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3. CURRENT STATUS OF NEU'1KON-SCATTERING FACILITIES IN 1~E
UNI'lbu STATES
In this chapter we describe briefly the existing neutron-
scattering facilities at the five National Laboratory neutron
university reactor facilities. We
sources and two major
also provide a summary of the trends in users and publications
In Chapter 4 we
associated with U.S. neutron facilities.
provide a comparison with facility development and user
trends at foreign laboratories.] It is clear from these
data that there has been a striking increase in users and
change in user patterns over the past decade along with
-
1A variety of sources of information were used by the
Panel in assembling summaries of users, publications,
instrumentation, and total neutron-scattering budgets.
These included the earlier National Academy of Sciences
and Department of Energy reports cited in the Introduction,
the Annual and special reports of the DOE and its National
Laboratories, the National Bore au of Standards, and the
University of Missouri, along with those of the Ins titut
Laue-Langevin at Grenoble and other neutron-scattering centers
in Europe. The Panel went further, however, to assure up-
to-date suitably coordinated information and statistics
by individually contacting the major neutron centers in
the United States, Western Europe, Japan, and Canada concerning
users, publications, and other information relevant to the
comparisons made in the report. It should be noted that
the Panel did not attempt to provide similar comparisons
with neutron-scattering facilities in the Soviet Union,
Eastern Europe, India, or other neutron efforts worldwide.
A summary of these facilities can be found in the earlier
NAS and DOE reports mentioned above.
6
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7
qualitatively new research opportunities in a variety of
fields.
It should be noted that in general U.S. neutron sources
also serve a wide variety of scientific and programmatic
needs that are unrelated to neutron-scattering research.
At present, about half of the total operating costs of major
neutron sources (about 613.5 million) are associated with
neutron scattering, while the remainder is related to other
highly important and diverse national needs, including isotope
production, chemical trace analysis, radiation damage, nuclear
physics, ultracold neutron research and radiation standards.
This multiple program use of neutron sources in the United
States is beneficial, since it can provide broad-based support
and cost-effective operation.
Bowever, it can sometimes
create serious difficulties if one of the programs loses
or withdraws support, thus threatening the stability or
schedule of source operation.
The major neutron sources in the United States used
for scattering research are briefly described in the following
summaries. The research reactors in general operate 24
hours a day in a quasi-continuous schedule with brief shutdowns
for maintenance and refueling. The pulsed-source schedules
are currently more curtailed, as noted in the summaries.
FACILITY DESCRIPTIONS
High Flux Beam Reactor (EFBR)--Broothaven National Laboratory
The High Flux Beam Reactor is a 60-MW reactor using enriched
fuel and D2O as a moderator and primary coolant. The core
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8
is small (48-cm diameter), resulting in a thermal neutron
density that is peaked outside of the core, where beam tubes
tangential to the core provide neutron beams with low fast-
neutron contamination. The thermal flus isl x1015 neutrons/cm2-
sec at the 8-cm-diameter thermal beam-tube tips. To provide
intense beams of low-energy neutrons, a liquid H2 moderator
has been installed in one beam tube that is equipped with
a small-angle scattering diffractometer and a high-resolution
three-axis spectrometer. Situated on the seven remaining
tangential beam tubes are four conventional three-axis
spectrometers that are used mostly for inelastic scattering
studies and powder diffraction, a three-axis spectrometer
and two diffractometers equipped with four-circle goniometers
for single-crystal and protein diffraction studies, as well
as two additional diffractometers used mainly for small-
angle scattering. Four diffractometers have position-sensitive
detectors. One of the three-axis spectrometers is often
devoted to polarized neutron studies. Under a cooperative
development are a new polarized-beam crystal spectrometer
with a spin-echo capability (with Japanese scientists) and
a medinm-resolution macromolecule diffractometer (with Exxon
Research Laboratories).
including conventional
Additional ancillary equipment,
and 3Be cryostats and high-pressure
sample environments are routinely available.
Staff scientists
carry out independent research programs in addition to assisting
external users, who make collaborative arrangements largely
through direct contact with interested staff scientists.
A more formal user policy including peer review will be
implemented in the near future.
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9
Intense Pulsed Neutron Source (IPNS)--Argonne National
Laboratory
The Argonne Palsed Neutron Source produces bursts of neutrons
with a peak thermal flux of ~4 ~ 1014 neutrons/cm2-sec at
a repetition rate of 30 Hz and is at present the most intense
pulsed source in the world. Neutrons at the IPNS are produced
by a 450-500 MeV proton-beam incident on a depleted uranium
target at an average current of ~12 pA. A polyethylene
moderator surrounds the target to reduce the energy of the
neutrons to allow neutron-scattering research. Twelve horizontal
and two vertical beam holes surround the moderator assembly.
A cold moderator (80~) is available for three of the beams.
A separate uranium target is used for fast-neutron irradiation
and arranged so that the samples can be irradiated at liquid
helium temperature. IPNS currently operates 6 months a
year. The radiation effects facility receives the beam
25 percent of the time, and the neutron-scattering target
75 percent of the time.
There are seven instruments currently available in
the user mode, including two high-resolution powder
diffractometers; a single-crystal diffractometer operating
on the Lane principle with a position-sensitive detector
of the scintillation type; a small-angle diffractometer,
also with a position-sensitive detector; a crystal-analyzer
spectrometer primarily for observing H-modes in chemical
systems; and two chopper spectrometers with incident energies
ranging from 50 to 1000 MeV, which allow scattering measurements
over a broad range of energy and wave-vector transfer.
These neutron-scattering instruments are scheduled in the
"user" mode, i.e., allocation of 75 percent time is made
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10
by a Program Committee, which reviews proposals twice a
year. Three additional instruments are under development:
a polarized neutron instrument for studying refraction from
surfaces; a diffractometer built to search for ordered nuclear
moment arrangements in 3Be below 1 my; and a spectrometer
for spectroscopy in the electron volt range.
Accelerator modifications and installation of an enriched
uranium target are planned over the next 2 years to increase
significantly the intensity of IPNS.
Massachusetts Institute of Technology Reactor (MITR)
The MITR is a 5-MOO, heavy-water moderated reactor whose
core and beam arrangement was modernized in the 1970s to
provide beam tubes with accessible fluxes approaching 1014
neutrons/cm2-sec. There are currently three two-axis
spectrometers in use, one with temperature stability control
for neutron interferometer studies and two for general-purpose
diffraction with changeable monochromators and wavelengths.
The MITR is also utilized for a variety of other research
and applications in nuclear engineering, trace analysis,
radiation effects, and isotope production.
National Bureau of Standards Reactor (NBSR)
The NBSR is a heavy-water moderated research reactor currently
operated at 10 M' and awaiting final Nuclear Regulatory
Commission approval to double the power to 20 ME, which
will provide a flux at the beamrtube entrances of 2 ~ 1014
neutrons/cm2-sec. The NBSR has eleven radial beams (15-
cm diameter), nine of which are currently dedicated to neutron-
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11
scattering research. The reactor geometry combines a split-
core fuel arrangement and large vertical divergence (~100
min) to provide high-intensity, low-background beams at
the sample position for scattering applications. The facilities
available for diffraction include a multiple-detector high-
resolution powder diffractometer; a four-circle single-crystal
diffractometer; a biological crystallography station (NBS-
NIH) using a position-sensitive detector; a small-angle-
scattering spectrometer that features a focusing collimating
O
system, tunable wavelength (4.5-12 A), and a large t65 cm
s 65 cm) position-sensitive detector that can be rotated
around the sample. Instruments for inelastic scattering
include three variable-incident energy triple-asisspectrometers,
one of which is equipped with a high-intensity beryllium
filter analyzer for chemical spectroscopy, and a multidetector
time-of-flight crystal-chopper spectrometer with variable
incident energy. A polarized-beam spectrometer is also
under development. Scattering experiments are possible
between 0.3 and 1800 ~ and at magnetic fields up to 7 T.
All neutron-scattering instruments are scheduled each month
by a committee of major users from the National Bureau of
Standards, other federal laboratories, and universities.
External requests for facility use can be addressed to committee
members or to the neutron group leader.
Funding has recently been provided for installation
of a large (25-cm-long, 36-cm-diameter) cold-neutron source
in the reactor core, which will serve a variety of instruments
for cold-neutron research on materials.
Sixteen other facilities at the NBSR serve research
and applications in chemical trace analysis, radiation standards,
nuclear physics, and isotope production.
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Oak Ridge National Laboratory Reactors (ORNL)
The High Flux Isotope Reactor (HFIR) at the Oak Ridge National
Laboratory operates at a power level of 100 ME. Light water
serves as coolant and moderator in the annular fuel region.
Target rods for production of transuranium isotopes are
located in a central flux-trap region. There are four horizontal
beam tubes of 10-cm inner diameter with an average flux
of 1 ~ 1015 at their tips.
These beams deliver neutrons
to nine scattering instruments: two variable incident energy
(Eo) triple-axis spectrometers; a fixed ED triple-axis unit;
a polarized-beam triple-axis spectrometer; an ultrasonically
pulsed time-of-flight instrument; a liquid diffractometer;
a four-circle, single-crystal diffractometer; a double perfect-
crystal small-angle scattering (SANS) instrument; and a
30-m SANS facility with an area detector. The last instrument
was constructed with NSF funds and is operated by the National
Center for Small-Angle Scattering Research. A new high-
intensity two-axis diffractometer with a curved position-
sensitive detector is being developed with Japanese support
with a potential for real-time crystallographic studies.
The Oak Ridge Research Reactor (ORR) operates at 30
ME with light water as coolant and moderator and beryllium
as reflector. The primary purpose of this reactor is for
materials-irradiation experiments, but there are six horizontal
beam tubes of 17-cm diameter for scattering experiments.
The thermal flux near the beam-tube entrances is about 2
1014 neutrons/cm2-sec. The Ames Laboratory operates three
instruments at the ORB: a variable-E triple-axis diffractometer,
a polarized-beam diffractometer, and a two-axis diffractometer.
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13
In addition, ORNL operates a 5-m SAN S instrument with an
area detector and a two-axis diffractometer.
Proposals for the NSF-supported SAN S facility are reviewed
by a special committee and scheduled as they are received;
there is normally a three- to four-month waiting period.
Other ORNL instruments are available to users either by
informal arrangements or by written proposals that are reviewed
by Oak Ridge staff members.
University of Missouri Research Reactor (MURR)
MURR is a 10-MW pressurized-water, beryllium-reflected flux-
trap reactor located in Columbia, Missouri. There are six
beam ports with four used for neutron-scattering research.
The flux available at the source end of the beam ports is
1014 neutrons~cm2-sec. There are currently seven neutron-
scattering instruments: two four-circle single-crystal
diffractometers; one triple-axis spectrometer; two powder
diffractometers--one with a position-sensitive detector,
the other with a five-detector system; a fized-wavelength
o
(4.7A)small-angle scattering facility that uses amultidetector
and has 4.5-m flight paths before and after the sample;
and a double-crystal monochromator-interferometer instrument.
Facilities are open to outside users by informal arrangements
with neutron-scattering staff members at HERR.
The reactor has a number of other major facilities
used for gamma-ray scattering (diffraction, quasi-elastic
scattering, and Compton scattering), neutron activation
analysis, radio-pharmaceutical and transmutation-doped silicon
production, radiation-effects studies, neutron radiography,
and key neutron beams for tomography and cross-section work.
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An improved triple-axis spectrometer and another diffractometer
are expected to be built during the next 2 years, and an
engineering study has been funded for a possible doubling
of the reactor power.
Weapons Neutron Research/Proton Storage Ring Facility (WNR/PSR)
Los Alamo s National Laboratory
The WNR/PSR being developed at the Los Alamo s National Laboratory
is a pulsed spallation neutron source for neutron-scattering
research in condensed-matter physics, chemistry, materials
science, biology, and polymers. It is an interdisciplinary
facility that is shared with nuclear- and neutrino-physics
research. A beam of 800-MeV protons is provided by the
Los Alamo s Meson Physics Facility (LAMPF). At present,
the WNR can utilize only about 0.5% (~5 pA) of the LAMPF
beam. However, the PSR will permit by 1986 the use of 100
pA of LAMPF protons with a much reduced pulse width of 0.27
psec. At that time, the peak thermal neutron flux in the
pulse is expected to be 1016 neutrons/cm2-sec at 12 Hz,
making WNR/PSR directly competitive in neutron intensity
with the new British pulsed source (SNS) at the Rutherford
Laboratory.
At present six beam lines are available for condensed-
matter research, three each for elastic and inelastic scattering
studies. Two of these instruments, a filter difference
spectrometer for vibrational spectroscopy and a single-crystal
diffractometer, are operated in a user mode, while the remaining
instruments are under development. A general-purpose powder
diffractometer is expected to become a user instrument in
1984. A program advisory committee (shared with ANL) currently
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15
meets twice a year to decide on proposals for beam time.
The total time available for neutron-scattering studies
currently is 60 percent of the LAMPF operating schedule
(6 months/year in 1982-1983) and will increase to 80 percent
in 1986. A total of ten neutron-scattering instruments
is planned for completion by the end of 1986.
Summary of Facilities
Other neutron-diffraction facilities also exist at smaller
university reactors for student training and research, most
notably several instruments at the University of Rhode Island.
In Table 1 we summarize the neutron-scattering instruments
currently available at major U.S. neutron sources. The
table shows that there are a total of 53 instruments (compared,
e.g., with 114 instruments currently operating and over
40 under development in Western Europe). The relative
effectiveness of these facilities is, of course, closely
related to intensity, energy and momentum range, and flexibility,
for example, factors that are impossible to reflect in a
single table. Ingeneral, currentneutron-scattering capabilities
in the United States are clearly still competitive
internationally in the areas of triple-axis spectrometry
with resolutions >0.2 meV, single-crystal and powder diffraction
for both steady-state and pulsed sources, polarized-beam
research, high-resolution biological diffraction, and neutron
interferometry. In a later section, critical neutron
instrumentation and measurement capabilities currently
unavailable or not fully competitive in the United States
will be summarized.
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16
TABLE 1 Snamary of Nentron- Scat taring Instruments Avail able
in the United States
A. RESEARCH REACTORS
1. Diffractometers
BNL
MIT
NBS
ORNL
MURR
2
2. Spectrometers
Inter Three-
ferometer SAN S Axis
2~ 5C
BNL
MIT 1
NBS
ORNL - 3
H~ 1 1 1
Two-Axis
Two- (Multisector Four-
Axis or PSD) Circle
Four-
Circle
(PS0)
2 1b
1
2a
1 1b
1
2
Time-of- Polarized
Flight Beam
-
1 4c
4 1 2
B. PULSED NEUTRON SOURCES
1. Diffractometers (Elastic)
Single
Powder Crvstal
SANS Beam
ANL 2a 1 1
LASL 1 1
2. Time-of-Flight Spectrometers
ANL
LASL -
Chopper Crystal Filter
Analyzer Analyzer Analvzer
2 1
1
. .
aDedicated high-resolution powder diffractometers.
bThese instruments configured primarily for biological structure
research.
COne of these three-axis instruments is sometimes used for polarized
beam studies.
dPrimarily for structure of liquids and glasses.
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17
It should also be noted that aside from the facilities
described above, there are ongoing state-of-the-art efforts
at the various neutron centers in the development of area
detectors, multilayer focusing and polarizing monochromators,
focusing collimators, neutron interferometers and choppers,
all of which are important for the development of advanced
instrumentation for reactor or pulsed sources. While in
some cases U.S. laboratories have been pioneers in such
advances, our efforts in general have a low-to-modest level
of support and manpower compared with instrumentation development
projects in Europe (some of which are described below).
As a result, the implementation of new classes of instruments
based on these developments has been generally much slower
in the United States.
THE USER COMMUNITY
The U.S. neutron-scattering user community has changed
considerably since the 1977 report of the National Research
Council (Neutron Research on Condensed Matter, National
Academy of Sciences, Washington, D.C., 1977), both in the
number of users and in the kinds of science being done.
A summary of the total number of users per year at O.S.
neutron-scattering facilities during the past 6 years is
given in Figure 1. For the purposes of this report a "user,'
has been defined as a scientist who directly participated
in a neutron-scattering experiment at least once during
a given year. A scientist who visited a given neutron center
more than once to perform experiments is counted only once.
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18
500
400
300
200
100
o
Users /
0~
-
-
~/
/Publ ications
D
1977 1 978 1979 1980
YEAR
1981 1982 1983
FIGURE 1 IJ. S. neutron-scattering research--users and
publ ications .
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19
No attempt has been made to identify scientists who might
have used more than one neutron source. Also shown in Figure
1 are the number of publications in the 1977-1983 period.
The user trends in Figure 1 show that the number of
U.S. users of neutron-scattering facilities has more than
doubled during the past 6 years and has gone up 80 percent
between 1980 and 1983. This rapid increase in the total
user community is broadly reflected in the individual numbers
for the majority of the neutron research centers. Major
factors include the installation of new or improved small-
angle scattering facilities at the research reactors, the
commissioning of the Intense Pulsed Neutron Source at Argonne
National Laboratory, and other reactor instrumentation
developments including high-resolution diffraction and improved
polarized-beam and triple-axis spectrometers. It should
be noted that this large increase occurred in spite of the
shutdown of the CP-5 reactor at Argonne during 1978-1979.
It is clear from the user trends that, as has occurred in
Europe, the introduction of new or improved neutron instruments
that provide new measurement capabilities greatly increases
the utilization of such neutron facilities by the scientific
community.
The expanded neutron-scattering community shown in
Figure 1 also reflects a significant change in the distribution
of users from the various scientific disciplines and in
some cases the introduction of almost entirely new user
groups (e.g., polymer science). In broad terms, the neutron
user community in 1983 is distributed as follows: condensed-
matter physics, 35 percent; chemistry, 23 percent; materials
science, 16 percent; polymer science, 13 percent; biology,
13 percent. Thus while condensed-matter physics has shown
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20
a healthy increase over the past 6 years (-33 percent),
these users now represent a considerably smaller percentage
of the total community than in 1977 (~45 percent). Other
user groups, most notably in polymer and materials science
and biology, have shown much greater relative increases
(~150 percent), stimulated largely by the availability of
new state-of-the-art SAN S and high-resolution diffraction
facilities. The chemistry community has also grown at
approximately twice the rate of the condensed-matter physics
community.
Since the number of full-time scientists at the major
neutron centers has increased very little during the past
few years, these numbers represent a decided increase in
part-time users of neutron-scattering facilities. In fact,
this has put a great strain on the scientific and technical
staff at the National Laboratories in seeking to serve the
increasing user community while continuing to meet the program
needs of their own agencies. Currently the approximate
distribution of users is as follows: federal laboratories
and agencies, 30 percent; universities, 60 percent; and
industry, 10 percent.
The breadth of the current neutron-scattering community
is reflected in the diversity of the organizations that
participate in research at the various neutron centers.
A list of universities, industries, and laboratories doing
independent or cooperative neutron research during this
past year is given in Appendix A. One notable trend in
the user distribution is the considerable increase over
the past 6 years in the number of students using neutron-
scattering facilities either full time or part time in their
research. Between July 1982 and June 1983, there were 92
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21
student users at the various neutron centers. This number
is both significant and encouraging since the education
and participation of young scientists in modern neutron-
scattering science is essential for the future health and
vitality of the field. It should be noted here that, while
the majority of users utilize the federal laboratory facilities
(almost 90 percent in 1983), the university facilities have
trained or provided facilities for close to 30 percent of
the student users.
Another measure of the productivity and vitality of
the neutron-research community is, or course, the number
of publications resulting from the use of neutron-scattering
facilities. The publication numbers assembled from the
various neutron centers for the past 6 years are shown in
Figure 1. It can be seen that a large increase in neutron-
scattering publications has occurred that roughly parallels
the rapid increase in the user community. Thus we observe
an increase of slightly more than 60 percent over this period,
almost all during the past 3 years. This increase is smaller
than the overall percentage increase in users. This lag
is to be expected for new users (in many cases using new
facilities) in any field. In fact an even greater lag in
publications was noted during the rapid expansion of users
at the Institut Laue-Langevin (ILL) in Grenoble during the
1970s. In addition it should be noted that part-time users
of any major facility will rarely be as productive in publication
as the core of full-time users (who represented a much larger
fraction of the total neutron user community in the mid-
1970s). As will be seen below, the current number of
publications per user compares quite favorably with comparable
figures for the ILL and other European facilities.
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22
It is also interesting to note that a combination of
the facility numbers in Table 1 with the user figures in
Figure 1 gives about 10 users/instrument. This is rather
close to the comparable ratios assumed for synchrotron facilities
in the Report of the Subcommittee on U.S. Synchrotron Radiation
Facilities (Current Status of Facilities Dedicated to the
Production of Svnchrotron Radiation, National Academy Press,
Washington, D.C., 1983).
COMPARISON WITH TEE EUROPEAN COMMUNITY
We now present a brief review of foreign neutron-scattering
users and facilities, concentrating on Western Europe, where
the major expansion has occurred during the past 12 years.
Western Europe has over the last decade developed a user
community more than double the size of that in the United
States, driven by a major investment (most notably at the
ILL) in new classes of instrumentation and a highly organized,
well-funded user policy. A summary of users and publications
over the past 6 years is given in Figure 2. In developing
the user numbers we have applied the same criteria as we
outlined above for the United States, but there is a greater
uncertainty in the n user" figures for non-ILL facilities
owing to the greater chance of "double counting" scientists
who use both ILL and their own neutron facilities. It should
be noted that while the total European user community tripled
during the 1970s, the period shown in Figure 2 shows a less
dramatic rise, reflecting the saturation of facilities at
ILL and elsewhere. A notable feature of these current-user
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1 ,300
1 ,200
1,100
1 ,000
900 _
_
800
cr:
m 700
5
~ 600
o
500
400
300
200
100
o
_ ~
_ /
P'
/
. _
,:
23
_
-
Total User
ILL Users
Total Publications
_ ~C1
. _
I LL Publication
1977 1978 1979 1980
YEAR
1 981 1982 1 983
FIGllRE 2 Summary of users and publications from Western
Europe .
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24
numbers is the dominant position of ILL, which accounts
for about half of the users and publications in Western
Europe. In fact, the figures show that the ILL alone has
about 25 percent more "users" than the total for the United
States. The current number of neutron-scattering instruments
at the ILL is 26, and the total annual budget (including
a program to fund the expenses of users from France, Germany,
and Great Britain) is about 625 million (roughly the same
as the entire O.S. effort in neutron-scattering research).
Taking into account the rapid development and planning of
new instruments (~50) in Western Europe, a user community
exceeding 1500 would be expected by about 1987.
Beam time on the ILL is scheduled almost entirely in
the "user" mode through the review of formal proposals by
panels assembled to represent various disciplines and kinds
of instruments. In addition, every neutron facility has
instrument-responsible scientists and technicians associated
with it who are assigned to assist outside scientists in
using the facilities. While the average number of users
per instrument per year in this mode (about 20) is considerably
higher than in the United States, the number for the United
States (10) is somewhat higher than the average of the other
European facilities. Publication rates per user are roughly
the same for the United States as for Western Europe. By
comparison, figures for neutron-scattering publications
in Canada, which has maintained a traditional role in this
field, show an average rate of about 40 publications in
recent years. The Japanese, who are engaged in a vigorous
expansion in both reactor-based and pulsed neutron research,
now show a publication rate approaching 100 papers per year.
While these comparisons attest to the continuing productivity
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25
of the U.S. neutron centers, the O.S. ability to serve the
needs of the user community is limited by the lack of incremental
resources for scientists and technicians to provide direct
user support at the major neutron centers.
Another key problem facing the U.S. neutron facilities
in seeking to maintain an internationally competitive position
in this field is the lack of resources for the development
of new classes of instrumentation (leading to new science).
A major advantage of the ILL and other European centers
over the past decade has been the flexibility and funding
to develop such new instruments and the cold neutron sources,
guide tubes, and focusing monochromators, for example, needed
for their development. In the next chapter we will briefly
review the impact of this relative lag in U.S. capabilities.
Representative terms from entire chapter:
neutron centers
