3B Scientific Teltron Luminescence Tube D User Manual

3B SCIENTIFIC

Luminescence Tube D 1000648

Instruction sheet

12/12 ALF

-

®

PHYSICS

1 4-mm sockets for connecting

7

5.1

5.2

5.3

5.4

heater supply and cathode
2 Heater filament
3 Cathode
4 4-mm plug for connecting an-

ode
5 Luminescence screen

5.1 Zinc sulfide, activated with

silver

5.2 Yttrium vanadate, activated

with europium

5.3 Zinc sulfide, activated with

silver and cobalt

5.4 As 6.3 but graphite-coated back

to prevent heat radiation
6 Boss
7 4-mm plug for luminescence

screen

1345

Hot cathode tubes are thin-walled, highly evacu­ated glass tubes. Treat them carefully as there
is a risk of implosion.

• Do not subject the tube to mechanical

stresses.

• Do not subject the connection leads to any

tension.

• The tube may only be used with tube holder

D (1008507).

If voltage or current is too high or the cathode is
at the wrong temperature, it can lead to the tube
becoming destroyed.

• Do not exceed the stated operating parame-

ters.

• Only change circuits with power supply

equipment switched off.

• Only exchange tubes with power supply

equipment switched off.

2

1. Safety instructions

6

When the tube is in operation, the stock of the
tube may get hot.

• Allow the tube to cool before dismantling.

The compliance with the EC directive on elec­tromagnetic compatibility is only guaranteed
when using the recommended power supplies.

2. Description

The luminescence tube serves to demonstrate
the luminescence of a phosphorous anode when
excited by electrons (cathodoluminescence) or
ultraviolet light (photoluminescence).

The luminescence tube is a highly evacuated
tube with an electron gun consisting of a pure
tungsten heater filament inside an apertured
“cathode can” and a cylindrical anode contained
in a clear glass bulb. A luminescence screen
with three mica flags with different phosphors is
mounted on a metal support.

1

3. Technical data

Filament voltage: 6.3 V AC/DC (8.0 V max.)

Filament current: 1.8 A typical at U

= 6.3 V

F

Anode voltage: 2000 - 5000 V DC
Anode current: 180 µA typical at

U

= 4000 V

A

Screen current: 100 µA typical at

U

= 4000 V

S

Glass bulb: 130 mm diam. approx.
Total length: 260 mm approx.
Luminescence screen:

5.1: fluorescent blue, approx. 450 nm, me­dium decay time

5.2: fluorescent red, approx. 625 nm, me­dium short decay time

5.3: fluorescent green, approx. 510 nm fluo­rescent, approx. 515 nm phosphorescent,
long decay time

4. Operation

To perform experiments using the luminescence
tube, the following equipment is also required:

1 Tube holder D 1008507
1 High voltage power supply 5 kV (115 V, 50/60 Hz)

1003309
or
1 High voltage power supply 5 kV (230 V, 50/60 Hz)

1003310
1 Analogue multimeter AM51 1003074
1 High-pressure mercury vapour lamp 1000852
Spectrum tube power supply (115 V, 50/60 Hz)

1003195
or
Spectrum tube power supply (230 V, 50/60 Hz)
1003196

1 Infra-red light source

Additionally recommended:
Protective Adapter, 2-Pole 1009961

4.1 Setting up the tube in the tube holder

• The tube should not be mounted or removed

unless all power supplies are disconnected.

• Push the jaw clamp sliders on the stanchion

of the tube holder right back so that the jaws
open.

• Push the bosses of the tube into the jaws.

• Push the jaw clamps forward on the stan-

chions to secure the tube within the jaws.

• If necessary plug the protective adapter onto

the connector sockets for the tube.

4.2 Removing the tube from the tube holder

• To remove the tube, push the jaw clamps

right back again and take the tube out of the
jaws.

5.1 Excitation by cathode ray bombardment

• To better observe the afterglow effects

(phosphorescence), carry out the the last
step of the experiment in a darkened room.

• Set up the luminescence tube as shown in

fig.1.

• Connect both the screens and the anode to

earth for maximum safety.

• Set the voltage U

• Observe the luminescence.

The three phosphors fluoresce at different wave­lengths (colours).

• Vary the voltage between 2000 V and 4000 V.

• Observe the change of the luminous phe-

nomenon.

While the intensity of the fluorescence varies
with the voltage, wavelength does not.

• With U

scope to view the emissions from each
phosphor.

Note that the emission from the red phosphor
comprises a number of discrete emission lines.

• Switch off the power supply and observe the

afterglow (phosphorescence).

The removal of the source of thermionic bom­bardment causes luminescence to cease. The
decay of emission from the phosphors is particu­larly apparent on the green phosphor.

5.2 Excitation by ultra-violet light

• Carry out the experiment in a darkened

room.

• Set up the luminescence tube as shown in

fig.2.

• Do not switch on the power supply.

Note that there is no visible photoluminescence
due to the ambient light levels.

• Illuminate the gun side of the screen with

ultra-violet light and note the initial time de­pendency of emission intensity.

The three phosphors fluoresce at the same
wavelength as when excited by cathode ray
bombardment.

• Vary the intensity of the ulta-violet light, ei-

ther by changing the distance between the
light source and the phosphor, or by inter­posing suitable filters.

While the intensity of the fluorescence varies
with the intensity and energy of the exciting ra­diation, wavelength does not.

• Remove the ultraviolet light and observe the

afterglow (phosphorescence).

The decay characteristic of the green phosphor
appears longer than was observed after removal
of cathode ray bombardment. The reason for
this is that the phosphorescence of this material
is quenched by infra-red radiation. When the
filament supply is switched off there remains

5. Example experiments

at 4000 V use a hand held spectro-

A

to about 3500 V.

A

2