&lt;title&gt;NIST programs for calibrations in the far ultraviolet spectral region&lt;/title&gt;

Vest, Robert E.; Canfield, L. R.; Furst, Mitchell L.; Graves, Rossie M.; Hamilton, Andrew D.; Hughey, L. R.; Lucatorto, Thomas B.; Madden, R. P.

doi:10.1117/12.364157

Cited by 9 publications

(6 citation statements)

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“…The Lyman alpha photomultiplier detector was calibrated absolutely against a NIST calibrated photo-diode at the Far UV Calibration Facility [10] at NIST. Continuous Lyman alpha radiation was generated by a hydrogen discharge and narrow band monochromator.…”

Section: Methodsmentioning

confidence: 99%

Observation of the 3He(n,tp) reaction by detection of far-ultraviolet radiation

Thompson¹,

Coplan²,

Cooper³

et al. 2008

J. Res. Natl. Inst. Stand. Technol.

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We have detected Lyman alpha radiation, 121.6 nm light produced from the n = 2 to n = 1 transition in atomic hydrogen, as a product of the 3He(n, tp) nuclear reaction occurring in a cell of 3He gas. The predominant source of this radiation appears to be decay of the 2p state of tritium produced by charge transfer and excitation collisions with the background 3He gas. Under the experimental conditions reported here we find yields of tens of Lyman alpha photons for every neutron reaction. These results suggest a method of cold neutron detection that is complementary to existing technologies that use proportional counters. In particular, this approach may provide single neutron sensitivity with wide dynamic range capability, and a class of neutron detectors that are compact and operate at relatively low voltages.

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Section: Methodsmentioning

confidence: 99%

Observation of the 3He(n,tp) reaction by detection of far-ultraviolet radiation

Thompson¹,

Coplan²,

Cooper³

et al. 2008

J. Res. Natl. Inst. Stand. Technol.

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“…The absolute response function of the SEM instrument (with the exception of the soft X-ray portion of the 0.1 -50 nm channel) was measured prior to the launch of SOHO at NIST SURFIII (Furst, Graves, and Madden, 1993;Vest et al, 1999) on beam-line 9, which is equipped with a monochromator that allows the channel response functions to be measured with 1 nm resolution over a spectral range from about 15 to 49 nm. The response function of the zeroth-order channel for soft X-ray wavelengths shorter than 15 nm is modeled based on photoabsorption and transmission values for the relevant materials found in Henke, Gullikson, and Davis (1993).…”

Section: Instrument Overviewmentioning

confidence: 99%

Resolving Differences in Absolute Irradiance Measurements Between the SOHO/CELIAS/SEM and the SDO/EVE

Wieman¹,

Didkovsky²,

Judge³

2014

Coronal Magnetometry

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The Solar EUV Monitor (SEM) onboard SOHO has measured absolute extreme ultraviolet (EUV) and soft X-ray solar irradiance nearly continuously since January 1996. The EUV Variability Experiment (EVE) on SDO, in operation since April of 2010, measures solar irradiance in a wide spectral range that encompasses the band passes (26 -34 nm and 0.1 -50 nm) measured by SOHO/SEM. However, throughout the mission overlap, irradiance values from these two instruments have differed by more than the combined stated uncertainties of the measurements. In an effort to identify the sources of these differences and eliminate them, we investigate in this work the effect of reprocessing the SEM data using a more accurate SEM response function (obtained from synchrotron measurements with a SEM sounding-rocket clone instrument taken after SOHO was already in orbit) and timedependent, measured solar spectral distributions -i.e., solar reference spectra that were unavailable prior to the launch of the SDO. We find that recalculating the SEM data with these improved parameters reduces mean differences with the EVE measurements from about 20 % to less than 5 % in the 26 -34 nm band, and from about 35 % to about 15 % for irradiances in the 0.1 -7 nm band extracted from the SEM 0.1 -50 nm channel.

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“…The two selected harmonics are each directed to their detectors via one grazing-incidence reflection on bare-gold mirrors. The 11 th harmonic is measured with a NIST-calibrated Al 2 O 3 windowless photoemissive detector 47 , and the 17 th harmonic is measured using an aluminium-foil-coated silicon photodiode (Opto Diode AXUV100Al). The Si photodiode is calibrated against the NIST photoemissive detector by measuring the 17 th harmonic power with both detectors sequentially, under easily-repeatable conditions (unheated pure Xe).…”

Section: Experimental Apparatusmentioning

confidence: 99%

Phase-matched extreme-ultraviolet frequency-comb generation

et al. 2018

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Laser-driven high-order harmonic generation 1,2 (HHG) provides tabletop sources of broadband extreme-ultraviolet (XUV) light with excellent spatial 3 and temporal 4 coherence. These sources are typically operated at low repetition rates, f rep 100 kHz, where phase-matched frequency conversion into the XUV is readily achieved 5,6 . However, there are many applications that demand the improved counting statistics or frequency-comb precision afforded by operation at high repetition rates, f rep > 10 MHz. Unfortunately, at such high f rep , phase matching is prevented by the accumulated steady-state plasma in the generation volume 7-11 , setting stringent limitations on the XUV average power. Here, we use gas mixtures at high temperatures as the generation medium to increase the translational velocity of the gas, thereby reducing the steady-state plasma in the laser focus. This allows phase-matched XUV emission inside a femtosecond enhancement cavity at a repetition rate of 77 MHz, enabling a record generated power of ∼2 mW in a single harmonic order. This power scaling opens up many demanding applications, including XUV frequency-comb spectroscopy 12,13 of few-electron atoms and ions for precision tests of fundamental physical laws and constants 14-20 .The highly-nonlinear HHG process requires peak laser intensities around 10 14 W/cm 2 , which necessitates large laser pulse energies 10 µJ, and short pulse durations 100 fs, as typically reached with low repetition rate, chirped-pulse amplified 21 laser systems. However, high repetition rates are desirable for applications such as photoelectron spectroscopy 22-24 and microscopy 25 as well as electron-ion coincidence spectroscopy 26,27 , which are limited by counting detection or space-charge effects to few XUV ionization events per shot. Most notably, precision frequency-comb spectroscopy 12,13 requires f rep 10 MHz in order to stabilize the comb. Recent efforts allowed HHG to be directly driven at f rep 1 MHz, using either the direct output of a high-power oscillator 22,28 or the coherent combination of several fibre amplifiers 29,30 . Achieving the necessary intensity for HHG with f rep 10 MHz requires lasers with average power in the kW range. Apart from one demonstration at 20 MHz, where the measured XUV power was extremely low 31 , higher repetition rates up to 250 MHz 32 have been facilitated only by using passive enhancement cavities, which store ∼10 kW of laser power, where a gas jet is introduced at an intracavity focus 7,10-12,33-35 .In a macroscopic extended medium, efficient HHG requires matching the phase velocities of the generating laser and the generated fields. This can be achieved by balancing neutral and plasma dispersion, the geometric phase shift due to focusing (the Gouy phase), and the HHG intrinsic dipole phase 5,36 . Achieving this balance becomes increasingly challenging as the repetition rate increases above ∼10 MHz. The reason for this difficulty is that the plasma generated by one pulse does not have time to clear the focal volume before t...

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<title>NIST programs for calibrations in the far ultraviolet spectral region</title>

Cited by 9 publications

References 0 publications

Observation of the 3He(n,tp) reaction by detection of far-ultraviolet radiation

Observation of the 3He(n,tp) reaction by detection of far-ultraviolet radiation

Resolving Differences in Absolute Irradiance Measurements Between the SOHO/CELIAS/SEM and the SDO/EVE

Phase-matched extreme-ultraviolet frequency-comb generation

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