Fast photomultiplier tube gating system for photon counting applications

Creasey, D. J.; Halford-Maw, Peter A.; Heard, D. E.; Spence, J.; Whitaker, Benjamin J.

doi:10.1063/1.1149252

Cited by 31 publications

(19 citation statements)

References 16 publications

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“…Individual photons detected by the CPM were processed by a gated photon counting (Becker and Hickl, PMS MSA 400A), and counted over an integration period of 252 ns, delayed by 450 ns from the laser pulse. The gain of the CPM was switched to zero during the laser pulse using a home-built gating system in order to further reduce the background signal due to laser-scattered light (Creasey et al, 1998). The signal was subsequently normalised for laser power, as measured by a photodiode (New Focus-2032) mounted at the exit of the fluorescence cell.…”

Section: Methodsmentioning

confidence: 99%

Measurements of OH and HO2 yields from the gas phase ozonolysis of isoprene

et al. 2010

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Abstract. The reactions of ozone with alkenes are an important source of hydroxyl (OH) radicals; however, quantification of their importance is hindered by uncertainties in the absolute OH yield. Hydroxyl radical yields for the gas-phase ozonolysis of isoprene are determined in this paper by four different methods: (1) The use of cyclohexane as an OH scavenger, and the production of cyclohexanone, (2) The use of 1,3,5-trimethylbenzene as an OH tracer, and the diminution in its concentration, (3) A kinetic method in which the OH yield was obtained by performing a series of pseudo-first-order experiments in the presence or absence of an OH scavenger (cyclohexane), (4) The OH and HO 2 yields were determined by fitting the temporal OH and HO 2 profiles following direct detection of absolute OH and HO 2 concentrations by laser induced fluorescence at low pressure (Fluorescence Assay by Gas Expansion-FAGE). The following OH yields for the ozonolysis of isoprene were obtained, relative to alkene consumed, for each method: (1) Scavenger (0.25±0.04), (2) Tracer (0.25±0.03), (3) Kinetic study (0.27±0.02), and (4) Direct observation (0.26±0.02), the error being one standard deviation. An averaged OH yield of 0.26±0.02 is recommended at room temperature and atmospheric pressure and this result is compared with recent literature determinations. The HO 2 yield was directly determined for the first time using FAGE to be 0.26±0.03.

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Section: Methodsmentioning

confidence: 99%

Measurements of OH and HO2 yields from the gas phase ozonolysis of isoprene

et al. 2010

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“…A home-built gating system (a modified form of the one described in Creasey et al 39 ) was used to switch the CPM off during the laser pulse to avoid optical damage. The CPM then was switched on again 205 ns after the beginning of each laser pulse.…”

Section: Aerosol Generation and Characterizationmentioning

confidence: 99%

Measurements of uptake coefficients for heterogeneous loss of HO2 onto submicron inorganic salt aerosols

George

Matthews

Whalley

et al. 2013

Phys. Chem. Chem. Phys.

103

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“…The solid angle of fluorescence collected was approximately doubled using a spherical mirror mounted opposite the collection optics. The CPM was switched off ∼2 µs before the laser pulse using a gating system developed at Leeds (Creasey et al, 1998) to provide a +100 V potential difference on the cathode relative to the channeltron body. The CPM is held in this low gain state until ∼100 ns after the peak of the laser pulse.…”

Section: Instrumental Detailsmentioning

confidence: 99%

Concentrations of OH and HO2 radicals during NAMBLEX: measurements and steady state analysis

et al. 2006

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Abstract. OH and HO 2 concentrations were measured simultaneously at the Mace Head Atmospheric Research Station in the summer of 2002 during the NAMBLEX (North Atlantic Marine Boundary Layer EXperiment) field campaign. OH was measured by laser-induced fluorescence employing the FAGE (Fluorescence Assay by Gas Expansion) technique, with a mean daytime detection limit of 2.7×10 5 molecule cm −3 (5 min acquisition period; signal-tonoise ratio = 1). HO 2 was detected as OH following its chemical conversion through addition of NO, with a mean detection limit of 4.4×10 6 molecule cm −3 . The diurnal variation of OH was measured on 24 days, and that of HO 2 on 17 days. The local solar noon OH concentrations ranged between (3-8)×10 6 molecule cm −3 , with a 24 h mean concentration of 9.1×10 5 molecule cm −3 . The local solar noon HO 2 concentrations were (0.9-2.1)×10 8 molecule cm −3 (3.5-8.2 pptv), with a 24 h mean concentration of 4.2×10 7 molecule cm −3 (1.6 pptv). HO 2 radicals in the range (2-3)×10 7 molecule cm −3 were observed at night. During NAMBLEX, a comprehensive suite of supporting measurements enabled a detailed study of the behaviour of HO x radicals under primarily clean marine conditions. Steady state expressions are used to calculate OH and HO 2 concentrations and to evaluate the effect of different free-radical sources and sinks. The diurnally averaged calculated to measured OH ratio was 1.04±0.36, but the ratio displays a distinct diurnal variation, being less than 1 during the early morning and late afternoon/evening, and greater than 1 in the middle of the day. For HO 2 there was an overprediction, with the agreement between calculated and measured concentrations improved by including reaction with measured IO and BrO radicals and uptake to aerosols. Increasing the concentration of IO radicals included in the calculations to above that measured by a DOAS instrument with an absorption path located mainly Correspondence to: D. E. Heard (d.e.heard@leeds.ac.uk) over the ocean, reflecting the domination of the inter-tidal region as an iodine source at Mace Head, led to further improvement. The results are compared with previous measurements at Mace Head, and elsewhere in the remote marine boundary layer.

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Fast photomultiplier tube gating system for photon counting applications

Cited by 31 publications

References 16 publications

Measurements of OH and HO<sub>2</sub> yields from the gas phase ozonolysis of isoprene

Measurements of OH and HO<sub>2</sub> yields from the gas phase ozonolysis of isoprene

Measurements of uptake coefficients for heterogeneous loss of HO2 onto submicron inorganic salt aerosols

Concentrations of OH and HO<sub>2</sub> radicals during NAMBLEX: measurements and steady state analysis

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Fast photomultiplier tube gating system for photon counting applications

Cited by 31 publications

References 16 publications

Measurements of OH and HO&lt;sub&gt;2&lt;/sub&gt; yields from the gas phase ozonolysis of isoprene

Measurements of OH and HO&lt;sub&gt;2&lt;/sub&gt; yields from the gas phase ozonolysis of isoprene

Measurements of uptake coefficients for heterogeneous loss of HO2 onto submicron inorganic salt aerosols

Concentrations of OH and HO&lt;sub&gt;2&lt;/sub&gt; radicals during NAMBLEX: measurements and steady state analysis

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Product

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Measurements of OH and HO<sub>2</sub> yields from the gas phase ozonolysis of isoprene

Measurements of OH and HO<sub>2</sub> yields from the gas phase ozonolysis of isoprene

Concentrations of OH and HO<sub>2</sub> radicals during NAMBLEX: measurements and steady state analysis