Hi Stefan
Blue glow is perfectly normal:
http://www.thetubestore.com/Resources/Matching-and-other-tube-info/Blue-Glow
Dave
> -----Original Message-----
> From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Teslalabor
> Sent: Friday, September 19, 2014 04:35
> To: Co60bishop; Tesla Coil Mailing List
> Subject: Re: [TCML] Homemade Crookes Tube?
>
> Hi Cobalt 60,
>
> when I was experimenting with large transmitting tubes
> (graphite anodes) at
> only arround 6kV anode voltage, there was a bright blue
> glowing visible
> arround the complete inner surface of the glas bulb.
> I'm sure, this "fluorescence" was generated by x-rays,
> hitting the glas.
> Although not sure, which amount of x-rays really was able to
> go through the
> glas and hitting me, this was the main reason, I immediately
> canceled all my
> further experiments with such tubes, because I was afraid of
> x-rays, even at
> such low voltages. So I think the dangerous level is far
> below 30kV, as you
> stated.
> I even have some QB5/1750 Tetrodes, which are only 5kV anode
> voltage or so,
> and this tubes have "Danger X-Ray radiation" warning's on it.
>
> Regards,
> Stefan
>
>
> ----- Original Message -----
> From: "Co60bishop via Tesla" <tesla@xxxxxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Friday, September 19, 2014 6:35 AM
> Subject: Re: [TCML] Homemade Crookes Tube?
>
>
> > Paul, David is absolutely correct. I test semiconductors
> for radiation
> > hardness using x-rays and the tube you had made sounds like
> it has low
> > pressure argon gas and there is also a small amount of
> mercury on one of
> > the electrodes when a " neon" tube is made. I say neon but
> tube color
> > depends on which gas is in the tube and the phosphorous
> coating inside of
> > the tube. I can assume your tube is plain glass with no
> coating. I had one
> > of every color made years ago by our local neon sign
> company and I hold
> > one end in my bare hand and arc to my tesla coils at the
> other end. You
> > need to wrap each end with aluminum foil to spread the
> power out when
> > holding it. Dangerous x-rays require a minimum voltage of
> 30 kV with some
> > tubes operating with as much as 200 kV. Tungsten is the
> typical target and
> > a very hot high current filament is necessary to produce
> powerful 10 keV
> > and higher x-rays. The super hot filament is required to
> emit enough
> > electrons to generate the x-rays. What you have is
> > not much different than using a fluorescent lamp to arc to
> the secondary
> > output.
> >
> > A Bishop
> > Principal Device Physics Tech
> >
> > Sent from my iPad
> >
> >> On Sep 18, 2014, at 7:05 PM, David Rieben <drieben@xxxxxxx> wrote:
> >>
> >> Paul,
> >>
> >> I am certainly no authority on this matter but from what I
> have gleaned,
> >> you are not going to produce "hard" x-rays in this manner.
> Besides the
> >> hard vacuum, this would also require a white-hot filament (for an
> >> electron source) for the cathode, a heavy metal target
> (usually tungsten)
> >> for the anode, and well over ~50 kVDC potential between
> the said cathode
> >> and anode to really produce the ionizing, body penetrating
> hard x-rays
> >> (even dental x-ray tubes typically run about 70 kV(DC)).
> That being said,
> >> if you are powering your tube with say 10 to 20 kVDC, you
> may produce
> >> some low energy "soft" x-rays, but I don't think it's
> going to be a
> >> significantly ionizing radiation source. I'm not even sure
> if you can
> >> produce any kind of x-rays at all with AC? That's just
> "my" 2 cents. ;^)
> >>
> >> David
> >>
> >>
> >> On Thursday, September 18, 2014 6:01 PM, Paul B. Thompson
> >> <mrapol@xxxxxxxxxxxx> wrote:
> >>
> >>
> >>
> >> I just recently found a local neon sign maker and asked
> him to make me a
> >> simple vacuum tube, which he did, gratis (!). It's 18
> inches long, clear
> >> glass tubing about 3/4 inch in diameter, with electrodes
> at opposite
> >> ends. I
> >> don't know how hard a vacuum he pulled on this, but very
> quick tests show
> >> a
> >> pale blue glow from end to end. A strong magnet placed
> next to the tube
> >> pinches the beam, intensifying it at the spot.
> >>
> >> I've not run this for more than a few seconds. I am
> concerned about
> >> x-rays.
> >> I'd like advice about operating this tube safely.
> >>
> >> Thanks,
> >>
> >> Paul
> >>
> >>
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