M C Bellachioma

Publications (12)11.15 Total impact

• Conference Proceeding: STUDY OF THE PRESSURE PROFILE INSIDE THE NEG COATED CHAMBERS OF THE SIS 18

  M.C. Bellachioma, H. Kollmus, A. Kraemer, J. Kurdal, H. Reich-Sprenger, L. Urban, M. Wengenroth
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  ABSTRACT: In the context of the technical developments for the construction of FAIR at GSI, an intensive programme for the vacuum upgrade of the existing SIS 18 was started in 2005, with the aim to improve the beam lifetime and intensity. To reach these purposes also the installation of NEG coated dipole and quadrupole chambers was foreseen. During the upgrade shutdowns performed between 2006 and 2009 the vacuum chambers of approximately 65% of the SIS 18 circumference were replaced by NEG coated pipes. To evaluate in detail the pressure profile inside the coated chambers mounted into the accelerator a dedicated experimental set-up, which reproduces a vacuum environment similar to the one of the SIS 18, was built. Using three gauges, mounted in different positions of a coated chamber, it was possible to measure the pressure in the range of 10^-12 mbar inside the activated NEG pipe and 10^-11 mbar outside the pipe at the pumping posts. Additionally, a modelling of a SIS 18 vacuum sector was realised and the pressure variation values obtained by simulations were compared with those measured. In this paper the experimental results and the vacuum simulations are described and discussed.
  IPAC2012, New Orleans, Louisiana, USA; 01/2012
• Article: Heavy-ion induced desorption of a TiZrV coated vacuum chamber bombarded with 5 MeV/u Ar8+ beam at grazing incidence

  E. Hedlund, O. B. Malyshev, L. Westerberg, A. Krasnov, A. S. Semenov, M. Leandersson, B. Zajec, H. Kollmus, M. C. Bellachioma, M. Bender, A. Kramer, H. Reich-Sprenger
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  ABSTRACT: 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 5 MeV / u Ar ⁸⁺ 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 2600 molecules /ion. The desorption yields after saturation for C H ₄ , H ₂ , and C O ₂ were found to be very close to the yields measured after the activation, while CO increased by up to a factor of 5. The total desorption yield for the saturated tube is up to 7000 molecules /ion. The large value of the desorption yield of the activated NEG coated tube, an order of magnitude higher than the desorption yield from a stainless steel tube at normal incident angle, could be explained by the grazing incident angle.
  Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 02/2009; · 1.25 Impact Factor
• Conference Proceeding: Thin Film Coating for the Upgrade of the Ion Synchrotron SIS18 at GSI

  M.C. Bellachioma, H. Kollmus, J. Kurdal, A. Krämer, H. Reich-Sprenger, M. Bender
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  ABSTRACT: For the future FAIR facility intensities up to 10^12 U28+ ions per second are required. For this purpose the existing heavy ion synchrotron SIS18, which will serve as injector, has to be upgraded. Since the required base pressure is 10^-10 Pa, among the different measures undertaken to improve the existing UHV system, the installation of NEG coated magnet chambers is foreseen. Two magnetron sputtering facilities were designed and commissioned at GSI to perform the coating. The characterization of the thin films has been carried out by RBS and XPS. Considering that the vacuum chambers mounted in accelerators undergo several venting-activation cycles, a deep investigation on the NEG ageing was performed by ERDA. Fourteen dipole and one quadrupole chambers were coated and installed in the SIS18, and the replacement of the remaining magnet pipes will follow in the next years. Additionally to overcome the dynamic vacuum instability a collimation system equipped with thin film coated absorbers was successfully tested in 2008. The coating facilities, their operating mode, the results achieved on the thin film characterisation, and the ones obtained in the SIS18 are presented.
  PAC09, Vancouver, BC, Canada; 01/2008
• Source

  Available from: L.R. Prost

  Article: Heavy-ion-induced electronic desorption of gas from metals.

  A W Molvik, H Kollmus, E Mahner, M Kireeff Covo, M C Bellachioma, M Bender, F M Bieniosek, E Hedlund, A Krämer, J Kwan, O B Malyshev, L Prost, P A Seidl, G Westenskow, L Westerberg
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  ABSTRACT: 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_{e}/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.
  Physical Review Letters 03/2007; 98(6):064801. · 7.37 Impact Factor
• Article: Thin film getter coatings for the GSI heavy-ion synchrotron upgrade

  M.C. Bellachioma, J. Kurdal, M. Bender, H. Kollmus, A. Krämer, H. Reich-Sprenger
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  ABSTRACT: 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 3m long, and are characterised by a wall thickness of 0.3mm 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.
  Vacuum 01/2007; 82:435-439. · 1.32 Impact Factor
• Conference Proceeding: VACUUM ISSUES OF SIS18 UPGRADE AT GSI

  H. Kollmus, M.C. Bellachioma, M. Bender, J. Kurdal, H. Reich-Sprenger, A. Krämer
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  ABSTRACT: The FAIR project “Facility for Antiproton and Ion Research” at GSI is designed to deliver heavy ion beams of increased energy at highest luminosity. The gain in energy compared to the existing facility will be about a factor of 15, while the gain in intensity is planned to be in the range of up to a factor of 1,000 for primary beams and up to a factor of 10,000 for secondary beams. The existing GSI facility including the heavy ion synchrotron SIS18 will act as injector for the FAIR accelerator complex. The higher intensities compared to the present situation will be realized by a faster cycling time and, for heavy ions, lower charge state which enters quadratically into the space charge limit. However, the lower charge state, e.g. U28+, leads to an enhanced ionization cross section compared to high charge states. The design-value for SIS18 is to deliver 10^12 U28+ ions per second in a 4 Hertz operation mode. To minimize beam loss by charge exchange a dynamic vacuum (vacuum during beam operation) in the 10−12 mbar region –with a low fraction of heavy residual gas components– is required. At the moment SIS18 has a static pressure of about 10−11 mbar, but during operation local pressure rises were observed due to ion induced desorption limiting the ion beam life time. An intensive program to upgrade the vacuum system of SIS18 is in progress. Here, we will report on the three major tasks: ion induced desorption, new dipole and quadrupole chamber design and NEG coating.
  EPAC 2006, Edinburgh, Scotland; 01/2006
• Conference Proceeding: THE VACUUM SYSTEM OF FAIR ACCELERATOR FACILITY

  A. Krämer, M.C. Bellachioma, H. Kollmus, H. Reich-Sprenger, St. Wilfert
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  ABSTRACT: The FAIR accelerator complex consists of two superconducting synchrotrons (SIS100 and SIS300) with a circumference of 1083.6 m each, a high energy beam transport system (HEBT) with a total length of about 2.4 km and four storage rings (CR, RESR, HESR and NESR). Their length varies between 212 m and 574 m. For each of the subsystems different vacuum requirements have to be fulfilled. The vacuum system of SIS100 and SIS300 consists of cryogenic and bakeable room temperature sections, where a pressure in the low 10-12 mbar range is needed. For HEBT, also a combination of cryogenic and room temperature sections, a vacuum pressure of 10-9 mbar is sufficient. The storage rings will be operated in a pressure range from 10-9 mbar to 10-12 mbar, also some of them with cryogenic sections. In this paper an overview of the preliminary vacuum layout of the synchrotron rings, the storage rings and the transfer beam lines will be given.
  EPAC 2006, Edinburgh, Scotland; 01/2006
• Article: Measurements on Ion‐beam Loss Induced Desorption at GSI

  H. Kollmus, M. Bender, M. C. Bellachioma, E. Mahner, A. Krämer, L. Westerberg, E. Hedlund, O. B. Malyshev, H. Reich‐Sprenger
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  ABSTRACT: 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. © 2005 American Institute of Physics
  AIP Conference Proceedings. 06/2005; 773(1):207-210.
• Conference Proceeding: Ion Beam-Loss Induced Desorption and Consequences for Heavy Ion Synchrotrons

  H. Kollmus, M. Bender, A. Krämer, M.C. Bellachioma, E. Mahner
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  ABSTRACT: For the GSI Future Project FAIR a beam intensity of 10^12 U28+ ions per second 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 the increasing number of injected particles. This is caused by pressure rises due to ion beam-loss induced desorption: the primary beam hits, e.g., aperture limiting devices and gas is released. Along this way the number of charge exchanged particles –which gets lost after the dipole magnets– will grow and will probably trigger vacuum instabilities. During the last 2 years experiments were performed to study desorption yields under high energy ion bombardment on various materials with different surface treatments in dedicated test stands at GSI as well as at CERN. In the talk we will give an overview about resent results, consequences for the SIS18 upgrade and future perspectives, e.g., in situ ERDA measurements of the surface an bulk behavior under heavy ion irradiation.
  SHIM 2005, Aschaffenburg; 01/2005
• Conference Proceeding: R&D VACUUM ISSUES OF THE FUTURE GSI ACCELERATOR FACILITIES

  H. Reich-Sprenger, H. Kollmus, A. Krämer, M. Bender, J. Kurdal, M.C. Bellachioma, P. Spiller
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  ABSTRACT: The new GSI accelerator facilities (FAIR project) are planned to deliver heavy ion beams of increased energy and highest intensity [1]. Whereas the energy is planned to be increased roughly by a factor of 30, the ion beam intensities are planned to be enlarged by three orders of magnitude. To achieve highest beam intensities, medium charged heavy ions (e.g. U28+) are accelerated. Since the ionization cross sections for these ions are comparably high, a UHV-accelerator system with a base pressure in the low 10-12 mbar regime is required, even under the influence of ion beam loss induced desorption processes. An intensive program was started to upgrade the UHV system of the existing synchrotron SIS18 (bakeable) and to design and lay out the UHV systems of the future synchrotrons SIS100 and SIS300 (mainly cryogenic). One special technical difficulty common to SIS18 and SIS100 is the restriction on thin walled (<0.5mm), large aperture vacuum chambers, which have to withstand 300°C bakeouts or liquid helium temperatures inside the fast cycling magnets (minimum eddy – currents). The strategy of this program includes basic research on the physics of the ion induced desorption effects as well as technical developments, design and prototyping on bakeable UHV components (vacuum chambers, diagnostics, bakeout-control, pumping speed), collimator for controlled ion beam loss, NEG coating and cryogenic vacuum components.
  EPAC 2004, Lucerne, Switzerland; 01/2004
• Article: Heavy ion-induced desorption investigations using UHV-ERDA

  H. Kollmus, M. Bender, W. Assmann, A. Krämer, M.C. Bellachioma, H. Reich-Sprenger
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  ABSTRACT: 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.
  Vacuum. 82(4):402-407.
• Article: Ar ion induced desorption yields at the energies 5–17.7MeV/u

  E. Hedlund, L. Westerberg, O.B. Malyshev, E. Edqvist, M. Leandersson, H. Kollmus, M.C. Bellachioma, M. Bender, A. Krämer, H. Reich-Sprenger, B. Zajec, A. Krasnov
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  ABSTRACT: 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.
  Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 599(1):1-8. · 1.21 Impact Factor