XII. E L E (■ T n O K M I C H O S C O P Y 403 



Physical Arrangement. Auxiliary Equipment. A research type 

 electron microscope is u rather bulky piece of equipment standing 

 7 feet high and weighing several hundred pounds. There are, in 

 addition, as separate units, a mechanical pump and usually a line 

 voltage regulator transformer or some other auxiliary piece of the 

 power supply equipment. The instrument is somewhat susceptible 

 to vibration, though not excessively so. This means that it should 

 be located in a section of the laboratory that is reasonably free 

 from vibration. It is not usually necessary to provide a special 

 vibration-free mounting, though this has occasionally been the case 

 in difficult circumstances where heavy machinery has been installed 

 in nearby rooms or where peculiar geological formations have trans- 

 mitted vibrations from nearby roads or railroad tracks. The me- 

 chanical pump should be mounted as close as possible to the instrument. 

 Since these pumps are usually quite noisy, it is highly desirable to 

 enclose them in a soundproof box or to mount them in an adjacent 

 room or below the floor. It is of course necessary to prevent any 

 vibrations produced by the pumps from afTecting the microscope. 

 Usually flexible rubber mountings for the pump are sufficient. 



It is essential that electron microscope laboratories include a 

 conveniently located dark room. The most satisfactory arrangement 

 seems to be to have the dark room adjacent to the microscope room 

 and communicating with it through a maze or light lock. The 

 dark room equipment should include a high quality enlarger, a print 

 box, an X-ray type negative viewer, print dryers, preferably of the 

 heater type, and the usual sink with suitable developing trays. The 

 room itself should be large enough to permit two or three people to 

 work in it simultaneously. 



The electron microscope room need not be too large, since it is 

 essential that it, too, be arranged so that it can be completely dark- 

 ened. Generally speaking, the last requirement makes it undesirable 

 to place any other equipment in the same room with the electron 

 microscope. It is essential that the electron microscope room be pro- 

 vided with good ventilation, particularly in those regions of the 

 country that experience hot, humid weather. Most electron micro- 

 scopes dissipate somewhat more than a kilowatt of power when in 

 operation, which is usually sufficient to make a small room very un- 

 comfortable unless well ventilated. The remainder of an electron 

 microscope laboratory should consist of at least one relatively large, 

 well lighted room. In this would be placed a bench for specimen 



