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06/05-W97-Sel

Instruction sheet 554 161

Discharge tube, with luminescent screen (554 161)

1 Luminescent screen

2 4-mm hole

3 Electrode

4 Female ground joint

1 Description

 At reduced pressure, the characteristic luminescent

phenomena of electrical discharge and the cathode and canalrays outside the discharge path can be observed andinvestigated in the discharge tube.

Safety note

2 Technical data

Material: Glass

Vacuum connection: Female ground joint NS 19/38Electrical connections: 4-mm holes

Required voltage: 3 ... 5 kV 

Dimensions: 70 cm × 4 cm ∅ 

Weight: 0.5 kg

3 Accessories

1 Rotary-vane vacuum pump D 2.5 E 378 752

1 Small flange DN 10 KFwith male ground joint NS 19/39 378 023

1 Cross 378 0154 Centering rings for DN 16 KF 378 0454 Clamping rings 378 0501 Variable leak valve 378 7761 Ball valve with 2 flanges DN 16 KF 378 777

1 Vacuum meter THERMOVAC TM 21 378 5001 Gauge tube TR 211 378 5011 Gauge head cable, 3 m 378 502

1 High-vacuum grease 378 701

1 High voltage power supply, 10 kV 521 70

2 High voltage cable, 1m 501 05

or 

1 Safety connection lead, 1m, red 500 641

1 Safety connection lead, 1m, blue 500 6422 Adapter for safety connection lead 500 17 008

When the discharge tube is operated at high voltages over 5 kV, X-rays are generated.

• Do not operate the discharge tube with high voltagesover 5 kV.

There is danger of implosion when a damaged dischargetube is evacuated:

• Handle the discharge tube carefully and protect it frommechanical stresses.

• Before evacuating the tube, examine it for damage suchas cracks.

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Instruction sheet 554 161 Page 2/2

LD Didactic GmbH . Leyboldstrasse 1 . D-50354 Huerth / Germany . Phone (02233) 604-0 . Fax (02233) 604-222 . e-mail: info@ld-didactic.de

by LD Didactic GmbH Printed in the Federal Republic of GermanyTechnical alterations reserved

4 Operation

- Firmly clamp the ball valve with two flanges (a) onto theintake connector of the rotary-vane pump and connect thecross over it.

- Install variable leak valve (b) and gauge tube (c) onto theside of the cross.

- Evenly spread a thin coating of high-vacuum grease on thefemale ground joint of the discharge tube; slide the

discharge tube straight into the male ground joint (d)without excessive force and connect cross to male ground joint.

- Carefully close clamping ring.

- Connect the gauge tube to the vacuum meter THERMOVACTM 21.

Remark: For optimum observation of the luminescent 

 phenomena, carry out the experiment in a completely darkened 

room.

- Connect the electrode of the discharge tube to the right kVoutput ( I < 2 mA) of the high voltage power supply.

- Switch on the high voltage power supply and set the outputvoltage U = 5 kV.

- Switch on the vacuum meter THERMOVAC TM 21.

- Completely open the variable leak valve, partially open theball valve with two flanges and turn on the rotary-valvevacuum pump.

- Gradually and carefully close the variable leak valve, so thatthe pressure in the discharge tube continuously drops andobserve the discharge phenomena during pressuredecrease.

- Hold the pressure constant for a suitable observation periodby carefully operating the variable leak valve (while the

pump is operating) whenever a characteristic luminosity isvisible.

-  At approximately 0.04 hPa, use a permanent magnet todeflect the visible cathode and canal rays onto the screen.