INSTRUMENTATION
Cary
instrument abstracts
Applied
Physics
Figure 2 shows t h e disassembled camera, consisting of a pressure spring, retaining ring, specimen, and backing plate.
Corporation/Pasadena/California
Radioactivity Measurements Made Faster, Cheaper with Vibrating Reed Electrometer M e a s u r e m e n t of radioactivity in radioisotope d e t e r m i n a t i o n , r e a c t o r control, a i r c o n t a m i n a t i o n studies, oil •well logging·, a n d o t h e r p r o b l e m s in volving precise m e a s u r e m e n t of small c u r r e n t s , v o l t a g e s a n d c h a r g e s , such a s precise p H d e t e r m i n a t i o n a n d m a s s spectrometry, can n o w be made faster, s i m p l e r a n d c h e a p e r b y u s i n g t h e C a r y Model 31 V i b r a t i n g Reed Electrometer., U n u s u a l l y h i g h sensitivity plus h i g h zero s t a b i l i t y a n d ease of instal lation a n d o p e r a t i o n a r e responsible for t h e g r e a t e r speed a n d savings. T h e Model 31 d e t e c t s a s little a s 10--167 amperes, and measures u p to 10 a m p e r e s w i t h a precision of 1%. Zero drift is less t h a n 0.2 m V in 24 h o u r s and less t h a n .02 m V p e r hour. C1*, H 3 DETERMINATIONS SIMPLIFIED One w i d e s p r e a d application in which t h e Model 31 h a s been of p a1r4 t i c u l a r v a l u e is in d e t e r m i n i n g C , H 3 , a n d S 3 5 . W i l z b a c h a n d his co workers a t Argonne National Labo r a t o r y h a v e developed p r o c e d u r e s * which simplify t h e s e d e t e r m i n a t i o n s in a wide v a r i e t y of o r g a n i c com pounds. S a m p l e s a r e converted di r e c t l y t o a g a s suitable for m e a s u r e m e n t w i t h a n ionization c h a m b e r a n d t h e Model 3 1 . T h i s simple procedure e l i m i n a t e s t h e necessity for u s e of a p r e c i p i t a t e , -with i t s i n a c c u r a c y a n d t i m e - c o n s u m i n g , tedious p r e p a r a t i o n . Since a s little a s 10- 1 2 curies of r a d i o a c t i v i t y c a n be detected, use of expensive " t a g g e d " m a t e r i a l s c a n be g r e a t l y reduced, often e n o u g h t o r e t u r n t h e cost of t h e i n s t r u m e n t in a relatively s h o r t time.
T h e Model 31 can be used in a n y l a b o r a t o r y a n d does n o t require costly, vibration-free m o u n t i n g s o r o t h e r special conditions of installa tion o r operation. F o r additional in f o r m a t i o n on t h e Model 31, w r i t e f o r bulletin AC-9 t o d a y . I t gives y o u d e tails on applications, references, per formance, o p e r a t i n g principle, speci fications, modifications, accessories. 'Wilzbach. Brown, Kaplan, Science, 118, 522-523 (1953) Wilzbach, Van Pyken, Kaplan. Anal. Chem..26.880 (1954) Wilzbach, Sykes, Science 120, 494-496 (1954).
Figure 2. Disassembled camera
A typical example of t h e microradiographs which can be t a k e n with t h i s i n s t r u m e n t is shown in Figure 3 , which is cigarette p a p e r a t 60-fold magnification. T h e fiber s t r u c t u r e is clearly revealed and this, of course, would be completely t r a n s p a r e n t t o h a r d x-rays. An example shown in Figure 4, t h a t of a 9 0 % copper—2% beryllium foil, reveals a n a p p r o a c h which h a s some a d v a n t a g e s over t h e surface replica technique required in electron mi croscopy.
The Cary Model 31 Vibrating Reed Electro meter is capable of detecting a current as small as 1.0 X 10-17 amperes originating in a high impedance source. Charges as small as 5 X 10- l6 coulombs and voltages as small as .02 mV can be measured.
CARY MODEL 36 VIBRATING REED AMPLIFIER IMPROVES MASS SPECTROMETER PERFORMANCE The Cary Vibrating Reed Amplifier, Model 36, is being used in an increasing number of mass spectrometer installa tions where high molecular 'weight anal yses make rapid scanning of mass num bers desirable. The Model 36 combines rapid response with high sensitivity. Response is critically damped, with an 0.1 sec. natural period (98.6 percent re sponse in 0.1 second). Thus a range of 100 mass numbers can be accurately scanned in as little as one minute. Sen sitivity and range are such that as little
SPECTROPHOTOMETERS
Cary
V I B R A T I N G REED AMPLIFIERS
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as 10-15 amperes and up to 10-U am peres can be measured to a reproduci bility of 0.2 percent without change of range. The stability of the Model 36 is superior too-zero drift is less than 10-15 amperes. The Model 31 is preferred for mass spectrometer applications where ex treme response speed is not required, such as isotope determinations. Sensi tivity of the Model 31 is 10-17 amperes, and like the 36 it has high stability—less than 5 χ 10-17 amperes zero drift.
instruments:
R A M A N SPECTROPHOTOMETER INFRARED ANALYZERS
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ELECTROMETERS ULTRAVIOLET
ANALYZERS
APPLIED PHYSICS C O R P O R A T I O N / 3 6 2 WEST C O L O R A D O STREET / PASADENA I / C A L I F O R N I A For further information, circle numbers 46 A-1, 46 A-2 on Readers' Service Card, page 51 A
46 A
F i g u r e 3 . M i c r o r a d i o g r a p h of cigarette paper
E n g s t r o m h a s developed a q u a n t i t a t i v e analysis t e c h n i q u e based u p o n microradiography [A. E n g s t r o m , Acta Radiol., Sup. L X H I (1946) ; 3 6 , 305 (1951)]. Although t h i s technique a n d t h e fine new i n s t r u m e n t are of greater ANALYTICAL
CHEMISTRY
