WPM-E - Instrumentation 2 Baltimore 1-2 14:30 - 16:45
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| Chair(s): Zaijing Sun
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WPM-E.1
14:30 Developing a Remote Gamma Spectra Collection System for Nuclear Sciences ZJ Sun*, University of Nevada Las Vegas
; KD Nangeelil, University of Nevada Las Vegas; H Searcy, University of Nevada Las Vegas; M Turner, University of Nevada Las Vegas
Abstract: During the pandemic, students and researchers suffered from the interruption of experimental activities, especially in nuclear detection and measurement experiments. Some related activities in teaching and research were canceled. To address this challenge, we developed a remote gamma spectra collection system in radiation laboratories, which allows students and researchers to obtain gamma spectra through the Internet and control the sample exchangers remotely. Implementing the project benefits teaching and research and simultaneously reduces the personnel in laboratories. It supports students' success in completing nuclear-related degrees on time during the pandemic years.
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WPM-E.2
14:45 Dosimetry in Pulsed Radiation Fields R Collatz*, Berthold Technologies GmbH & Co. KG
; R Greim, Berthold Technologies GmbH & Co. KG
Abstract: The detection of both gamma and neutron dose and dose rate respectively in pulsed fields is a particular challenge. Due to the detector timing characteristics, a reliable detection of the dose arising from ultra-short accelerator pulses is not guaranteed due to the early onset of saturation effects. For gamma dose rate meters this effect is typically irrelevant when current measurement is applied, usually in conjunction with ionization chambers. In the present case, we demonstrate an alternative, a proportional counter in current mode. This technique allows a far higher sensitivity while simultaneously reducing the detector size.
For neutron detection in pulsed fields a unique method is described. Due to nuclear reactions of intermediate and high energy neutrons in matter like the moderator or an organic scintillator, short lived particles emitting those reaction residuals can be detected easily between the accelerator bursts. Saturation effects can hardly occur in this detection technique resulting in an unusually large dynamic dose range starting from background level up to some µSv per pulse, irrespective of the pulse length.
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WPM-E.3
15:00 Using Monte Carlo Calculation Modeling to Predict Minimal Detectable Activity for Large Article/Waste Contamination Monitors RL Palatine*, RT Technologies Inc
; G Manessi, Else Nuclear
Abstract: Abstract:
There can be considerable operational and financial risk associated with purchasing large article monitors (LAMS) and/or large waste container monitors that cannot ultimately function as intended in field environments that they are placed. Varying background radiation levels combined with the desire to optimize process efficiency often leads to alarm thresholds that cannot be attained. Consequently, purchasing these monitors and not being able to use them as intended can be costly mistakes.
Else Nuclear (Italy) has combined with RT Technologies/Advetage Solutions (US) to provide proactive computer-based radiological modeling to ensure that the optimal configuration of the contamination monitors is identified and prescribed prior to deployment for users of the Easy Scan and LAM ID Monitors. The computer modeling is based on Monte Carlo simulations that are performed using the MCNP6.2 Monte Carlo code (Monte Carlo N–Particle® Transport Code System Version 6.2 ( )), as approved by the Nuclear Regulatory Commission (US NRC). The code allows for the prediction or estimating of the expected Minimal Detectable Activity (MDA) and related uncertainty of specific isotopes for a given gamma background radiation level, shielding environment, and sample counting times. In this study, Monte Carlo simulations were used to estimate the 60Co, 94Nb, and 137Cs MDA’s of the ELSE LAM ID/Box Counter and Easy Scan Waste Monitors.
This study will review the methods and findings of the Monte Carlo Modeling Tool used to predict operating performance and ultimate MDA’s for the LAM ID Large Article Monitor and the EASY SCAN Waste Container Monitor.
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WPM-E.4
15:15 Comparison of GEANT 4 simulation and experimental measurements of CosmicGuard background reduction system KD Nangeelil*, University of Nevada, Las Vegas
; S Pak, University of Nevada, Las Vegas; ZJ Sun, University of Nevada Las Vegas; Kr Nangeelil
Abstract: CosmicGuard system is an addon to the HpGe counting systems, which performs the Cosmic background reduction that cannot be achieved through lead shielding. Typical background reduction of 10-35% is envisaged with such systems, which helps to use the HPGe systems for low active samples, resulting a lower Minimum Detectable Activity. A GEANT 4 simulation of the experimental set up with several cosmic ray interactions were carried out by simulating the detector geometry and its surrounding, the source particles and background spectra in ground level. Interactions of cosmic rays in the HPGe detector was investigated experimentally and by GEANT4 simulations and compared. A very good agreement qualitative and quantitative between the measured and simulated spectra was achieved, confirming that GEANT 4 is a suitable detector simulation tool for this type of studies.
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WPM-E.5
15:30 BREAK
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WPM-E.6
16:00 DIY Neutron Spectrometer N Rashidifard*, Mirion
Abstract: Traditional neutron spectrometers are large, complex, bulky, and difficult to use. With the popularity and accessibility of low cost 3-D printers and off the shelf solid state neutron detectors one could potentially create a simple system. For this setup a commercially available solid state thermal neutron detector was paired with moderating caps of varying thickness generating multiple response functions. Moderating caps were printed using a common popular 3-D printer paired with PLA filament and PLA filament with additives creating various response functions. Modeling was done in MCNP6 to develop response curves and then for evaluating effectiveness in multiple neutron fields. Testing will be done after on characterized neutron sources to benchmark the exercise. If successful, this will be a valuable approach for the collection of spectral data where barriers, either financially or logistically, are present.
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WPM-E.7
16:15 Analysis of the Neutron Radiographic Image Quality and Beam Intensity Produced by a Compact Multi-channel Collimator HL Snyder*, Worcester Polytechnic Institute
; BW Jolicour, Worcester Polytechnic Institute; N Hugger, Worcester Polytechnic Institute; DC Medich, Worcester Polytechnic Institute
Abstract: We investigated the image quality and beam intensity of thermal neutron radiography after replacing a standard single-channel neutron collimator with a compact array of micro-collimators. In this study, the MCNP6 Monte Carlo computer code was used to simulate a 2cm x 2cm area isotropic thermal neutron source which then was collimated by an array of micron-sized neutron collimators that measured 29.8 m in diameter and with lengths that varied from 0.6mm to 3mm. These micro-collimators were spaced 30m apart and assembled into a 2cm x 2cm array. The image quality of the neutron beams produced by the resulting collimator arrays was assessed by imaging the edge of a very thin (~0.01mm) gadolinium foil to obtain the image Modulation Transfer Function (MTF). The MCNP6 resulting flux map from each simulation then was converted into a grey-scale Tiff image and the image’s resulting MTF obtained using the ImageJ computer program with the imaging beam’s geometric unsharpness, which is a limiting factor in the image resolution, determined at the 10% value of the MTF curve. In this study, we found that a 2 cm x 2 cm x 0.298 cm micro-collimator, corresponding to a length to hole-diameter ratio of 100:1 and collimator length of 2.98 mm, produced a beam with a geometric unsharpness of 32m. Compared to a standard single-channel collimator with a 2cm x 2cm aperture, the single-channel collimator would need to be 660 cm long to produce an equivalent geometric sharpness. Yet because of its shorter length, the imaging beam intensity from our 2.98 mm thick collimator-array was approximately 50 times greater than that of an equivalent single channel collimator. A physical test of this collimator is ongoing using a neutron source at Worcester Polytechnic Institute.
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WPM-E.8
16:30 A Novel Integrated Continuous Quality Control Method for Gamma Spectroscopy Systems FL Bronson*, Mirion Technologies - Canberra
; Fr Bronson
Abstract: A critical element of a Quality Assurance program is to periodically document that the system has been stable in its performance since the last calibration. This includes tests for stability of the gain [peak centroid], stability of the detector performance [peak width or FWHM], and stability of the detector efficiency [nuclide activity for a constant source geometry]. The normal method is to interrupt the sample measurement process, insert and count a Quality Control sample. Where this works OK in the laboratory, albeit with a loss of sample assay time, it does not work very well for remote continuous measurements systems [e.g. effluent monitoring systems] that would have to be removed from their primary monitoring task to do the QC tests. In recent systems we have embedded a very weak natural Thorium source inside the shield near the detector in a location where the presence or absence of a sample does not affect it. Thorium has many gamma energies, going up to 2615 keV. We shield out the low energy lines with 2-3 cm of Tungsten, and monitor the performance of the high energy peak. The activity of the thorium is low enough that when combined with the spectral analysis the performance for the normal sample is not significantly reduced. However, for QC measurements with this weak source, the count time can be very long to get adequate statistics. What makes this system work is the Mirion Data Analyst. It can perform short sample count times for normal assays with the appropriate libraries to analyze those samples and to remove any weak thorium activity. And it can perform very long counts using the modified thorium library to determine the thorium QC parameters on the peak of interest. And it can do both of those at the same time. And it can do the QC measurements repeatedly and continuously for a 100% continuous uninterrupted record of the detector performance – not just periodic checks. Examples of systems using this method will be presented.
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