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Agilent Technologies — Technical Presentation (December 2015)
28 slides from Agilent Technologies's technical presentation, Dec 16, 2015
Slide 1: ION Pumps for UHV Systems, Synchrotrons & Particle Accelerators
ION Pumps for UHV Systems, Synchrotrons & Particle Accelerators Mauro Audi, Academic, Government & Research Marketing Manager
Slide 2: ION Pumps
ION Pumps Agilent Technologies 1957-59 Varian Associates invents the first ION Pump Agilent Confidential December 16, 2015 2
Slide 3: ION Pumps: Main choice for UHV systems
ION Pumps Main choice for UHV systems, synchrotron & particle accelerators Why? 1.Closed pump Do not need any baking pump No contamination from the roughing line 2.No moving parts There is no rotation or moving parts 3.No lubricant There are no oil or solvents and is fully contamination free 4.Can w
Slide 4: Basic Pumping Mechanism
ION Pumps Basic Pumping Mechanism Pumping principle: • Plasma discharge in crossed electric and magnetic field act as an electron trap • Ionizing collision between electron and gas • Ion bombardment of titanium cathode • Some ions diffuse into the cathode ( pumped ) • Sputtering of chemically active
Slide 5: Basic Pumping Mechanism – Noble gases
ION Pumps Basic Pumping Mechanism – Noble gases • This works only for all active (getterable) gases • Noble gases do not react with Ti film • No chemisorption of neutral molecules • Some ion bombarding the cathode are neutralized and reflected • Some of them maintain enough energy to be physically i
Slide 6: Diode Ion Pump
ION Pumps Diode Ion Pump Highest pumping speed for all getterable gases (H2, CO, CO2, N2, H2O) Highest pumping speed at low pressures Limited speed (5 to 10%) and low capacity when pumping noble gases such as Argon, Helium The only reason for different and more expensive ion pumps is to improve pump
Slide 7: Diode
ION Pumps Diode In UHV application, where: • Ion pumps are started below 1E-6 mbar • The system is rarely vented to air • There are no air leaks • The ion pump is used to pump the outgassing of the vacuum chamber • The Pressure is lower than 1E -8 mbar Diode pumps can work for 20 years before Argon
Slide 8: Different types of pump: Diode, Noble Diode and StarCell
ION Pumps Different types of pump: Diode, Noble Diode and StarCell However, in real life… • Air leaks may be present • Venting to air may be more frequent than desired • Working pressure may be higher than design values …then more Argon than expected has to be pumped ION Pumps with improved stabilit
Slide 9: Noble Diode & StarCell vs Diode design
ION Pumps Different Noble Diode & StarCell vs Diode Ion Pumps for Noble Gases design Improve the number/probability of Noble Gas ions reflection vs implantation after bombarding the catodo After being reflected, they may be physically buried into the anode (no chemical interaction) Two different app
Slide 10: Noble Diode & StarCell vs Diode
ION Pumps Noble Diode & StarCell vs Diode Noble Diode vs Diode • Much lower capacity and speed for H2 • Lower speed for all getterable gases (N2, CO, CO2) • Improved stability and speed for Noble Gases (factor up to 10 - 20 times) • Argon speed up to 15% 20% of Air Pumping speed Starcell vs Diode •
Slide 11: StarCell vs Noble Diode
ION Pumps StarCell vs Noble Diode • Much higher capacity for H2 (one order of magnitude) • Similar speed for all getterable gases (N2, CO, CO2) • Higher stability for Noble Gases (factor of 5 to 10 times) • Higher speed for Noble Gases (almost double , up to 40 % vs 20% of Air) • When Noble gases mu
Slide 12: How to choose the correct ion pump
ION Pumps How to choose the correct ion pump Essential parameters of a UHV system 1.Operation mode 3.Size of the chamber • Venting frequency • Surface exposed to vacuum • Starting pressure (roughing pumps) • Outgassing 2.Gases • Conductance • Noble Gases (He, Ar, Kr, Xe...) 4.Base Pressure • Gettera
Slide 13: Agilent Ion Pumps elements comparison table 1/2
ION Pumps Agilent Ion Pumps elements comparison table 1/2 Agilent Confidential December 16, 2015 13
Slide 14: Agilent Ion Pumps elements comparison table 2/2
ION Pumps Agilent Ion Pumps elements comparison table 2/2 Agilent Confidential December 16, 2015 14
Slide 15: Specific design for Large UHV Systems, Synchrotron & Particle Accelerator
ION Pumps Specific design for Large UHV Systems, Synchrotron & Particle Accelerator Pumping speed is not the most important parameter to reach UHV • outgassing • contamination • vacuum leaks (corrosion) …may be more critical than pumping speed for large UHV systems, i.e. Synchrotron CERN Geneva Swit
Slide 16: Specific design for Synchrotron & Particle Accelerator
ION Pumps Specific design for Synchrotron & Particle Accelerator Pump designed to minimize outgassing/contamination 1.Material choice 2.Material cleaning 3.Pump process HV feedthrough and HV cable designed radiation and corrosion proof to avoid potential problems (leaks) Agilent Confidential Decembe
Slide 17: Material choice and cleaning
ION Pumps Specific design for Synchrotron & Particle Accelerator Material choice Material Cleaning • Only UHV compatible materials: Metals and • Degreasing in Alkaline bath (NaOH-Na2CO3) Ceramic • Ultrasonic degreasing in Alkaline bath • Body, Flange, Anode : Stainless Steel 304 or 316, L or LN • Co
Slide 18: Manufacturing
ION Pumps Manufacturing • The ion pump element must be the cleanest surface exposed to vacuum , because its outgassing is due to both thermal and bombardment induced effect • The surface will eventually be removed (sputtered): not only the surface , but the bulk too must be hydrogen free • Ion pump
Slide 19: Manufacturing
ION Pumps Manufacturing • Pumps are individually processed • Residual gas analysis for each pump • Individual records of each pump ( outgassing , spectra…) • Pumps are processed in nitrogen atmosphere to prevent external oxidation (no more beadblasting needed) • Pumps can be leak-checked at high tem
Slide 20: Manufacturing - RGA
ION Pumps Manufacturing - RGA Agilent Confidential December 16, 2015 20
Slide 21: Corrosion free
ION Pumps Corrosion free • Corrosion free feedthrough • HV feedthrough and connector are subjected to corrosion • Transition metal to Kovar (or similar) to ceramic is critical • Temperature cycling , humidity , high electric field gradient may cause corrosion Vacuum Side Brazing for Corrosion Free •
Slide 22: Safety Interlock
ION Pumps Safety Interlock From passive to active safety Passive Safety • The control unit and HV cable connector must be intrinsically safe Safety Interlock Contacts • No live parts can be touched Active Safety • Interlock on HV connection to ensure that HV is switched off whenever the HV cable is
Slide 23: Controller Design to Optimize Pump Performances
ION Pumps Controller Design to Optimize Pump Performances in the Entire Operating Pressure Range Summary • Little efforts dedicated in the recent past to IP controller developments • Properly Designed Ion Pump controller maximizes IP performances in the entire operating range • Variable voltage maxi
Slide 24: Variable Voltage Optimizes Ion Pump Pumping Speed
Variable Voltage Optimizes Ion Pump Pumping Speed Pumping Speed vs. Applied Voltage Ion bombarding energy of approx 3 keV ensure efficient sputtering Space charge effect reduces ion energy • Space charge effect is a function of pressure • At «0» pressure ion energy equals applied voltage • Marginal
Slide 25: Variable Voltage Optimizes Ion Pump Pumping Speed
Variable Voltage Optimizes Ion Pump Pumping Speed Pumping Speed vs. Applied Voltage Agilent Confidential December 16, 2015 25
Slide 26: Pressure measurement
ION Pumps Pressure measurement • An Ion Pump is a Penning cell, Ion Current Proportional to Pressure • IP Parameters (V , B , cell dimensions) optimized for pumping, not for pressure reading • Current reading may be affected by Field Emission Current (independent of pressure) • Total current (Ion +
Slide 27: Field Emission (leakage) current effect
ION Pumps Field Emission (leakage) current effect Agilent Confidential December 16, 2015 27
Slide 28: Field Emission (leakage) current effect
ION Pumps Field Emission (leakage) current effect Agilent Confidential December 16, 2015 28
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