Hinode/XRT response functions

Stray Light Correction of the XRT Temperature Response Functions

(7, September, 2015 by Aki Takeda)
(11 Sep,2015 added ratio curves & estimation of open fraction.)
(16 Dec,2019 figures of telescope.)

1. Introduction.

What is the XRT temperature response functions?

[Physically ...]
Expected number of photons which will be detected by the CCD (or the number of electrons produced by them) by observing the model plasma (i.e., isothermal plasma with the unit emission measure, e.g., 1 cm^[-5]) through each analysis filter.
[Mathematically ...]
XRT's effective area functions integrated (with respect to wavelength) with the synthesized solar spectra. The former is the spectral response (spectral sensitivity) modified by each analysis filter. The latter is calculated for a given elemental abundance and ionization balance under a certain emission model (e.g., isothermal plasma) of the solar spectra.
```
 
[Temperature response func.] = [Factor(geometrical, etc.)] * [Model Solar Spectra] # [XRT Effective Area]
           (T)                                                       (T, λ)                   (λ)
```

2. XRT's effective area function.

[Effective Area] = [aperture] * [prefilter] * [mirror1] * [mirror2] * [filter1] * [filter2] * [ccdqe] * [contamination]

aperture=2.28 cm^2
filter1=1.0 (FW1=OPEN)
filter2=1.0 (FW2=OPEN)

Effective Area modified partially opened prefilter (without X-ray filters).

3. Modified response functions.

After multiplying the FW1 and FW2 responses, take convolution with the model solar spectra calculated based on Chianti version 7.1.3.
Here we assume the Open Fraction having the value of 0.45 and 0.95 (see Section 5 for derivation).

Open/Al-mesh	Open/Ti-poly

Al-poly/Open	Thin-Be/Open

Open/thick-Al	Open/thick-Be

4. Modification of the Filter Ratio.

Al-poly/Al-mesh	Ti-poly/Al-mesh

thin-Be/Al-poly	thick-Be/thick-Al

5. Estimation of the "Open Fraction" of the prefilter.

G-band images taken with VLS(visible light shutter) Open or Close can be used to estimate the amount of stray light coming through the open area of the prefilter.

Sample case of phase 1 (10-Jan-2013)

VLI transmission from the Blue Book section 2.5.1.


	Ratio of total image intensity : [VLS_close]/[VLS_open]=0.446..

Sample case of phase 2 (10-Jul-2015)


	Ratio of total image intensity : [VLS_close]/[VLS_open]=0.953..

6. Software to use the modified response functions.

Under development....