Energy dependent X-ray maps of clusters of galaxies are discussed. A design for a stacked, etched grid collimator is discussed

Ulmer, M. P.

English

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%’ 325 r R82* 2 6 0 7 0  
X-RAY IMAGING ABOVE 3 keV 
M e l v i l l e  P. Ulrner 
Department of Physics and Astronomy 
Northwestern Univer i  s t y  
Evanston , I 1  1 i noi s 60201 
I . INTROD2CTION 
My o r i g i n a l  mot iva t ion  for  the designs presented here was t o  produce 
energy dependent x - r a j  maps of c lus te rs  of galaxies. 
can a l so  be used t o  study supernova remnants, ga lac t i c  nuc le i ,  etc. 
Of course, these designs 
11. PENCIL REAM DESIGN 
The f i r s t  design i s  t ha t  f o r  a stacked, etched g r i d  co l l imator ,  shown i n  
Figure 1. This could, i n  p r i nc ip le ,  be pu t  on the  XTE. This would a l low the 
XTE s a t e l l i t e  t o  be used f o r  d i f f u s e  object  study as wel l  a s  for  po in t  sources 
i n  confused regions o f  the galaxy. 
ezi;sion. The AXAF’s la rge  focal plane scale i s  not optimal f o r  10‘ t o  lo 
extents, however. 
out t o  15 o r  20 keV q u i t e  eas i l y ,  and AXAF o ~ l y  has a token e f f e c t i v e  area 
above -7 keV. 
Admittedly, AXAF w i l l  study d i f f u s e  
Furthermore, the stacked, etched g r i d  design can be used 
The p a r t i c u l a r  design and experiment parameters tha t  we present below a r e  
hased on a Space Lab proposal done i n  co l labora t ion  w i t h  G. F r i t z  and R. 
Cruddace. 
The co l l imator  design has more than one so ut ion;  the one presented here was 
done by the Rendix Corporation. 
design on the XTE i s  t h a t  the po in t i ng  requirements are higher than those o f  
the XTE s a l t e l l i t e .  Also, note t h a t  the 8 x 
good, and i s  achievable because o f  the small f i e l d  o f  view. 
It demonstrates the power of t h  s r e l a t i v e l y  simple experiment. 
Note, the only  drawback t o  usage o f  t h i s  
UFU s e n s i t i v i t y  i s  q u i t e  
https://ntrs.nasa.gov/search.jsp?R=19820018194 2020-03-21T07:35:33+00:00Z
326 
Experiment Summary Table 1 
Cbject ive To stbdy c lus te rs  of galaxies, ga lac t i c  nuc le i  and other  extended 
and po in t  x-ray sources with h igh  s e n s i t i v i t y  and l a r g e  dynamic 
energy range. 
Technique Passive co l l imators  and gas f i l l e d  propor t ional  counters. 
F i e l d  o f  View 4' x 4 '  and 12' x 12'. 
Col l imators 9 u n i t s  o f  stacked electroformed invar  gold coated mesh. 
Detectors Low background wi re wal l  propor t ional  counters. 
- Energy Range -25 - 15 keV. 
E f fec t i ve  Area 
S e n s i t i v i t y  
3000 cm' a t  2-10 keV, 1000 cm2 a t  0.1-0.25 keV and 10-15 keV. 
( 5 0 )  Point  source 8 x UFU i n  lo5 seconds, 2-6 keV. 
Required Point ing S t a b i l i t y  and accuracy 1' o f  arc, measurement t o  b e t t e r  
20" of  arc. 
Accomodation 
Mass 215 kg power 100 watts.  
1 meter square by 0.6 meter i n  height. 
-
Table 2: Col l imator Propert ies 
F i e l d  o f  View 4 x 4 arc min and 12 x 12 arc min 
Transmission 50 per cent 
E f fec t i ve  Area (each) 320 cm' 
Size (each c o l l  imator)  
(Over ac t i ve  area of  propor t ional  counter) 
230 mn x 280 mn x 360 mn high 
Weight 13.1 Kg 
Thennal Heat Leak (each) 7Y @ O C  (10 watts rF 30° C) 
Total Ueight (9  co l l imators ,  op t i ca l  135 Kg 
bench, thermal cover) 
Total Heat Leak ( 9  c o l l  imators 81W 
and thermal cover) 
32 7 
111. M I R R O R  ARRAY DESIGN 
The second design we present overlaps wi th  the c a p a b i l i t i e s  of AXAF, but  
the design i s  optimized t o  work a t  7 keV. 
the present design i s  qu i te  good fo r  sources tha t  are t o  be s tud ied on scales 
>1' 
Relow, we show below t h a t  a t  7 keV, 
The basic design was used f o r  a Space Lab proposal which I submitted i n  
co l labora t ion  w i t h  the Un ivers i ty  o f  Birmingham group (A. P. Willmore, P.I.). 
A s ing le  m i r ro r  module consis ts  of 4 nested Wolter Type I mi r ro rs  (Figure 2). 
Then 80 o f  these modcles would be combined as shown i n  Figure 3. 
separate images would be formed, and combined l a t e r  by software. 
and sens i t i v i  t i es a re  sumna r i zed bel  ow. 
The 80 
The design 
Experiment Sumnary: Table 3 
80 m i r r o r  un i ts ,  each comprising 4 nested sections, focal leng th  200 cm, 
maximum mi r ro r  -12 cm diameter, -40 cm long (Figure 2) 
Grazing angle 25'  a l lowing operat ion t o  a t  l e a s t  8 keV 
Resolution 2 ' ;  F ie ld  of  view -20' diameter 
Large 2 f fec t i ve  area from one p o s i t i o n  sens i t i ve  propor t ional  counter 
f o r  de tec t ing  the images from 20 m i r r o r  un i ts .  
minimized by la rge  guard region surrounding each image region and 
manufacturing problems reduced. 
Cost minimized by: 
* 
* 
* 
* 
Background consequently 
* 
(1) 
( 2 )  'Mass' producing m i r ro rs  by e l e c t r o  forming rep l i cas  from a 
Aiming f o r  moderate resolut ion,  as above 
superpol i shed master 
328 
Table 4: S e n s i t i v i t y  i n  4 x l o 4  seconds (50) 
Energy Point  Source 20' Diameter Source 
2-7 keV 2 x UFU 2 x UFU 
7-9 keV 6 x UFU 6 x 1W2 UFU 
a t  6.7 keV, i r o n  l i n e  5 x 1W6 photons/cm sec 5 x photons/cm sec 2 2 
Table 5 
Source Detected Time Required 
ergs/sec a t  the Galact ic  Nucleus..................200 seconds 
5 lo3' ergs/sec ir t  M31 Nucleus+. ........................ .4 x 10 seconds 
NGC4151-like ob ject  a t  2 . -13.. ...................... .4 x 10 seconds 
I ron  l i n e  from Coma-like Cluster  a t  Z . .3.......4 x 10 seconds 
4 
4 
r, 
Cluster 1/3 as b r i g h t  as Coma w i t h  10' 
isothermal sphere 80 reso lu t i on  elements > ~cJ........ 4 x 10 secdnds 
3 Cluster 1/30 as b r i g h t  as Coma--simple detect ion if 10' radius..............................4 x 10 seconds 
'2' reso lu t ion  al lows a region of .2kpc rad ius  t c  be iso la ted.  
_.... 
We calcu lated the  e f fec t i ve  area of the  e n t i r e  system, and t h i s  i s  shown 
i n  Figure 4. 
estimated losses due t o  scat ter ing,  shadowing, and propor t ional  counter 
response. This area o f  -300 cm2 compares q u i t e  wel l  w i t h  the  AXAF area a t  7 
keV o f  -200 cm'. The AXAF quoted area does not take i n t o  account losses due 
t o  sca t te r i ng  o r  the  propor t ional  counter. 
e f f e c t i v e  area could be as low as 100 cm2, and hence the  design we present 
here has 1.5 t o  3 times the area of AXAF a t  7 keV. The focal  plane scale o f  
AXAF i s  -5 times tha t  of our design, and therefore,  fo r  d i f f u s e  sources, w i t h  
scales >I1, the s ignal  t o  noise r a t i o  w i l l  be s i m i l a r  f o r  AXAF and the design 
presented he r e  . 
Note, t h i s  area i s  on ly  -303 o f  the geometrical area, because of 
We est imate t h a t  the  t r u e  
1V. MIRROR REPLICATION 
Is i t  poss ib le  t o  make many m i r ro rs  cheaply? We have been re-evaluat ing 
and o l d  technique--electro-forming. 
"low sca t te r "  o r  "super pol ished" f i n i s h  can be q u i t e  e a s i l y  reproduced. 
Total in tegra ted  sca t te r i ng  (Bennett, 1978) t e s t s  were performed on both the 
mandrel ( p r i o r  t o  use) and the 14th electro-formed n i cke l  pieces. For both 
pieces, the r.m.s. surface roughness was 15 2 2 A (Bennett, p r i v a t e  
comnunication). 
analyzed. 
beams from the f l a t s  had c 1.4' h a l f  power r a d i i ,  and the  t o t a l  r e f l e c t i v i t y  
o f  the  f l a t s  was > 60 Z.  Electro-forming op t i ca l  f l a t s  i s  ac tua l l y  more 
d i f f i c u l t  than e lect ro- forming c y l i n d r i c a l  pieces. Thus, we are o p t i m i s t i c  
about t h i s  technique, and we are proceeding ahead w i t h  plans t o  reproduce 
super-polished c y l i n d r i c a l  pieces. 
We found t h a t  op t i ca l  f l a t s  t h a t  have a 
0 
The 7 keV x-ray sca t te r ing  r e s u l t s  we performed are being 
The present pre l iminary analys is  showed t h a t  the re f l ec ted  x-ray 
3 30 
V. CONCLUDING REMARKS 
I n  conclusion, designs of modest p ro jec ts  tha t  are not covered by 
AXAF are d i f f i c u l t  t o  f ind.  The designs presented here would 
more observing t ime fo r  p ro jec ts  tha t  would not requ i re  the h 
reso lu t ion  c a p a b i l i t i e s  o f  AXAF. Given the  funding s i t u a t i o n  
i n t e r e s t  i n  -7 keV astronomy, modest instruments w i t h  capabil 
overlap XTE and AXAF should be given consideration. 
REFERENCES 
Bennett, H. E. 1978, Opt ical  Engineering, - 17, 480. 
Rake ava 
and 
e 
gh spa t ia l  
and the  h igh  
t i e s  t h a t  
XTE 
1 a3 

332 
ORIGINAL PAdk Is 
OF POOR  QUAL^^^ Ezz 
e??zzz? 
I 
k 
I 
i I
I 
I 
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Figure 2 Four ne,:ed Wolter Type I mirrors. One o f  80 modules 
333 
ORIGINAL PAGE tS 
OF POOR QUALITY 
Figure 3 Four u n i t s ,  each comprised of  20 nests  o f  4 m i r r o r s  and 
approximately .64x.64x2.5m a r e  mounted 2 on each s i d e  o f  
the Birmingham SL2 p o i n t i n g  system. 
e tc . ,  a r e  s i t u a t e d  i n  the  c e n t r a l  space. 
The s t a r t r a c k e r ,  gyros, 
3 34 
I ooc 
I O 0  
I C  
I 
0 
ORIGINAL PAdE IS 
OF POOR QUALITY 
2 
\ 
5 
Energy ( k e V )  
IO 
figure 4 The effective area versus energy for the f u l l  8Cl mirror/ 
proportional counter system 


X-ray imaging above 3 keV

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