Facility Modification

Overview

Advanced LIGO technical requirements will necessitate modifications and upgrades to the LIGO buildings, and vacuum equipment. In addition, the strategy for executing the Advanced LIGO construction will require some facility accommodations.

The principal impact on this WBS element is as follows:

• It is a program goal to minimize the period during which LIGO is not operating interferometers for science. For this reason, major subsystems such as the seismic isolation and suspension subsystems should be fully assembled and staged in locations on the LIGO sites ready for installation into the vacuum system as fully assembled and vacuum compatible units. This will require prepared assembly and staging space, materials handling equipment, and softwall clean rooms.
• Increasing the arm cavity length for the Hanford 2-kilometer interferometer to 4 kilometers will require removing and reinstalling the existing mid-station chambers and replacing them with spool pieces in the original locations. An alternate strategy would be to fabricate additional vacuum tanks for the end stations, and associated spool pieces and preparation. Moving the existing chambers is the choice for the baseline design.
• The larger optical beams in the input optics section (and possibly the output optics section) will necessitate changing out the input optics vacuum tube for a larger diameter tube.

Functional Requirements

    Vacuum Equipment

All vacuum equipment functional requirements are the same as those in the initial LIGO design except that the vacuum level must be one order of magnitude lower (<10^-7 torr). Additional equipment (chambers, spool pieces, softwall clean rooms) is needed to accommodate additional arm cavity length for one interferometer and the desire for parallel assembly and installation in more chambers and staging areas. A larger diameter spool piece for the IO Mode Cleaner beam path (and possibly for a similar output mode cleaner) is required. The seismic isolation system requirements call for the Advanced LIGO subsystems to be compatible with the original LIGO vacuum envelope.

    Beam Tube

The original end-pumped beam tube system requires no modifications or additions for Advanced LIGO. There is sufficient margin in the present vacuum performance to permit the operation of the more sensitive Advanced LIGO instrument with no changes.

    Conventional Facilities

Preassembly of all large Advanced LIGO seismic isolation units prior to installation in the vacuum tanks requires clean onsite staging and assembly space. At both the Hanford and Livingston Observatories there exist suitable staging buildings with appropriate height and basic configuration; portable clean rooms and benches are required. Transporters for delivering fragile systems from the central buildings to the end stations are required.

Concept/Options

    Vacuum Equipment

Two softwall cleanrooms of the BSC type will be acquired for seismic assembly in the Hanford staging building. Two will be required for Livingston. For each of the interferometers, additional clean rooms will be acquired to support parallel installation in additional chambers to facilitate reducing the duration of Advanced LIGO installation.

Four additional spool pieces will be acquired to replace the Hanford mid-station BSC chambers and to connect these chambers to the end-station BSC chambers once relocated. The chambers will be removed and reinstalled at the end stations. An alternative approach involves acquiring new BSC chambers and leaving the original chambers in place. Vacuum controls will be added at the end stations to accommodate the BSC chambers in their new location.

The IO (and potentially the output) Mode Cleaner requires a larger diameter spool piece, ~15m in length, to accommodate the larger mirrors used.

The requirement of base pressure for Adv LIGO (<10^-7 torr) is already met by the present system (which is operating at <10^-8 torr).

    Beam Tube

No action needed. The original installation meets requirements for Advanced LIGO.

    Conventional Facilities

The existing staging buildings at both observatories will require additions of flow benches, fume hoods, vacuum bake ovens, and other minor equipment to support clean processing operations. In addition, at LHO some retrofit of the HVAC system will be necessary in the Staging Building to meet the cleanliness requirements. HEPA filters and a more powerful motor are needed.

R&D Status/Development Issues

There are no development issues or R&D associated with this WBS element.

Work Plan

Long lead procurements dominate this schedule sensitive WBS element. With funding assumed to commence in FY2005, contracts can be placed promptly for the softwall clean rooms and flow benches. These must be in place prior to commencement of seismic assembly by mid 2006. Procurement of vacuum equipment for conversion of the Hanford 2-kilometer interferometer should commence in 2006.

WBS Definition

This element includes modifications and additions to buildings, vacuum systems, and permanent fixed infrastructure that are needed to support the Advanced LIGO detectors. It does not include other facility additions or modifications carried out as normal operations or maintenance tasks.

Detail Estimate Sheets

Baseline Plan