Mitchell L. Furst

SURF III - an improved storage ring for radiometry

The National Institute of Standards and Technology (NIST) operates the newly upgraded Synchrotron Ultraviolet Radiation Facility (SURF III) mainly as a light source for radiometry. SURF III provides continuum radiation from the far-infrared to the soft X-ray spectral range and has its peak output in the extreme ultraviolet. SURF III is a circular-orbit, weak-focusing (single dipole magnet) storage ring, a feature which is advantageous if the synchrotron radiation output is calculated. We report the improvements achieved during a recent upgrade from SURF II to SURF III and our strategy to accurately determine the magnetic flux density, radio frequency (RF), beam current, and beam size, which are the parameters necessary to characterize the source completely.

Synchrotron ultraviolet radiation facility (SURF II) radiometric instrumentation calibration facility

Spectrometer calibrations have been performed at the National Institute of Standards and Technology (formerly the National Bureau of Standards) for over 10 yr using the calculable synchrotron radiation from the SURF II electron storage ring. SURF II is now a high-performance storage ring that can operate at electron energies up to 300 MeV and with over 250 mA of stored current. One beam line, operationally supported by the National Aeronautics and Space Administration (NASA), is dedicated for use as a radiometric instrumentation calibration facility for outside users.

Dual grating monochromator for detector calibrations using synchrotron radiation as an absolute source at NIST

Abstract A new monochromator system has been developed that permits the in situ calibration of its optical components and allows the calibration of a photodiode against a calculable synchrotron radiation source in the spectral range extending from 116 to 254 nm. The instrument has been operated at the Spectrometer Calibration Facility (BL-2) of the SURF II electron storage ring located at the National Institute of Standards and Technology (NIST). Significant reductions in the uncertainty of far ultraviolet detector calibrations are anticipated due to the use of this instrument.

Radiometry at the NIST SURF II storage ring facility

The National Institute of Standards and Technology (NIST) in Gaithersburg, MD, is the site of the Synchrotron Ultraviolet Radiation Facility (SURF II). The synchrotron radiation from the 300 MeV electron storage ring is used for most of the NIST radiometry programs in the far ultraviolet. Continuum radiation from SURF II extends from the infrared to about 4 nm (310 eV) and is a standard source for the calibration of integrated optical systems, particularly space experiments. The SURF II facility is also used for a large portion of the NIST far ultraviolet transfer detector standards program, in which spectrally calibrated detector standards are available from 5 nm (248 eV) to 254 nm (4.9 eV). One of the most recent activities has been the development of a new apparatus designed to qualify working standards for calibration of the NIST MgF2 windowed far ultraviolet transfer standard detectors. Additionally, new radiometric quality silicon photodiodes have now been developed. These detectors offer many impro...

Synchrotron ultraviolet radiation facility SURF III

The National Institute of Standards and Technology (NIST) has operated the Synchrotron Ultraviolet Radiation Facility (SURF) continuously since the early 1960s. The original accelerator was converted into a storage ring, called SURF II, in 1974. Then in 1998, motivated mainly by limitations in the accuracy of radiometric calibrations and the wish to extend the spectrum of the emitted synchrotron radiation to shorter wavelengths, a second major upgrade was performed. This time the whole magnet system was replaced to improve the calculability and allow for higher magnetic fields. Since the recommissioning of SURF III we have been working to improve the stability of the stored electron beam through modifications of the radio-frequency system, leading to operations with unprecedented stability and new record injection currents topping 700 mA.

SDO EVE ESP radiometric calibration and results

The Solar Dynamics Observatory (SDO) Extreme ultraviolet Spectro-Photometer (ESP), as a part of the Extreme ultraviolet Variability Experiment (EVE) suite of instruments, was calibrated at the National Institute of Standards and Technology (NIST) on the Synchrotron Ultraviolet Radiation Facility (SURF) Beam Line 2 in February 2007. Precise ESP alignment to the SURF beam was achieved through successive scans in X, Y, Pitch and Yaw, using a comparison of the four channels of the ESP quad photodiode as a measure of alignment. The observed alignment between the ESP and the other instruments in the EVE package was found to be in very good agreement with that measured at the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado during ESP/EVE integration. The radiometric calibration of the ESP photometers in the spectral range around 4.4 nm (central zeroth order), and the four first order channels centered at about 18.9, 25.4, 29.8, and 36.1 nm was performed with SURF synchrotron radiation. The co-alignment of the SURF beam and the ESP optical axis for each energy and injected current was determined based on quad diode (QD) photometer responses (photodiode count-rate data). This determined beam position was later used to obtain exact energy-wavelength-flux profiles for each of the calibration energies and to calculate the quantum efficiency of the ESP channels. The results of this calibration (quantum efficiencies) are compared to the previous ESP NIST calibration results at SURF Beam Line 9 and to SOHO/SEM efficiencies.

NIST programs for calibrations in the far ultraviolet spectral region

The National Institute of Standards and Technology (NIST) serves the growing ultraviolet user community by providing calibration services throughout the spectral range from 2 nm to 400 nm. In this paper we describe the far ultraviolet transfer standard detector program, the NASA-supported Spectrometer Calibration Beamline at the Synchrotron Ultraviolet Radiation Facility, SURF III, and the recent upgrade of the SURF electron storage ring. Several types of transfer standard detectors are issued by NIST in the spectral range from 5 nm to 254 nm; Al2O3 windowless photoemissive devices, CsTe photoemissive devices with integrated MgF2 windows, and radiation-hardened, semiconductive Si photodiodes. The Spectrometer Calibration Beamline makes use of the cathode, undispersed synchrotron radiation from SURF III as a standard of spectral irradiance from 2 nm to 400 nm. The upgrade of SURF has greatly improved the accuracy of calibrations based on SURF, as well as extending the useful spectral range to shorter wavelengths. Taken together, the transfer standard detector program and the calibration beamline at SURF III offer a unique calibration resource for scientists and engineers working in the far ultraviolet spectral region.

High resolution vuv photo-absorption cross sections of O2 near 83.4 nm

Abstract The O+ (2s2p4 4P → 2s22p3 4S0) 83.4 nm triplet is of great interest in ionosphere physics primarily for its role in remote sensing of the ionosphere. Absolute photoabsorption cross sections of O2 near 83.4 nm have been made utilizing the Very High Resolution Spectrometer at the National Institute of Standards and Technologys Synchrotron Ultraviolet Radiation Facility (SURF II). The 6.65 m spectrometer has a resolving power of ∼ 100,000 near 80 nm (FWHM = 0.8 pm). Cross sections were measured over the range 83.0 – 83.5 nm. The value of the cross sections at the positions of the triplet emission lines located at 83.4465, 83.3329, and 83.2757 nm are 14.4 ± 0.7, 18.4 ± 0.8, and 38.2 ± 1.5 Mb respectively. The cross section at the peak of the absorption band at 83.268 nm is 40.6 ± 1.6 Mb. The large discrepancies between our values and those of other investigators are probably due to their low instrumental resolution.

The very high resolution spectrometer at the National Institute of Standards and Technology

Abstract The Very High Resolution Spectrometer at the Synchrotron Ultraviolet Radiation Facility of the National Institute of Standards and Technology has been upgraded with improved beamline throughput, instrument control and data acquisition. Since this upgrade, a number of high resolution measurements have been made in the vacuum ultraviolet region of the electromagnetic spectrum between 40 nm and 100 nm. Utilizing the features of this instrument, on-line photoelectric recording at intervals of 0.1 pm in first order from a synchrotron light source can be made. A resolution of 0.9 pm has been obtained at 80 nm.

SURF III - A New Electron Storage Ring at NIST

The National Institute of Standards and Technology (NIST), formerly the National Bureau of Standards (NBS), has operated the Synchrotron Ultraviolet Radiation Facility (SURF), based on an electron accelerator, continuously since the early 1960s. SURF I was established in 1961, utilizing a 180 MeV electron synchrotron at NBS in Washington, D.C. This accelerator was moved to the Gaithersburg, MD site in 1968, specifically for the continuation of SURF I operations. It was converted to an electron storage ring, SURF II, in 1974 under contract with the Physical Sciences Laboratory (PSL) at the University of Wisconsin-Madison (UW), and became a national standard of irradiance in the UV and VUV spectral region. To improve its performance in this application and broaden its spectral range, SURF II has been converted to SURF III, commissioned in December 1998. The design and construction of the new system were overseen by PSL and the Synchrotron Radiation Center at UW. SURF III remains a weak-focusing, single-magn...