ESS Vacuum Systems TAC 6 November 2012 Peter Ladd Senior Vacuum Expert

Scope The vacuum team has overall responsibility for all ESS technical vacuum systems used on the: Accelerator, Target and Neutron Scattering Instruments and Neutron Guides Providing guidance and on going support to ensure the implementation of compatible vacuum designs for e.g. vacuum chambers, components and other equipment exposed to a technical vacuum environment.

Vacuum Requirements Vacuum requirements are dictated by physics and individual system requirements. Accelerator – Levels required for the various areas of the accelerator are summarized in the ESS Parameter List together with the gas flow rate and gas species required for the Ion Source. – Typically vacuum levels will be in the mbar range. Target – The requirements for target system are not currently defined. Neutron Scattering Instruments and Neutron Guides – Vacuum levels required for the various Neutron Scattering Instruments will vary depending on the science to be performed. – Vacuum levels will typically range from the to mbar. – Neutron guides will operate in the – range.

An Integrated Approach As previously noted the vacuum team is responsibly for all ESS technical vacuum systems across the project. Working closely with our partners across the project one of the primary goals is commonality of equipment and to meet this goal a Vacuum Equipment Standardization Task Force will be established. This Task Force will be led by the ESS vacuum team with representatives from the various ESS partners involved in the use of vacuum equipment for the various accelerator vacuum subsystems. The mandate of the task force will be to develop a list of standard vacuum equipment that will be used for the various subsystems in order to minimize project costs, spares holding, training and achieve other benefits to be gained from standardization.

Accelerator Systems This activity encompasses the design, selection of equipment and integration of the vacuum systems into various accelerator systems: – Warm linac, comprising the front end systems (FES) and drift tube linac – Cold linac, comprising the spoke cavities and medium  and high  cryomodules – High Energy Beam to Target (HEBT), the beam line that delivers beam from the cold linac to the target and tuning beam dump

Front End Systems (FES) The front-end systems comprise: – the Ion Source (IS) » high hydrogen gas loads need to be handled » turbomolecular pumps (TMP’s) selected to meet requirement » TMP exhaust handled appropriately to eliminate potential for formation of explosive mixtures in the exhaust gas stream – Low Energy Beam Transport (LEBT), » similar pumping system to IS, same requirement to handle explosive mixtures in the exhaust stream – Radio Frequency Quadrupole (RFQ) » TMP’s are selected for commonality with the IS and LEBT and distributed along RFQ – Medium Energy Beam Transport (MEBT) » ion pumps selected since gas load primarily outgassing

Drift Tube Linac (DTL) Gas loads associated with the DTL tanks will be primarily outgassing Ion pumps selected for pumping and mounted directly to the DTL tanks. RF screens incorporated at inlet of each pump to prevent the regurgitation of gas due to RF power. Getter pumps used for maximum pumping speed between the RF window and iris within limited space available. Pump provided with isolation gate valve to allow reactivation of getter when heated. TMP backed scroll pump used to pump out the gas released from the getter during reactivation. The DTL tanks initially pumped down using mobile pump carts before the ion pumps are started.

Spoke Cavities, Medium  and High  Cryomodules The accelerating cavities of the spoke, medium and high β cryomodules cooled with liquid helium and are self-pumping. The cavities conditioned prior to installation in the tunnel where connections to warm sections are made. Connections made under clean room conditions using portable cleanrooms to minimize particulate contamination of cavities. Following connection warm section evacuated and interconnecting valves adjacent to each cavity and cryomodule opened. The vacuum jacket (insulating jacket) evacuated prior to cool down of cryomodule. Vacuum jacket is self pumping following cool down.

LEDP and HEDP Pumping Sections The LEDP (Low Energy Differential Pumping) section – Provides pressure reduction between last DTL tank and first spoke cavity to limit flow of gas from warm to cold section of machine. – Uses distributed ion pumps and beam pipe providing minimum conductance possible to maximum pressure reduction. – Includes beam instrumentation and fast closing valve to protect the first spoke cavity in case of loss of vacuum event occurring in warm section of the machine. The HEDP (High Energy Differential Pumping) section – Provides controlled pressure rise between last cryomodule and HEBT to limit flow of gas from HEBT into cold section of machine. – Configured in similar manner to the LEDP including fast valve to protect last cryomodule from loss of vacuum event occurring in the HEBT.

LEDP Installed at SNS

LWU’s (Warm Sections) LWU’s provide beam line connections between individual spoke cavity modules and individual medium  and high  cryomodules. LWU’s have centrally located ion pump, beam instrumentation, vacuum gauging and manual vent valve with micron filter to allow LWU’s to be vented. LWU’s isolated from cavities and cryomodules during installation by isolation gate valves located on end of each cavity or cryomodule. connections between LWU’s and spoke cavities and cryomodules made under clean room conditions, as previously noted, using portable cleanrooms to minimize particulate contamination of the cavities.

Warm Section Prep at SNS DI Water TankUltrasonic Tank Assembly/Bake AreaFinal Assembly

Warm Section Prep at SNS

LWU Clean Connection Clean room set up Clean connection equipment

Warm Section Installation at SNS

High Energy Beam to Target (HEBT) Beam line expands rapidly in vicinity of collimator leading to target window and tuning beam dump window. Areas potentially activated requiring special precautions for maintenance, i.e. the use of shielding, long handled tools and/ or remote handling techniques. Larger beam line and maintenance requirements provide challenges in selection of appropriate metal seal design for beam line flanges and providing remote leak testing capability. During hands on maintenance upstream of the collimator a gamma blocker is rotated into the beam line to block back streaming radiation from target, tuning beam dump and collimator. Radiation hard components with high reliability used where possible. Local shielding and a strategy to utilize redundant components in activated areas. Ion pumps used for pumping having no onboard electronics and controllers that can be located remotely.

HEBT A2T and Tuning Beam Dump

Target Systems The vacuum group will assist in developing the design of the vacuum interface and design of the proton beam window, target safety valve and interconnecting beam line between these components. Area activated and design will need to be compatible with replacement of components using long handled tools and/ or remote handling techniques. Forming part of the beam line helium leak testing required and with monolith filled with helium, testing with He 3 may need to be considered. HEBT operates at relatively high pressure ~10 -6 mbar therefore a reasonable level of leak tightness needed following component change out to minimize the gas load to ion pumps and maximize operational life due to saturation. The vacuum team will also assist in design of embedded vacuum system within the He Target cooling and the He monolith circuits.

Instruments and Neutron Beam Lines Overview of Vacuum Teams Support Activities – provides guidelines for design of vacuum chambers and selection of vacuum components and equipment, – performs materials testing, e.g. outgassing studies on materials installed in vacuum environment, – advises on and reviews designs of instrument chambers and components from a vacuum prospective e.g. weld design and material selection etc., – Inspects fabricated components and chambers for vacuum compatibility and witnesses vacuum testing at vendor premises, – performs testing and start up of vacuum systems following installation.

Neutron Scattering Instruments and Neutron Guides approximately 2900 m of neutron guide installed to support the full suite of instruments. vacuum pumping required about every 20 m along the neutron guides and need to provide an operating pressure in – range. assists in vacuum design of neutron guides and interfacing components e.g. choppers and designs, procures, fabricates and installs vacuum pumping equipment. neutron guides pumped with mobile pumping units allowing ready exchange of units for servicing. Approximately units required to support initial instruments suite.

Vacuum Facilities Vacuum facilities provided to support both construction and pre operational activities, including: – outgassing test chamber for material and component investigations, – general purposes bake out and drying ovens for preparation of equipment prior to installation, – support equipment including pump carts, leak detectors etc., – ISO Standard 209 Class 4/5 (Fed Standard 209D Class 10/ 100) cleaning and washing area for preparation of warm sections and other critical components prior for installation, – pump carts, leak detectors, portable cleanrooms and other equipment dedicated to “clean” cryomodule beam line connections, – provision of limited spares to support vacuum operations through the pre operational phase, – provision of pump carts, leak detectors, cold traps and other equipment to support maintenance of activated and/or contaminated equipment.

Material Outgassing Studies at SNS Outgassing decay RGA Scan

WP11 Vacuum Schedule

Accelerator Cost Distribution

Vacuum Systems Cost Distribution

Thank you for your attention to the preceding presentation where nothing really is a sign of a job well done…………