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Overview

The following paragraphs, updated in early April 2011, but not since, are taken from the NCNR's 2010 Annual Report.
(The 2011 Annual Report has several photographs that document Expansion Initiative activities.)

Introduction

The NCNR is midway through an Expansion Initiative to increase its cold neutron measurement capability by more than 25% by installing a new cold source and new beamlines, setting the foundation for a new generation of world-class instruments directly supporting the needs of science and industry. The Initiative is a complex multi-year project that includes the coordination of civil construction work for new buildings to house the expanded instrument suite in addition to refurbishment projects for facility improvements to the neutron source. The Initiative is proceeding on a schedule that required a 10½ month shutdown of the neutron source, beginning in April 2011. During this outage period new cold neutron guides are to be run from the confinement building in readiness to serve new and relocated instrumentation in the expanded guide hall. Over the past year the Facility's engineering and technical staff have been working hard to reach a series of major milestones required for the outage and this first phase of installation work.

Civil construction

Construction work on the guide hall addition and new technical services and administrative building (TSB) is now complete (Fig. 1). The guide hall extension (Fig. 2) adds 16,000 sq ft to the 20,000 sq ft area of the current building for the new guides, shielding, and instrumentation envisaged through the Initiative. The two-story TSB houses the Facility User Office and includes shop space and a conference facility along with some 40 new offices. Staff began moving into this new accommodation during the summer of 2010. The availability of new office space is a key component in the ongoing program to improve and renovate the NCNR laboratories used by both visitors and staff, enabling a number of the rooms vacated to be refurbished and returned to laboratory space as originally purposed. A second 18 month construction phase, scheduled for the autumn of 2010, will deliver new buildings to house support infrastructure for the neutron source and, during the outage period, core bore holes from the confinement building through to the guide hall, marking the start of the guide installation program.

NCNR TSB
FIGURE 1. Panoramic view showing the completed TSB (foreground, left side) with a bridge walkway connecting to the guide hall. The guide hall extension (slightly different wall pattern) is visible on the right-hand side.
NCNR guide hall
FIGURE 2. Inside the recently completed guide hall extension. As part of the second construction phase, the dividing wall between the existing guide hall and the extension (shown on the left) will be removed.

Outage activities: Guide and shielding installation

The central tenet of the Expansion Initiative is the installation of five new supermirror guides (outlined below) to service new and re-located cold-neutron instruments in the guide hall extension. The MACS spectrometer will be relocated to a new cold source at BT-9, thereby opening a viewport on the current facility cold source to accommodate the new guides (Figs. 3 and 4). During the outage period the first stage of a carefully choreographed and multi-phase installation sequence begins with the installation of new guide sections running from the confinement building and through the D-wing. All guide components for this first phase have been delivered and are undergoing characterization and pre-alignment. Staff members have also been working to complete the huge inventory of engineered ancillary components required to install the guides including main shutters, shielding, and vacuum jackets. Close to the face the guides are housed in large monolith assemblies and detailed installation sequences have been established to guarantee that there is clearance to maneuver the assemblies in place and also to ensure appropriate access to re-check guide alignment.

NCNR early 2012
FIGURE 3. Design drawing showing the current layout of the confinement building and D-wing (on the left). The MACS at NG-0 (kidney-shaped analyzer) and the Double Focusing Triple Axis spectrometer at BT-7 to MACS' right can be seen in the center of the figure. To the right of BT-7 is the residual stress facility at BT-8, and beyond that (circular gray object) is BT-9, to which MACS will be moved.
NCNR end 2012
FIGURE 4. Design drawing showing the planned layout of the confinement building and D-wing post-outage in early 2012 with the new guides installed. MACS (analyzer not shown) is in place at BT-9.

Guide specifications

The new guides utilize the latest in supermirror coating technology, yet must conform to existing installations and have only a restricted viewing angle of the cold source. Extracting five new beams presented an engineering and neutronics design challenge solved through judicious use of curved sections close to the source followed by straight sections: NG-A is a 41 m long guide earmarked for the Neutron Spin Echo instrument. To restrict beam divergence lower critical angle, high reflectivity coatings are used on the straight portions and inner radii of the guides. NG-B is also a low divergence guide for use by small angle neutron scattering (SANS) instruments. At a distance of just under a meter from the cold source, the guide divides into discrete upper (48 m long) and lower (52 m long) sections designed for the 30 m and 10 m SANS instruments respectively. NG-C is also a high-flux high reflectivity guide and will service a "reflectometer village" comprising the current vertical polarized beam reflectometer plus the new instruments MAGIk and CANDoR. The end station of NG-D will be the new location for the chemistry Prompt Gamma Activation Analysis and Neutron Depth Profiling stations.

Second cold source installation

The displacement of MACS has necessitated the design and building of a second cold source dedicated to the instrument. The new "PeeWee" source has disk geometry, optimized for MACS subject to the geometric constraints imposed at BT-9 (Fig. 5), and will provide a factor two gain in brightness for the spectrometer. PeeWee follows the same design philosophy applied to the existing cold source and utilizes a thermosiphon as the simplest means to supply liquid hydrogen to the source. The new source operates with half a liter of liquid hydrogen, as compared with five liters in the existing cold source, and so the additional heat load is readily handled by the current refrigerator unit.


NCNR C-100 current
FIGURE 5. Design drawing showing the location of major components of the BT-9 cold source. The H2 condenser is seen above the beam port; warm H2 gas lines run through a support structure for MACS to a ballast tank seen on the left. The in-pile assembly is shown inset.

Source facility developments

Source facility operations and engineering personnel will take the opportunity of the outage period to schedule a number of projects serving to enhance reliability. As part of the Initiative, the control room is the subject of a program to replace obsolete components and a new liner for the fuel storage pool is to be fitted. Funding through the American Recovery and Reinvestment Act (ARRA) will improve further source operations through replacement of the thermal shield system. The thermal shield reduces radiation heating in the pressure vessel and biological shield by means of water flow through a series of pipes and ring headers located between the vessel and biological shield and its replacement is the third and final major evolution of work undertaken in the confinement building during the outage period.

Post-outage period

Source operations are scheduled to restart early in 2012 at which time the Facility instrumentation will be configured as shown in Fig. 6. During the first half of 2012, the remaining sections of the new supermirror guides will be installed into the new guide hall addition. New experimental capabilities will be achieved at the end of the expansion project in late 2012 (Fig. 7), after which time the NCNR will continue its program of instrument development, based around the new guide infrastructure.
NCNR C-100 planned
FIGURE 6. Expected facility configuration post outage, early 2012.
NCNR BT9 source
FIGURE 7. Expected Facility configuration at the end of the Expansion Initiative, late 2012.
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