model instruments baseline specification and key open issues – x-ray imaging telescope (xit) –

Solar-C Meeting @ St Andrews 1

Model Instruments Baseline Specification and Key Open Issues

– X-ray Imaging Telescope (XIT) –

Taro Sakao (ISAS/JAXA)

2012/8/13


Imaging Observation of the Corona

Phenomenological “connectivity” between the base of the corona and the chromosphere/transition region with EUV-line images

Heating and activities of hot loops with broad-band soft X-ray images

TRACE 171Å EIS 195Å

EIS 284Å SXR (XRT)

“What corona do we want to see?”2012/8/13


Introduction• X-ray Imaging (Spectroscopic) Telescope for Solar-C

– Solar-C: Perform seamless observations of the solar atmosphere (photosphere, chromosphere, transition region and corona) with a suite of 3 telescopes.

– Expected contributions from imaging observations of the corona• Reveal forms and mechanisms of (storage and) dissipation of energy • Quantitative understanding on the reconnection physics• Connectivity with the lower atmosphere

• Two possibilities under study for the X-ray telescope– (1) Ultra-high-resolution normal incidence EUV telescope

Context information for LEMUR– (2) Photon-counting imaging-spectroscopic grazing incidence

X-ray telescope

2012/8/13


Current Concept of X/EUV Telescope for Solar-CA Pair of NI and GI Channels

• Normal Incidence– Ultra-high-resolution with high-cadence imagery in EUV

wavebands• Connectivity with lower atmosphere• Context information for LEMUR

– 0.2-0.3” angular resolution (0.1”/pixel) with cadence <10 s for AR/FL– 171, 94 and 304 (or 1548 UV) Å bands

• Grazing Incidence– Highest spatial-resolution soft X-ray imaging-spectroscopy

• Provide physical context (entire loop info.) for NI observations with its wide temperature coverage

• Photon-counting capability for reconnection structure etc.– ~< 1” angular resolution (0.4-0.5”/pixel)– 0.9o (~<2 keV) and 0.45o (~0.5-10 keV) grazing angles

• Photon-counting with 0.45o2012/8/13


Preliminary Illustration of Solar-C X/EUV Telescope“Everything in a package”

3 NI Channels: 94, 171, 304 Å (or 1548 Å)2 GI Channels: 0.9 deg & 0.45 deg graz. angles * 0.45 deg Photon Counting

(Figure courtesy of SAO)

2012/8/13


Ultra-High-Resolution EUV Telescope

2012/8/13


Correspondence of low corona and chromosphere at ultra-fine scales

Ji, Cao, and Goode 2012, ApJ - BBSO/NST He I 10830Å - SDO/AIA 171 ÅStructure with diameter ~100 km

AIA 193ÅNST He I 10830-0.25Å

2012/8/13

Solar-C Meeting @ St Andrews 82012/8/13


Preliminary Features of Ultra-High-Resolution EUV Telescope

Item EUV Telescope EUVS/LEMUR

Telescope 32cmφ primary mirror3 sector coating(Ritchey-Chretien; ~4 m length)Tip-tilt control of the secondary

Wavelength channelTemperature coverage

171 Å, 94 Å, and 304 Å or UV band(0.8MK / 1MK & 8MK(FL) / 0.05 MK)[some from 94/171/195/211/304/335Å]

Spatial resolution 0.2” – 0.3” (0.1” pixel) 0.16” pixel

Exposure cadence Exposure time：　 AR (<3 MK) – 1 s, FL – 0.1 sCadence：　 < 10 s (for AR <3 MK)

Exposure time：　 AR – 1-5 s　 (w/ 0.33” spatial sampling)

Field of view ~400” x 400” 200” nominal> 300” extended

2012/8/13

Provide context for EUVS/LEMUR

Image- Lower TR- Lower corona- Hot corona (with 1 MK)

10

NI Line Selection• Science with NI telescope(s) largely depends on which wavelength

bands are to be employed.• In addition to 171 Å band:

Will there be 304 Å (He II) band? Yes (or UV-band?)• Imaging of spicules and prominences can be made at spatial resolution similar to

SOT-FG. (Joint observation with SUVIT.)• Will there be science output beyond SOT-FG?

– Temperature difference between 0.1 MK (lower TR with NI) and 0.02 MK (upper choromosphere with SOT) would be important?

– Will there be wavelength bands with >5 MK contribution (94 Å and/or 335 Å) besides 1-2 MK bands? Yes, 94 Å• High-temperature bands would be useful in identifying heating sites.

• The current baseline NI bands (171, 304, 94 Å) are more oriented to take narrow-temperature-band (“single-temperature”) images, overlapping with LEMUR temperatures.[171 (5.9), 304 (4.7), 94 (blend of 6.0 & 6.9 for flares)]


Grazing-Incidence X-ray Telescope with Photon-Counting Capability

2012/8/13


Science Targets of the GI Telescope (Photon-Counting)

• Energy dissipation processes in the corona that lead to dynamic activities of the corona.

• MHD structures assoc. with magnetic reconnection during flares– Identify, e.g., shock structures (slow shock, fast shock)

• Plasma conditions (temperature, heating status) in the upstream/downstream regions of a shock

– Electron temperatures from continuum spectra– Spatial distribution and evolution of supra-thermal electrons

(which serve as the seed for accelerated electrons)• Heating mechanism for active regions

– In particular, for hot plasmas in the AR core:• Spatial and temporal evolution of spectra with high time resolution by virtue of non-

dispersive imaging-spectroscopy* Particularly powerful under the nano-flare-heating picture for ARs.

– Spatial distribution of spectral features (Disk AR ・・ lateral, Limb AR ・・・ vertical）2012/8/13

Solar-C Meeting @ St Andrews 14(Tsuneta, Ap. J. 1997)

Possibilities: Shocks in the Reconnection Structure

(Tsuneta, Ap. J. 1996)(Tsuneta, Ap. J. 1996)

e- distribution spectra outside diffusion region

e- distribution spectra around reconnection point

Imada et al.JGR 2011

Electron acceleration at Earth’s magnetotail

10 keV

Supra-thermalelectrons

Thermalelectrons

Energy range covering up to ~10 keV should clearly identify presence of supra-thermal electron components

2012/8/13


Expected Observation Target Regarding Reconnection Physics

2012/8/13

(Tsuneta et al. 1997)

1% of Peak EM

20% of Peak EM

(Aschwanden et al. 1996)

Typ. Electron TOF distance ~ 1.43 x Loop half-length Not much far from SXR loop main bodyMay be able to perform proper photon-counting imagery around e- start point!


Expected AR Count Spectra

~15 s Integration for 1.2”-square Area

Red: with 10MK componentBlack: without 10MK compo.

(Attenuation filter: Be 2mm)

0.5 5

Fe lines sensitive to LogT=7

2

1% of 1-3 MK plasmas assumed

2012/8/13


XRT Filter-Ratio Temperatures

(Narukage et al. 2011)

Ti/Poly – Al/Mesh Pair

Med-Be – Thin-Be Pair(Texp = 20s / 4.3s)

(Texp = 2.1s / 0.9s)

Red: AR with 10MK componentBlack: AR without 10MK compo.

No significant difference between with and without 10 MK component.

2012/8/13


Key Features of the Photon-Counting Soft X-ray Telescope

Item Description

Optics Wolter I segment mirror (1/3 of entire circle), Ir-coatedGrazing incidence angle: 0.45 degFocal length: 4 mPlate scale: 0.4”-0.5”/pixel

Focal-Plane Detector CMOS-APS. 2k x 2k. 8-10 mm pixel sizeFrame read-out rate: 1000 fpsEnergy resolution equivalent to CCD (Si detector)

Energy range ~0.5 – 10 keV

Photon-counting area Baseline: ~80” x 400”Goal: ~200” x 400” (cover NS x EW extent of ARs)[Photon integration: ~400” x 400”]

Ang. res. & temporal res. for imaging spectroscopy

Energy spectrum in each 1”-2” square area for every 20-10 s. ... Even faster for line imaging.

Telescope envelope ~40 cm x 40 cm x 4.5 m

2012/8/13


FL (M2) AR QS CH

q = 0.45°

Electron rate (e-/s/pxl) 1.2 x 108 2.6 x 104 2.8 x 102 5.0 x 101

Exp. Time (s)*1 2.5 x 10-1 ms 1.1 s 1.1 x 102 s 6.0 x 102 s

q = 0.9°

Electron rate (e-/s/pxl) 5.6 x 108 1.4 x 105 1.4 x 103 2.6 x 102

Exp. Time (s) *1 5.4 x 10-2 ms 2.2 x 10-1 s 2.1 x 101 s 1.1 x 102 s

XRT (FW = Open-Open)

Electron rate (e-/s/pxl*2) 8.2 x 108 1.8 x 105 2.2 x 103 4.0 x 102

Exp. Time (s) *1 3.6 x 10-2 ms 1.7 x 10-1 s 1.4 x 101 s 7.5 x 101 s

*1: Time for accumulating 30 ke-. *2: GI telescope pixel size set to be 0.4” while XRT 1”.

Exposure Times with Photon Integration Mode

For q = 0.45° : Single mirror piece of 120o opening angle, 8 cm paraboloid section For q = 0.9° : Single mirror piece of 68o opening angle, 20 cm paraboloid section

For q=0.45o, good Texp for FL & AR while less performance for QS & CH, for full-res. imaging.For q=0.9o, comparable Texp to XRT expected for all targets, even with full-res. imaging.

2012/8/13


Issues (Personal View)• If we can have both NI and GI as a telescope suite, it would be great.

However, if it turns out not realistic, what would be the choice?• NI scientific weaknesses

– What is its own science?• Little spectroscopic info. available• Can sparse wavelength bands helpful?• Can it be beyond a context imager?

– Probably miss many temperature components in the corona such as AR core. Overall loop geometry not visible.

• GI scientific weaknesses– Base of the corona not well addressed

• Limited angular resolution (~1” vs 0.2-0.3”)– Insufficient imagery performance particularly for QS and CH with the

photon-counting GI. • Question: What Solar-C can do for QS & CH ?

• Who is to do?2012/8/13


Backup Slides

2012/8/13


XIT/GI

Item DescriptionTelescope Ritchey-Chretien telescope: diameter of aperture: ~30 cm

Focal plane detector Back-illuminated CCD

Wavelength range 9 – 34 nm (some from 9.4nm, 17.1nm, 19.5nm, 21.1nm, 30.4 nm, 33.5nm)

Plate scale 0.1 arcsec/pixel sampling

Spatial resolution 0.2 – 0.3 arcsec within 200 arcsec off-axis distance

Exposure cadence < 10 sec

Filed of view 400 arcsec × 400 arcsec

Item DescriptionTelescope Wolter-I telescope: diameter of aperture: ~25 cm

Focal plane detector Back-illuminated CMOS-APS

Energy range 0.5 – ~10 keV

Energy resolution ~150 eV at 5.9 keV

Plate scale 0.5 arcsec sampling

Spatial resolution 1.0 arcsec within 200” off-axis distance

Exposure cadence Photon integration mode: < 1 sec Photon counting mode: 10 (20) sec for 2” (1”) area

Filed of view Photon integration mode: 400 arcsec × 400 arcsecPhoton counting mode: ~80 arcsec × 400 arcsec (baseline) ~200 arcsec × 400 arcsec (goal; cover NS×EW extent of ARs)

XIT/NI

2012/8/13


XIT(GI, NI)Item Science requirements Science

backgroundsRelated hardware limitations

Wavelength selection GI: soft X-rays 0.5 – 5 keV (baseline) 0.5 – 10 keV (goal)NI: some from 6 EUV bands

GI: revealing the site of heating in the coronaNI: image low corona as well as flare high temperature plasmas

GI: photon-counting possible in soft X-raysNI: contribution of many other lines

Wavelength resolution λ/Δλ

GI: ΔE ~ 150 eV

NI: λ/Δλ > 30

GI: obtain emission-line structure in energy spectrumNI: avoid confusion due to nearby emission lines

GI: available energy resolution of Si NI: resolution of multi-layers < 40

Spatial resolution GI: 1.0” (0.5” sampling)

NI: 0.2” (0.1” sampling)

GI: ~1/3 scale size of known flare structures near reconnection siteNI: coronal volume filling factor ~0.1 from Hinode observations of 2” spatial resolution

GI: telescope length < spacecraft

NI: trade between spatial resolution and wide field coverage

Field of view GI: - integration mode: 400×400 arcsec- ph-counting mode: 80×400 arcsecNI: 400×400 arcsec

GI & NI: Full coverage of an active region

GI: - APS detector format of 2K×2K and spatial sampling - on-board ph-counting speed NI: CCD format of 4K×4K and spatial sampling

Exposure cadence GI: ph-integration mode < 1 sec ph-counting mode 10 (20) sec for 2” (1”) areaNI: < 10 sec

GI: rapid heating of coronal structures

NI: Faster cadence than LEMUR for providing context images

GI: - Effective area

NI: readout speed of 4K×4K (can be improved by CMOS) telemetry amount

2012/8/13


Fig. 6.3-2

Imagery cadence ~<10 sfor 171 and 304 Å

2012/8/13


Three-Channel NI Layout

Primary: Φ32 cm, efl=16 mSector: Ageom≈ 100, 200, 300 cm2

Channel selection via focal plane filters!

171Å

UV or304Å

94Å

(Figure courtesy of SAO)

2012/8/13


Key Features of the Photon-Counting Soft X-ray Telescope

Item Description

Optics Wolter I segment mirror (1/3 of entire circle), Ir-coatedGrazing incidence angle: 0.45 degFocal length: 4 mPlate scale: 0.4”-0.5”/pixel

Focal-Plane Detector CMOS-APS. 2k x 2k. 8-10 mm pixel sizeFrame read-out rate: 1000 fps, sRON ~ 5 e- rmsEnergy resolution equivalent to CCD (Si detector)

Energy range ~0.5 – 10 keV

Photon-counting area min.: 100 x 100 pixels goal: 512x512 pixels out of the 2k x 2k array

Ang. res. & temporal res. for imaging spectroscopy

Energy spectrum in each 1”-2” square area for every 20-10 s. ... Even faster for line imaging.

Telescope envelope ~40 cm x 40 cm x 4.5 m

Photon counting ROI:> 80” x 400”

Photon counting ROI:> 200” x 400”

2012/8/13


GI Mirror Effective Area

GI#2 (0.9°)

GI #1 (0.45°)

XRT(0.9°)

GI #1 (0.45°)• Similar Aeff as XRT even for <2 keV• Larger Aeff than GI #1 (0.9°) for >~5 keV• Photon Counting observation

GI #2 (0.9°=XRT)• Exp. time per pixel consistent with XRT by use of a large mirror

2012/8/13


Summary

Itms Photon-Counting X-ray Telescope Ultra-high-resolution EUV Telescope

Angular resolution Moderate Good

Temperature coverage High T OK, Not suited for low TT complementary to EUVS/LEMUR

Low T OK, High T limitedWithin EUVS/LEMUR range

Temporal resolution Moderate - Low? Maybe OK? (Good for EUVS/LEMUR)* But matches with ang. res.?

Spectroscopic capability Yes No, unless multiple channels equipped

Scientific strength Cover all coronal T incl. flares jointly with EUVS/LEMURSpectroscopy on high T plasmas

Provide good context info. for EUVS/LEMUR to jointly investigate small-scale dynamics

Technology matureness Not high, but technology growing rapidly

Maybe high (AIA etc. heritage)

NI & GI under consideration for coronal imager

2012/8/13

model instruments baseline specification and key open issues – x-ray imaging telescope (xit) –

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