Engineering design specifications and development of the large area detector and photomultiplier tube assemblies for the Burst and Transient Source Experiment (BATSE) of the Gamma Ray Observatory (GRO) mission are examined

Stephan, E. A., Jr.

English

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FINAL TECHNICAL REPORT 
CONTRACT NAS8-35012 
PREPARED FOR: 
GEORGE C.  MARSHALL SPACE FLIGHT CENTER 
MARSHALL SPACE FLIGHT CENTER, ALABAMA 3 5 8 1 2  
FROM : 
UNIVERSITY OF CALIFORNIA, SAN D I E M  
SEPTEMBER 12, 1986 
PREPARED BY: 
EDWINA. STEPHAN, JR. 
PROJECT MANAGER 
UNIVERSITY OF CALIFORNIA, 
SAN DIEGO 
CENTER FOR ASTROPHYSICS 6 
SPACE SCIENCES 
LA JOLLA, CA. 92093 
FINAL TECHNICAL REPORT 
Contract NAS8-35012 
1.0 Synopsis 
Marshall Space Flight Center (MSFC ) awarded the University of California, 
San Diego (UCSD) NASA Contract NAS8-35012 effective November 15, 1982. The 
contract provided design support of the Burst and Transient Source 
Experiment (BATSE) of the Gamma Ray Observatory (GRO) mission. The 
contract as amended, involved engineering design specification and 
development of the BATSE large area detector and photomultiplier tube 
assemblies. The contract work directly supported the BATSE Preliminary and 
Critical Design Reviews. A total of seven modifications served to extend 
the period of performance and increase the scope until contract 
expiration, February 28, 1985. Final contract value totalled $159,110. 
UCSD became a formal member of the BATSE team as a co-investigating 
institution under direction of Dr. James L. Matteson as of June 1, 1984 
under a new NASA Contract NASE-36081. Subsequent UCSD involvement in BATSE 
continues under this new contract. 
2.0 Background 
\ 
During 1979,'1980 and early 1981, research and technical staff at UCSD in 
the Center for Astrophysics and Space Sciences (CASS ) were involved in the 
study phase of the Garmna Ray Spectroscopy Experiment (GRSE) for GRO. 
UCSD's involvement with GRSE ended at the conclusion of the study phase. 
The availability of UCSD's technical staff and our continuing interest in 
the GRO, and the BATSE instrument in particular, prompted submission of 
UCSD proposal 8638. We proposed to MSFC's space Science Laboratory for 
design specification development on BATSE. This proposal was subsequently 
accepted and resulted in the subject contract. 
3.0 Contract History 
The original contract Statement of Work specified four tasks: 
1) A requirements study and preliminary design of the BATSE large 
area NaI crystal assembly. 
2) Submission of a material specification and preliminary design 
drawing of the crystal assembly. 
3) A preliminary design meeting BATSE requirements for a 5 inch, 9 
stage photomultiplier tube assembly (PMT) . 
4) Submission of a material specification and preliminary design 
drawing for the photomultiplier tube assembly. 
All four tasks were completed prior to the BATSE Preliminary Design Review 
(PDR) on February 22, 1983. 
Following c o n t r a c t  award on November 158 1982, des ign  s t u d y  of Large Area 
Detector (LAD ) mechanical p r o p e r t i e s  began i n  which six d i f f e r e n t  
s t r u c t u r a l  suppor t  and fused s i l ica  window des ign  concepts  were proposed 
and i n v e s t i g a t e d .  By February,  1983 a t e n t a t i v e  s e l e c t i o n  w a s  made which 
u t i l i z e d  a 3/4 i nch  t h i c k ,  21 i nch  diameter f u s e d  si l ica window w i t h  a 1/2 
i nch  t h i c k ,  20 i nch  diameter N a I  crystal. The crystal w a s  retained b y  
adhes ive  suppor t  t o  the fused s i l i c a  through t h e  optical  coupl ing .  The 
fused  s i l i ca  w a s  t o  be suppor ted  by a clamp r i n g  and an  elastomeric 
i s o l a t o r  i n  o r d e r  t o  reduce dynamic loads t o  acceptable l e v e l s .  A t h i n  
aluminum window w a s  t o  be bonded t o  t h e  q u a r t z  u s ing  Hysol EA-934 epoxy t o  
p rov ide  a vacuum seal. T h i s  des ign  w a s  submi t ted  t o  MSFC for review and 
dynamic a n a l y s i s .  This conf igu ra t ion  w a s  p re sen ted  February 22, 1983 at 
t h e  BATSE Pre l imina ry  Design Review. 
A p r e l i m i n a r y  des ign  o f  a 5" phototube assembly w a s  performed. The des ign  
u t i l i z e d  a s e l e c t e d  v e r s i o n  o f  an  EM1 9791 photo tube  and inco rpora t ed  a 
s i l i c o n e  rubber encapsula ted  h igh  vo l t age  bias ( b l e e d e r )  s t r i n g ,  h igh  
v o l t a g e  and s i g n a l  connec tors  and an aluminum hous ing .  
Modif ica t ion  1, dated May 15, 1983, provided a one month no c o s t  ex tens ion  
of the period of performance t o  June 13 , 1983. 
Modi f i ca t ion  2,  dated June 3, 1983, provided change of P r i n c i p a l  
I n v e s t i g a t o r  from E.C.  Whipple t o  J .L .  Matteson t o  p rov ide  more d i r e c t  
s c i e n t i f i c  i n p u t  f o r  t h e  p r o j e c t  s c i e n t i f i c  requi rements .  
Modi f ica t ion  3, dated  June 15, 1983, provided a d d i t i o n s  t o  t h e  scope of 
work and d e l i v e r a b l e s ,  added $36,816 t o  t h e  c o n t r a c t  va lue  and extended 
the end date t o  June 14, 1984. Under t h i s  mod i f i ca t ion ,  UCSD performed 
des ign  and s p e c i f i c a t i o n  development and supp l i ed  t h e  fo l lowing  
d e l i v e r a b l e s :  
N a I  d e t e c t o r  (LAD) design/drawing and s p e c i f i c a t i o n  package 
5 inch ,  9 s t a g e  PMT design/drawing and s p e c i f i c a t i o n  package 
5 inch ,  11 s t a g e  PMT design/drawing and s p e c i f i c a t i o n  package 
2 i nch ,  PMT design/drawing and s p e c i f i c a t i o n  package 
Molds f o r  5 inch ,  9 s t a g e  and 5 inch ,  11 s t a g e  PMT and 2 i nch  PMT 
Modif ica t ion  4, dated September 15, 1983, i nc reased  t h e  scope o f  work t o  
i n c l u d e  p r e l i m i n a r y  des ign  o f  a Gamma Ray Spectroscopy De tec to r  ( S D )  t o  be 
added to t h e  BATSE. P re l imina ry  des ign  drawings,  materials lists and 
p r e l i m i n a r y  s p e c i f i c a t i o n s  were prepared pu r suan t  t o  t h i s  mod i f i ca t ion .  
The s p e c i f i c a t i o n s  inc luded  d e t e c t o r  envelope,  mass, materials mounting 
method, a l lowab le  tempera ture  range, and measurement requi rements .  
Laboratory s t u d i e s  t o  determine t h e  s u i t a b i l i t y  of the b a s e l i n e  BATSE 
analog e l e c t r o n i c s  were performed. As a r e s u l t  of t h i s  s t u d y  it w a s  
determined t h a t  the basic des ign  was acceptable. I n  the cour se  of t h i s  
s tudy ,  fundamental  problems w i t h  t h e  MQ!C c i r c u i t r y  w e r e  d i scovered  and 
s o l u t i o n s  found which w e r e  of important  t o  b o t h  t h e  Large Area and 
Spectroscopy Detectors. 
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T h i s  c o n t r a c t  modi f ica t ion  a l s o  called for  e v a l u a t i o n  of a s u i t a b l e  5" 
p h o t o m u l t i p l i e r  tube and a s s o c i a t e d  bleeder s t r i n g .  D a t a  on PMT 
requi rements ,  power consumption, temperature ,  and magnet ic  f i e l d  
s h i e l d i n g  were provided. It w a s  determined t h a t  t h e  9 stage BATSE PMT 
d e s i g n  o p t i o n  p r e v i o u s l y  considered for  the LAD would m e e t  the d e s i g n  
requi rements  for the Spectroscopy Detector ( S D )  . 
Modif ica t ion  5, dated February 7, 1984, extended the period of performance 
through Ju ly  31, 1984. This modif ica t ion  expanded the scope of work t o  
c o n t i n u e  wi th  de t a i l  d e s i g n  and a n a l y s i s  of detector components of BATSE 
which inc luded  the fo l lowing  specific tasks which were accomplished prior 
t o  the BATSE Cr i t i ca l  Design R e v i e w  (CDR):  
1) D e t a i l  d e s i g n  of LAD 5" and 2" and S D  5" p h o t o m u l t i p l i e r  
assemblies. The need for  Compton shield layers of copper, t i n  and 
lead on t h e  phototube housings w a s  i d e n t i f i e d  and the d e s i g n  changes 
i n c o r p o r a t e d .  
2) Development of detailed mechanical and electrical PMT purchase  
s p e c i f i c a t i o n s .  These were developed i n  c o o r d i n a t i o n  w i t h  MSFC. 
3 )  D e t a i l  mechanical d e s i g n  o f  the  LAD i n  c o o r d i n a t i o n  w i t h  the 
BATSE s t r u c t u r a l  and dynamic des igns  and q u a l i f i e d  detector crystal 
manufacturers .  T h i s  effort  lead t o  a conceptua l  change i n  the 
detector mounting method. P r i o r  t o  CDR, the  elastomeric mount had 
been envis ioned .  This c o n f i g u r a t i o n  had t w o  s i g n i f i c a n t  drawbacks. 
MSFC found adequate  model l ing of the elastomer proved d i f f i c u l t  and 
there w a s  concern over the l i g h t  absorb ing  properties of the 
elastomer. I n  a d d i t i o n ,  GRO dynamic load requi rements  had r e c e n t l y  
been revised downward, These f a c t o r s  prompted re-eva lua t ion  of the 
d e s i g n  approach, r e s u l t i n g  i n  adopt ion  of a r i g i d  mounted d e s i g n .  
The new d e s i g n  f e a t u r e d  EA-934 epoxy mounting of a 20.4 i n c h  
diameter fused  s i l ica  window i n t o  a n  I n v a r  housing.  I n v a r  w a s  chosen 
t o  minimize thermal  stess on the epoxy j o i n t  which provided both 
mechanical r e t e n t i o n  and vacuum s e a l i n g .  This d e s i g n  w a s  also 
submi t ted  t o  MSFC for  dynamic a n a l y s i s  and w a s  found acceptable w i t h  
the i n c o r p o r a t i o n  of some minor enhancements. 
4 ) Laboratory c h a r a c t e r i z a t i o n  and performance t e s t i n g  of the PMT 
and ana log  e l e c t r o n i c s  which included s t a b i l i t y ,  high count ing  rate 
performance and PMT bleeder s t r i n g  trade off parameters and overall 
detector r e s o l u t i o n .  T h i s  e f f o r t  i d e n t i f i e d  the need for  z e n e r  d i o d e  
r e g u l a t i o n  of the last  dynode o p e r a t i n g  v o l t a g e  and specific t u n i n g  
of the cathode t o  first dynode o p e r a t i n g  voltage for optimum 
r e s o l u t i o n  performance. 
5 )  D e t a i l  d e s i g n  and performance requirement  d e f i n i t i o n  on the 
Spectroscopy d e t e c t o r  w a s  as presented  at  CDR. D e t a i l s  of reflector 
materials and i n t e r n a l  packaging elements  were d e f i n e d .  
Modif ica t ion  6 ,  dated November 26, 1985 provided a n  i n c r e a s e  of $17,388 t o  
c o v e r  cost e s c a l a t i o n  i n c u r r e d  dur ing  p r e p a r a t i o n  for  CDR as a r e s u l t  of a 
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f i v e  month d i s a b l i l i t y  of t h e  p r o j e c t  manager manager and p r i n c i p a l  
development engineer ,  Mac Chapman. This m o d i f i c a t i o n  brought  the total  
contract v a l u e  t o  the  f i n a l  va lue  of $159,110. 
Modif ica t ion  7 dated effective August 1, 1984 provided a no-cost e x t e n s i o n  
t o  the f i n a l  c o n t r a c t  end date of February 28, 1985. 
No s c i e n t i f i c  o r  t e c h n i c a l  papers were produced as a r e s u l t  of t h i s  
c o n t r a c t ,  however, t h e  r e s u l t s  of the t e c h n i c a l  trade s t u d i e s ,  d e s i g n s  and 
requi rements  are presented  i n  t h e  BATSE PDR and CDR report documents. 
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Design support of the Burst and Transient Source Experiment (BATSE) of the Gamma Ray Observatory (GRO) mission

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