Chromospheric Lyman-alpha spectro-polarimeter (CLASP)

Kano, Ryouhei; Bando, T.; Narukage, Noriyuki; Ishikawa, R.; Tsuneta, S.; Katsukawa, Y.; Kubo, Masahito; Ishikawa, Shin-­nosuke; Hara, Hirohisa; Shimizu, Toshifumi; Suematsu, Y.; Ichimoto, Kiyoshi; Sakao, Taro; Goto, M.; Kato, Yoshiaki; Imada, Shinsuke; Kobayashi, K.; Holloway, Todd; Winebarger, Amy R.; Cirtain, Jonathan; Pontieu, Bart De; Casini, R.; Bueno, J. Trujillo; Štěpán, Jiří; Sainz, R. Manso; Belluzzi, L.; Ramos, A. Asensio; Auchère, F.; Carlsson, Mats

doi:10.1117/12.925991

Cited by 48 publications

(25 citation statements)

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“…Using CLASP, a single dataset can be acquired in 1.2 s [12,14]; however, the time variation of the VUV flux during the same time period due to solar variation, vehicle attitude jitter, or vehicle drift generates a false polarization signal (hereafter referred to as Δ Q I ). In solar visible-light polarimetry, the false polarization is known to be significantly decreased by the optical arrangement of the symmetric dual-channel optics, each of which has similar throughput and simultaneously records the orthogonal (linear or circular) polarization [15].…”

Section: Key Considerations For the Vuv Spectropolarimetermentioning

confidence: 99%

“…The CLASP project [12,13] adopted the design concept described in Section 3. The optical prescription of the spectropolarimeter as applied to CLASP is tabulated in Table 2, and the design considerations leading to the optical prescription are briefly described in Appendix B.…”

Section: Application To Claspmentioning

confidence: 99%

“…2) [12,13] sounding rocket aims to infer the magnetic fields around the solar upper chromosphere with precise measurements of the linear polarization in the Ly α line for the first time. Table 1 tabulates the design specifications and requirements to guarantee detection of the weak polarization signal (see Kano et al [12] and Kobayashi et al [13] for details). The key requirements include (1) polarization measurement error less than 0.1% (1σ value) and (2) spectral resolution better than 0.01 nm for observing the Ly α line.…”

Section: Introductionmentioning

confidence: 99%

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Vacuum ultraviolet spectropolarimeter design for precise polarization measurements

et al. 2015

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Precise polarization measurements in the vacuum ultraviolet (VUV) region provide a new means for inferring weak magnetic fields in the upper atmosphere of the Sun and stars. We propose a VUV spectropolarimeter design ideally suited for this purpose. This design is proposed and adopted for the NASA-JAXA chromospheric lyman-alpha spectropolarimeter (CLASP), which will record the linear polarization (Stokes Q and U) of the hydrogen Lyman-α line (121.567 nm) profile. The expected degree of polarization is on the order of 0.1%. Our spectropolarimeter has two optically symmetric channels to simultaneously measure orthogonal linear polarization states with a single concave diffraction grating that serves both as the spectral dispersion element and beam splitter. This design has a minimal number of reflective components with a high VUV throughput. Consequently, these design features allow us to minimize the polarization errors caused by possible time variation of the VUV flux during the polarization modulation and by statistical photon noise.

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Section: Key Considerations For the Vuv Spectropolarimetermentioning

confidence: 99%

Section: Application To Claspmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Vacuum ultraviolet spectropolarimeter design for precise polarization measurements

et al. 2015

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“…Therefore the two cameras must be synchronized to a high accuracy and optimized for precision and stability. 1,2 The strict science requirements imposed on the CLASP cameras require a complicated design and a demanding development process. For this reason, the Heliophysics Instrument Group at MSFC deemed it necessary to develop the CLASP cameras in-house.…”

Section: Introductionmentioning

confidence: 99%

Performance characterization of UV science cameras developed for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)

et al. 2014

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The NASA Marshall Space Flight Center (MSFC) has developed a science camera suitable for sub-orbital missions for observations in the UV, EUV and soft X-ray. Six cameras will be built and tested for flight with the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), a joint National Astronomical Observatory of Japan (NAOJ) and MSFC sounding rocket mission. The goal of the CLASP mission is to observe the scattering polarization in Lyman-α and to detect the Hanle effect in the line core. Due to the nature of Lyman-α polarization in the chromosphere, strict measurement sensitivity requirements are imposed on the CLASP polarimeter and spectrograph systems; science requirements for polarization measurements of Q/I and U/I are 0.1% in the line core. CLASP is a dual-beam spectro-polarimeter, which uses a continuously rotating waveplate as a polarization modulator, while the waveplate motor driver outputs trigger pulses to synchronize the exposures. The CCDs are operated in frame-transfer mode; the trigger pulse initiates the frame transfer, effectively ending the ongoing exposure and starting the next. The strict requirement of 0.1% polarization accuracy is met by using frametransfer cameras to maximize the duty cycle in order to minimize photon noise. The CLASP cameras were designed to operate with ≤ 10 e − /pixel/second dark current, ≤ 25 e − read noise, a gain of 2.0 +-0.5 and ≤ 1.0% residual non-linearity. We present the results of the performance characterization study performed on the CLASP prototype camera; dark current, read noise, camera gain and residual non-linearity.

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“…One difficulty for polarization measurements is that a UV polarimeter must operate above the terrestrial atmosphere to avoid radiation absorption. After some pioneering solar missions devoted to FUV polarimetry from space, next developing or proposed solar physics missions, such as CLASP 1 and 2 [1,2], SolmeX [3], and SCORE [4], plan to perform improved polarimetry in the UV and FUV. Key spectral lines for polarimetry of the solar atmosphere are H Lyman α (121.6 nm) and β (102.6 nm), O VI doublet (103.2 and 103.8 nm), C IV (155 nm), and, in the UV, Mg II k line (280 nm).…”

Section: Introductionmentioning

confidence: 99%

Polarizers tuned at key far-UV spectral lines for space instrumentation

et al. 2017

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Polarimetry is a valuable technique to help us understand the role played by the magnetic field of the coronal plasma in the energy transfer processes from the inner parts of the Sun to the outer space. Polarimetry in the far ultraviolet (FUV: 100-200 nm), which must be performed from space due to absorption in terrestrial atmosphere, supplies fundamental data of processes that are governed by the Doppler and Hanle effects on resonantly scattered line-emission. To observe these processes there are various key spectral lines in the FUV, from which H I Lyman α (121.6 nm) is the strongest one. Hence some solar physics missions that have been proposed or are under development plan to perform polarimetry at 121.6 nm, like the suborbital missions CLASP I (2015) and CLASP II (2018), and the proposed solar missions SolmeX and COMPASS and stellar mission Arago. Therefore, the development of efficient FUV linear polarizers may benefit these and other possible future missions. C IV (155 nm) and Mg II (280 nm) are other spectral lines relevant for studies of solar and stellar magnetized atmospheres.High performance polarizers can be obtained with optimized coatings. Interference coatings can tune polarizers at the spectral line(s) of interest for solar and stellar physics. Polarizing beamsplitters consist in polarizers that separate one polarization component by reflection and the other by transmission, which enables observing the two polarization components simultaneously with a single polarizer. They involve the benefit of a higher efficiency in collection of polarization data due to the use of a single polarizer for the two polarization components and they may also facilitate a simplified design for a space polarimeter. We present results on polarizing beamsplitters tuned either at 121.6 nm or at the pair of 155 and 280 nm spectral lines.

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Chromospheric Lyman-alpha spectro-polarimeter (CLASP)

Cited by 48 publications

References 0 publications

Vacuum ultraviolet spectropolarimeter design for precise polarization measurements

Vacuum ultraviolet spectropolarimeter design for precise polarization measurements

Performance characterization of UV science cameras developed for the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)

Polarizers tuned at key far-UV spectral lines for space instrumentation

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