# Presentation: 108851

## Astro-E2 X-Ray Telescopes

- XRT Setup & Structure
- Performance  Characteristics
- Effective Area
- Angular Resolution
- Optical Axes
- Field of View

## XRT Set up

- 5 XRT’s on extended bench
- 4 on imagers with f=4.75m
- 1 on spectrometer with f=4.50m
- Same external dimension for XRT-I & XRT-S
- ~ 40 cm diameter, ~25 cm height

## Structure 

- Optic
- Reflective optics
- Grazing incidence
- Conical approximation to Wolter type I
- 2 reflections in 2 stages
- Collimation 1 stage
- Gold surface
- Nested shells of segmented “cylinder”

- Angle of incidence (on-axis) varies from inner (smaller) to outer (larger)
- spectral response: Critical angle ~ 1/*E*

## Geometry and Mechanics
Segmented circular elements
Reflectors positioned in slots
(Almost) all constructed out of Al
Sandwiched elements: Gold surface / epoxy adhesion layer / aluminum substrate
Thermal properties
Operational T: 20 +/- 7.5 C
Sun shields
Heating elements
Thermal Shields

- Segmented circular elements
- Reflectors positioned in slots
- (Almost) all constructed out of Al
- Sandwiched elements: Gold surface / epoxy adhesion layer / aluminum substrate
- Thermal properties
- Operational T: 20 +/- 7.5 C
- Sun shields
- Heating elements
- Thermal Shields

- Quadrant construction: 4- fold symmetry in image

- Sandwiched structure: dependence on temperature from CTE mismatch

- On ground, slight resolution dependence on orientation: displacement & gravity sag

## Basic parameters of XRT

|  | Astro-E2 XRT-I | Astro-E2 XRT-S | ASCA |
| --- | --- | --- | --- |
| Number of telescope | 4 | 1 | 4 |
| Focal length | 4.75 m | 4.5 m | 3.5 m |
| Inner Diameter | 118 mm | 119 mm | 120 mm |
| Outer Diameter | 399 mm | 400 mm | 345 mm |
| Height | 279 mm | 279 mm |  |
| Mass/Telescope | 19.5 kg | 18.5 kg | 9.8 kg |
| Number of nested shells | 175 | 168 | 120 |
| Reflectors/Telescope | 1400 | 1344 | 960 |
| Geometric area/Telescope | 873 cm2 | 887 cm2 | 558 cm2 |
| Reflecting surface | Gold | Gold | Gold |
| Substrate material | Aluminum | Aluminum | Aluminum |
| Substrate thickness | 155 m | 155 m | 127 m |
| Reflector slant height | 101.6 mm | 101.6 mm | 101.6 mm |

## XRT Characterization from ISAS Measurements

- ISAS 30 m pencil beam

-  ISAS pencil beam
-  Full illumination

*Data from JAXA/ISAS*
*Y.Maeda*

## Full XRT Images

- I0

- I1

- I2

- I3

- S

## Effective Area

- Full Telescope Effective Area at 4.51 keV:
- XRT-I: I0-I3: 340 / 334 / 331 / 335 cm2
- XRT-I average 335 cm2
- XRT-S: 332 cm2

- ~ 4% up from E1

- ~ 9% down from E1

## Effective Areas

- Rough numbers, for each XRT
- ~ 450 cm2 at 1.5 keV
- ~ 335 cm2 at 4.5 keV
- ~ 245 cm2 at 8.0 keV (smaller ~ 90% for XRT-S at higher E)
- ~ 175 cm2 at 9.4 keV
- Au M edge at ~ 2 keV
- Efficiency slight improved (a few %) from Astro-E1
- For XRT-S, difference is mainly due to Pt  Au
- Especially at higher energy due to larger critical angle of Pt

## Point Spread and Encircled Energy Functions

- Angular Resolution

## Angular Resolution: HPD

## Angular Resolution

- Measured with Half-Power Diameter from Encircled Energy Function
- No dependence of angular resolution on energy
- Indirect energy dependence on radial position of responsible reflectors
- Errors in angular resolution (axial figure errors, positioning errors, etc.) are largely radius independent
- HPD ~1.8’
- Focal length errors absorbed
- Sharp core: inner *r* ~ 0.1’: sharply rising (~ linear) EEF ; no flat PSD (c.f. ASCA mirrors)
- 90% encircled power within 4’ diameter

## Focal Lengths & Orientation Dependence

-  Focal Length variation
-  as large as 50 mm
-  all errors due to focal length deviation are absorbed (measurement done at nominal *f*)
-  Dependence on orientation

- Hope (optimistic) that resolution will be better in space:
-  no displacement
-  no gravity sag

## Optical Axes

## Optical Axis

- Optical axes defined as the direction of maximum output
- Not the bore sites (which are well sub-arc-minutes)
- Optical axes of quadrants are located within +/-1 arcmin from the nominal telescope axes
- Do not contribute to angular resolution (double reflection)
- Lower throughput by <~5% at 1 arc minute

## Field of View

- X-ray

- W

- D

- C

- U

- Q3

- (Configuration)

- 

- F.O.V. (FWHM)

- 	 0’  45’ 90’
- Al-K	12  17   36
- Ti-K	12  17   32
- Cu-K	 9   13   26
- Pt-L	 8   12   22

- (arcmin.)

- (XRT-I)

- FOV of full XRT at 4.51 keV

## Field of View

- Collimator limits stray light, but not significantly restricts the aperture
- Full XRT Field of View ~ 20’ at 4.5 keV
- Energy dependence via radial dependence of responsible reflectors
- Smaller FOV for higher energy x-ray (smaller critical angle of reflection)

## Parameters for the Pre-collimator

|  | XRT-I | XRT-S |
| --- | --- | --- |
| Number of Collimators | 4 | 1 |
| Height | 32 mm | 32 mm |
| Blade substrate | Aluminum | Aluminum |
| Blade Thickness | 120 m | 120 m |
| Blade Height | 22 mm | 22 mm |
| Height from Blade Top to Reflector Top | 30 mm | 30 mm |
| Number of nested shells | 175 | 168 |
| Blade/Telescope | 700 | 672 |
| Mass/Collimator  | 2.7 kg | 2.7 kg |

## Satellite Alignment