Cathode Ray Tubes
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NEVA Finebeam tube
Close-up of the gun.
 The fadenstrahlrohre or Finebeam tube is used in conjunction with two
 Helmholtz coils to investigate the deflection of electron beams in electrical
 and magnetic fields, particularly the determination of the specific
 electron charge e/m, the Electron Charge to Mass Ratio.
 This tube has been used in classroom demonstrations.
 The manufacturer of this tube, the German NEVA factory closed in 1969.
 An interesting article about this tube can be found at the Middlebury College.

Philips DG7-32 exploded view box for educational use.
Didactic CRTs
Braun tube after Thomson, second quarter 20th Century. Length 65cm.
This from origin cold cathode Braun tube is equipped with two deflection plates to bent the beam electrostatically instead of magnetically as with the Braun tube.
This tube became forerunner of the static CRT used in measuring equipment like the oscilloscope. The neck contains an aluminum diaphragm to form the beam.
    The phosphor mica screen.
The first lines appear on the screens in this type of early tube in order to measure the amount of voltage supplied
to the deflection plates in respect of the
deviation of the beam. In later tubes the glass front is internally covered with phosphor like in modern CRT's.
Deflection section
Braun tube sold by P J Kipp & Zonen (1920)
The crude phosphor screen seen from the inside.
  The Dutchman Petris Jacobus Kipp started a scientific
  company in chemical and Physics instruments in 1830. After
  his death in 1864 two of his sons, Antonius Johannes Kipp,
  mechanic, and Wilhelmus Arnoldus Kipp, apothecary took
  over the company under a new name: J P Kipp & Zonen,
  producing and trading medical, chemical and Physics
  instruments. The company was sold to Otto Arnold Ankersmit
  in 1917 who registered NV P.J. Kipp & Zonen.

  The company still exists in Holland
Wehnelt CRT after Thomson ca 1930
This nice tube is the first demonstration CRT with a direct heated filament cathode and a Wehnelt cylinder for focussing the electron beam.
This tube, probably imported from E Leybolds Nachfolger and sold by W Edwards & co London.
Special is the fact that this tube has four static deflection plates .
Arthur Wehnelt a German Physicist discovered in 1904 that if an incandent platinum cathode is covered with an alkaline earth like Calcium or Barium  oxide the electron output is much more efficient and the tube will work with a lower voltage. This started a new era in vacuum tube technology.

The filament
The Wehnelt cylinder
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CRT after Braun - Wehnelt ca1940
The deflection plates in this tube are with mica isolated in a separate glass chamber for a more stable beam.
length 60cm
A BR2 Braun tube ca1950
These tubes were made by NARVA VEB after the war in the DDR.
Modern Leybold finebeam tube
These tubes are still used in classrooms
Electron gun and deflection plates