WINDOWLESS, FLOW TYPE, PROPORTIONAL COUNTER FOR COUNTING C-14
WINDOWLESS, FLOW TYPE, PROPORTIONAL COUNTER FOR COUNTING C-14
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DOI：
10.1126/science.112.2903.198
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发表时间：
1950-01-01
期刊：
影响因子：
56.9
通讯作者：
ROBINSON, CV
中科院分区：
文献类型：
--
作者：
ROBINSON, CV
图1所示。流量计和换样器部分。绝缘，屏蔽和线路隔离的电路比盖革-穆勒计数的情况下。整个计数装置包括(1)计数器，(2)换样器，(3)电子装置，(4)供气罐和连接件。使用的气体是氩气加5%的一氧化碳，并且已经混合。气体流量由带有加长手柄的针形阀和两个止动阀控制，一个用于冲洗位置，一个用于稳定流量。气体从阀门通过管道输送到起泡器，然后再输送到计数器。气体可以从板子周围逸出，并通过下面的洞。电子单元是由核仪器与发展实验室制造的162型放大比例尺。放大器的最大增益为400，刻度器将通过。40-v脉冲。计数器通过一段短同轴线直接耦合到放大器输入端。这种安排不需要前置放大器，并且在连接中拾取的干扰被最小化。110v电源中的隔离变压器是必要的，以防止线路干扰。计数器和样品转换器的部分如图1所示。计数器有一个% &-in。直径黄铜的阴极和阳极组成的回路。002年。-直径钨丝。环是9毫米乘17毫米，并达到在5毫米的板材底部。使用的板子是不锈钢的，有9/16英寸的凹槽。在钻石和。037年。深的。对该计数器灵敏度的不对称性进行了测量。对于放置在凹槽边缘附近的小板上的小点源，在环路平面上与源计数的比率比从该位置900处计数的比率高10%。因此，对于一个相当均匀的样品，不对称性可以忽略不计。样品交换器具有如图1所示的旋转盘，有两个用于板条的孔和一个弹簧（未示出），该弹簧通过抓住圆盘边缘的两个缺口中的每一个来将板条定位在计数器中。
FIG. 1. Section of flow counter and sample changer. sulation, shielding, and line isolation of the circuits than is the case with Geiger-MUller counting. The entire counting apparatus consists of (1) the counter,(2) the sample changer,(3) the electronic unit, and (4) the gas supply tank and connections. The gas used is argon plus 5% CO, and is purchased already mixed. The gas flow is controlled by a needle valve with an extended handle and two stops, one for the flush position and one for steady flow. From the valve the gas is piped to an oil bubbler and thence to the counter. The gas can escape around the planchet and through the hole below.The electronic-unit is a Model 162 amplifier-scaler made by Nuclear Instrument and Development Labora-tories. The amplifier has a maximum gain of 400 and the scaler will pass. 40-v pulses. The counter is coupled directly into the amplifier input by a short piece of coaxial line. With this arrangement no preamplifier is required and the interference picked up in connections is minimized. An isolation transformer in the 110-v supply is necessary to prevent line interference. A section of the counter and the sample changer is shown in Fig. 1. The counter has a% &-in. diam brass cathode and an anode consisting of a loop of. 002-in.-diam tungsten wire. The loop is 9 mm by 17 mm and reaches to within 5 mm of the bottom of the planchet. The planchets used are of stainless steel and have a recess 9/16 in. in diam and. 037 in. deep. Measurements of the asymmetry of sensitivity of this counter have been made. For a small spot source placed on a planchet near the edge of the recess, therate of counting with the source in the plane of the loop is 10% more than at 900 from this position. For a reasonably uniform sample, there-fore, the asymmetry is negligible. The sample changer has a rotating disk as shown in Fig. 1, with two holes for planchets and a spring, not shown, which positions the planchets in the counter by catching in each of two notches in the rim of the disk.