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.
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.
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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.
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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.
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.
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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.
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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.
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.
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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.
FIGURE 6. Expected facility configuration post outage, early 2012.
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FIGURE 7. Expected Facility configuration at the end of the Expansion
Initiative, late 2012.
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