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

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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

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5 10 15 20 25

Position

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bent 1 polished

unbent polished

Bent Silicon Intensity

<111> Si 30 degree detector angle, 1 kW

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5 10 15 20 25

Position

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bent 2 unpolished

Pryolitic Graphite Intensity

Crystal alignment, 1 kw, 30 degree detector angle

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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

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Crystal Position

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PG Spectrum SEBP by Angle

PG Tangential beamport spectrum 1 kW

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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)

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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

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57%