GSI vacuum group Who we are: 5 physicists (Bellachioma, Kollmus, Krämer, Reich-Sprenger, Wilfert) 7 engineers (Bender, Bevcic, Kaminski, Kurdal, Schäfer, Welzel, Wolff) 23 technicans (Emmerich, de Cavaco, Gaj, Gustafson, Hammann, Herge, Heyl, Horn, Jagsch, Kischnik, Kolligs, Kredel, Leiser, Lück, Mühle, Müller, Norcia, Quador, Savino, Sigmund, Stagno, Thurau, Volz) Responsible for: operation and service of all GSI accelerator vacuum systems, R&D on vacuum physics and techniques, Design & Layout of new accelerator vacuum systems, Installation & reconstruction of accelerator structures and experimental setups H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Overview The existing GSI facility and its Future extension SIS18 UHV Status / Upgrade Ion Induced Desorption H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

The GSI Future Accelerator Facility for Beams of Ions and Antiprotons (FAIR) From protons to uranium In future also antiprotons 1 MeV/u to 2 GeV/u In future up to 30 GeV/u 109 to 1011 particles/cycle In future 1012 particles/cycle 0.1 Hz to 1 Hz Repetition rate In future up to 3 Hz 100m Acceleration II III Nuclear and Hadron Physics Nuclear Chemistry Atomic Physics Material Science Plasma Physics Biophysics, Medical I Experiments H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

The GSI Future Accelerator Facility for Beams of Ions and Antiprotons H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

GSI International Accelerator Facility UHV system requirements Due to ion beam lifetime requirements (e.g.: U28+ in SIS18): SIS18: bakeable p≈5·10-12 mbar ESR: bakeable p≈5·10-12 mbar SIS100: cold arcs T=7-20K bakeable straight sections T=300K p≈5·10-12 mbar SIS300: cold arcs T=4.2K NESR: p≈5·10-12 mbar HESR: p≤10-10 mbar RESR: p≤10-10 mbar CR: p≤10-9 mbar HEBL: length 2.5 km, 70% cold *all pressures: N2 equivalent SIS100/300 from SIS18 HESR CR RESR NESR H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

The heavy ion synchrotron SIS 18 present status 12 sectors each: 18 m long  200 mm 4 TSP 3 Ion pumps (triode type) 1-2 extractor gauge 2 single cryopumped collimators 7 vacuum sectors One pumping station with turbo molecular pump (rough pumping + bake-out) 1 RGA H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

High Ion Beam Intensity Operation of Medium Charged Heavy Ions  influence of intensity on lifetime 8.75 MeV/u U28+ Desorption processes degenerate the residual gas pressure ( U28+ case ) Initiated by : Systematic beam losses on acceptance limiting devices (septa) ( 8MeV/u < E <100MeV/u ) Stripped beam ions ( 8MeV/u < E <100MeV/u ) Ionized and accelerated residual gas ( E < keV) : minor effect at “zero ion beam current”: lifetime could be increased up to 6s (first steps of UHV upgrade in 2003) beam losses increase with number of injected ions presently the maximum accelerated U28+ ion beam intensity is limited by dynamic UHV conditions H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

SIS18 residual gas composition (10/2003) RGA spectra examples  existing "micro-leaks"and contaminations Ar CxHy S03 total pressure: 3*10-12 mbar S08 total pressure: 6.8*10-11 mbar H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Requirements + Strategy for SIS18 UHV-Upgrade Beam lifetime has to be significantly larger than cycling time of the SIS18 (Lifetime of at least 10 seconds for all kinds of operation) Total pressure lower 1∙10-11 mbar with a small fraction of high Z gases even for highest beam intensities optimized static conditions: minimized outgassing rate by material and production control, cleaning, bakeout, quality control  established, removal of contaminations or "micro-leaks"  measurements during shutdowns on TSP + SIP efficient and distributed pumping  NEG coating. optimized dynamic conditions: efficient ion beam loss control, low desorption at localized ion beam losses  Desorption / ERDA Experiments, maximized local pumping speed at locations of ion beam loss  collimation Desorption / ERDA. H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Beam Lifetime measurements 132Xe18+ (March 2005) SIS /ESR ("zero" beam intensity) @ 7,6 MeV/u @ 15 MeV/u @ 30 MeV/u @ 50 MeV/u SIS ~ 3 sec ~ 4,5 sec ~ 6 sec ESR ~50 sec ~66 sec Main Differences of SIS18 and ESR UHV system: Argon partial pressure concentration: ESR < 1%, SIS > 2 % bakeout ability: ESR >200°C, SIS18 ~ 180°C ESR 6.3.2005 H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Program for Optimized Static Conditions: 2005 2006 2007 2008 Detection and removal of micro-leaks or contaminations ( Ar !) Rebuilt of one SIS Vacuum sector to optimized distributed pumping speed :  2 NEG coated Dipole chambers, 1 NEG coated prototype Quadrupole chamber Replacement of all 24 dipole chambers ( bakeout to 300°C, coating?) [existing new spare chambers] Replacement of all 12 quadrupole chambers ( bakeout to 300°C, coating?) [prototype and new chambers to be designed and built] Ion Pumps (TSP, SIP): optimized IP operation, if necessary: replacement by noble diodes, optimized sublimation cycles ( improved pumping speed) H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Static Pressure Improvements by NEG coating Remarks: calculation fitted to measured Ptot and RGA locations in S03 H2 and CO pumping speed (H2:0.05 ls-1cm-2; CO: 0.1 ls-1cm-2) for NEG coated chambers underastimated (has to be reduced by factor of 10 for H2 and by a factor of 50 for CO in VakTrac simulation due to calculation errors), Total pressure will be dominated by CH4 after NEG coating  minimzing the number of installed SIPs, changing SIP type?, H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Ion Beam Loss Induced Desorption: U28+ ion beam operation of SIS18(up to 1010 injected ions) SIS Extraction SIS Injection Observations: beam loss + pressure rises at all SIS sectors, pressure rises in TK9, Scraper H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Desorption Processes in SIS18 vacuum chamber wall S: pumping speed/therm. desorption X septum or collimator X hloss X X UZ+ UZ+ UZ+ q e sX sloss X F50 Volt space charge potential X X X Xq+ UZ+q hX hloss beam loss induced desorption ion induced desorption desorption yield h: H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Experimental Setup for Ion Beam Induced Desorption Yield Measurements Experiments by: M. Bender (GSI) H. Kollmus (GSI) A. Krämer (GSI) E. Mahner (CERN) H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Partial Pressure Increase due to Ion Beam Induced Desorption 1.4MeV/u 1.8-3.1·109 Pb27+  stainless steel 304 The measured ion current was corrected for the ionization probabilities of the different gases: H2: x2.3 CO: x0.95 CO2: x0.71 CH4: x0.625  Desorption dominated by H2 (87%) and CO (11%) H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Total Pressure Increase due to Ion Beam Induced Desorption 1.4MeV/u 1.8-3.1·109 (1.9-3.3mA, 4ms) Pb27+  stainless steel 304 H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Optimized Dynamic Conditions efficient ion beam loss control, low desorption at localized ion beam losses ( Desorption / ERDA Experiments), maximized local pumping speed at locations of ion beam loss ( collimation Desorption / ERDA). 1011 (10% lost ions) x 104 (desorption yield) -> 1015 desorbed gas atoms inside a volume of 1 cm3: ca. 4* 10-2 mbar inside a volume of 4* 106 cm3: 1* 10-8 mbar (SISVolumen) equivalent gasload l/s : ca. 4* 10-5 mbar l /s  factor of 100 more than the total wall degassing for P = 10-12 mbar : Seff = 4 * 107 l/s for distributed pumping: Seff = 4 * 107 l/s / 240m = Seff = 1.6 * 105 l/sm NEG: pumping speed for reactive gas species (CO, H2,..) : max 10 l/s cm2  107 l/s for a complete NEG coating of all SIS UHV surfaces and optimum activation P = 10-12 mbar possible if: optimized pumping speed is installed (pumping time ~ 2ms) and ion loss is homogeniously distributed along the ring for localised losses NEG coating can not deliver the neccesary pumping speed, differential pumping has to be applied (anti-chamber) H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)

Optimized Dynamic Conditions: collimators at locations of known ion beam loss: injection section / septum extraction / septum with integrated high pumping speed: 2 cryopumps NEG coated anti-chambers? low desorption materials: experiments at test bench with ion beam distributed pumping speed: NEG ? May/June 2003 March 2004 2006 ? since April 2003 final decision depends on desorption experiment results H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005)