Vacuum issues concerning the Proton Source and LEBT

Salvo Marletta, Luigi Celona, Lorenzo Neri, Franco Chines, David Mascali.

Nomenclature

TMP for Turbomolecular PumpPP for Primary PumpFull Range for vacuum gauge Pir For for Foreline Pirani gaugeFV 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 valveRGA for Residual Gas AnalyisMFC for Mass Flow Controller

Present design of P.S. and LEBT: pumps, gauges and residual gas analyzer

Low Energy Beam Transport Line Proton Source

Expected Operative Pressures

BEAM OFF – Static Vacuum

P.S. range 10E-6 mbarLEBT range 10E-7 mbar

BEAM OFF – Gas IN

P.S. range 10E-3 mbarLEBT range 10E-5 mbar

2100 mm 400 mm

RFQ (Diaphragm Φ = 6-8 mm; Depth = 10mm

General Vacuum layout

Full Range 1Full Range 2

Positioning of:• n.2 Primary Pumps • n. 2 TMP• n. 2 Full Range gauges• n.2 Pirani• n.1 RGA (res. gas analyser)

RGA

Present design of P.S. and LEBT: pumps, gauges and residual gas analyzer

Present design of P.S. and LEBT: Pumps characteristics 1

Flange Pumping speed (H2)

Pumping speed (N2)

Compr. Ratio (H2) Maintenance

DN 200CF-F 580 l/s 800 l/s 4 · 10e5 In situ

Drag Turbomolecular pump

LNS proposalPFEIFFER 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 ball bearing and the operating fluid 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.

Present design of P.S. and LEBT: Pumps characteristics 2

Flange Pumping speed

Final Pressure

Frequency Converter Maintenance

DN 25 ISO-KF 28 m3/h 3 · 10e-2 Yes >2 years

Primary Pump

LNS proposalPRIMARY 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)

Present design of P.S. and LEBT: Full range gauges

Flange Operating Range Inferface Maintenance

DN 35 CF-F Atmosphere to 10e-8 mBar

RS485/Analog In situ

Full Ranges

LNS proposal974 QuadMag™ Cold Cathode/MicroPirani™/Piezo Vacuum Transducer(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

Present design of P.S. and LEBT: Pirani gauge

Flange Operating Range Inferface Maintenance

DN 25 ISO-KF Atmosphere to 10°-5 mBar RS485/Analog In situ

Pirani

LNS proposal910 DualTrans™ MicroPirani™/Absolute Piezo Vacuum Transducer(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 setpoints with fast response time for reliable process control

Present design of P.S. and LEBT: Residual Gas Analyzer

Flange Operating Range Gas Mass Company

DN 35 CF-F ≈ 10e-5 mBar 1-100 AMU any

RGA

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.

Present design of P.S. and LEBT: Vacuum equipments

GDV-2GDV-1

GDV-3

Gate Valve 2

Gate Valve 1

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

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

Present design of P.S. and LEBT: Mass Flow Controller

Fitting Full Scale Inferface

6mm Svagelok 5 sccm RS485/Analog

MFC: for gas input (H2) in the proton source

LNS proposalGE50A 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

Performance (in terms of expected leak rate & outgassing)

BEAM OFFDue to copper sealing, expected leak rate is in the range of 10-9 mbar l/sThe 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 ONHowever, 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.

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

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)