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What are the most interesting vacuum tubes in your collection?

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radhoo

Sat Mar 19 2011, 10:06AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699

A nice relay tube, but filament broken :(

Proud Mary

Sat Mar 19 2011, 10:20AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

radhoo wrote ...

A nice relay tube, but filament broken :(

It's an HT delay relay - used to delay the application of high voltage to thermionic valves until their heaters have reached full temperature.

radhoo

Wed Mar 23 2011, 09:50AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699

The hottest tube I got so far: JAN-1B22 - A Radium-226 Spark Gap:

The maximum reading was 9uSv/h . According to this source it contains up to 2.95uC of Ra226.

The 1B22 is an aluminium cathode spark gap tube for radar modulator use. It was developed for the ASH (later AN/APS-4) radar, where two tubes in series switched a peak power of around 105kW into a 725A magnetron. In order to maintain operation at high altitudes even if the pressurised container failed, the peak switching voltage was kept to 4kV. The tubes could pass a current pulse of 67A for 0.75Âµs at either 600 or 1000 pulses per second. They could also operate for short periods at 2.25Âµs/330pps.

Anode/cathode spacing is 150 mils, and the gas mixture at 20" pressure is 75% hydrogen and 25% argon. Life expectancy was 500 hours at 0.75Âµs.

Corona points at the end of the cathode opposite the end of the anode assist firing, the firing voltage being 2.7kV. The tube also contains a small quantity of radium in this region.

By design the tube must be operated with the cathode opening downward; the aluminum eroded by sparks is mostly transferred to anode, leaving approximately constant the electrode spacing through the useful life.

Proud Mary

Wed Mar 23 2011, 10:08AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

radhoo wrote ...

it contains up to 2.95uC of Ra226.

That's 109150 disintegrations per second - a good illustration of the very low gamma detection efficiency of GM tubes, when you think of the small number actually counted.

radhoo

Wed Mar 23 2011, 12:03PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699

Proud Mary wrote ...

That's 109150 disintegrations per second - a good illustration of the very low gamma detection efficiency of GM tubes, when you think of the small number actually counted.

Indeed.

BTW, I got my scintillation probes up and running. Funny - they are not responding to my gamma sources, but quite the opposite when put close to an X-ray emitting tube.

radhoo

Wed Mar 23 2011, 12:33PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699

4 nice Klystron tubes:

Raytheon RK-6037
Raytheon JAN-5837
Beam Tube Corp. 6236
Raytheon RK-707

Proud Mary

Wed Mar 23 2011, 12:49PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

radhoo wrote ...

BTW, I got my scintillation probes up and running. Funny - they are not responding to my gamma sources, but quite the opposite when put close to an X-ray emitting tube.

Well, that is good news!

This is what we'd expect to see with a thin scintillator. Low energy X-ray/gamma photons and high energy beta particles will be stopped by it, and cause a flash of light, while higher energy photons pass straight through it without interaction. The thin scintillator allows more of the light pulses to escape and be detected by the photomultiplier, and so has a higher detection efficiency.

Proud Mary

Wed Mar 23 2011, 02:14PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

radhoo wrote ...

4 nice Klystron tubes:

Raytheon RK-6037
Raytheon JAN-5837
Beam Tube Corp. 6236
Raytheon RK-707

Here's a miniature reflex klystron with rectangular waveguide flange underneath.

The cavity tuning screw is at upper right.

radhoo

Mon Mar 28 2011, 08:47PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699

That's a nice one , Stella, I was wondering how to power these little things ( I do have detector UHF diodes as well).

Here'a GU81m and the GMI90:

Proud Mary

Mon Mar 28 2011, 10:25PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

radhoo wrote ...

That's a nice one , Stella, I was wondering how to power these little things ( I do have detector UHF diodes as well).

I got these details from Gintaras. I bought two from the same series, but with different frequencies. I haven't tried them out yet!

Heater 6.3V @ 0.5-1.3A
Resonator Voltage 350V
Negative repeller Voltage -50V to -350V
The resistance value in the repeller circuit no more than 100KOhm
Load SWR 1.2 max.
Cathode current 10mA to 50mA
Frequency stabilization time 5min max

Leads:

Yellow - Repeller
Green - Filament
White - Cathode
White - Cathode & Filament
Red - Resonator

Cooling: forced air. Air flow velocity should be 3meters/second.

When switching on apply voltages in following order:

1. Apply forced air.
2. Apply filament voltage, let the klistron heat up for 1 minute.
3. Apply negative repeller voltage.
4. Apply the resonator voltage.

Repeat steps 1-4 backwards when switching the klystron off.

Frequency goes up when turning the tuning screw counterclockwise.

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