The design of the nuclear particle detector located in Purdue University's Get Away Special package which was flown aboard STS-7 is detailed. The experiment consisted of a stack of particle-detecting polymer sheets. The sheets show positive results of tracks throughout the block. A slide of each sheet was made for further analysis. Recommendations for similar experiments performed in the future are discussed

Weber, D.

Weber, M.

English

NASA Technical Reports Server

Nuclear P a r t i c l e  Detection U s i n g  
a Track-Recording Sol id  
Mark Weber and David Weber 
bY 
Abstract 
This paper details the  design of t he  nuclear particle de tec tor  
located i n  Purdue University 's  "Get Away Special" package which was 
flown aboard STS-7 i n  June, 1983. 
of par t ic le-detect ing polymer sheets ,  
of t racks  throughout t he  block. 
fur ther  ana lys i s .  
i n  t he  fu ture  are discussed. 
The experiment consisted of a s tack  
A s l i d e  of each sheet has been made f o r  
The shee ts  show pos i t ive  r e s u l t s  
Recommendations f o r  similiar experiment& performed 
1. Introduction 
This experiment w a s  one of th ree  t h a t  were chosen t o  ride i n  
Purdue"s 2.5 cubic foo t  can is te r .  
by Christopher klachs, a s tudent  a t  Purdue. 
The or ig ina l  proposal was suggested 
The other  t i 0  experiments 
were t o  study the  effect of gravi ty  on seed germination and t o  f i l m  t he  
motion of mercury i n  a clear l i qu id  under low gravi ty .  Electrical and 
mechanical malfunctions prevented the  proper operation of these 
experiments. The rad ia t ion  experiment was divided i n t o  two parts: 
rad ia t ion  badges and the  main detector .  The badges were used t o  give a 
rough reading t o  back up data from the  main detector .  The main.detector 
itself was designed t o  record the passing of particles i n  t h e  atmosphere. 
Being e n t i r e l y  passive, it was not effected by the  other  malfunctions. 
2. Film Badges 
Film badges are used i n  nuclear related indus t r i e s  t o  keep t rack  
of exposure t o  personel. 
t h e  type of rad ia t ion  and energy range t h a t  they are sens i t i ve  to .  
Two types of badges were included i n  the  canis ter .  
were t h e  types T1 and B1 from the R.  S. Landauer company. 
They are d i f f e ren t i a t ed  from each other  by 
The badges chosen 
These can 
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https://ntrs.nasa.gov/search.jsp?R=19840019701 2020-03-22T09:34:33+00:00Z
detect neutron, x-ray, gamma, and beta  doses. 
obtained from t h e  Bionuclear Department of Purdue University, one being 
a cont ro l  and t h e  other  placed i n  the  canis ter .  
t he  Bionuclear Department t o  be processed normally. 
Two of each type were 
They were returned t o  
The badges do ind ica te  t h a t  higher than normal rad ia t ion  l eve l s  were 
present which is t o  be expected. 
as gamma and x-ray rad ia t ion  along with traces of beta and ' fas t  neutron 
radiat ion.  
badges ind ica te  a general  dose t o  the  experiment of twenty millirems 
which is thought t o  be a realistic value, Since the  de tec tor  material 
is not d i r e c t l y  sens i t i ve  t o  t h e  rad ia t ion  indicated by t h e  >ba,dges, it 
has not  been determined whether there  are any concurrent conclusions t o  
be drawn. 
The energy deposited appeared mainly 
One of t he  badges a l s o  gave a "high energy" indication. Both 
3. Main Detector 
In  recent years ,  dielectric s o l i d  p a r t i c l e  de tec tors  have become a 
viable  a l t e r n a t i v e  t o  older,  conventional methods for t h e  detect ion and 
measurement of radiat ion.  Charged p a r t i c l e s  passing through the  de tec tor  
material leave a path of damage on the  molecular scale. 
is p l a s t i c  i n  nature ,  it can then be etched i n  a caus t i c  solut ion which 
preferen t ia l ly  a t t acks  t h e  damaged spots  rendering them v i s i b l e  under an 
ordinary l i g h t  microscope. 
developed i n  a method similiar t o  that done f o r  ordinary camera f i l m  
a l s o  yielding a t r ack  that can be studied. 
If the  de tec tor  
If the  material is an emulsion, it can be 
The o r ig ina l  experiment idea used a s i l v e r  hal ide emulsion, which 
when processed i n t o  th in  shee ts  (called pe l l i c l e s )  of the proper 
dimensions, would be stacked and used as t h e  detect ion block. As C h a r g e d  
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particles pass through the material, they would be activated similiar t o  
camera film and could be developed t o  show the tracks. The manufacture 
of the emulsion pe l l i c l e s  and the developing thereaf ter  is a timely and 
complicated process. 
mechanical pressure, and a need f o r  a well controlled atmosphere, made the  
emulsion an impractical choice for a detector material, 
This, along with its sens i t iv i ty  t o  l i g h t  and high 
A s  the experiment developed, it became evident that pblymers would 
be a much better choice f o r  a detector material. 
as being al ternat ives:  cellulose n i t r a t e  and a l l y l  diglycol polycarbonate 
(trademark by Pittsburgh Pla te  Glass as CR39). After some investigation, 
it was found that i n  addition t o  greater  sens i t iv i ty  and be t te r  physical 
Two were singled out 
character is t ics ,  CR39 was cheaper and could be purchased i n  the mount 
needed. 
f o r  experimental requirements but could not be purchased i n  the quantity 
desired. 
alpha source. 
posit ive r e su l t s ,  it was decided t o  go with the CR39 monomer. 
The cel lulose n i t r a t e  material sold by Kodak was suf f ic ien t  
A sample of CR39 was acquired and tes ted by exposing it t o  an 
Upon etching i n  a solution of sodium hydroxide and noting 
In addition t o  the p las t ic ,  a boron converter was added i n  order 
t o  detect neutrons through secondary emissions of alpha particles. 
Alphas a r e  the r e su l t  of neutron capture i n  a boron nucleus. 
made by mixing boron oxide with polyeurethane wood f in i sh  and then 
"painting" it on a two inch by three inch piece of paper. 
it was placed on the stack of detector material. 
The monomer was received i n  sheets of .O25 inch i n  thickness. 
This was 
After drying, 
It 
was then cut t o  two inch by three inch rectangles by scribing and 
breaking it i n  a manner similiar t o  tha t  used f o r  glass.  The box was cut 
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from sheet aluminum (four sides,  top and bottom) so as t o  give inside 
dimensions of two inches by three inches by two inches. (See figure 1 .) 
A flange used t o  secure the box was machined as an in tegra l  part of the  
bottom plate .  
Each of the seventy-five sheets were engraved with a number and placed in to  
the box along with the previously mentioned boron converter and then 
bolted onto the canis ter  k se .  
It was held together with brass metal screws and tapped holes. 
4. Development 
Upon receiving the  canis ter  from NASA after the  f l i g h t ,  the  box 
was unbolted and stored u n t i l  the f a l l  school session. A t  t h i s  time 
the sheets were removed from the box. A Teflon rack was made t o  hold 
, 
the sheets during etching. 
normal solution of sodium hydroxide kept a t  approximately f i f t y  degrees 
Celsius by a hot plate .  
Forty sheets at  a time were etched i n  a 6.25 
To etch a l l  the sheets the process was carried out 
twice. Each time two control sheets were included i n  the solution. The 
t o t a l  etching time was eleven days for  each group. During t h i s  time the 
solution was s t i r r e d  daily.  Upon completion of the etching, the p l a s t i c  
was v is ib ly  spotted with w h a t  appeared t o  be p i t s .  The sheets were 
rinsed and then dried. 
5. Results 
A visual  inspection of the sheets has varif ied tha t  the experiment 
did detect particles. The par t ic les  are revealed by conical p i t s  i n  the  
surface of the p las t ic .  (see f igure  2.) 
can be used t o  determine the angle a t  which the  par t ic le  entered the 
plast ic .  
The shape of the surface pat tern 
Some of the par t ic les  l e f t  only a s ingle  p i t .  Others l e f t  a 
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Fig. 1. The components of the main detector of the radiation experiment. 
Shown are the container (upper right), its lid (upper left), 
and the sheets of CR39 plastic. 
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Fig. 2. An enlargement (20X) of a por t ion  of t h e  top shee t  of p l a s t i c  
( the  one next t o  t h e  boron impregnated paper), showing t h e  
conica l  entrance hole  of a p a r t i c l e .  The blurred e x i t  ho le  
is a l s o  v i s i b l e .  
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pai r  of cones i n  the sheet. 
top of the  sheet and then exited a t  the bottom. 
l e f t  pairs of cones through the top twelve sheets. 
tracks are only s ingle  p i t s  o r  i n  two or  three sheets. It is interest ing 
t o  note t h a t  some of the tracks start and end i n  the middle of the block. 
This indicates where the par t ic le  entered the 
The longest of these tracks 
However, most of the 
The analysis  of the sheets has been complicated by p i t s  caused by 
the etching tha t  are not particle tracks. 
since the p i t s  are rounded as opposed t o  the pointed track p i t s .  
t h i s  requires t ha t  each p i t  be looked at  t o  determine i f  it is a track 
ra ther  than j u s t  counting the par t ic les  on the surface of each sheet. 
A count of the par t ic les  on the sheet next t o  the boron is about f i f t een  
t o  twenty. 
These are easily distinguished 
However, 
The middle sheets a r e  l e s s  dense than the boron qoated end, 
6. Future Plans and Recommendations 
The r e su l t s  of the experiment a re  not obvious a t  first glance and an 
intensive catalog of a l l  tracks needs t o  be made, 
and wil l . take some time and e f fo r t .  This w i l l  enable ident i f icat ion 
of par t ic le  types and energies. 
and radiation planes i n  space w i l l  be determined. 
This is a major ac t iv i ty  
Also t rack direct ion r e l a t ive  t o  the shu t t l e  
Experience with t h i s  experiment has brought out some methods tha t  
The sheets should have an should be used i n  any similiar experiments. 
index of some s o r t  t ha t  w i l l  allow t h e  tracks t o  be accurately realigned 
a f t e r  development. 
p i t t i ng  should be used t o  ease counting of the tracks. 
could be used t o  speed the numerical calculations and keep a catalog of the 
tracks. If the expense is not prohibit ive,  another detector such as 
cel lulose n i t r a t e  would be used t o  verify data from the CR39 sheets. 
Products that reduce the amount of i r re levant  surface 
A small computer 
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7. Acknowledgemerits 
Thrt au tho r s  would l i k e  t o  g r a t e f u l l y  acknowledge t h e  he lp  of 
D r .  John Snow (Department of Geosciences),  the  p r o j e c t  f a c u l t y  advisor ;  
D r .  Richard Sanderson for t h e  use  of h i s  microscope; t h e  PUR-1 nuclear 
staff f o r  t he  use of t h e i r  a lpha  sources  and t h e  Purdue Bionuclear 
I h \ p l  t * I . i t t t > t i l .  l'ot* l . I 1 ( 1  ti:;(! < ) I '  1 , I i c : i  I *  I'i lrtt t x ~ . ( l c ] j ~ ~ c ~ : ; .  
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Nuclear particle detection using a track-recording solid

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