(P.0, NO ) FINAL RZPOPT

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DISCLAIMER

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DISCLAIMER

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NOTICE

This report was prepared as an account of work sponsored by the

United States Government. Neither the United States nor the United States Energy Research and Development Administration,

nor their employees, nor any of their contractors, subcontractors,

or their employees. makes any warranty, express or implied, or

assum any legal liability or responsibility for the accuracy,

completeness or usefulness of any information, apparatus, product

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. . . . C.

E .

Canada . L .

D.

H a n u I - . -- .. ' DEVELOPMENT D I V I S I O N NOTICE DIis 'wrt was P n P a e d as an a w u n t or

I sponsored by the United stater c ~N~~~~~~ ~ ~ ~ ~ ~ ~ ~ ~ .

I United States nor the united slate

1 their Research cmployeer~lopm~nt and De Administration nor any

i rubcontracton, or nyhe;ny Of their kntractorr i warranty e x p r l u ., i m p t i ~ m I$ ~ m ,

/ ' L b u t ~ rSSWnsihility for th6,muracy

, 0' u r f u l n c n of any informtion, . p p a r a , ' ~ ~ $ ~ ~

1. Pmces disclo*d or represents that it*

I infnnse Privately b m e d rights. 1.- 1 - ~. -

A p r i l - &Time 1 9 7 5

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ABSTRACT

A t e c h n i q u e has been d e v i s e d t o determine t h e c o n f i g u r a t i o n dependent i n d u c t i o n t i m e f o r t r a n s f e r o f d e t o n a t i o n from a small diameter c o n f i n e d donor t o a l a r g e d i a m e t e r unconfined a c c e p t o r v i a t h e d e t o n a t i o n e l e c t r i c e f f e c t . T h i s r e p o r t e x p l a i n s some o f t h e a t t r i b u t e s and l i m i t a t i o n s o f t h e t e c h n i q u e and i n c l u d e s t e s t d a t a f o r PETN, RDX/Sylgard, and HNS e x p l o s i v e assemblies.

DISCUSSION

E x p l o s i v e t r a i n s a r e f r e q u e n t l y used i n ERDA components f o r t i m e sequencing

,

o r i n f o r m a t i o n t r a n s m i t t a l requirements. A t y p i c a l e x p l o s i v e t r a i n may

c o n s i s t o f a d e s i r e d l e n g t h o f small diameter MDF, which i s t e r m i n a t e d w i t h a much l a r g e r d i a m e t e r b o o s t e r s e c t i o n f o r a c t i v a t i o n o f downstream components. - P r o p a g a t i o n c h a r a c t e r i s t i c s a r e determined by i n t e r a c t i o n s between geometry and m a t e r i a l dependent waves generated a t t h e i n t e r f a c e between t h e MDF and b o o s t e r .

The purpose o f work r e p o r t e d here i s t o e s t a b l i s h a technique s u i t a b l e f o r p r e d i c t i o n o f these geometry and m a t e r i a l induced e f f e c t s thereby a i d i n g component design. T r a n s i t t i m e v a r i a t i o n as a f u n c t i o n o f t h e i n t e r f a c e c o n f i g u r a t i o n was s e l e c t e d as t h a t p r o p a g a t i o n c h a r a c t e r i s t i c t o be measured. T h i s v a r i a b l e p r o v i d e s i n s i g h t i n t o t h e e f f e c t s o f wave i n t e r a c t i o n s and i s c e r t a i n l y t h e most convenient and l e a s t expensive of t h e dynamic c h a r a c t e r i s t i c s t h a t c o u l d be measured.

EXPERIMENTAL TECHNIQUE A N D RESULTS

The experimental technique i s i l l w t r a t e d i n F i g . 1.. The small diameter c o n f i n e d donor i s segmented i n t o known l e n g t h s , which a r e i n t u r n

. . separated by a i r gaps o f known thicknesses. The a i r gaps p r o v i d e . heterogeneous i n t e r f a c e s which, ,when shocked, generate e l e c t r o m a g n e t i c d i s t u r b a n c e s d e t e c t a b l e byathe antenna(1). O f those m a t e r i a l s t e s t e d ( w a t e r , P l e x i g l a s , Krylon, and a i r ) t h e a i r gap produced both. t h e f a s t e s t r i s e and h i g h e s t a m p l i t u d e s i g n a l s .

The p i e c e s o f t h e e x p l o s i v e t r a i n a r e supported by a hardwood b l o c k which has been p r e c i s e l y machined t o c o n f i n e each p i e c e halfway around.

i t s c i r c u m f e r e n c e . The donor segments were h e l d i n a s p e c i a l l y made f i x t u r e w h i l e b e i n g c u t t o l e n g t h w i t h a r a z o r blade. Of t h e v a r i o u s methods t r i e d , t h i s produced t h e most p e r p e n d i c u l a r c u t w i t h t h e l e a s t 'gouging o f t h e e x p l o s i v e c o r e m a t e r i a l . The a i r gap thicknesses were

c o n t r o l l e d by punching c i r c u l a r holes i n ' p l a s t i c shim s t o c k and i n -

s e r t i n g t h e s e shims between t h e segments o f t h e donor w i t h proper alignment o f t h e h o l e s .

a

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Since a f i n i t e t i m e i s r e q u i r e d f o r a shock wave t o t r a v e r s e an a i r gap and r e i n s t i t u t e d e t o n a t i o n , i t was a t f i r s t t h o u g h t necessary t o d e t e r - mine t h i s t i m e f o r each t y p e of donor. One method used was t o v a r y t h e

l e n g t h s o f t h e donor segments, w h i l e h o l d i n g t h e a i r gap t h i c k n e s s e s c o n s t a n t . The excess t r a n s i t t i m e due t o gap e f f e c t s equals t h e t i m e a x i s i n t e r c e p t o f a l i n e a r f i t t o t h e d i s t a n c e - t i m e data. Another

method used t o d e f i n e a i r gap excess t r a n s i t t i m e s was t o h o l d t h e donor l e n g t h s c o n s t a n t w h i l e v a r y i n g t h e a i r gap t h i c k n e s s e s . An a n a l y s i s s i m i l a r t o t h a t o f t h e f i r s t method i s t h e n used t o f i n d t h e excess t r a n s i t times. F i g . 2 shows r e s u l t s f r o m such an e v a l u a t i o n . Here t h e donor, e i t h e r 0.21 g/m o r 2.1 g/m commercially a v g i l a b l e PETN MDF, was segmented i n t o 6.35 mm l e n g t h s . A sequence o f a i r gaps w i t h t h i c k n e s s e s o f 25, 51, 127, 51, and 25 pm, r e s p e c t i v e l y , were i n t r o d u c e d between segments o f t h e donor. The r e s u l t a n t i n t e r f a c i a l s i g n a l s were t h u s separated by t h e t i m e r e q u i r e d f o r d e t o n a t i o n o f a 6.35 mm segment p l u s t h e t i m e t o t r a v e r s e an a i r gap. Average i n t e r f a c i a l times correspond- i n g t o t h e sequence noted above were 917, 925, 938, 925 and 917 ns f o r t h e 0.21 g/m MDF and 900, 908, 921, 908 and 900 ns f o r t h e 2.1 g/m MDF. Since t h a t t i m e i n t e r v a l which i n c l u d e s t h e t r a n s i t t i m e o f t h e 127 pm

gap should be maximum, these d a t a i n d i c a t e t h a t t h e s t a r t o f an i n t e r - f a c i a l s i g n a l i s generated when t h e shock wave e x i t s r a t h e r t h a n e n t e r s a donor segment. As may be seen from t h e curves o f F i g . 2, t h e t i m e r e q u i r e d f o r a shock t o t r a v e r s e an a i r gap i s n o t a l i n e a r f u n c t i o n of t h i c k n e s s . I n f a c t t h e e f f e c t i v e v e l o c i t y a t which t h e d e t o n a t i o n

process propagates across an a i r gap, a p ~ a r e n t l y i n c r e a s e s w i t h i n c r e a s i n g gap t h i c k n e s s . T h i s anomaly, a l t h q u g h i n t e r e s t i n g , was n o t pursued here s i n c e a knowledge g f t h e t r a n s i t t i m e f o r an a i r gap i s i n f a c t n o t necessary t o determine excess t r a n s i t times i n a c c e p t o r s as w i l l be e x p l a i ned be1 ow.

P r e l i m i n a r y v e r i f i c a t i o n t e s t s were conducted u s i n g PETN as b o t h donor and a c c e p t o r . F i g . 3 shows a t y p l c a l r e c o r d f g r t h i s work, and F i g . 4 i l l u s t r a t e s t h e method used t o determine excess t r a n s i t times. F i g . 3 i s d e r i v e d f r o m t h e assembly o f an EX-12B d e t o n a t o r , a 5.1 mm diameter by 2.0 mm PBX 9407 p e l l e t , 6.35

mm

l o n g donor segments, and a 12.7 mm diameter by 6.35 mm a c c e p t o r p e l l e t . The donor was 2.1 g/m PETN MDF, and t h e a c c e p t o r was PETN a t a d e n s i t y o f 1.53 Mg/m3. Each donor s e y ~ r ~ e n t and t h e i n t e r f a c e between a c c e p t o r and antenna were separated w i t h 25 pm a i r gaps. However, t h e l a s t donor segment was i n d i r e c t

.contact w i t h t h e a c c e p t o r s i n c e a gap a t t h i s i n t e r f a c e would p e r t u r b p r o p a g a t i o n c h a r a c t e r i s t i c s . Eleven s i g n a l s a r e v i s i b l e I n F i g . 3. The f i r s t two s i g n a l s a r i s e from t h e d e t o n a t o r w h i l e t h e t h i r d one i s

generated by a 25 pm a i r gap between t h e PBX 9407 p e l l e t and t h e f i r s t

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between t h e l a s t two s i g n a l s . I f s i g n a l s were generated as t h e shock e n t e r e d a donor segment t h i s s u b t r a c t i o n would' not. be v a l i d and a know- l e d g e o f a i r gap t r a n s i t times would be necessary f o r d a t a r e d u c t i o n . The expected v e l o c i t y f o r PETN a t a d e n s i t y o f . 1.53 Mg/m3 i s 7.482

km/sec(2). The curves o f F i g . 4 a r e least-squares f i t s assuming a slope o f 7.482. These l i m i t e d da'ta thus i n d i c a t e excess t r a n s i t times (equal t o t h e t i m e a x i s i n t e r c e p t s ) of .40 .ns and 130 ns, r?espective.ly, f o r t h e

2.1 g/m and 0.21 g/m donor systems. . , .

Tests u s i n g an RDXjSylgard e x p l o s i v e as donor and acceptor were a l s o conducted.' F i g . 5 shows a t y p i c a l r e c o r d . Here t h e donor c o n s i s t e d o f f o u r each.19.05 mm l o n g segments which were e x t r u s i o n loaded s t a i n l e s s s t e e l tubes w i t h w a l l t h i c k n e s s . o f 0.25 mm. The acceptor was an uncon- f i n e d 12.7 mm.diameter by 6.35 mm extrusi.on formed p e l l e t . As above t h e donor segments and t h e i n t e r f a c e between acceptor and antenna were

separated w i t h 25 pm a i r gaps, a n d . t h e l a s t donor segment was i.n d i r e c t

c o n t a c t w i t h t h e acceptor. These t e s t s , however, proved u n s a t i s f a c t o r y because o f e l e c t r i c a l p o 1 a r i z a t i o . n w i t h i n , t h e acceptor. . As may be seen immediately b e f o r e t h e seventh s i g n a l i n ,Fig. 5, t h e s i g n a l s due t o shock induced p o l a r i z a t i o n a n d . t h e a i r gap i o n i z a t i o n s i g n a l a r e super- imposed. An a c c u r a t e knowledge o f shock wave. a r r i v a l a t t h e acceptor p e l l e t o u t p u t s u r f a c e i s t h u s n o t o b t a i n a b l e f o r t h e c o n f i g u r a t i o n used. F i g . 3 a l s o shows t h e e f f e c t o f p o l a r i z a t i o n . . . However, f o r PETN systems t h e r e l a t i v e s i g n a l amplitudes f o r p o l a r i z a t i o n . a n d a i r gap were such t h a t t i m i n g i n f o r m a t i o n was o b t a i n a b l e ;

T h i s problem f r o m p o l a r i z a t i o n w i t h i n t h e acceptor was a l l e v i a t e d by s i m p l y i n c r e a s i n g t h e a i r gap t h i c k n e s s a t t h e acceptor antenna i n t e r - face. Gaps o f 6.35 mm and 12.7 mm were i n v e s t i g a t e d f o r PETN systems. Both gap thicknesses gave unambiguous s i g n a l s , 'and e i t h e r would be acceptable. However, a gap t h i c k n e s s o f 6.35 mm i s p r e f e r r e d and.was used f o r a l l subsequent t e s t i n g , s i n c e measured s i g n a l amplitudes vary i n v e r s e l y w i t h d i s t a n c e between source and d e t e c t o r .

The n e x t o b j e c t i v e s were t o a p p l y t h e method t o HNS and t o r e f i n e t h e technique. Two types o f compacted HNS I 1 MDF were prepared. P e r t i n e n t p r o p e r t i e s a r e g.iven i n Table I. Acceptor p e l l e t s were pressed t o 2.54 mm t h i c k n e s s x 12.7 mm diameter. Up t o t h r e e p e l l e t s were stacked on each s h o t . The HNS I 1 p e l l e t s were made from t h e same two l o t s used f o r m a n u f a c t u r i n g t h e MDF; t h e HNS I p e l l e t s were made from Ensign-Bickford L o t 5737 and Chemtronics L o t 66-48.

I n i t i a l i n t e r e s t was i n d e t e r m i n i n g whether d e t o n a t i o n would t r a n s f e r f r o m t h e MDF t o a p e l l e t pressed from t h e same m a t e r i a l a t approximately t h e same d e n s i t y as i n t h e MDF. The p e l l e t s were pressed from HNS

I 1

t o 1.65 Mg/m3. D e t o n a t i o n d i d n o t t r a n s f e r f o r e i t h e r t h e E-B o r t h e

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t h i c k n e s s x 12.7 mm diameter i n f r o n t o f t h e p e l l e t w i t h t h e MDF i n s e r t e d through a h o l e i n t h e c e n t e r of t h e d i s k and c o n t a c t i n g t h e . p e l l e t . The t h i r d was t h e 'placement o f a PBX 9407 b o o s t e r p e l l e t 2.0 mm t h i c k x 5.1 mm diameter a t 1.62 Mg/m3 between t h e MDF 'and p e l l e t . With t h i s m o d i f i - c a t i o n r e a c t i o n occurred i n one o f t h r e e shots.

The e f f o r t was t h e n d i r e c t e d toward more c l o s e l y s i m u l a t i n g t h e con- d i t i o n s e x i s t i n g i n t h e end t i p s f o r t h e C-4 energy t r a n s f e r system. P a r t i a l r e s u l t s o f a p r e s s i n g s t u d y which was b e i n g done a t Pantex i n d i c a t e d t h a t HNS I when pressed a t 220 MPa ( t h e pressure a t which t h e end t i p s a r e f i l l e d ) y i e l d s a d e n s i t y o f approximately 1.55 Mg/m3(3). Therefore, p e l l e t s were pressed from b o t h Ensign-Bickford and Chemtronics HNS

I

a t 1.55 Mg/m3. Shots were b u i l t t o a s c e r t a i n whether t r a n s f e r would occur from E-B MDF t o an E-B p e l l e t , from E-B MDF t o a Chemtronics p e l l e t , f r o m Chemtronics MDF t o a Chemtronics p e l l e t , and from Chemtronics MDF t o an E-B p e l l e t . A t y p i c a l r e c o r d i s shown i n F i g . 6. R e s u l t s a r e g i v e n i n Table 11. Both t r a n s f e r and n o n t r a n s f e r o f d e t o n a t i o n t o t h e a c c e p t o r p e l l e t was observed. The c a l c u l a t e d excess t r a n s i t times f o r t h e acceptor p e l l e t s a r e based upon a d e t o n a t i o n v e l o c i t y o f 6.75 km/s f o r HNS I a t 1.55 Mg/m3, which i s an i n t e r p o l a t i o n from measurements on Chemtronics L o t 66-48 a t d e n s i t i e s o f 1.50 and 1.60 Mg/rn3(4). E v i d e n t l y t h e donor s i z e was near t h e t h r e s h o l d f o r i n i t i a t i o n o f t h e HNS

I

a t 1.55 Mg/m3. A l s o evidence from t h e s h o t remains, e.g. pieces of t h e p e l l e t s t i l l i n t a c t and l e s s d e s t r u c t i o n than expected, i n d i c a t e d t h a t t h e e n t i r e p e l l e t d i d n o t detonate i n many o f t h e shots.

For comparison w i t h a i r gap excess t r a n s i t times i n PETN systems, those f o r HNS were determined. HNS MDF segment l e n g t h s were 6.35 mm and 12.7 mm and a l l a i r gaps were 25 pm. Excess t r a n s i t times due t o a i r gap

e f f e c t s were c a l c u l a t e d by two methods:.

Excess T t = 2 Tt (6.35 mm l e n g t h segment)

-

T t (12.7 mm l e n g t h segment) and

Len t h o f Se ment Excess Tt = T t ( f o r a segment l e n g t h )

-

Detznation

V ~ l o ~ t y The d e t o n a t i o n v e l o c i t y used i n t h e second f o r m u l a i s t h a t g i v e n i n Table I. Average excess t r a n s i t times c a l c u l a t e d by each formula f o r E-B MDF were 12 and 11 ns, r e s p e c t i v e l y ; f o r Chemtronics MDF they were 13 and 12 ns. A f t e r s u b t r a c t i n g these excess t r a n s i t times from t h e t o t a l segment t r a n s i t times, t h e c a l c u l a t e d average v e l o c i t y o f each MDF agreed w i t h t h a t i n Table I w i t h i n 0.1%. For PETN MDF excess times f o r a 2.5 pm a i r gap was 9 t o 10 ns. T h i s decreased t i m e i n t e r v a l r e l a t i v e

t o HNS systems i s p r o b a b l y i n d i c a t i v e o f m a t e r i a l s e n s i t i v i t y .

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had a l l been l a i d d i r e c t l y upon t h e s t e e l pad and t h e s i g n a l - t o - n o i s e r a t i o was v e r y good. However, when t h e shots were placed upon a wooden s t a n d about 0.6 m above t h e pad, an o r d e r of magnitude i n c r e a s e i n e l e c t r i c a l n o i s e r e s u l t e d . Records a r e shown i n Fig. 7 f o r a comparison o f n o i s e p i c k u p under i d e n t i c a l circumstances except f o r s h o t placement.

C O N C L U S I O N S . .

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Donor

>

Detonator

. .

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20 4 0 60 80 100 120 Gap Thickness (pm)

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a d

thdrd

domr

s e g w ~ ~ t s

A i r

gap

bWam1~l

%hYN

%mJ

f@v%A

&mr

s m . n t s

fitr

gap

be%wwn

faup& anel

QOFtYl

&nap

sqp-ren.ts

A i r

gap betmiwn

f t f t h

and

sixth

donor

segments

A i r gap

between

s W h

and seventh

donor

segments

A f r

gap

ktwrrew

seventh

and

eight donor

segments

Air gap

between

acceptor and antenna

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Fig. 4, Transi' '

PETN PEllet Thickness (mn)

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Camnent

- S t a r t

o f current flow i n bridgewire

B r i dgewi

r e burst

A i r gap

between

detonator and f i r s t donor segment

A i r

gap

between f i r s t and second

donor

segments

A i r

gap between second

and

t h i r d donor segments

A i r

gap

between

t h i r d and fourth donor segments

A i r

gap between acceptor and antenna

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r

Final

Donor

Segment-Acceptor

Pellet

Interface

0

Sweep i s f i r s t Part

o f A

Sweep

Expanded

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Shot Above Pad

Shot

On

Pad

Fig.

7.

Comparison o f CDU

Induced NoSse

as a FunctSon

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Tab1 e I . P e r t i nent Properties of HNS MDF

~nsi~n- irkf ford

Chemtroni cs

Property HUS 5737-IIB HNS 6647-IIA

MDF Inner Diameter (mm)

MDF

Outer Diameter (rnm)

MDF Load Size (g/m) 0.364 0.386 :

HNS F i nal Densi t y (Flg/m3) 1.69 1.67

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MDF

able

11. Results of HNS Work f o r an Acceptor

P e l l e t Density of 1.55 Mg/m3

~ n s i ~ n - ~ i c k f o r d ~ Ens i gn-Bi ckford

Acceptor Pel 1 e t Acceptor Excess Trans i

t

Time (nsec) d Ensign-Bickford Chemtroni cs 4

2

Ensign-Bi ckford Chemtronics b Chemtroni cs Chemtronics , Chemtroni cs Chemtroni cs

4

1 Ensign-Bickford 43 Ensign-Bi ckford Chemtroni cs

.

Chemtronics a P r o p e r t i e s given i n Table I. b ~ r o p e r t i e s given i n Table I. c

1 2 . 7 nun diameter peZZet pressed from HNS-IB, Lot No. 5737.

d12. 7 mm diameter p e l l e t pressed from HNS-IA, Lot No. 66-48.

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. . . . . . . .. . . . . .. REFERE,NCES' . . . . .

Bernard 'Hayes, "The D e t o n a t i o n . E l e c t r i c E f f e c t ,I1 J o u r n a l d f Appl i e d Physics, Vol

.

38, No. 2.. (February 1967). . .

" P r o p e r t i e s of Chemical Explosives 'and E x p l o s i v e Simulants

,"

Compi l e d and. E d i t e d . by, D. M,. Dobraty; UCRL-51319, Rev.

1

( J u l y 31, 1974).

J. A. ~ r u t c h ~ e r ,."HNS ~ r e ' s s ~ b i . . . 1 i ty Study," MHSMP-75-27 (June 1975). . .

R. J . Slape, " ~ e t o n c i t i o n ~ r e s s h r e o f HElS I and 1 1 MHSMP-75-23, June 1975.

R. B. L i n v i 1 l e y 'Signal Enhancement f o r t h e D e t o n a t i o n E l e c t r i c E f f e c t , " PXD-13-75 (June'1975)., ' . . '

. ,

Figure

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References

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