INSTRUMENTATION Mode! SC 700
N e w Eldorado S C 7 0 0 Decimal Scaler with
better than I microsecond resolution Designed f o r general radiation counting, Eldorado's compact new SC700 Decimal Scaler provides high performance a t a budget price, $ 5 9 5 . • Precision Integral Discriminator
FEATURES
• Building Black Construction
• Small Size — 3 y 2 " panel height, weighs only 16 pounds.
• Built-in Test Circuit
• 25 Millivolt Sensitivity
• Provision lor External Timer
• Seven Decades of Count Storage
For complete technical i n f c i m o t i o n , please address Dept. A 4
• Calibrated Input Amplifier
Eldorado
See our e x h i b i t a t the A t o m Fair, Cleveland, April 5 - 1 0 Booth 8 1 1
Electronics 2821 TENTH ST. ·
BERKELEY 10, CALIF. 13
Phone THornwoll 1 -4613 Circle No. 56 on Readers' Service Card
New
Precision!
New C o n v e n i e n c e !
Hiher MICRO-FOCUS X-RAY UNIT features: EXTRA-FINE, HIGH INTENSITY FOCAL SPOT . . . best for all diffraction studies . . . ideal for large lattice structures
Brilliant point source offers matched performance in diffraction analyses -of natural and synthetic fibers, plastics, waxes, greass, steroids, proteins, pharmaceuticals; in metals research. Extra-fine, high intensity microsource assures fastest exposure on large lattice materials or microsamples. No need for large, hard-to-grow crystals. Write for new catalog today.
ONLY
MICRO-FOCUS
OFFERS:
• • •
Greater x-ray flux Less scattered radiation Superior resolution
•
Shortest exposure
EXCELLENT FOR X - R A Y M I C R O R A D I O G R A P H Y : Hilger Micro-Focus lends itself t o many applica'ions in studies o f b i o l o g i c a l microstructures: microporosity a n d inclusions in metals; microparticle analyses in criminology, efc. Interchangeable 4 0 a n d 1 0 0 micron f o c a l spots sharpen details in l a r g e radiograms.
Jarrell-Ash Company 3 2 Farwell Street, Newtonville 6 0 , Massachusetts Circle No. 121 on Readers' Service Carl 76
A
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ANALYTICAL CHEMISTRY
An automatic windowless sample counter is usually used when a large number of relatively weak samples must be counted with maximum efficiency. These counters may operate in either the Geiger or proportional region. Up to fifty samples of any size up to 2 inches in diameter can be accommodated by this unit. The samples are placed on special planchet holders and loaded into a clear glass sample tower which is clamped onto the main unit. The sample changing mechanism takes a sample from the bottom of this tower and inserts it into the gas filled counting chamber. When the sample has been counted the information is fed to the data recording printer, the sample is removed from the detector and raised into a glass collecting tower. This operation is repeated until all samples have been counted. Geiger or proportional gas is fed first to the detector and from the detector is split into two streams and vented after passing through the sample towers, thus keeping all samples in a sealed atmosphere of counting gas at all times. The importance of a detector's ability to accommodate extra large samples is one that cannot be overemphasized. If sufficient active material is available to prepare 2-inch samples a marked reduction can be made either in counting time or the lower limit of specific activity detectable. For example, 1inch samples of BaC0 3 (infinitely thick) with an absolute specific activity of approximately 1.0 d.p.m./mg. can be counted to a 5% probable error in approximately 100 minutes on the SC-50B. If 2-inch samples of the same material are prepared, only 22 minutes are required for similar results. In addition to the basic equipment described above, these automatic sample counting systems include a scaler and data recording printer. The scaler used contains special connectors and relay circuits, which are necessary to activate the changer itself and the data printer. I t should also contain both preset count and preset time controls. Because it is usually desirable to count all samples to the same probable error, the preset count is an essential feature. Since on occasions a very weak sample is encountered, preset time is a desirable feature to cut short any unprofitably long counting run. The data recording printer provides a permanent record of the sample number and the time required for a given number of counts. In our own nuclear researches, for lack of manpower, it has been found necessary to embark on an extensive program of automation and the design of mechanisms using relays and pneumatic devices to perform routine manipulations. These enable one to collect data overnight and leave regular hours for setting up new experiments and collating data.
