anticathode

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An electrode that is the target in a cathode-ray tube, especially in an x-ray tube.

from The Century Dictionary.

• noun The plate, often of platinum, placed opposite the cathode in a vacuum-tube, on which the cathode rays, or streams of electrified particles, impinge and thus produce the Röntgen rays.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Phys.) The part of a vacuum tube opposite the cathode. Upon it the cathode rays impinge.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The opposite of a cathode, an anode.
• noun The target at which electrons from the cathode in a CRT or x-ray tube are directed.