New neutrino–nucleus interaction cross-section measurements are required to improve nuclear models sufficiently for future long baseline neutrino experiments to meet their sensitivity goals. A time ...projection chamber (TPC) filled with a high-pressure gas is a promising detector to characterise the neutrino sources used for such experiments. A gas-filled TPC is ideal for measuring low-energy particles, which travel further in gas than in solid or liquid detectors and using high-pressure increases the target density, resulting in more neutrino interactions. We examine the suitability of multiwire proportional chambers (MWPCs) from the ALICE TPC for use as the readout chambers of a high-pressure gas TPC. These chambers were previously operated at atmospheric pressure. We report the successful operation of an ALICE TPC outer readout chamber (OROC) at pressures up to 4.2 bar absolute (barA) with
Ar-CH
4
mixtures with a
CH
4
content between 2.8 and 5.0%, and so far up to 4 bar absolute with
Ar-CO
2
(90-10). The charge gain of the OROC was measured with signals induced by an
55
Fe
source. The largest gain achieved at 4.2 bar was
(
29
±
1
)
·
10
3
in
Ar-CH
4
with 4.0%
CH
4
with an anode voltage of
2975
V
. In
Ar-CO
2
with 10%
CO
2
at 4 barA, a gain of
(
4.2
±
0.1
)
·
10
3
was observed with anode voltage
2975
V
. We extrapolate that at 10 barA, an interesting pressure for future neutrino experiments, a gain of 5000 in
Ar-CO
2
with 10%
CO
2
(10,000 in
Ar-CH
4
with
∼
4
%
CH
4
) may be achieved with anode voltage of
4.6
kV
(
∼
3.6
kV
).
We present studies of proton fluxes in the T10 beamline at CERN. A prototype high pressure gas time projection chamber (TPC) was exposed to the beam of protons and other particles, using the 0.8 ...GeV/c momentum setting in T10, in order to make cross section measurements of low energy protons in argon. To explore the energy region comparable to hadrons produced by GeV-scale neutrino interactions at oscillation experiments, i.e., near 0.1 GeV of kinetic energy, methods of moderating the T10 beam were employed: the dual technique of moderating the beam with acrylic blocks and measuring scattered protons off the beam axis was used to decrease the kinetic energy of incident protons, as well as change the proton/minimum ionising particle (MIP) composition of the incident flux. Measurements of the beam properties were made using time of flight systems upstream and downstream of the TPC. The kinetic energy of protons reaching the TPC was successfully changed from ∼0.3 GeV without moderator blocks to less than 0.1 GeV with four moderator blocks (40 cm path length). The flux of both protons and MIPs off the beam axis was increased. The ratio of protons to MIPs vary as a function of the off-axis angle allowing for possible optimisation of the detector to select the type of required particles. Simulation informed by the time of flight measurements show that with four moderator blocks placed in the beamline, (5.6 ± 0.1) protons with energies below 0.1 GeV per spill traversed the active TPC region. Measurements of the beam composition and energy are presented.
Abstract New neutrino–nucleus interaction cross-section measurements are required to improve nuclear models sufficiently for future long baseline neutrino experiments to meet their sensitivity goals. ...A time projection chamber (TPC) filled with a high-pressure gas is a promising detector to characterise the neutrino sources used for such experiments. A gas-filled TPC is ideal for measuring low-energy particles, which travel further in gas than in solid or liquid detectors and using high-pressure increases the target density, resulting in more neutrino interactions. We examine the suitability of multiwire proportional chambers (MWPCs) from the ALICE TPC for use as the readout chambers of a high-pressure gas TPC. These chambers were previously operated at atmospheric pressure. We report the successful operation of an ALICE TPC outer readout chamber (OROC) at pressures up to 4.2 bar absolute (barA) with $$\text {Ar-CH}_4$$ Ar-CH 4 mixtures with a $$\text {CH}_{4}$$ CH 4 content between 2.8 and 5.0%, and so far up to 4 bar absolute with $${\text {Ar-CO}}_2$$ Ar-CO 2 (90-10). The charge gain of the OROC was measured with signals induced by an $$^{55}\text {Fe}$$ 55 Fe source. The largest gain achieved at 4.2 bar was $$(29\pm 1)\cdot 10^{3}$$ ( 29 ± 1 ) · 10 3 in $$\text {Ar-CH}_4$$ Ar-CH 4 with 4.0% $$\text {CH}_{4}$$ CH 4 with an anode voltage of $${2975}\,\hbox {V}$$ 2975 V . In $${\text {Ar-CO}}_2$$ Ar-CO 2 with 10% $$\text {CO}_{2}$$ CO 2 at 4 barA, a gain of $$(4.2\pm 0.1)\cdot 10^{3}$$ ( 4.2 ± 0.1 ) · 10 3 was observed with anode voltage $${2975}\,\hbox {V}$$ 2975 V . We extrapolate that at 10 barA, an interesting pressure for future neutrino experiments, a gain of 5000 in $${\text {Ar-CO}}_2$$ Ar-CO 2 with 10% $$\text {CO}_{2}$$ CO 2 (10,000 in $$\text {Ar-CH}_4$$ Ar-CH 4 with $$\sim \!{4}{\%}$$ ∼ 4 % $$\text {CH}_{4}$$ CH 4 ) may be achieved with anode voltage of $${4.6}\,\hbox {kV}$$ 4.6 kV ( $$\sim \!{3.6}\,\hbox {kV}$$ ∼ 3.6 kV ).
Abstract New neutrino–nucleus interaction cross-section measurements are required to improve nuclear models sufficiently for future long baseline neutrino experiments to meet their sensitivity goals. ...A time projection chamber (TPC) filled with a high-pressure gas is a promising detector to characterise the neutrino sources used for such experiments. A gas-filled TPC is ideal for measuring low-energy particles, which travel further in gas than in solid or liquid detectors and using high-pressure increases the target density, resulting in more neutrino interactions. We examine the suitability of multiwire proportional chambers (MWPCs) from the ALICE TPC for use as the readout chambers of a high-pressure gas TPC. These chambers were previously operated at atmospheric pressure. We report the successful operation of an ALICE TPC outer readout chamber (OROC) at pressures up to 4.2 bar absolute (barA) with $$\text {Ar-CH}_4$$ Ar-CH 4 mixtures with a $$\text {CH}_{4}$$ CH 4 content between 2.8 and 5.0%, and so far up to 4 bar absolute with $${\text {Ar-CO}}_2$$ Ar-CO 2 (90-10). The charge gain of the OROC was measured with signals induced by an $$^{55}\text {Fe}$$ 55 Fe source. The largest gain achieved at 4.2 bar was $$(29\pm 1)\cdot 10^{3}$$ ( 29 ± 1 ) · 10 3 in $$\text {Ar-CH}_4$$ Ar-CH 4 with 4.0% $$\text {CH}_{4}$$ CH 4 with an anode voltage of $${2975}\,\hbox {V}$$ 2975 V . In $${\text {Ar-CO}}_2$$ Ar-CO 2 with 10% $$\text {CO}_{2}$$ CO 2 at 4 barA, a gain of $$(4.2\pm 0.1)\cdot 10^{3}$$ ( 4.2 ± 0.1 ) · 10 3 was observed with anode voltage $${2975}\,\hbox {V}$$ 2975 V . We extrapolate that at 10 barA, an interesting pressure for future neutrino experiments, a gain of 5000 in $${\text {Ar-CO}}_2$$ Ar-CO 2 with 10% $$\text {CO}_{2}$$ CO 2 (10,000 in $$\text {Ar-CH}_4$$ Ar-CH 4 with $$\sim \!{4}{\%}$$ ∼ 4 % $$\text {CH}_{4}$$ CH 4 ) may be achieved with anode voltage of $${4.6}\,\hbox {kV}$$ 4.6 kV ( $$\sim \!{3.6}\,\hbox {kV}$$ ∼ 3.6 kV ).
New neutrino-nucleus interaction cross-section measurements are required to improve nuclear models sufficiently for future long-baseline neutrino experiments to meet their sensitivity goals. A time ...projection chamber (TPC) filled with a high-pressure gas is a promising detector to characterise the neutrino sources planned for such experiments. A gas-filled TPC is ideal for measuring low-energy particles as they travel much further in gas than solid or liquid neutrino detectors. Using a high-pressure gas increases the target density, resulting in more neutrino interactions. This paper will examine the suitability of multiwire proportional chambers (MWPCs) taken from the ALICE TPC to be used as the readout chambers of a high-pressure gas TPC. These chambers were previously operated at atmospheric pressure. We tested one such MWPC at up to almost 5 bar absolute (barA) with the UK high-pressure test stand at Royal Holloway, University of London. This paper reports the successful operation of an ALICE TPC outer readout chamber (OROC) at pressures up to 4.8 bar absolute with Ar-CH\(_{4}\) mixtures with a CH\(_{4}\) content between 2.8% and 5.0%, and so far up to 4 bar absolute with Ar-CO\(_{2}\) (90-10). We measured the charge gain of this OROC using signals induced by an \(^{55}\)Fe source. The largest gain achieved at 4.8 bar was \(64\pm2)\cdot10^{3}\) at stable conditions with an anode wire voltage of 2990 V in Ar-CH\(_{4}\) (95.9-4.1). In Ar-CO\(_{2}\) a gain of \((4.2\pm0.1)\cdot10^{3}\) was observed at an anode voltage of 2975 V at 4 barA gas pressure. Based on all our gain measurements, we extrapolate that, at the 10 barA pressure necessary to fit 1 tonne of gas into the ALICE TPC volume, a gain of 5000 in Ar-CO\(_{2}\) (90-10) (10000 in Ar-CH\(_{4}\) with \(\sim\!\) 4% CH\(_{4}\) content) may be achieved with an OROC anode voltage of 4.2 V (\(\sim\!\) 3.1 kV).
We present studies of proton fluxes in the T10 beamline at CERN. A prototype high pressure gas time projection chamber (TPC) was exposed to the beam of protons and other particles, using the 0.8 ...GeV/c momentum setting in T10, in order to make cross section measurements of low energy protons in argon. To explore the energy region comparable to hadrons produced by GeV-scale neutrino interactions at oscillation experiments, i.e., near 0.1 GeV of kinetic energy, methods of moderating the T10 beam were employed: the dual technique of moderating the beam with acrylic blocks and measuring scattered protons off the beam axis was used to decrease the kinetic energy of incident protons, as well as change the proton/minimum ionising particle (MIP) composition of the incident flux. Measurements of the beam properties were made using time of flight systems upstream and downstream of the TPC. The kinetic energy of protons reaching the TPC was successfully changed from \(\sim0.3\) GeV without moderator blocks to less than 0.1 GeV with four moderator blocks (40 cm path length). The flux of both protons and MIPs off the beam axis was increased. The ratio of protons to MIPs vary as a function of the off-axis angle allowing for possible optimisation of the detector to select the type of required particles. Simulation informed by the time of flight measurements show that with four moderator blocks placed in the beamline, (\(5.6 \pm 0.1\)) protons with energies below 0.1 GeV per spill traversed the active TPC region. Measurements of the beam composition and energy are presented.
The goal of many metabolomic studies is to identify the molecular structure of endogenous molecules that are differentially expressed among sampled or treatment groups. The identified compounds can ...then be used to gain an understanding of disease mechanisms. Unfortunately, despite recent advances in a variety of analytical techniques, small molecule (<1000 Da) identification remains difficult. Rarely can a chemical structure be determined from experimental “features” such as retention time, exact mass, and collision induced dissociation spectra. Thus, without knowing structure, biological significance remains obscure. In this study, we explore an identification method in which the measured exact mass of an unknown is used to query available chemical databases to compile a list of candidate compounds. Predictions are made for the candidates using models of experimental features that have been measured for the unknown. The predicted values are used to filter the candidate list by eliminating compounds with predicted values substantially different from the unknown. The intent is to reduce the list of candidates to a reasonable number that can be obtained and measured for confirmation. To facilitate this exploration, we measured data and created models for two experimental features; MS Ecom50 (the energy in electronvolts required to fragment 50% of a selected precursor ion) and HPLC retention index. Using a data set of 52 compounds, Ecom50 models were developed based on both Molconn and CODESSA structural descriptors. These models gave r 2 values of 0.89 to 0.94 depending on the number of inputs, the modeling algorithm chosen, and whether neutral or protonated structures were used. The retention index model was developed with 400 compounds using a back-propagation artificial neural network and 33 Molconn structure descriptors. External validation gave a v 2 = 0.87 and standard error of 38 retention index units. As a test of the validity of the filtering approach, the Ecom50 and retention index models, along with exact mass and collision induced dissociation spectra matching, were used to identify 1,3-dicyclohexylurea in human plasma. This compound was not previously known to exist in human biofluids and its elemental formula was identical to 315 other candidate compounds downloaded from PubChem. These results suggest that the use of Ecom50 and retention index predictive models can improve nontargeted metabolite structure identification using HPLC/MS derived structural features.
Aptamers are, in general, easier to produce, easier to store and are able to bind to a wider variety of targets than antibodies. For these reasons, aptamers are gaining increasing popularity in ...environmental monitoring as well as disease detection and disease management applications. This review article examines the research and design of RNA and DNA aptamer based biosensor systems and applications as well as their potential for integration in effective biosensor devices. As single stranded DNA or RNA molecules that can bind to specific targets, aptamers are well suited for biomolecular recognition and sensing applications. Beyond being able to be designed for a near endless number of specific targets, aptamers can also be made which change their conformation in a predictable and consistent way upon binding. This can lead to many unique and effective detection methods using a variety of optical and electrochemical means.
The goal of many metabolomic studies is to identify the molecular structure of endogenous molecules that are differentially expressed among sampled or treatment groups. The identified compounds can ...then be used to gain an understanding of disease mechanisms. Unfortunately, despite recent advances in a variety of analytical techniques, small molecule (<1000 Da) identification remains difficult. Rarely can a chemical structure be determined from experimental "features" such as retention time, exact mass, and collision induced dissociation spectra. Thus, without knowing structure, biological significance remains obscure. In this study, we explore an identification method in which the measured exact mass of an unknown is used to query available chemical databases to compile a list of candidate compounds. Predictions are made for the candidates using models of experimental features that have been measured for the unknown. The predicted values are used to filter the candidate list by eliminating compounds with predicted values substantially different from the unknown. The intent is to reduce the list of candidates to a reasonable number that can be obtained and measured for confirmation. To facilitate this exploration, we measured data and created models for two experimental features; MS Ecom... (the energy in electronvolts required to fragment 50% of a selected precursor ion) and HPLC retention index. Using a data set of 52 compounds, Ecom... models were developed based on both Molconn and CODESSA structural descriptors. These models gave r... values of 0.89 to 0.94 depending on the number of inputs, the modeling algorithm chosen, and whether neutral or protonated structures were used. The retention index model was developed with 400 compounds using a back-propagation artificial neural network and 33 Molconn structure descriptors. External validation gave a v... = 0.87 and standard error of 38 retention index units. As a test of the validity of the filtering approach, the Ecom50 and retention index models, along with exact mass and collision induced dissociation spectra matching, were used to identify 1,3-dicyclohexylurea in human plasma. This compound was not previously known to exist in human biofluids and its elemental formula was identical to 315 other candidate compounds downloaded from PubChem. These results suggest that the use of Ecom... and retention index predictive models can improve nontargeted metabolite structure identification using HPLC/MS derived structural features. (ProQuest: ... denotes formulae/symbols omitted.)
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