Image tube design and processing requirements for building an ICCD are discussed. Work is under way at EVC for building an ICCD using the Fairchild CCD 201 (100 x 100) array, and progress will be reported. Demountable tests have been made, exposing parts of a CCD 201 to 15 kilovolt electrons over five radiation levels from approximately 10 to 1 million rads. Other tubes built by EVC over the last few years which successfully use semiconductors to detect photoelectrons will be described briefly

Choisser, J. P.

English

NASA Technical Reports Server

EXPERIMENTS ON THE USE OF CCDs TO DETECT 
PHOTOELECTRON IMAGES 
John P. Choisser 
Electronic Vision Company 
A Division of Science Applications, Inc. 
San Diego, California 
This paper will discuss the image tube design 
and processing requirements for building an ICCD. 
Work is under way at EVC for building an ICCD using 
the Fairchild CCD 201 (100 X 100) array,  and progress 
will be reported. 
exposing parts of a CCD 201 t o  15-kilovolt electrons 
Over five radiation levels from approximately 1 0  to 
10 rads. 
years which successfully use semiconductors to detect 
Demountable tes ts  have been made, 
6 Other tubes built by EVC over the last few 
photoelectrons will be described briefly. 
I. DIGICON AND PHOTOSIL 
Two basic configurations of tubes we have built with semiconductor anodes 
a r e  shown in Figure 1. The Digicon, which is on the right, is a magnetically 
focused tube, and the Photosil, on the left, is electrostatically focused. The 
tubes are, respectively, approximately 2 inches in diameter by 6 inches long 
and 1 inch in diameter by 2 inches long. Both types of tubes a re  built using 
externally processed molecular-beam-formed photocathodes, a process we 
believe to be important in avoiding poisoning of the semiconductors by alkali 
metals. 
The design, fabrication, and use of Digicons have been described pre- 
viously (Refs, 1-7). 
been used. 
mounting CCDs, some Digicon headers will be shown as examples. 
Both parallel output and self-scanned diode a r rays  have 
Because one important facet of ICCD design concerns means for 
150 
https://ntrs.nasa.gov/search.jsp?R=19750020764 2020-03-22T19:53:58+00:00Z
F i g u r e  2 shows a heade r  built  for  a 212-channel Digicon fo r  Beaver  at 
USCD. 
the  geometry  of the diode leads  c a n  be different  on the  vacuum s ide  and the  air 
side.  
into a rec t i l inear  a r r a y  of pins on 0. 100-inch c e n t e r s  on the backside.  
lateral t r ave l  of the lead paths between ceramic l a y e r s  a l so  pe rmi t s  an  excel- 
lent  he rme t i c  seal, s ince  the  l a y e r s  are metal l ized before  the  ceramic is 
p res sed  and f i red.  The  diode manufac turer ,  in  th i s  case United Detector  
Technology, b r a z e s  the  s i l icon chip to  the  header  and at taches the lead w i r e s  
f r o m  the  subs t r a t e  to  the diodes. 
Serkowski at the University of Arizona using a different  a r r a y  of 200 diodes. 
F i g u r e  4 shows encapsulated and  unencapsulated 200-channel Digicons. 
The ceramic (alumina) header is of mul t i - layer  construction, so that 
The  basical ly  c i r c u l a r  contact  configuration shown h e r e  is t ransformed 
The 
F igure  3 shows a similar header  f o r  
The Photosi ls  have been  developed p r imar i ly  f o r  four-quadrant  photon- 
counting f o r  guiding on faint  objects  (Refs.  8 and 9). 
configuration that  wil l  be  used f o r  the CCD 201. 
Quadrant Photosi l  is 2 inches in  d i ame te r  and 5 inches long, including space  in  
the r e a r  f o r  preampl i f ie rs  (F igu re  5). 
planned f o r  u s e  in  gene ra l  photometry. 
This  is the bas ic  tube 
When encapsulated,  the 
One-  and two-channel Photos i l s  are 
All  of the previously descr ibed  tubes have para l le l  outputs, and it is 
na tura l  to cons ider  the u s e  of self-scanned a r r a y s  to pe rmi t  the  use  of increased  
numbers  of pixels. 
shows a header  f o r  tubes using the Reticon 1024 B a r r ay .  
tubes was  built 1 y e a r  ago f o r  Tu11 of the University of Texas, and has  been 
used successful ly  a t  the coude) spec t rograph  of the  107-inch te lescope at 
McDonald Observatory.  
This  has  been done in  the case of the  Digicon, and F igu re  6 
The  first of t hese  
To  prevent  damage  to the c i r cu i t ry  on the chip, a mechanical  m a s k  is 
mounted o v e r  the ch ip  to p e r m i t  photoelectron bombardment  only of the diodes.  
Radiation damage  t o  the diodes in  the Reticon a r r a y  causing increased  d a r k  
c u r r e n t s  up to a max imum of a f ac to r  of about 15 has  been measu red ,  and is 
reported by  Tull ,  Choisser ,  and Snow in  Reference 6. 
CCDs which m a y  i n c r e a s e  leakage c u r r e n t s  and adve r se ly  affect  cha rge  t r a n s -  
fer efficiency is a n  important  considerat ion in  designing, building, and using 
ICCDs. 
S imi l a r  damage  to  
151 
11. DEMOUNTABLE TESTS 
In cooperat ion with C u r r i e  at the University of Maryland, EVC i r rad ia ted  
a Fairchi ld  CCD 201 with 15-kilovolt e lec t rons  in a n  ul t rahigh vacuum system. 
A m a s k  was  fabricated with f ive 0,020-inch-diameter  holes,  spaced so  that  
they would have no rows o r  columns of the a r r a y  in common. 
with a single l a r g e r  hole, was  used to select the i r rad ia t ion  site f o r  a pa r t i cu la r  
run. 
picoammeter .  
which was i l luminated by a low-pres su re  m e r c u r y  lamp. 
A second mask ,  
The leads  f r o m  the a r r a y  w e r e  shorted together  and grounded through a 
Photoelectrons w e r e  provided by a palladium photocathode, 
3 4  5 F o u r  exposures  w e r e  made,  represent ing  approximately 10 , 10 , 10 , 
6 and 10 rads.  
high voltage off. 
A fifth exposure  was  made  with the m e r c u r y  l amp  on and the 
The a r r a y  was  then sen t  to  C u r r i e  f o r  tests. 
Observat ion of the operat ing a r r a y  showed no vis ible  effect on d a r k  c u r -  
ren t  except f o r  the spot  which had received the  highest  i r radiat ion.  
i n  d a r k  s ignal  at th i s  point was  of the same o r d e r  as the var ia t ions in  d a r k  c u r -  
r en t  which occur  normal ly  ove r  the area of the a r r ay .  
The inc rease  
Although these  r e su l t s  appea r  encouraging, they should be considered 
somewhat inconclusive. 
s ibly m o r e  damaging to  the a r r a y ,  i f  the  a r r a y  w e r e  operat ing during i r r a d i a -  
tion. In addition, it was  unfortunately not possible  to  make  the tests at higher  
voltage, and t h e r e  is s o m e  possibil i ty that  the 15-kilovolt e lec t rons  could not 
penetrate  to the regions where  damage would be  m o r e  pronounced. 
additional m o r e  careful ly  controlled tests wil l  be  possible  soon with the  a r r a y  
in  a tube, and with the protect ive oxide su r face  ove r  the a r r a y  removed. 
The tests would have been m o r e  realistic, and pos- 
In any case ,  
111. ICCD DESIGN AND FABRICATION 
Due p r i m a r i l y  to the  availabil i ty of the a r r a y ,  and because  of the poten- 
tial advantages of f ronts ide  bombardment  if damage  mechanisms pe rmi t  (i. e . ,  
economics and cooling s implici ty) ,  it was  decided to build a n  ICCD using a 
modified Fa i rch i ld  CCD 201 and a Photosi l  tube design. 
cooperat ion with C u r r i e  at the Universi ty  of Maryland, who wil l  pe r fo rm the 
test and analysis  of the  first devices  (Ref. 10). 
p ro jec t  sponsored by the A i r  F o r c e  Space and Miss i les  Systems Organization. 
The project  is in  
The  tubes are  being built  f o r  a 
152 
A s  previously stated, the tube will be made using the design of the 
electrostatically focused Photosil, shown in Figure 1. A 1 -inch-diameter 
header has been built which conforms to Fairchild specifications in the die 
attach and wire bond region. 
where they are brought out to a pin circle near the perimeter of the header. 
This leaves the center area of the air side of the header clear for  a cooling 
probe, and leaves most of the vacuum side available for brazing the copper 
The contact leads descend to a subsurface layer, 
sealing washer and Kovar anode cone mounting ring. 
Figure 7, along with a partially finished 2-inch header to be used in a Digicon 
with two parallel Reticon RL-1024 B arrays.  
Later this month (March 1975), the headers will be sent to Fairchild for  
The f i r s t  tube is scheduled to be built in April, and 
The header is shown in 
attachment of the arrays.  
tests will commence immediately. 
IV. SUMMARY 
Because of the number of successful image tubes built over the last few 
years at EVC using semiconductors of various types as anodes, we feel that 
the technology is at hand to build ICCDs as suitable a r rays  become available. 
In his paper (Ref.  l l ) ,  for example, Collins will describe CCD ar rays  built at 
Texas Instruments specifically designed and mounted for  rear  illumination by 
photoelectrons. 
semiconductor manufacturers, the potential advantages to their use as photo- 
electron detectors will be kept in mind. 
W e  are in hopes that, as future a r rays  are designed by the 
153 
REFERENCES 
1. Edward A. Beaver  and C a r l  E. McIlwain, "A Digital Multichannel 
2. 
3. 
4. 
5. 
6 .  
7. 
8. 
9. 
Photometer ,  I f  Review of Scientific Instruments ,  Vol. 42, No. 9, 
September  1971. 
Edward A. Beaver ,  C a r l  E. McIlwain, John P. Choisser ,  and W a l t e r  
Wys oczanski,  "Counting Image Tube Photoelectrons with Semiconductor 
Diodes, I '  Fifth Symposium on Photoelectronic Imaging Devices , London, 
1971 , Advances in Electronics  and Elec t ron  Phys ics  , Vol. 33B, Academic 
Press, 1972. 
John P. Cho i s se r  and Walter  Wysoczanski, "A Multi-channel Image Tube 
f o r  Photoelectron Counting, ' I  Proceedings of the Society of Photo-optical  
Instrumentat ion Engineers ,  Vol. 28 - Astronomy, Tucson, Arizona, 1972. 
Edward A. Beaver ,  E. M. Burbidge, C. E. McIlwain, H. W. Epps,  and 
P. A. S t r i t tma t t e r ,  "Digicon Spectrophotometry of the Quas i -s te l la r  
Object P H L  957, ' I  Astrophysical  Journal ,  November 1972. 
Edward A. Beaver ,  R. J. Harms ,  and G. W. Schmidt, "Digicon 
Applications in  Astronomy, ' I  Sixth Symposium on Photoelectronic Imaging 
Devices, London, 1974 (to be  published). 
R. G. Tull, John P. Choisser ,  and E. H. Snow, "The Self-scanned 
Digicon: A Digital Image Tube f o r  Astronomical  Spectroscopy, ' I  
September  1974 (to be  published). 
John P. Choisser ,  "Recent Developments on the U s e  of Parallel and 
Self-scanned Diode Ar rays  to  Detect Photoelectrons , ' I  Sixth Symposium 
on Photoelectronic Image Devices, London, 1974 (to be published). 
John V. Jel ley,  "Semiconductor Image Devices f o r  Spectroscopy, Auto- 
guiding and Photometry,  ' I  Cambridge Conference on Astrophysics , 
July 1972, The Observatory,  VOl. 93, p. 9, 1973. 
J. V. Jelley,  and A. N. Argue, "A Quadrant Photosi l  Autoguider f o r  the 
17/24 Inch Schmidt Telescope at the Institute of Astronomy, Cambridge,  I '  
Proceedings of the Society of Photo-optical Instrumentation Engineers ,  
Vol. 44 - Astronomy, Tucson, Arizona, 1974. 
154 
10. D. G. Cur r i e ,  "On a Photon-Counting ICCD Using the Fa i rch i ld  CCD 201, " 
Proceedings  of this  Symposium. 
11. D. R. Collins,  C. G. Roberts ,  W. W. Chan, W. C. Rhines, J. B. Barton, 
and S. Sobieski, "Development of a CCD for Ultraviolet  Imaging Using a 
CCD Photocathode Combination, ' I  Proceedings of this  Symposium. 
155 
Figure 1. Magnetically focused Digicon (right) and electrostatically focused 
Photosil (left) 
156 
Figure  2. Multi layer ceramic header  for  a 212-channel Digicon 
157 
Figure 3. Multilayer ceramic header for a 200-channel Digicon 
158 
Figure 4. Encapsulated and unencapsulated 200-channel Digicons 
159 
Figure 5. Quadrant Photosil for autoguiding on faint images 
160 
Figure 6. Multilayer ceramic header for a Digicon using the RL-1024 B 
Reticon array 
161 
Figure 7. 1 -inch-diameter Photosil header made for the Fairchild CCD-201 
(left) and 2-inch-diameter Digicon header for two parallel Reticon 
RL-1024 B ar rays  (right). 
162 


Experiments on the use of CCD's to detect photoelectron images

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