On the mechanism of Townsend avalanche for negative molecular ions

Dion, Michael P.; Martoff, C. J.; Hosack, M.

doi:10.1016/j.astropartphys.2010.02.002

Cited by 11 publications

(9 citation statements)

References 23 publications

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“…Previous works have shown that gas gains greater than 1000 can be achieved in electronegative gases with proportional wires [69], GEMs [70], and bulk Micromegas (Micro Mesh Gaseous Structure) [71]. In contrast to electron gases where only moderate electric fields of order 100 V·cm −1 Torr −1 are needed to accelerate electrons to energies close to the ionization potential of the gas, electronegative gases require much higher electric fields to initiate avalanche even though the electron affinity is usually much lower than the ionization poten- (b) 55 Fe energy spectrum after background subtraction Figure 11 tial [72]. For CS 2 , measurements show that the minimum reduced field, (E/p) min , needed to initiate avalanche is over one order of magnitude larger than for the electron drift gas P10 (10% methane in argon) [72].…”

Section: Gas Gainmentioning

confidence: 99%

“…In contrast to electron gases where only moderate electric fields of order 100 V·cm −1 Torr −1 are needed to accelerate electrons to energies close to the ionization potential of the gas, electronegative gases require much higher electric fields to initiate avalanche even though the electron affinity is usually much lower than the ionization poten- (b) 55 Fe energy spectrum after background subtraction Figure 11 tial [72]. For CS 2 , measurements show that the minimum reduced field, (E/p) min , needed to initiate avalanche is over one order of magnitude larger than for the electron drift gas P10 (10% methane in argon) [72]. A similar study can be done for SF 6 , but we leave this for the future and instead focus on gas gain in this section.…”

Section: Gas Gainmentioning

confidence: 99%

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The novel properties of SF₆ for directional dark matter experiments

et al. 2017

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SF 6 is an inert and electronegative gas that has a long history of use in high voltage insulation and numerous other industrial applications. Although SF 6 is used as a trace component to introduce stability in tracking chambers, its highly electronegative properties have limited its use in tracking detectors. In this work we present a series of measurements with SF 6 as the primary gas in a low pressure Time Projection Chamber (TPC), with a thick GEM used as the avalanche and readout device. The first results of an 55 Fe energy spectrum in SF 6 are presented. Measurements of the mobility and longitudinal diffusion confirm the negative ion drift of SF 6 . However, the observed waveforms have a peculiar but interesting structure that indicates multiple drift species and a dependence on the reduced field (E/p), as well as on the level of water vapor contamination. The discovery of a distinct secondary peak in the waveform, together with its identification and use for fiducializing events in the TPC, are also presented. Our measurements demonstrate that SF 6 is an ideal gas for directional dark matter detection. In particular, the high fluorine content is desirable for spin-dependent sensitivity, negative ion drift ensures low diffusion over large drift distances, and the multiple species of charge carriers allow for full detector fiducialization.

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Section: Gas Gainmentioning

confidence: 99%

Section: Gas Gainmentioning

confidence: 99%

The novel properties of SF₆ for directional dark matter experiments

et al. 2017

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“…Generation of a Townsend avalanche in the MWD requires detachment of the ionization electrons from the negative ions. This occurs in a strong electric field of the micro-well by collision of the negative ion with the gas molecules [68]. The free electrons are then accelerated in the micro-well producing the avalanche.…”

Section: Single Ionization Electron Detectionmentioning

confidence: 99%

A pair production telescope for medium-energy gamma-ray polarimetry

Hunter

Bloser

Depaola

et al. 2014

Astroparticle Physics

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We describe the science motivation and development of a pair production telescope for medium-energy (~5-200 MeV) gamma-ray polarimetry. Our instrument concept, the Advanced Energetic Pair Telescope (AdEPT), takes advantage of the Three-Dimensional Track Imager, a low-density gaseous time projection chamber, to achieve angular resolution within a factor of two of the pair production kinematics limit (~0.6° at 70 MeV), continuum sensitivity comparable with the Fermi-LAT front detector (<3 × 10-6 MeV cm-2 s-1 at 70 MeV), and minimum detectable polarization less than 10% for a 10 mCrab source in 106 s

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“…These negative ions then drift in the uniform electric field to the higher field region of the GEM holes. The electric field is strong enough inside the GEM holes to cause collisional detachment of the ions [14]. The liberated electrons are then multiplied and detected as described for the electron TPC.…”

Section: Introductionmentioning

confidence: 99%

Gas Gain Measurements From a Negative Ion TPC X-ray Polarimeter

Prieskorn

Hill

Kaaret

et al. 2011

IEEE Trans. Nucl. Sci.

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Abstract-Gas-based time projection chambers (TPCs) have been shown to be highly sensitive X-ray polarimeters having excellent quantum efficiency while at the same time achieving large modulation factors. To observe polarization of the prompt X-ray emission of a Gamma-ray burst (GRB), a large area detector is needed. Diffusion of the electron cloud in a standard TPC could be prohibitive to measuring good modulation when the drift distance is large. Therefore, we propose using a negative ion TPC (NITPC) with Nitromethane (CH 3 NO 2 ) as the electron capture agent. The diffusion of negative ions is reduced over that of electrons due to the thermal coupling of the negative ions to the surrounding gas. This allows for larger area detectors as the drift distance can be increased without degrading polarimeter modulation. Negative ions also travel ~200 times slower than electrons, allowing the readout electronics to operate slower, resulting in a reduction of instrument power.To optimize the NITPC design, we have measured gas gain with SciEnergy gas electron multipliers (GEMs) in single and double GEM configurations. Each setup was tested with different gas combinations, concentrations and pressures: P10 700 Torr, Ne+CO 2 700 Torr at varying concentrations of CO 2 and Ne+CO 2 +CH 3 NO 2 700 Torr. We report gain as a function of total voltage, measured from top to bottom of the GEM stack, and as a function of drift field strength for the gas concentrations listed above. Examples of photoelectron tracks at 5.9 keV are also presented.Index Terms-X-ray polarimetry, negative ion time projection chamber, x-ray detectors.

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On the mechanism of Townsend avalanche for negative molecular ions

Cited by 11 publications

References 23 publications

The novel properties of SF₆ for directional dark matter experiments

The novel properties of SF₆ for directional dark matter experiments

A pair production telescope for medium-energy gamma-ray polarimetry

Gas Gain Measurements From a Negative Ion TPC X-ray Polarimeter

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On the mechanism of Townsend avalanche for negative molecular ions

Cited by 11 publications

References 23 publications

The novel properties of SF6 for directional dark matter experiments

The novel properties of SF6 for directional dark matter experiments

A pair production telescope for medium-energy gamma-ray polarimetry

Gas Gain Measurements From a Negative Ion TPC X-ray Polarimeter

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Product

Resources

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The novel properties of SF₆ for directional dark matter experiments

The novel properties of SF₆ for directional dark matter experiments