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HRPD was installed in 1997 at HANARO and opened to the
external users after the performance test for one year. Many scientists
and graduate students from various fields of material science (crystal
structure analysis, quantitative phase analysis, magnetic structure analysis
and so on) are utilizing this facility.
Several sample environments such as CCR(10K-300K), Vacuum Furnace (RT-1000
) and Magnet+CCR (0.85T/10K) are available for the study of structural/magnetic
phase transition or change.
From the neutron powder diffraction, one can obtain informations about
the position and thermal behavior of light elements (H, Li, C, O etc.)
contained in a heavy element compounds and substitutional effects between
the transition metal group or lanthanide group, as a complementary tool
of X-ray diffraction.
By the virtue of the inherent property of neutron, large transmission
due to the small interaction with matter, neutron diffraction can be applied
to the study of bulk property of the specimen and QPA(quantitative phase
analysis) of bulk specimen (including powder) even though it takes much
longer time and needs much larger amount of sample than X-ray diffraction.
Figure 1. Synoptic diagram of HRPD
Instrument responsible : Dr. Yong Nam CHOI
Phone : +82-42-868-8439 E-mail : dragon@kaeri.re.kr |
Instrument Specification
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1. Monochromators
There is a 4-fold monochromator unit which has four crystal mounts and
are four beam paths taking-off the monochromatic neutron beams. Therefore
there are 4 4=16 choices of monochromatic beams, but actually we can choose
8 wavelengths since there installed 3 kinds of crystals in 4-fold mochromator
unit and only 8 combinations among 12 are practically useful.
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1) Monochromator crystals |
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| number
of slabs |
9 slabs
(vertically focused) |
| reflection
plane |
u(220),
Ge(331), Ge(335) |
| crystal
orientation |
min.
of arc |
| mosaic
width |
15-20
min (FWHM) |
| effective
area |
21mm(H)
120mm(W) per slab |
| thickness
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10 mm
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2) Wavelengths according to the take-off angles and crystals |
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| crystal
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dhkl(Å)
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2θm |
λ(Å) |
R(cm-1)* |
| Cu(220)
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1.278 |
44 |
0.957 |
149.8 |
65 |
1.373 |
214.9 |
| GE(331) |
1.298 |
65 |
1.395 |
214.9 |
90 |
1.836 |
282.8 |
120 |
2.248 |
346.4 |
| Ge(335)
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0.8628 |
65 |
0.927 |
214.9 |
90 |
1.220 |
282.8 |
120 |
1.494 |
346.4 |
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....*. 1/L0
+1/Lim=2 sinθm / R |
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2. Collimators |
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1) In-pile RSC (rotating shutter collimator) : 20'
, 30' , open(~50')
2) FCU (first collimator unit) : 6', 10', 20', open(~50')
3) Second collimator : 30' , open
4) Third collimator ( in front of detector window) : 10'(fixed)
Default setting : RSC=20', 1=open, 2=open, 3=10'(fixed) |
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3. Detectors |
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1) Multi-detector : 32 3He proportional
counters (tube: dia. 50mm)
2) PSD (position secsitive dectors) : 1-D (100mm 200mm and 200mm
100mm),
....................................................
2-D (200mm 200mm)
Usual set up is the full pattern (2 range : 0~160˚) measurement
mode using 32 multi detector system and sometimes PSD is used for
a special measurement at narrow angular region (Δ(2Θ)<7 ˚). |
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4. Beam Dimension
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1) At monochromator position : 40mm 200mm
2) At sample position : 30mm 60mm (without beam path), 14mm 48mm
(with beam path)
3) At detector position (3rd collimator) : 20mm 100mm |
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5. Resolution Characteristics
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Figure 2. Angular dependence of FWHM of diffaction peaks at 1.836Å
[Ge(331)/2ΘM90˚] and RSC=20'(present default). Blue thick
line is calculated result.
Resolution of instrument(Δd/d=cot Θs ΔΘs
The minimum resolution value of HRPD at α=1Θs/tanΘm=1.1
is 2.0X10-3. |
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6. Sample Environments |
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1) Low Temperature (CCR : Closed Cycle Refrigerator)
: 10K 300K |
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Characteristics
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..Temp.
Range
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..10K
~ 300K |
..Cooling
Power |
..0.5W@20K(cold
head:
..Leybold 210 two stage) |
..Cooling
Time |
..~2hr
(from RT to 10K) |
..Sensor |
..Si-diode |
| ..Control
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..automated sequential temp.
..control and HRPD ..measurement
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2) High Temperature (Vacuum Furnace) : RT 1000℃
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Characteristics
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..Temp.
Range
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..RT
~ 950℃ |
..Heating
Element |
..Graphite
(t 1.2mm) |
..Heating
Rate |
..abrupt
to 1℃/min |
..Cooling
Time |
..~1.5
hr(from 950℃ to RT) |
| ..Sensor
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| ..Control
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..automated
sequential temp. control and HRPD
..measurement
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3) Magnetic Field with Low Temperature (CCR+Magnet) : 0∼0.85T/9∼300K |
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Characteristics
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..Temp.
Range
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..10K
~ 300K |
..Field
Range |
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..CCR |
..0.5W@20K
(cold head : ..Leybold 210
two stage) |
..Cooling
Time |
..~1.5hr
(from RT to 10K) |
| ..Temp.
Sensor
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| ..Control |
..stand
alone control
..(not yet a automated) |
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Representative Publications
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1. Synthesis of Ba0.5K0.4BiO3 Superconductors and
Structural Analysis using
... Neutron Powder Diffaction, J. Kor.
Ceramic Soc. 38, 967-972(2001)
2. β-Ga2O3 nanowires synthesized from milled GaN powders, Applied
Physics Letters
... 80(3), 479-481(2002)
3. Role of Rare Earth lon in Spin Glass Behavior for R0.7Sr1.3MnO4,
Chemistry of
... Meterials 14, 1832-1838 (2002)
4. Structural origin of the pseudo-two-dimensional metalic state
in the
... A-type antiferromagnetic manganites,
Physical Review B 65,132414 (2002)
5. Measurement of very small hydrogen content in zirconium alloys
by measuring
... the thermal neutron incoherent
scattering, Applied Physics A 74[Suppl.] S1710-1712(2002) |
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