231 research outputs found
Effects of Urea, Borax and Ammonium Chloride on Flame Retarding Properties of Cellulosic Ceiling Board
This work involves the impregnation of urea, borax and ammonium chloride solutions prepared in varying concentrations into strips of cellulosic ceiling board. A formulated solution was also made of equal concentration of urea and borax solution and impregnated into strips of cellulosic ceiling board. The treated and blank samples were dried and investigated for ignitability, flame propagation and afterglow time. Urea was found to give a good effect for ignitability after 28.00sec than borax, ammonium chloride and blank after 26.00sec, 25.00sec and 16.80sec respectively. Urea gave a better effect for flame propagation of 0.13x10-2cm/sec than borax, ammonium chloride and blank which has 0.24x10-2cm/sec, 0.28x10-2cm/sec and 1.95x10-2cm/sec respectively and also urea has afterglow time of 0.22x102sec than borax (0.60 x102sec), ammonium chloride (0.70x102sec) and blank (2.25 x102sec). The formulated solution drastically improved the ignitability from 16.80sec (blank) to 34.00sec and zero flame propagation and afterglow time was recorded. With this result, urea was found to give a better retarding effect, hence could be incorporated in cellulosic ceiling board during production. Keywords: Urea, borax, ceiling board, ignitability, flame propagation, afterglow time
Gas Gains Over 10 and Optimisation using Fe X-rays in Low Pressure SF with a Novel Multi-Mesh ThGEM for Directional Dark Matter Searches
The Negative Ion Drift (NID) gas SF has favourable properties for track
reconstruction in directional Dark Matter (DM) searches utilising low pressure
gaseous Time Projection Chambers (TPCs). However, the electronegative nature of
the gas means that it is more difficult to achieve significant gas gains with
regular Thick Gaseous Electron Multipliers (ThGEMs). Typically, the maximum
attainable gas gain in SF and other Negative Ion (NI) gas mixtures,
previously achieved with an Fe X-ray source or electron beam, is on the
order of ; whereas electron drift gases like CF and similar mixtures
are readily capable of reaching gas gains on the order of or greater. In
this paper, a novel two stage Multi-Mesh ThGEM (MMThGEM) structure is
presented. The MMThGEM was used to amplify charge liberated by an Fe
X-ray source in 40 Torr of SF. By expanding on previously demonstrated
results, the device was pushed to its sparking limit and stable gas gains up to
50000 were observed. The device was further optimised by varying the
field strengths of both the collection and transfer regions in isolation.
Following this optimisation procedure, the device was able to produce a maximum
stable gas gain of 90000. These results demonstrate an order of magnitude
improvement in gain with the NID gas over previously reported values and
ultimately benefits the sensitivity of a NITPC to low energy recoils in the
context of a directional DM search
Performance of 20:1 multiplexer for large area charge readouts in directional dark matter TPC detectors
More target mass is required in current TPC based directional dark matter detectors for improved detector sensitivity. This can be achieved by scaling up the detector volumes, but this results in the need for more analogue signal channels. A possible solution to reducing the overall cost of the charge readout electronics is to multiplex the signal readout channels. Here, we present work on an expanded LMH6574 multiplexer system with a capability of reducing the number of readouts in such TPC detectors by a factor of 20. Results indicate that the important charge distribution asymmetry along an ionization track is retained after multiplexed signals are demultiplexed
Demonstration of ThGEM-multiwire hybrid charge readout for directional dark matter searches
Sensitivities of current directional dark matter search detectors using gas time projection chambers are now constrained by target mass. A ton-scale gas TPC detector will require large charge readout areas. We present a first demonstration of a novel ThGEM-Multiwire hybrid charge readout technology which combines the robust nature and high gas gain of Thick Gaseous Electron Multipliers with lower capacitive noise of a one-plane multiwire charge readout in SF6 target gas. Measurements performed with this hybrid detector show an ion drift velocity of 139 ± 12 ms−1 in a reduced drift field E/N of 93 Td (10−17 V cm2) at a gas gain of 2470±160 in 20 Torr of pure SF6 target gas
Effects of Urea, Borax and Ammonium Chloride on Flame Retarding Properties of Cellulosic Ceiling Board
Abstract This work involves the impregnation of urea, borax and ammonium chloride solutions prepared in varying concentrations into strips of cellulosic ceiling board. A formulated solution was also made of equal concentration of urea and borax solution and impregnated into strips of cellulosic ceiling board. The treated and blank samples were dried and investigated for ignitability, flame propagation and afterglow time. Urea was found to give a good effect for ignitability after 28.00sec than borax, ammonium chloride and blank after 26.00sec, 25.00sec and 16.80sec respectively. Urea gave a better effect for flame propagation of 0.13x10 -2 cm/sec than borax, ammonium chloride and blank which has 0.24x10 -2 cm/sec, 0.28x10 -2 cm/sec and 1.95x10 -2 cm/sec respectively and also urea has afterglow time of 0.22x10 2 sec than borax (0.60 x10 2 sec), ammonium chloride (0.70x10 2 sec) and blank (2.25 x10 2 sec). The formulated solution drastically improved the ignitability from 16.80sec (blank) to 34.00sec and zero flame propagation and afterglow time was recorded. With this result, urea was found to give a better retarding effect, hence could be incorporated in cellulosic ceiling board during production
Demonstration of radon removal from SF6 using molecular sieves
The gas SF6 has become of interest as a negative ion drift gas for use in directional
dark matter searches. However, as for other targets in such searches, it is important that radon
contamination can be removed as this provides a source of unwanted background events. In this
work we demonstrate for the first time filtration of radon from SF6 gas by using a molecular
sieve. Four types of sieves from Sigma-Aldrich were investigated, namely 3Ã…, 4Ã…, 5Ã… and 13X.
A manufactured radon source was used for the tests. This was attached to a closed loop system in
which gas was flowed through the filters and a specially adapted Durridge RAD7 radon detector.
In these measurements, it was found that only the 5Ã… type was able to significantly reduce the
radon concentration without absorbing the SF6 gas. The sieve was able to reduce the initial radon
concentration of 3875 ± 13 Bqm−3
in SF6 gas by 87% when cooled with dry ice. The ability of
the cooled 5Ã… molecular sieve filter to significantly reduce radon concentration from SF6 provides
a promising foundation for the construction of a radon filtration setup for future ultra-sensitive SF6
gas rare-event physics experiments
Directional dark matter readout with a novel multi-mesh ThGEM for SF6 negative ion operation
Direct searches for Weakly Interacting Massive Particle (WIMP) dark matter could greatly benefit from directional measurement of the expected induced nuclear recoils. Gas-based Time Projection Chambers (TPCs) offer potential for this, opening the possibility of measuring WIMP signals below the so-called neutrino floor but also of directional measurement of recoils induced by neutrinos from the Sun, for instance as proposed by the CYGNUS collaboration. Presented here for the first time are results from a Multi-Mesh Thick Gas Electron Multiplier (MM-ThGEM) using negative ion gases for operation with such a directional dark matter TPC. Negative ion drift gases are favoured for directionality due to their low diffusion characteristics. The multiple internal mesh structure is designed to provide a high gain amplification stage when coupled to future large area Micromegas, strip or pixel charge readout planes. Experimental results and simulations are presented of MM-ThGEM gain and functionality using low pressure pure CF4, SF6 and SF6:CF4 mixtures irradiated with alpha particles and 55Fe x-rays. The concept is found to work well, providing stable operation with gains over 103 in pure SF6
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