SAES Project: Combination of NEG module and sputter ion pump S.Meunier TE-VSC

Objectives To compare base pressure between a combination of NEG module and ion pump and only for ion pump, for a bake out vacuum system Compare base pressure for different bake-out duration for these two configurations Compare base pressure for a combination of NEG module and different ion pump (different pumping speed of ion pump) S.Meunier TE-VSC

SAES NEG Module CapaciTorr-D 2000 MK5 Alloy type: St 172 Getter Alloy Mass : 225g Getter Surface : 1900 cm² Pumping speed (l/s): 2000 l/s (H2) and 1000 l/s (CO) S.Meunier TE-VSC

NEG Module Cartridge: The Capacitor cartridges are configured in the form of sintered porous disks of St172. These sintered porous bodies are arranged in the cartridge structure in a way to optimize speed and capacity performances. Pump Body: The optional pump body is a simple double flanged nipple Heater: The heater of the D 2000 consists of a tantalum wire spiral wound on an alumina element supported by a stainless steel rod. This heater is part of the pump cartridge structure. Thermocouple: The thermocouple is a K type electrically insulated within an alumina tube. It is assembled on the support flange and connected to the electrical connector with compensated contact terminations. S.Meunier TE-VSC

Ion pump Ion pumps selected for this project: StarCell 400l/s and StarCell 200l/s StarCell 75 l/s and StarCell 40 l/s S.Meunier TE-VSC

Project description Systematic evaluation of NEG module and ion pump combinations: ultimate vacuum pressure and test for shorter bake out duration. Task list: Construction of a dedicated vacuum system Pumping speed measurement of each ion pump Pumping speed measurement of the NEG module Calibration of the system and base pressure Influence of baking time at 150°C for 5 different values of pumping speed with and whithout NEG module S.Meunier TE-VSC

NEG Module Pumping speed measurement Pumping speed measurement of the NEG module with a Fischer-Mommsen dome : Injection of H2 and CO gas SNEG (l/s) = C (l/s) (αΔP1/ΔP2 -1) – S turbo(l/s) With the conductance C : C= 34.4 l/s for H2 and C= 9.19 l/s for CO With the calibration SVT1/SVT2, α = 0.85 for H2 and α = 1 for CO ΔP = P - P initiale P= P x SN2/SH2 pour H2 et P= P x S N2 /S CO Sensibility S N2 S H2 S CO SVT1 43 16.35 36.64 SVT2 34 16.42 28.97 S.Meunier TE-VSC

NEG Module Pumping speed measurement S (l/s) for H2 S (l/s) for CO NEG activation 45min at 450°C 1990 l/s 936 l/s 24 h at 450°C 2201 l/s 1530 l/s SAES data: 2000 l/s (H2) and 1000 l/s (CO) for 45min at 450°C activation S.Meunier TE-VSC

Vacuum test stand S.Meunier TE-VSC

Vacuum test stand S.Meunier TE-VSC

Influence of the bake out duration 24 hours,12 hours, 6 hours and 3 hours Bake out température : 250°C for stainless steel vacuum chambers 250°C gate valve DN150CF 250°C NEG module 300°C ion pump 350°C VGI gauges and residual gas analyser 140°C injection valve 200°C valve on the turbo pump Ion pump: 400 l/s S.Meunier TE-VSC

Test procedure(1) Venting of the system 15 hours (except NEG module which stay under vacuum) Pumping of the system+ leak detection+ open gate valve to pump NEG module Start bake out (300°C) At the end of the maximum temperature level, reduction of the temperature at 180°C for gas analyser and B.A.G gauges and 150°C for the rest of the vacuum system Flash of the ion pump Degasing of the B.A.G gauges 45 min at 50 mA Degasing of the R.G.A 45 min at 20 mA S.Meunier TE-VSC

Test procedure (2) At the end of the degasing, activation of the NEG module 45 min at 450°C Degasing 5 min and start gauges and gas analyser Start ion pump Close valve on the turbo pump and injection valve Stop bake-out 24 hours after the bake out stop, note pressure of the two BAG gauges and save a scan Close the gate valve, wait 30 min and note the pressures and save a scan. S.Meunier TE-VSC

Results of the base pressure without NEG module Base pressure with 400 l/s ion pump Bake out duration hours P1 (torr) P2(torr) 24 h at 300°C 1,5. 10-10 1,6. 10-10 12 h at 300°C 1,4. 10-10 6 h at 300°C 1,5.10-10 3 h at 300°C 1,6.10-10 S.Meunier TE-VSC

Results of the base pressure with NEG module activated Base pressure with combination of NEG module and 400l/s ion pump Bake out duration hours P1 (torr) P2 (torr) 24 h at 300°C 0,8. 10-11 1,0. 10-11 12 h at 300°C 0,4. 10-11 6 h at 300°C 1,1.10-11 3 h at 300°C 1,1. 10-11 S.Meunier TE-VSC

Mass scan after bake-out S.Meunier TE-VSC

Influence of the bake-out temperature Bake out duration: 6 hours Bake out température : 150°C for stainless steel vacuum chambers 140°C gate valve DN150CF 150°C NEG module 150°C ion pump 350°C VGI gauges and residual gas analyser 140°C injection valve 150°C valve on the turbo pump Ion pump: 400 l/s The same procedure as before was applied. we only reduced the temperature of the bake-out to 150°C except for the gauges and gas analyser S.Meunier TE-VSC

Influence of the bake-out temperature P1 (torr) with NEG activated P2 (torr) without NEG 300°C 6 hours 1,1.10-11 1,0. 10-11 1,5.10-10 150°C 3,1. 10-11 1,4. 10-11 2,0.10-10 S.Meunier TE-VSC

First conclusions 1.We have the same pressure for all the different bake-out duration: P= 1,5. 10-10 torr only with ion pump (gate valve closed) P= 1,5. 10-11 torr with NEG module and ion pump 2. We have the same base pressure at 150°C and 300°C for a 6 hours bake-out duration with and without NEG module 3. We have the same base pressure for a 24 hours bake-out duration at 300°C and for a 6 hours bake-out at 150°C with and without NEG module. It is possible to reduce duration and temperature of bake-out to achieve the same base pressure. S.Meunier TE-VSC

Influence of other parameters Bake out 150°C, 6 hours P1 (torr) with NEG activated P2 (torr) without NEG NEG under vacuum during air venting, TLabo=28°C 3,1.10-11 1,4. 10-11 2,0.10-10 1,5.10-10 NEG air venting 3,5.10-11 1,6. 10-11 1,2.10-10 NEG under vacuum during air venting, T Labo =20°C 3,6.10-11 1,5. 10-11 1,1.10-10 NEG activated during all the bake-out duration (6 hours) 4,9.10-11 2,5. 10-11 1,7.10-10 S.Meunier TE-VSC

Modulation of the gauges Modulation of the two Bayard-Alpert gauges SVT1 and SVT2 Pressure before modulation: P1= 2,1.10-11 torr P2= 1,1.10-11 torr After 20 minutes of modulation: For SVT1: Pres= 1,1.10-11 torr (high value!) For SVT2 : Pres= 3,2.10-12 torr S.Meunier TE-VSC

Modulation of the gauges Problem with SVT1: leakage current S.Meunier TE-VSC

Outgasing rate of the vacuum system 1.When the gate valve is closed (only ion pump) P= 1,5. 10-10 torr Q= P.S= (1,5. 10-10 x 100)/0,45=3,3. 10-8 torr.l/s (pour H2) 2. When the gate is opened (NEG + ion pump)) P= 1,5. 10-11 torr Q= P.S= (1,5. 10-11 x 2000)/0,45=6,4. 10-8 torr.l/s (pour H2) Conclusion: The base pressure of this vacuum system is limited by the outgasing of the gate valve. S.Meunier TE-VSC

Base pressure measurement Remove the gate valve. Bake-out at 300°C for 24 hours with the same procedure as before. Measure 24 hours after bake-out stop: P1= no value or 7. 10-12 torr (without modulation factor) P2= 3. 10-12 torr (P2= 1.5 10-11 torr with the gate valve) S.Meunier TE-VSC

Mass scan for base pressure S.Meunier TE-VSC

Next steps Precise measurement of the pressure of the two gauges for the base pressure. Calibration of the two gauges and gas analyser using the gas injection line. Change the 400 l/s for the other smaller ion pumps and compare the measurements. Continue pumping speed measurement on the Fischer Mommsen dome for the different ion pumps S.Meunier TE-VSC

Thank you for your attention S.Meunier TE-VSC