背景
For nearly two decades pupils have been hearing about nuclear power plants, atomic submarines, and nuclear missiles. They always desire to “see” the strange powers of radiation that are associated with those enormous man-made nuclear devices, especially since they have been taught to fear the phenomenon of radiation by their preceding generations.
By concentrating radioactivity contained on luminous dial, you can make your own high reading source for impressive classroom experiments at practically no cost. Your source will be at least four times more powerful than standard purchased gamma courses selling for about 30 dollars. It will also be permanent as the half-life of your alpha and gamma emitter is 1622 years.
材料
While preparing the source, and for later experiments, you will need an audible detecting instrument such as a rate meter or Geiger-Mueller counter. Readings can reach 50 mr/hr at cm from the source. If you do not have a meter, check with your local Defense Civil Preparedness Agency (formerly Civil Defense) for the possibility of borrowing one.
获得放射性物质
Radium dial alarm clocks that were manufactured in abundance 30-50 years ago, or surplus World War Two U.S. Army compasses, serve as source material. A request for these in the classroom usually results in obtaining at least one clock per class. The zinc sulfide fluorescent paint containing radium from four or five dials and hands will be sufficient.
Procedure
取消前面的时钟,撬的手s, and remove the face. Prepare the work area as noted from proper procedure when working with radioactive materials.
Grasp the face with tongs and hold it vertically over a 3 or 4-inch watch glass. Squirt a few numerals at a time with acetone from a squeezable wash bottle. The radium paint will start to dissolve within 20 seconds and the excess acetone will drip into the watch glass. Assist the dissolving by skillfully dabbing the numerals with an ordinary medium size water-color brush, dipping repeatedly into the acetone reservoir contained in the watch glass. This procedure is about the opposite of how the numerals were painted on decades ago (Chemistry, April 1969, page 18).
Within a minute the group of numerals will be dissolved. Flush them off completely with more quick rinses from the wash bottle. Use the same procedure for the hands.
通过仔细摇动手表玻璃，较重的镭将迁移到中心区域。通过使用吸管剂转移丙酮残留物进入另一个蒸发的附近的玻璃玻璃。随着溶剂完全蒸发，清洁的镭将粘在第一间手表玻璃上。重复连续拨号的过程。
如果您希望建立一个供应，请将清洁镭的每个沉降清洗到铅包裹的药瓶中。在封盖之前，允许溶剂蒸发或用眼部滴管将其除去。标记供应和存储在足够的屏蔽后面，远离好奇的手指。
预防措施
在程序处理放射性物质with thoughtful respect and your maximum exposure dose per clock face or compass dial will not exceed 1 milli rem. The hazards of radiation of this amount are far less dangerous than the dozens of toxic, caustic, and corrosive chemicals that students handle in a school year. Use caution to prevent unwarranted contamination upon yourself or the surroundings. The following points should be kept in mind.
在私人区域工作，这些地区免于公开访问。
Cover the surface of the counter with aluminum foil. Then cover again with a smaller piece, edges folded upward, where the dissolving procedure is carried out. This will contain any spills and they be salvaged with the brush.
Wear protective clothing such as a lab coat and waterproof gloves that will not be harmed by acetone.
附近有一个可听的辐射探测器，不断监控背景或检查可能的污染点。
Do not try to scrape the numerals off. This would introduce airborne alpha contamination that will be inhaled.
请勿将管道代替滴注器。
必要时用毛巾和丙酮进行净化。（时钟面不能被净化。它仍然会留下读数，因为它已经在涂料中的少年被辐照。）
丢弃固体受污染的废物，如时钟面，手，罗盘针，油漆刷，铝箔等在坚固的塑料袋或容器中，并在陆地填充垃圾堆中亲自处理它。
Uses
It is an audible radiation detector and substantial gamma readings that produce for the experimentor an unforgettable introduction to “seeing” the mysteries of radiation. By moving the source stepwise toward the probe (or vice versa) from 128, 64, 32, and 16 cm, you can test the inverse square law as it applies to distance when you subtract the background readings. With a Geiger-Mueller counter you can move in to 8 cm from the source.
Shieldings of various types of thickness, including lab counter tops, bricks, water, and volunteer hands, are most impressive with this gamma source. An avalanche of eager questions will erupt from demonstrations so be ready.
