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- Hedlund, E., et al.
(author)
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A new test stand for heavy ion induced gas desorption measurements at TSL
- 2008
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 586:3, s. 377-381
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Journal article (peer-reviewed)abstract
- 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 occurs due to the collisions of beam ions and residual gas molecules leading to the change of charge of the ions and their loss on the vacuum chamber walls, which in turn cause ion-induced gas desorption and further pressure increase. To gain a deeper understanding of the ion-induced desorption process in the energy range 5-45 MeV/u, a dedicated test stand was built at the end of the K beamline at The Svedberg Laboratory (TSL) in Uppsala, Sweden. The energy range was chosen due to the fact that the injection energy of the heavy ion synchrotron SIS18 at GSI will be 10 MeV/u, and that there are insufficient data in this energy range. A Test Particle Monte-Carlo model of the experimental set-up was build-up, run and analysed for different sample configurations. An important result is that for the same sample material the desorption yield from a flat sample causes a 1.58 times larger pressure increase than that of a tubular sample. A detailed explanation of the set-up is presented.
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- Hedlund, E., et al.
(author)
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Ar ion induced desorption yields at the energies 5-17.7 MeV/u
- 2009
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 599:1, s. 1-8
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Journal article (peer-reviewed)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, n, (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 Lip 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 Lip 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.
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- Hedlund, E., et al.
(author)
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Heavy-ion induced desorption of a TiZrV coated vacuum chamber bombarded with 5 MeV/u Ar8+ beam at grazing incidence
- 2009
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 27:1, s. 139-144
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Journal article (peer-reviewed)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 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 2600 molecules/ion. The desorption yields after saturation for CH4, H-2, and CO2 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.
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- Kollmus, H., et al.
(author)
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Energy scaling of the ion-induced desorption yield for perpendicular collisions of Ar and U with stainless steel in the energy range of 5 and 100 MeV/u
- 2009
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 27:2, s. 245-247
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Journal article (peer-reviewed)abstract
- For the GSI future project Facility for Antiproton and Ion Research a beam intensity of 10(12)U(28+)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 10 MeV/u and U28+ ions are accelerated to 200 MeV/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 17.7 MeV/u were measured at the Cyclotron of The Svedberg Laboratory in Uppsala. High energy yields at 40, 80, and 100 MeV/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)(el)(n), with n between 2 and 3, decreasing for increasing impact energy above the Bragg maximum.
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- Malyshev, O. B., et al.
(author)
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Ar beam induced desorption from different materials at TSL
- 2010
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In: Vacuum. - : Elsevier BV. - 0042-207X .- 1879-2715. ; 85:2, s. 338-343
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Journal article (peer-reviewed)abstract
- 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 Laboratory in Uppsala (Sweden). These results are important for the update and design of the FAIR facility at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt (Germany) where the required increase in beam intensity is limited by ion induced pressure instability. It was shown that lowest desorption yields can be achieved with gold coatings, whereas grazing incident loss increases the desorption yield by roughly an order of magnitude compared to perpendicular loss. The desorption yield of saturated NEG samples was measured to be higher compared to any non pumping samples. The desorption yield of copper can be lower and higher compared to stainless steel depending on cleaning procedure and sample history. Additionally the secondary electron and ion yield was measured to be a few tens of electrons and ions emitted per projectile impact in backward direction. Their influence on the desorption yield due to secondary effects was less than 5% compared to the primary desorption by the high energetic projectile. (C) 2010 Elsevier Ltd. All rights reserved.
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- Agar, Cetin, et al.
(author)
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beta(2)-Glycoprotein I can exist in 2 conformations: implications for our understanding of the antiphospholipid syndrome
- 2010
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 116:8, s. 1336-1343
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Journal article (peer-reviewed)abstract
- The antiphospholipid syndrome is defined by the presence of antiphospholipid antibodies in blood of patients with thrombosis or fetal loss. There is ample evidence that beta(2)-glycoprotein I (beta(2)GPI) is the major antigen for antiphospholipid antibodies. The autoantibodies recognize beta(2)GPI when bound to anionic surfaces and not in solution. We showed that beta(2)GPI can exist in at least 2 different conformations: a circular plasma conformation and an "activated" open conformation. We also showed that the closed, circular conformation is maintained by interaction between the first and fifth domain of beta(2)GPI. By changing pH and salt concentration, we were able to convert the conformation of beta(2)GPI from the closed to the open conformation and back. In the activated open conformation, a cryptic epitope in the first domain becomes exposed that enables patient antibodies to bind and form an antibody-beta(2)GPI complex. We also demonstrate that the open conformation of beta(2)GPI prolonged the activated partial thromboplastin time when added to normal plasma, whereas the activated partial thromboplastin time is further prolonged by addition of anti-beta(2)GPI antibodies. The conformational change of beta(2)GPI, and the influence of the autoantibodies may have important consequences for our understanding of the antiphospholipid syndrome. (Blood. 2010; 116(8): 1336-1343)
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- Han, Soo Min, et al.
(author)
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Maternal and Infant Factors Influencing Human Milk Oligosaccharide Composition : Beyond Maternal Genetics
- 2021
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In: Journal of Nutrition. - : Elsevier. - 0022-3166 .- 1541-6100. ; 151:6, s. 1383-1393
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Research review (peer-reviewed)abstract
- Maternal genetics is a key determinant of human milk oligosaccharide (HMO) composition in human milk. Beyond genetic status, other factors influencing the HMO profile are poorly defined. Thus, we aimed to review the existing evidence on the associations between nongenetic maternal and infant factors and HMO composition. A systematic search was performed on PubMed and Web of Science (without a time restriction) to identify any relevant studies published. In total, 1056 results were obtained, of which 29 articles were selected to be included in this review. The range of factors investigated include lactation stage, maternal pre-pregnancy BMI (ppBMI), maternal age, parity, maternal diet, mode of delivery, infant gestational age, and infant sex. The data suggest that, beyond maternal genetics, HMO composition seems to be influenced by all these factors, but the underlining mechanisms remain speculative. The published evidence is discussed in this review, along with potential implications for infant growth and development. For example, 2'-fucosyllactose, which was reportedly increased in mothers with higher ppBMIs, was also associated with increased infant weight and height. In addition, greater levels of sialylated HMOs after preterm birth may support brain development in these infants.
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- Sprenger, HG, et al.
(author)
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Cellular pyrimidine imbalance triggers mitochondrial DNA-dependent innate immunity
- 2021
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In: Nature metabolism. - : Springer Science and Business Media LLC. - 2522-5812. ; 3:5, s. 636-
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Journal article (peer-reviewed)abstract
- Cytosolic mitochondrial DNA (mtDNA) elicits a type I interferon response, but signals triggering the release of mtDNA from mitochondria remain enigmatic. Here, we show that mtDNA-dependent immune signalling via the cyclic GMP–AMP synthase‒stimulator of interferon genes‒TANK-binding kinase 1 (cGAS–STING–TBK1) pathway is under metabolic control and is induced by cellular pyrimidine deficiency. The mitochondrial protease YME1L preserves pyrimidine pools by supporting de novo nucleotide synthesis and by proteolysis of the pyrimidine nucleotide carrier SLC25A33. Deficiency of YME1L causes inflammation in mouse retinas and in cultured cells. It drives the release of mtDNA and a cGAS–STING–TBK1-dependent inflammatory response, which requires SLC25A33 and is suppressed upon replenishment of cellular pyrimidine pools. Overexpression of SLC25A33 is sufficient to induce immune signalling by mtDNA. Similarly, depletion of cytosolic nucleotides upon inhibition of de novo pyrimidine synthesis triggers mtDNA-dependent immune responses in wild-type cells. Our results thus identify mtDNA release and innate immune signalling as a metabolic response to cellular pyrimidine deficiencies.
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