Emily Grace | Northwestern College, Iowa (original) (raw)
Papers by Emily Grace
Single-molecule fluorescence microscopy has become a popular tool for exploring structural change... more Single-molecule fluorescence microscopy has become a popular tool for exploring structural changes and dynamics of biological systems. In our laboratory, we use single-molecule techniques to track conformational changes of immobilized nitric oxide synthase (NOS) and determine their relationship to catalytic activity. Properly immobilizing biomolecules like NOS on a glass surface requires careful attention to coverslip cleaning and preparation. There are many protocols available for cleaning glass coverslips, but these protocols are time-consuming and often use harsh conditions. Alternatively, commercially cleaned and passivated coverslips are available but are quite expensive. In this poster, we examine the possibility of using purchased pre-cleaned coverslips (Schott Nexterion) that come ready to be prepared for single-molecule measurements. We present figures and measurements of merit comparing the pre-cleaned coverslips with ozone cleaned coverslips; demonstrating the effectivene...
Large liquid argon detectors have become widely used in low rate experiments, including dark matt... more Large liquid argon detectors have become widely used in low rate experiments, including dark matter and neutrino research. However, the optical properties of liquid argon are not well understood at the large scales relevant for current and near-future detectors.The index of refraction of liquid argon at the scin- tillation wavelength has not been measured, and current Rayleigh scattering length calculations disagree with measurements. Furthermore, the Rayleigh scattering length and index of refraction of solid argon and solid xenon at their scintillation wavelengths have not been previously measured or calculated. We introduce a new calculation using existing data in liquid and solid argon and xenon to extrapolate the optical properties at the scintillation wavelengths using the Sellmeier dispersion relationship.
There is wealth of evidence that the majority of the matter in the universe is composed of non-ba... more There is wealth of evidence that the majority of the matter in the universe is composed of non-baryonic dark matter. One candidate for dark matter is weakly interacting massive particle (WIMP). There are many detectors searching for evidence of WIMP particle interaction. A common active medium is liquid argon. Argon, like all noble elements is a scintillator, meaning it produces light when exposed to radiation. Within these large, liquid argon detectors, one method of determining the significance of the event is by determining the event location. This involves a deep understanding of how the scintillation light optically propagates through the detector, including the Rayleigh scattering length. The Rayleigh scattering length of liquid argon was formerly contention, as experimental results did not agree with a theoretical calculation. We will discuss an update calculation of the wavelength dependent scattering in argon using historical measurements. These calculations were tested usi...
International Journal of Christianity & Education
This article is a small empirical study based on two assignments, both involving reading and writ... more This article is a small empirical study based on two assignments, both involving reading and writing, in two physics courses at a Christian college. Students read theological, philosophical, and scientific arguments and produced research papers. By performing interdisciplinary intellectual work, students considered the compatibility of science and Christian faith through a specific issue: the age of the earth and universe. Students indicated that they both changed and formed beliefs through their completion of the assignments. Furthermore, students became more amenable to the possibility that the principles of Christianity and science are compatible. The authors argue that incorporating theological questions into science classes fosters students' faith as well as their learning and moral development.
Astroparticle Physics
The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors c... more The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors containing 3.0 kg of C 4 F 10 and collected an exposure of 231.4 kgd at SNOLAB between March 2012 and January 2014. We report on the final results of this experiment which includes for the first time the complete data set and improved analysis techniques including acoustic
Astroparticle Physics, 2015
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Pre-Print
This article is a small empirical study based on two assignments, both involving reading and writ... more This article is a small empirical study based on two assignments, both involving reading and writing, in two physics courses at a Christian college. Students read theological, philosophical, and scientific arguments and produced research papers. By performing interdisciplinary intellectual work, students considered the compatibility of science and Christian faith through a specific issue: the age of the earth and universe. Students indicated that they both changed and formed beliefs through their completion of the assignments. Furthermore, students became more amenable to the possibility that the principles of Christianity and science are compatible. The authors argue that incorporating theological questions into science classes fosters students' faith as well as their learning and moral development. Keywords Science and Christian faith, age of the earth, physics classroom
The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors c... more The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors containing 3.2 kg of C 4 F 10 and collected an exposure of 231.4 kg days at SNOLAB between March 2012 and January 2014. We report on the final results of this experiment which includes for the first time the complete data set and improved analysis techniques including acous-*
Physics Procedia, 2015
The direct search for dark matter is entering a period of increased sensitivity to the hypothetic... more The direct search for dark matter is entering a period of increased sensitivity to the hypothetical Weakly Interacting Massive Particle (WIMP). One such technology that is being examined is a scintillation only noble liquid experiment, MiniCLEAN. MiniCLEAN utilizes over 500 kg of liquid cryogen to detect nuclear recoils from WIMP dark matter and serves as a demonstration for a future detector of order 50 to 100 tonnes. The liquid cryogen is interchangeable between argon and neon to study the A 2 dependence of the potential signal and examine backgrounds. MiniCLEAN utilizes a unique modular design with spherical geometry to maximize the light yield using cold photomultiplier tubes in a single-phase detector. Pulse shape discrimination techniques are used to separate nuclear recoil signals from electron recoil backgrounds. MiniCLEAN will be spiked with additional 39 Ar to demonstrate the effective reach of the pulse shape discrimination capability. Assembly of the experiment is underway at SNOLAB and an update on the project is given.
ABSTRACT Phase slippage between plasma wave and electron bunch limits maximum energy gain in lase... more ABSTRACT Phase slippage between plasma wave and electron bunch limits maximum energy gain in laser-wakefield acceleration. Plasma-density spatial tailoring has been proposed as a way to overcome this dephasing problem [1]. In practice, such tailoring can be achieved in super-sonic gas jets by use of a nozzle with a tapered orifice. We have developed a 3-D temporally-resolved interferometric tomography technique to characterize dynamical density distribution of such gas jets. The SIRT (Simultaneous Iterative Reconstructive Technique) algorithm [2] was implemented. We also present preliminarily results on laser wakefield acceleration in the tailored gradient density profiles resulting from use of the characterized jets as targets. [4pt] [1] W. Rittershofer, C. B. Schroeder, E. Esarey, F. J. Gr"uner, and W. P. Leemans, ``Tapered plasma channels to phase-lock accelerating and focusing forces in laser-plasma accelerators,'' Physics of Plasmas 17, 063104, (2010). [0pt] [2] P. Gilbert, ``Iterative methods for the three-dimensional reconstruction of an object from projections,'' Journal of Theoretical Biology 36, 105 (1972).
Submitted to Journal of Nuclear Instruments and Methods
Like all the noble elements, argon and xenon are scintillators, i.e. they produce light when expo... more Like all the noble elements, argon and xenon are scintillators, i.e. they produce light when exposed to
radiation. Large liquid argon detectors have become widely used in low background experiments, including
dark matter and neutrino research. However, the index of refraction of liquid argon at the scintillation
wavelength has not been measured and current Rayleigh scattering length calculations disagree with
measurements. Furthermore, the Rayleigh scattering length and index of refraction of solid argon and solid
xenon at their scintillation wavelengths have not been previously measured or calculated. We introduce
a new calculation using previously measured data in liquid and solid argon and xenon to extrapolate the
optical properties at the scintillation wavelengths using the Sellmeier dispersion relationship. As a point
of validation, we compare our extrapolated index of refraction for liquid xenon against the measured value
and nd agreement within the uncertainties. This method results in a Rayleigh scattering length for liquid
argon at the triple point of 55 5 cm, a Rayleigh scattering length of 40 4 cm for solid argon at the
triple point, and a Rayleigh scattering length of 14 1 cm for solid xenon at the triple point.
Many current and future dark matter and neutrino detectors are designed to measure scintillation ... more Many current and future dark matter and neutrino detectors are designed to measure scintillation light with a large array of photomultiplier tubes (PMTs). The energy resolution and particle identification capabilities of these detectors depend in part on the ability to accurately identify individual photoelectrons in PMT waveforms despite large variability in pulse amplitudes and pulse pileup. We describe a Bayesian technique that can identify the times of individual photoelectrons in a sampled PMT waveform without deconvolution, even when pileup is present. To demonstrate the technique, we apply it to the general problem of particle identification in single-phase liquid argon dark matter detectors. Using the output of the Bayesian photoelectron counting algorithm described in this paper, we construct several test statistics for rejection of backgrounds for dark matter searches in argon. Compared to simpler methods based on either observed charge or peak finding, the photoelectron counting technique improves both energy resolution and particle identification of low energy events in calibration data from the DEAP-1 detector and simulation of the larger MiniCLEAN dark matter detector.
Recent results from the PICASSO dark matter search experiment at SNO-LAB are reported. These resu... more Recent results from the PICASSO dark matter search experiment at SNO-LAB are reported. These results were obtained using a subset of 10 detec-
New data are reported from the operation of a 4.0 kg CF3I bubble chamber in the 6800-footdeep SNO... more New data are reported from the operation of a 4.0 kg CF3I bubble chamber in the 6800-footdeep SNOLAB underground laboratory. The effectiveness of ultrasound analysis in discriminating alpha-decay background events from single nuclear recoils has been confirmed, with a lower bound of >99.3% rejection of alpha-decay events. Twenty single nuclear recoil event candidates and three multiple bubble events were observed during a total exposure of 553 kg-days distributed over three different bubble nucleation thresholds. The effective exposure for single bubble recoil-like events was 437.4 kg-days. A neutron background internal to the apparatus, of known origin, is estimated to account for five single nuclear recoil events and is consistent with the observed rate of multiple bubble events. The remaining excess of single bubble events exhibits characteristics indicating the presence of an additional background. These data provide new direct detection constraints on WIMP-proton spin-dependent scattering for WIMP masses >20 GeV/c 2 and demonstrate significant sensitivity for spin-independent interactions. 95.35.+d, 95.30.Cq
We propose to build a ton-scale bubble chamber to search for dark matter. This would be the next ... more We propose to build a ton-scale bubble chamber to search for dark matter. This would be the next in the series of COUPP bubble chambers that have been searching with ever increasing sensitivity over the last five years. This device would be built and commissioned at Fermilab before being deployed deep underground at SNOLAB.
Thesis Chapters by Emily Grace
There is a wealth of evidence that the majority of the matter in the universe is composed of non-... more There is a wealth of evidence that the majority of the matter in the universe is composed of non-baryonic dark matter. One candidate for dark matter is weakly interacting massive particle (WIMP). There are many detectors searching for evidence of WIMP particle interaction. A common active medium is a liquid argon. Argon, like all noble elements, is a scintillator, meaning it produces light when exposed to radiation. Within these large, liquid argon detectors, one method of determining the signi cance of the event is by determining the event location. This involves a deep understanding of how the scintillation
light optically propagates through the detector, including the Rayleigh scattering length. The Rayleigh scattering length of liquid argon was formerly contention, as experimental results did not agree with a theoretical calculation. We will discuss an update calculation
of the wavelength dependent scattering in argon using historical measurements. These calculations were tested using an experimental test stand, designed and constructed at Royal Holloway. This will show that the scattering length of the scintillation light of
liquid argon is 58 cm.
Single-molecule fluorescence microscopy has become a popular tool for exploring structural change... more Single-molecule fluorescence microscopy has become a popular tool for exploring structural changes and dynamics of biological systems. In our laboratory, we use single-molecule techniques to track conformational changes of immobilized nitric oxide synthase (NOS) and determine their relationship to catalytic activity. Properly immobilizing biomolecules like NOS on a glass surface requires careful attention to coverslip cleaning and preparation. There are many protocols available for cleaning glass coverslips, but these protocols are time-consuming and often use harsh conditions. Alternatively, commercially cleaned and passivated coverslips are available but are quite expensive. In this poster, we examine the possibility of using purchased pre-cleaned coverslips (Schott Nexterion) that come ready to be prepared for single-molecule measurements. We present figures and measurements of merit comparing the pre-cleaned coverslips with ozone cleaned coverslips; demonstrating the effectivene...
Large liquid argon detectors have become widely used in low rate experiments, including dark matt... more Large liquid argon detectors have become widely used in low rate experiments, including dark matter and neutrino research. However, the optical properties of liquid argon are not well understood at the large scales relevant for current and near-future detectors.The index of refraction of liquid argon at the scin- tillation wavelength has not been measured, and current Rayleigh scattering length calculations disagree with measurements. Furthermore, the Rayleigh scattering length and index of refraction of solid argon and solid xenon at their scintillation wavelengths have not been previously measured or calculated. We introduce a new calculation using existing data in liquid and solid argon and xenon to extrapolate the optical properties at the scintillation wavelengths using the Sellmeier dispersion relationship.
There is wealth of evidence that the majority of the matter in the universe is composed of non-ba... more There is wealth of evidence that the majority of the matter in the universe is composed of non-baryonic dark matter. One candidate for dark matter is weakly interacting massive particle (WIMP). There are many detectors searching for evidence of WIMP particle interaction. A common active medium is liquid argon. Argon, like all noble elements is a scintillator, meaning it produces light when exposed to radiation. Within these large, liquid argon detectors, one method of determining the significance of the event is by determining the event location. This involves a deep understanding of how the scintillation light optically propagates through the detector, including the Rayleigh scattering length. The Rayleigh scattering length of liquid argon was formerly contention, as experimental results did not agree with a theoretical calculation. We will discuss an update calculation of the wavelength dependent scattering in argon using historical measurements. These calculations were tested usi...
International Journal of Christianity & Education
This article is a small empirical study based on two assignments, both involving reading and writ... more This article is a small empirical study based on two assignments, both involving reading and writing, in two physics courses at a Christian college. Students read theological, philosophical, and scientific arguments and produced research papers. By performing interdisciplinary intellectual work, students considered the compatibility of science and Christian faith through a specific issue: the age of the earth and universe. Students indicated that they both changed and formed beliefs through their completion of the assignments. Furthermore, students became more amenable to the possibility that the principles of Christianity and science are compatible. The authors argue that incorporating theological questions into science classes fosters students' faith as well as their learning and moral development.
Astroparticle Physics
The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors c... more The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors containing 3.0 kg of C 4 F 10 and collected an exposure of 231.4 kgd at SNOLAB between March 2012 and January 2014. We report on the final results of this experiment which includes for the first time the complete data set and improved analysis techniques including acoustic
Astroparticle Physics, 2015
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Pre-Print
This article is a small empirical study based on two assignments, both involving reading and writ... more This article is a small empirical study based on two assignments, both involving reading and writing, in two physics courses at a Christian college. Students read theological, philosophical, and scientific arguments and produced research papers. By performing interdisciplinary intellectual work, students considered the compatibility of science and Christian faith through a specific issue: the age of the earth and universe. Students indicated that they both changed and formed beliefs through their completion of the assignments. Furthermore, students became more amenable to the possibility that the principles of Christianity and science are compatible. The authors argue that incorporating theological questions into science classes fosters students' faith as well as their learning and moral development. Keywords Science and Christian faith, age of the earth, physics classroom
The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors c... more The PICASSO dark matter search experiment operated an array of 32 superheated droplet detectors containing 3.2 kg of C 4 F 10 and collected an exposure of 231.4 kg days at SNOLAB between March 2012 and January 2014. We report on the final results of this experiment which includes for the first time the complete data set and improved analysis techniques including acous-*
Physics Procedia, 2015
The direct search for dark matter is entering a period of increased sensitivity to the hypothetic... more The direct search for dark matter is entering a period of increased sensitivity to the hypothetical Weakly Interacting Massive Particle (WIMP). One such technology that is being examined is a scintillation only noble liquid experiment, MiniCLEAN. MiniCLEAN utilizes over 500 kg of liquid cryogen to detect nuclear recoils from WIMP dark matter and serves as a demonstration for a future detector of order 50 to 100 tonnes. The liquid cryogen is interchangeable between argon and neon to study the A 2 dependence of the potential signal and examine backgrounds. MiniCLEAN utilizes a unique modular design with spherical geometry to maximize the light yield using cold photomultiplier tubes in a single-phase detector. Pulse shape discrimination techniques are used to separate nuclear recoil signals from electron recoil backgrounds. MiniCLEAN will be spiked with additional 39 Ar to demonstrate the effective reach of the pulse shape discrimination capability. Assembly of the experiment is underway at SNOLAB and an update on the project is given.
ABSTRACT Phase slippage between plasma wave and electron bunch limits maximum energy gain in lase... more ABSTRACT Phase slippage between plasma wave and electron bunch limits maximum energy gain in laser-wakefield acceleration. Plasma-density spatial tailoring has been proposed as a way to overcome this dephasing problem [1]. In practice, such tailoring can be achieved in super-sonic gas jets by use of a nozzle with a tapered orifice. We have developed a 3-D temporally-resolved interferometric tomography technique to characterize dynamical density distribution of such gas jets. The SIRT (Simultaneous Iterative Reconstructive Technique) algorithm [2] was implemented. We also present preliminarily results on laser wakefield acceleration in the tailored gradient density profiles resulting from use of the characterized jets as targets. [4pt] [1] W. Rittershofer, C. B. Schroeder, E. Esarey, F. J. Gr"uner, and W. P. Leemans, ``Tapered plasma channels to phase-lock accelerating and focusing forces in laser-plasma accelerators,'' Physics of Plasmas 17, 063104, (2010). [0pt] [2] P. Gilbert, ``Iterative methods for the three-dimensional reconstruction of an object from projections,'' Journal of Theoretical Biology 36, 105 (1972).
Submitted to Journal of Nuclear Instruments and Methods
Like all the noble elements, argon and xenon are scintillators, i.e. they produce light when expo... more Like all the noble elements, argon and xenon are scintillators, i.e. they produce light when exposed to
radiation. Large liquid argon detectors have become widely used in low background experiments, including
dark matter and neutrino research. However, the index of refraction of liquid argon at the scintillation
wavelength has not been measured and current Rayleigh scattering length calculations disagree with
measurements. Furthermore, the Rayleigh scattering length and index of refraction of solid argon and solid
xenon at their scintillation wavelengths have not been previously measured or calculated. We introduce
a new calculation using previously measured data in liquid and solid argon and xenon to extrapolate the
optical properties at the scintillation wavelengths using the Sellmeier dispersion relationship. As a point
of validation, we compare our extrapolated index of refraction for liquid xenon against the measured value
and nd agreement within the uncertainties. This method results in a Rayleigh scattering length for liquid
argon at the triple point of 55 5 cm, a Rayleigh scattering length of 40 4 cm for solid argon at the
triple point, and a Rayleigh scattering length of 14 1 cm for solid xenon at the triple point.
Many current and future dark matter and neutrino detectors are designed to measure scintillation ... more Many current and future dark matter and neutrino detectors are designed to measure scintillation light with a large array of photomultiplier tubes (PMTs). The energy resolution and particle identification capabilities of these detectors depend in part on the ability to accurately identify individual photoelectrons in PMT waveforms despite large variability in pulse amplitudes and pulse pileup. We describe a Bayesian technique that can identify the times of individual photoelectrons in a sampled PMT waveform without deconvolution, even when pileup is present. To demonstrate the technique, we apply it to the general problem of particle identification in single-phase liquid argon dark matter detectors. Using the output of the Bayesian photoelectron counting algorithm described in this paper, we construct several test statistics for rejection of backgrounds for dark matter searches in argon. Compared to simpler methods based on either observed charge or peak finding, the photoelectron counting technique improves both energy resolution and particle identification of low energy events in calibration data from the DEAP-1 detector and simulation of the larger MiniCLEAN dark matter detector.
Recent results from the PICASSO dark matter search experiment at SNO-LAB are reported. These resu... more Recent results from the PICASSO dark matter search experiment at SNO-LAB are reported. These results were obtained using a subset of 10 detec-
New data are reported from the operation of a 4.0 kg CF3I bubble chamber in the 6800-footdeep SNO... more New data are reported from the operation of a 4.0 kg CF3I bubble chamber in the 6800-footdeep SNOLAB underground laboratory. The effectiveness of ultrasound analysis in discriminating alpha-decay background events from single nuclear recoils has been confirmed, with a lower bound of >99.3% rejection of alpha-decay events. Twenty single nuclear recoil event candidates and three multiple bubble events were observed during a total exposure of 553 kg-days distributed over three different bubble nucleation thresholds. The effective exposure for single bubble recoil-like events was 437.4 kg-days. A neutron background internal to the apparatus, of known origin, is estimated to account for five single nuclear recoil events and is consistent with the observed rate of multiple bubble events. The remaining excess of single bubble events exhibits characteristics indicating the presence of an additional background. These data provide new direct detection constraints on WIMP-proton spin-dependent scattering for WIMP masses >20 GeV/c 2 and demonstrate significant sensitivity for spin-independent interactions. 95.35.+d, 95.30.Cq
We propose to build a ton-scale bubble chamber to search for dark matter. This would be the next ... more We propose to build a ton-scale bubble chamber to search for dark matter. This would be the next in the series of COUPP bubble chambers that have been searching with ever increasing sensitivity over the last five years. This device would be built and commissioned at Fermilab before being deployed deep underground at SNOLAB.
There is a wealth of evidence that the majority of the matter in the universe is composed of non-... more There is a wealth of evidence that the majority of the matter in the universe is composed of non-baryonic dark matter. One candidate for dark matter is weakly interacting massive particle (WIMP). There are many detectors searching for evidence of WIMP particle interaction. A common active medium is a liquid argon. Argon, like all noble elements, is a scintillator, meaning it produces light when exposed to radiation. Within these large, liquid argon detectors, one method of determining the signi cance of the event is by determining the event location. This involves a deep understanding of how the scintillation
light optically propagates through the detector, including the Rayleigh scattering length. The Rayleigh scattering length of liquid argon was formerly contention, as experimental results did not agree with a theoretical calculation. We will discuss an update calculation
of the wavelength dependent scattering in argon using historical measurements. These calculations were tested using an experimental test stand, designed and constructed at Royal Holloway. This will show that the scattering length of the scintillation light of
liquid argon is 58 cm.