Development of a Detector Testing Facility
P. M. WhaleyKansas State University
Overview
• Introduction & Motivation
• Design Considerations
• Generation I Diffraction System
• Generation II Diffraction System
• System Testing
• Conclusions
K-STATE REACTOR
• 1960: Construction Permit
100 kW Facility Operating License
• 1962: Initial criticality
• 1968: 250 kW (with pulsing) license
Reactor Experiment Facilities
• 2 Thermal columns • Reflector well • In-core tubes • Beam ports
NWBP (radial)
SWBP (radial)
NEBP (piercing)
SEBP (tangential)
NEBP difficult SEBP heavily used SWBP lightly used NWBP dormant
Beam Port Access
Inner Plug
Outer Plug
door seal
K-State Reactor
• 2000: Recovery of operating time
• 2002: Renewal request (to 1.25 MW)
• 2002: SMART Labs installed at K-State
K-State SMART Laboratories
• Design & production of radiation detectors – Semiconductor-based radiation detectors – Gas-filled radiation detectors
• Major research emphasis on neutron detectors– Opportunities for reactor utilization– Committed NWBP to diffracted beam test facility
• Low gamma contamination• Monoenergetic neutrons
• Set of facilities for specific processes/functions
Crystal Growth & Testing Labs
CdZnTe Growth
Condensation/Deposition Lab
HgI2 (B)
Material Testing
Surface & Volume Characterization
HgI2 (A)
Processing Labs
Class 1000 Clean RoomProcessing
Surface Examination
Crystal Growth
Vacuum/vapor deposition
Ion Mills & Plasma Etching
DESIGN CONSIDERATIONS
• Floor loading constraints
• Shielding manipulation
• Motion controls
• Beam intensity
• Collimator
Floor Loading Constraints
• Beam centerline 30 in. from floor
• Bay floor rated to110 lb ft-2 (UBC) – Concrete density nominally 150 psf– Untenable limit for shielding mass
• KSU Architect certified design 350 lbf ft-2
– Based on soil compaction– Very limiting, but workable
• Elevated shielding minimizes weight
Shielding Manipulation
• Manageable with facility equipment– Overhead crane– Manual pallet jack– Powered pallet jack
• Elevated– Positioned to shield beam – Reduced floor loading – Stability possible issue
Motion Controls
• Limited resources
• Computer interface, 2-axis controls– Rotation– Elevation
• Adjustable crystal orientation
• Experiments show floor extremely stable to impulse loading
Beam Intensity Implications
• MB distribution – Peak energy about 50 meV– Harmonics not an issue– approximately 1% flux available
• NWBP thermal flux 6x107 n cm-2 s-1
• Estimate 105 n cm-2 s-1 near peak energy available at monochromator
Collimator Design
• Beam & monochromator size– Shielding requirements compete with intensity– Radial beam port gamma is severe
• Limit consequences of beam port leakage
• Options to:– Evacuate flight tube (10% m-1 loss in air)– Install high energy neutron & gamma filters– Install instrumented equipment core-side
GENERATION I SYSTEM
• Motion controls/Monochromator
• Collimator
• Shielding
Generation I Motion Controls
• Newport 2-axis controller– Rotation stage– Goiniometer stage
• Stages mounted on vibration damper
• Labview controls– Scan rotation– Change angle of elevation
Generation I Monochromator
• Silicon monchromator cut from thcik, “perfect” crystal
Generation I Shielding
• Rotating shield/integral shutter • Apertures for 2 angles & main beam • Elevated platform to minimize mass• Wire enclosure
Generation I Shield Details
Generation I Collimator
• 1 ½ inch tubes (3) for flight tube variations
• Penetrations for inst., gas or cooling lines
• Active seal on beam port flange
• Thin Al plates seal flight tube in a flange
• Connectors for vacuum or helium (1 tube)
Generation I Conclusion
• Min. footprint & weight, adequate shielding
• Low intensity
• Clear peak
Problems
• Resources with appropriate knowledge– Personnel – Limited experience
• Diffracted beam intensity– Perfect crystal: high resolution, low intensity– Mosaic permits range of energies– Inducing mosaic spread in Si is not trivial
• Shielding aesthetics
GENERATION II SYSTEM
• Research Assistant
• Large collimator
• Motion controls & monohromators– Cannibalized Huber theta-2theta stack– LabView Virtual Instrument motion control
• Shielding
Graduate Available Soon
• Licensed reactor operator• LabView programming• MCNP modeling• 3-D CADD (fabrication & CNC drawings)• Mechanical aptitude & abilities
– Maintenance & repairs laboratory equipment– Millwright & pipefitting
• ABC News feature“Can I get your picture? My roommate will never believe
that a couple of cute girls visited the reactor.”
Gen II Monochromator Stand
Monochromator Stage
Stage to locate beam
Scan at Test Stand
Gen II Monochromators
• Pyrolitic graphite
• Silicon
• Crystal bender
Gen II Collimator Design
Generation II Collimator
Gen II Collimator Mounted
Thin Al window
Vacuum connection
Equipment from SANS
Filter Tests
Sapphire
Bismuth
Concrete Block Manufacture & Use
Customized Building Blocks
“Industrial” Concrete Blocks
Gen II Shutter
Shielding Assembly
Completed Stack
Access Controls
System Testing
• Measurements of spectrum
• Monochromator tests for intensity
• Filter test for operational characteristics
Measured Spectrum (PG)
1 KW Spectrum
100
1000
10000
0.001 0.01 0.1 1
Energy (eV)
Co
un
ts
Monochromator Tests
• Silicon
• Bent Silicon
• Pyrolitic graphite
Detector Test Stand
Detector Testing
BN Detector Test
Conclusions
• Facility is essentially complete– Remount area monitor– Finish enclosure
• Experiment status
sensor
• Testing programs
in progress
Lessons Learned
• Bias of experience affected perceptions– Spectral measurement as a lab exercise
• Using a system versus• Building a system
– Copper monochromator
– Beam extracted from D2O tank adj. to core
• Filtering (bismuth & sapphire) perceptions– Not needed– Degrades intensity unacceptably
Lessons Learned
• Crystal orientation perception:– Need to have the crystal fully indexed– Flats in Si wafer indicate principle plane
• Mosaic spread was not considered necessary
Lessons Learned
• Design objectives need to:– Reflect actual needs– Be specified and fixed
• Concrete terminology– Concrete is rated for structural load– Architectural load is different
• Focus on beam, disregarding background
Lessons Learned
• Bigger is not always better (collimator)– Shielding & background exacerbated– No gain in intensity
• Aesthetics
Lessons Learned
• Only single stage required for test beam– The circle is only use to find the beam– Shielding prevents using the circle
• Stepped shielding– Concrete manufacturers are flexible– Customization is easy
• Bismuth, like water, more dense as liquid
Reference Spectra
• GA Report (KENO code)
• LiF Spectrometer
GA Report 4361
KSU TRIGA Full Power Neutron Flux at 23C
1.0E+04
1.0E+11
2.0E+11
3.0E+11
4.0E+11
5.0E+11
6.0E+11
7.0E+11
8.0E+11
0.01 0.1 1 10
Energy (eV)
Neu
tro
ns/
cm^2
F Ring
LiF Spectrometer Testing
BACK
Monochromator Intensity
• Silicon
• Bent silicon
• Pyrolitic graphite
• Spectrum measurements– Si– PG
Silicon Intensity
<111> Si 30 degree detector angle, 1 kw
0
50
100
150
200
250
300
350
5 10 15 20 25
Position
Co
un
ts p
er 3
sec
on
ds
bent 1 polished
unbent polished
Bent Silicon Intensity
<111> Si 30 degree detector angle, 1 kW
0
50
100
150
200
250
300
350
400
450
500
5 10 15 20 25
Position
Co
un
ts p
er 3
sec
on
ds
bent 2 polished
bent 2 unpolished
Pryolitic Graphite Intensity
Crystal alignment, 1 kw, 30 degree detector angle
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10 11 12 13 14 15 16 17 18 19 20
Position
cts
Si Spectrum SEBP by Angle
<111> Si bent Tangential beamport spectrum 1 kW
0
50
100
150
200
250
300
350
400
450
500
0 5 10 15 20 25 30
Crystal Position
Co
un
ts p
er 3
se
co
nd
s
PG Spectrum SEBP by Angle
PG Tangential beamport spectrum 1 kW
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 5 10 15 20 25 30 35 40 45 50
Crystal Position
co
un
ts p
er 3
sec
on
ds
Filter Testing
• Pyrolitic graphite
• Bismuth
Spectrum Bare and PG Filtered
100
1100
2100
3100
4100
5100
6100
7100
8100
9100
0.001 0.011 0.021 0.031 0.041 0.051 0.061 0.071 0.081 0.091
Energy (eV)
Co
un
ts
Sapphire filter CORE III
Bare beam CORE III
PG Spectrum Filtered
78%
Bi Filtered Spectrum
Spectrum Bare and Bismuth Filtered
0.E+00
1.E+04
2.E+04
3.E+04
4.E+04
5.E+04
6.E+04
0 5 10 15 20 25 30 35 40 45 50
Angle
Co
un
t
57%
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