Advanced Vacuum System Design for Proton Source and LEBT: Equipment and Technologies

1. Vacuum issues concerning the Proton Source and LEBTSalvo Marletta, Luigi Celona, Lorenzo Neri, Franco Chines, David Mascali.

2. Nomenclature TMP for Turbomolecular Pump PP for Primary Pump Full Range for vacuum gauge Pir For for ForelinePirani gauge FV for TMP foreline section GDV for Gas Dosing Valve (i.e. the inlet valve for support gas used for space charge compensation) GV for Gate Valve, i.e. line gate valve RGA for Residual Gas Analyis MFC for Mass Flow Controller

3. Present design of P.S. and LEBT: pumps, gauges and residual gas analyzer Expected Operative Pressures BEAM OFF – Static Vacuum P.S. range 10E-6 mbar LEBTrange 10E-7 mbar BEAM OFF – Gas IN P.S. range 10E-3 mbar LEBT range 10E-5 mbar Low Energy Beam Transport Line Proton Source 2100 mm 400 mm RFQ (Diaphragm Φ = 6-8 mm; Depth = 10mm

4. General Vacuum layout

5. Presentdesign of P.S. and LEBT: pumps, gauges and residual gas analyzer RGA • Positioning of: • n.2 Primary Pumps • n. 2 TMP • n. 2 Full Range gauges • n.2 Pirani • n.1 RGA (res. gas analyser) Full Range 1 Full Range 2

6. Present design of P.S. and LEBT: Pumps characteristics 1 Drag Turbomolecular pump LNS proposal • PFEIFFER Hi Pace TURBO PUMP: • BENEFITS • Ceramic ball bearing on the fore-vacuum side and a permanent magnetic radial bearing on the high vacuum side. • Bearing technology does not require electromagnets: long service life with 4 years maintenance. The ballbearing and theoperatingfluid reservoir can be replaced on site within less than 30 minutes. • High Compression ratio and high gas throughput at full rotational speed for H2. • Rotation speed variable 60-100%. • Mounting in any orientation.

7. Present design of P.S. and LEBT: Pumps characteristics 2 Primary Pump LNS proposal • PRIMARY PUMP ACP 28 : • BENEFITS • Designed for dust-free and non corrosive gases. Equipped with a gas ballast device to improve pumping of light gases and avoid condensation of vapours. • Air cooling: no water supply required • Frequency converter: hour meter, remote operation mode (RS-485, dry contacts, Profibus on request), multiple rotational speed selection (power saving, noise reduction, adaptation to application cycle) • No particle contamination, thanks to frictionless design: no wearing parts in the pumped gases path • Constant performances (Pumping speed, max. and ultimate pressure)

8. Present design of P.S. and LEBT: Full range gauges Full Ranges LNS proposal • 974 QuadMag™ ColdCathode/MicroPirani™/PiezoVacuumTransducer
(1x10-8 to 1500 Torr) • BENEFITS • The 974 QuadMag™ vacuum transducer combines cold cathode inverted magnetron, MicroPirani™ and Piezo differential vacuum sensor technologies. • User serviceable to decrease downtime • Both analog and digital communication • Optional local display

9. Present design of P.S. and LEBT: Pirani gauge Pirani LNS proposal • 910 DualTrans™ MicroPirani™/Absolute PiezoVacuumTransducer
(1.0x10-5 to 1500 Torr) • BENEFITS • 2 sensors in one ultra-compact unit saves space • Wide measurement range • Gas independent above 10 Torr • Optional 3 setpointswith fast response time for reliable process control

10. Present design of P.S. and LEBT: Residual Gas Analyzer During Vacuum test (especially in the start-up phase) the use of a mass spectrometer is very useful for the analysis of partial pressures due to the different gases in the source/line. RGA

11. Present design of P.S. and LEBT: Vacuum equipments GDV-3 Gate Valve 1 GDV-2 GDV-1 Gate Valve 2 • Positioning of: • n.2 Gate Valves for line sectioning • n. 3 GDV for gas supply (space charge compensation) • N. 1 Mass Flow Controller (for H2 supply) MFC

12. Present design of P.S. and LEBT: Gas Dosing Valves For proton beams featuring I>50 mA space charge effects cannot be neglected: reciprocal coulombian repulsion affects the beam quality (emittance) with a poor coupling to RFQ. Compensation of the positive proton space charge is possible through additional supply of gases (e.g. Ar) in the LEBT: gas ionisation provides compensating electrons to the beam, thus mitigating the emittance growth. Additional gas injection must be ensured along the LEBT in three different points, using suitable Gas Dosing Valves as UDV140-Thermomechanical Gas Dosing Valve

13. Present design of P.S. and LEBT: Mass Flow Controller MFC: for gas input (H2) in the proton source LNS proposal • GE50A General Purpose Multi-gas, Multi-range Elastomer-sealed Mass Flow Controller • BENEFITS • fast and repeatable response to setpoint throughout the device control range. • Typical response times are on the order of 500 milliseconds. • 1% of setpoint accuracy on the calibration gas. • thermal sensor design for exceptional zero stability • Embedded user interface - easily change device range & user gas, monitor & measure performance

14. Performance (in terms of expected leak rate & outgassing) BEAM OFF Due to copper sealing, expected leak rate is in the range of 10-9 mbar l/s The manufacturing of the LEBT items (in terms of polishing, specifics of metals employed, workshop manufacturing, etc.) will minimize background outgassing with respect to the H2 gas load during machine’s operations. BEAM ON However, during operations and pulsed beam production outgassing will be affected by (e.g.) the chopped beam impinging on chopper plates and/or diaphragm. Another critical point could be the beam interaction with the iris designed for cutting beam halos. This will require dedicated characterisation of “machine-running” outgassing during the early phase of prototype characterisation at LNS.

15. Other points • Material + welding (mainly related to flanges+tubes+bellows) Materials provided by LNS funds. Welding done by LNS mechanical workshop • Sealing technology Metal gasket, except in Foreline piping (viton).

16. Questions • Instrumentation & cabling (in case it won't be provided by ESS) ?? •  Leak testing procedure and reports ??(Leak detector could be helpful if provided by ESS)