source will be shown.

CERN's Linac4 accelerator H− ion source, currently under construction, will operate at a 2 Hz repetition rate, with pulse length of 0.5 ms and a beam current of 80 mA. Its reliability must exceed 99 % with a mandatory 3 month uninterrupted operation period. A Penning ion source is successfully operated at ISIS; at 50 Hz repetition rate it reliably provides 55 mA H− pulses of 0.25 ms duration over 1 month. The discharge plasma ignition is very sensitive to the temperatures of the discharge region, especially of its cathode. The investigation by modeling and measurement of operation parameters suitable for arc ignition and H− production at 2 Hz is of paramount importance and must be understood prior to the implementation of discharge ion sources in the Linac4 accelerator. In its original configuration, the ISIS H− source delivers beam only if the repetition rate is above 12.5 Hz, this paper describes the implementation of a temperature control of the discharge region aiming at lower repetition rate operation. The experimental results of the modified source successfully operated down to 1.6 Hz and providing 30 mA H− pulses of 0.75 ms duration are presented. A thermal modeling of the ISIS ion source gives insight to the relevant parameters. The analysis demonstrates the adaptability of discharge sources for the operating conditions of the Linac4.

At CERN, a high performance negative ion (NI) source is required for the 160 MeV H− linear accelerator Linac4. The source is planned to produce 80 mA of H− with an emittance of 0.25 mm mradN-RMS which is technically and scientifically very challenging. The optimization of the NI source requires a deep understanding of the underling physics concerning the production and extraction of the negative ions. The extraction mechanism from the negative ion source is complex involving a magnetic filter in order to cool down electrons’ temperature. The ONIX (Orsay Negative Ion eXtraction) code is used to address this problem. The ONIX is a selfconsistent 3D electrostatic code using Particles-in-Cell Monte Carlo Collisions (PIC-MCC) approach. It was written to handle the complex boundary conditions between plasma, source walls, and beam formation at the extraction hole. Both, the positive extraction potential (25kV) and the magnetic field map are taken from the experimental set-up, in construction at CERN. This contribution focuses on the modeling of two different extractors (IS01, IS02) of the Linac4 ion sources. The most efficient extraction system is analyzed via numerical parametric studies. The influence of aperture’s geometry and the strength of the magnetic filter field on the extracted electron and NI current will be discussed. The NI production of sources based on volume extraction and cesiated surface are also compared.